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\n \n 2023\n \n \n (2)\n \n \n

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\n \n\n \n \n Wakita, S.; Johnson, B. C.; Soderblom, J. M.; Shah, J.; Neish, C. D.; and Steckloff, J. K.\n\n\n \n \n \n \n \n Modeling the Formation of Selk Impact Crater on Titan: Implications for Dragonfly.\n \n \n \n \n\n\n \n\n\n\n The Planetary Science Journal, 4(3): 51. March 2023.\n Publisher: IOP Publishing\n\n\n\n
\n\n\n\n \n \n $\"Modeling$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{wakita_modeling_2023,\n\ttitle = {Modeling the {Formation} of {Selk} {Impact} {Crater} on {Titan}: {Implications} for {Dragonfly}},\n\tvolume = {4},\n\tissn = {2632-3338},\n\tshorttitle = {Modeling the {Formation} of {Selk} {Impact} {Crater} on {Titan}},\n\turl = {https://iopscience.iop.org/article/10.3847/PSJ/acbe40/meta},\n\tdoi = {10.3847/PSJ/acbe40},\n\tlanguage = {en},\n\tnumber = {3},\n\turldate = {2023-10-06},\n\tjournal = {The Planetary Science Journal},\n\tauthor = {Wakita, Shigeru and Johnson, Brandon C. and Soderblom, Jason M. and Shah, Jahnavi and Neish, Catherine D. and Steckloff, Jordan K.},\n\tmonth = mar,\n\tyear = {2023},\n\tnote = {Publisher: IOP Publishing},\n\tpages = {51},\n}\n\n

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\n \n\n \n \n Hamann, C.; Kurosawa, K.; Ono, H.; Tada, T.; Langenhorst, F.; Pollok, K.; Genda, H.; Niihara, T.; Okamoto, T.; and Matsui, T.\n\n\n \n \n \n \n \n Experimental Evidence for Shear-Induced Melting and Generation of Stishovite in Granite at Low (\\textless18 GPa) Shock Pressure.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 128(6): e2023JE007742. 2023.\n _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023JE007742\n\n\n\n
\n\n\n\n \n \n $\"Experimental$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{hamann_experimental_2023,\n\ttitle = {Experimental {Evidence} for {Shear}-{Induced} {Melting} and {Generation} of {Stishovite} in {Granite} at {Low} ({\\textless}18 {GPa}) {Shock} {Pressure}},\n\tvolume = {128},\n\tcopyright = {© 2023 The Authors.},\n\tissn = {2169-9100},\n\turl = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023JE007742},\n\tdoi = {10.1029/2023JE007742},\n\tabstract = {Knowledge of the shock behavior of planetary materials is essential to interpret shock metamorphism documented in rocks at hypervelocity impact structures on Earth, in meteorites, and in samples retrieved in space missions. Although our understanding of shock metamorphism has improved considerably within the last decades, the effects of friction and plastic deformation on shock metamorphism of complex, polycrystalline, non-porous rocks are poorly constrained. Here, we report on shock-recovery experiments in which natural granite was dynamically compressed to 0.5–18 GPa by singular, hemispherically decaying shock fronts. We then combine petrographic observations of shocked samples that retained their pre-impact stratigraphy with distributions of peak pressures, temperatures, and volumetric strain rates obtained from numerical modeling to systematically investigate progressive shock metamorphism of granite. We find that the progressive shock metamorphism of granite observed here is mainly consistent with current classification schemes. However, we also find that intense shear deformation during shock compression and release causes the formation of highly localized melt veins at peak pressures as low as 6 GPa, which is an order of magnitude lower than currently thought. We also find that melt veins formed in quartz grains compressed to {\\textgreater}10–12 GPa contain the high-pressure silica polymorph stishovite. Our results illustrate the significance of shear and plastic deformation during hypervelocity impact and bear on our understanding of how melt veins containing high-pressure polymorphs form in moderately shocked terrestrial impactites or meteorites.},\n\tlanguage = {en},\n\tnumber = {6},\n\turldate = {2023-06-28},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Hamann, Christopher and Kurosawa, Kosuke and Ono, Haruka and Tada, Toshihiro and Langenhorst, Falko and Pollok, Kilian and Genda, Hidenori and Niihara, Takafumi and Okamoto, Takaya and Matsui, Takafumi},\n\tyear = {2023},\n\tnote = {\\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023JE007742},\n\tkeywords = {granite, melt vein, numerical modeling, shock metamorphism, shock recovery, stishovite},\n\tpages = {e2023JE007742},\n}\n\n

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\n \n 2022\n \n \n (10)\n \n \n

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\n \n\n \n \n Wakita, S.; Genda, H.; Kurosawa, K.; Davison, T. M.; and Johnson, B. C.\n\n\n \n \n \n \n \n Effect of Impact Velocity and Angle on Deformational Heating and Postimpact Temperature.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 127(8): e2022JE007266. 2022.\n _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022JE007266\n\n\n\n
\n\n\n\n \n \n $\"Effect$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{wakita_effect_2022,\n\ttitle = {Effect of {Impact} {Velocity} and {Angle} on {Deformational} {Heating} and {Postimpact} {Temperature}},\n\tvolume = {127},\n\tcopyright = {© 2022. The Authors.},\n\tissn = {2169-9100},\n\turl = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JE007266},\n\tdoi = {10.1029/2022JE007266},\n\tabstract = {The record of impact-induced shock heating in meteorites is an important key for understanding the collisional history of the solar system. Material strength is important for impact heating, but the effect of impact angle and impact velocity on shear heating remains poorly understood. Here, we report three-dimensional oblique impact simulations, which confirm the enhanced heating due to material strength and explore the effects of impact angle and impact velocity. We find that oblique impacts with an impact angle that is steeper than 45-degrees produce a similar amount of heated mass as vertical impacts. On the other hand, grazing impacts produce less heated mass and smaller heated regions compared to impacts at steeper angles. We derive an empirical formula of the heated mass, as a function of the impact angle and velocity. This formula can be used to estimate the impact conditions (velocity and angle) that occurred and caused Ar loss in the meteoritic parent bodies. Furthermore, our results indicate that grazing impacts at higher impact velocities could generate a similar amount of heated material as vertical impacts at lower velocities. As the heated material produced by grazing impacts has experienced lower pressure than the material heated by vertical impacts, our results imply that grazing impacts may produce weakly shock-heated meteorites.},\n\tlanguage = {en},\n\tnumber = {8},\n\turldate = {2023-10-06},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Wakita, S. and Genda, H. and Kurosawa, K. and Davison, T. M. and Johnson, B. C.},\n\tyear = {2022},\n\tnote = {\\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022JE007266},\n\tkeywords = {asteroids, impact heating, meteorites, numerical modeling, oblique impacts},\n\tpages = {e2022JE007266},\n}\n\n

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\n \n\n \n \n Wakita, S.; Johnson, B. C.; Soderblom, J. M.; Shah, J.; and Neish, C. D.\n\n\n \n \n \n \n \n Methane-saturated layers limit the observability of impact craters on Titan.\n \n \n \n \n\n\n \n\n\n\n The Planetary Science Journal, 3(2): 50. 2022.\n Publisher: IOP Publishing\n\n\n\n
\n\n\n\n \n \n $\"Methane-saturated$ Paper\n \n \n\n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{wakita_methane-saturated_2022,\n\ttitle = {Methane-saturated layers limit the observability of impact craters on {Titan}},\n\tvolume = {3},\n\turl = {https://iopscience.iop.org/article/10.3847/PSJ/ac4e91/meta},\n\tnumber = {2},\n\turldate = {2023-10-06},\n\tjournal = {The Planetary Science Journal},\n\tauthor = {Wakita, Shigeru and Johnson, Brandon C. and Soderblom, Jason M. and Shah, Jahnavi and Neish, Catherine D.},\n\tyear = {2022},\n\tnote = {Publisher: IOP Publishing},\n\tpages = {50},\n}\n\n

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\n \n\n \n \n Luther, R.; Raducan, S. D.; Burger, C.; Wünnemann, K.; Jutzi, M.; Schäfer, C. M.; Koschny, D.; Davison, T. M.; Collins, G. S.; Zhang, Y.; and Michel, P.\n\n\n \n \n \n \n \n Momentum Enhancement during Kinetic Impacts in the Low-intermediate-strength Regime: Benchmarking and Validation of Impact Shock Physics Codes.\n \n \n \n \n\n\n \n\n\n\n The Planetary Science Journal, 3(10): 227. October 2022.\n Publisher: IOP Publishing\n\n\n\n
\n\n\n\n \n \n $\"Momentum$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{luther_momentum_2022,\n\ttitle = {Momentum {Enhancement} during {Kinetic} {Impacts} in the {Low}-intermediate-strength {Regime}: {Benchmarking} and {Validation} of {Impact} {Shock} {Physics} {Codes}},\n\tvolume = {3},\n\tissn = {2632-3338},\n\tshorttitle = {Momentum {Enhancement} during {Kinetic} {Impacts} in the {Low}-intermediate-strength {Regime}},\n\turl = {https://iopscience.iop.org/article/10.3847/PSJ/ac8b89/meta},\n\tdoi = {10.3847/PSJ/ac8b89},\n\tlanguage = {en},\n\tnumber = {10},\n\turldate = {2022-10-14},\n\tjournal = {The Planetary Science Journal},\n\tauthor = {Luther, Robert and Raducan, Sabina D. and Burger, Christoph and Wünnemann, Kai and Jutzi, Martin and Schäfer, Christoph M. and Koschny, Detlef and Davison, Thomas M. and Collins, Gareth S. and Zhang, Yun and Michel, Patrick},\n\tmonth = oct,\n\tyear = {2022},\n\tnote = {Publisher: IOP Publishing},\n\tpages = {227},\n}\n\n

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\n \n\n \n \n Ormö, J.; Raducan, S. D.; Jutzi, M.; Herreros, M. I.; Luther, R.; Collins, G. S.; Wünnemann, K.; Mora-Rueda, M.; and Hamann, C.\n\n\n \n \n \n \n \n Boulder exhumation and segregation by impacts on rubble-pile asteroids.\n \n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 594: 117713. September 2022.\n \n\n\n\n
\n\n\n\n \n \n $\"Boulder$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n\n\n\n

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@article{ormo_boulder_2022,\n\ttitle = {Boulder exhumation and segregation by impacts on rubble-pile asteroids},\n\tvolume = {594},\n\tissn = {0012-821X},\n\turl = {https://www.sciencedirect.com/science/article/pii/S0012821X22003491},\n\tdoi = {10.1016/j.epsl.2022.117713},\n\tabstract = {Small asteroids are often considered to be rubble-pile objects, and such asteroids may be the most likely type of Near Earth Objects (NEOs) to pose a threat to Earth. However, impact cratering on such bodies is complex and not yet understood. We perform three low-velocity (≈ 400 m/s) impact experiments in granular targets with and without projectile-size boulders. We conducted SPH simulations that closely reproduced the impact experiments. Our results suggest that cratering on heterogeneous targets displaces and ejects boulders, rather than fragmenting them, unless directly hit. We also see indications that as long as the energy required to disrupt the boulder is small compared to the kinetic energy of the impact, the disruption of boulders directly hit by the projectile may have minimal effect on the crater size. The presence of boulders within the target causes ejecta curtains with higher ejection angles compared to homogeneous targets. At the same time, there is a segregation of the fine ejecta from the boulders, resulting in boulders landing at larger distances than the surrounding fine grained material. However, boulders located in the target near the maximum extent of the expanding excavation cavity are merely exhumed and distributed radially around the crater rim, forming ring patterns similar to the ones observed on asteroids Itokawa, Ryugu and Bennu. Altogether, on rubble-pile asteroids this process will redistribute boulders and finer-grained material heterogeneously, both areally around the crater and vertically in the regolith. In the context of a kinetic impactor on a rubble-pile asteroid and the DART mission, our results indicate that the presence of boulders will reduce the momentum transfer compared to a homogeneous, fine-grained target.},\n\tlanguage = {en},\n\turldate = {2022-07-22},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Ormö, J. and Raducan, S. D. and Jutzi, M. and Herreros, M. I. and Luther, R. and Collins, G. S. and Wünnemann, K. and Mora-Rueda, M. and Hamann, C.},\n\tmonth = sep,\n\tyear = {2022},\n\tkeywords = {impact cratering, rubble-pile asteroids},\n\tpages = {117713},\n}\n\n

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\n \n\n \n \n Bray, V. J.; Hagerty, J. J.; and Collins, G. S.\n\n\n \n \n \n \n \n “False peak” creation in the Flynn Creek marine target impact crater.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 57(7): 1365–1386. 2022.\n _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/maps.13822\n\n\n\n
\n\n\n\n \n \n $\"“False$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{bray_false_2022,\n\ttitle = {“{False} peak” creation in the {Flynn} {Creek} marine target impact crater},\n\tvolume = {57},\n\tissn = {1945-5100},\n\turl = {https://onlinelibrary.wiley.com/doi/abs/10.1111/maps.13822},\n\tdoi = {10.1111/maps.13822},\n\tabstract = {Impacts into marine targets are known to create abnormal crater morphologies. We investigate the formation of the 4 km diameter Flynn Creek marine target impact crater using the iSALE hydrocode. We compare simulation results to topographic profiles, mineral pressure indicators, and breccia sequencing from drill cores to determine the most likely sea depth at this location at the time of impact ( 360 Ma, Tennessee, USA): 700–800 m. Both the peak shock pressure produced by the impact and the mechanism(s) of central peak formation differ with sea depth. The large central mound of Flynn Creek could have been produced in three distinct ways, all requiring the presence of an ocean: (1) a relatively cohesive rim collapse deposit that reached the crater center as part of a ground flow and came to rest on top of the existing crater stratigraphy; (2) chaotic resurge of ejecta with the returning ocean that deposited at the crater center; (3) large uplift facilitated by the removal of overburden pressure from a deep ocean. The first two of these mechanisms create “false peaks” in which high-shock uplifted material and original crater floor are buried beneath {\\textgreater} 200 m of relatively low shock material. Our simulations suggest that drilling of marine impact sites might require deeper than expected drill cores, so that any high-pressure mineralogical indictors at depth can be accessed.},\n\tlanguage = {en},\n\tnumber = {7},\n\turldate = {2022-07-07},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Bray, V. J. and Hagerty, J. J. and Collins, G. S.},\n\tyear = {2022},\n\tnote = {\\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/maps.13822},\n\tpages = {1365--1386},\n}\n\n

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\n \n\n \n \n Wiggins, S. E.; Johnson, B. C.; Collins, G. S.; Jay Melosh, H.; and Marchi, S.\n\n\n \n \n \n \n \n Widespread impact-generated porosity in early planetary crusts.\n \n \n \n \n\n\n \n\n\n\n Nature Communications, 13(1): 4817. August 2022.\n Number: 1 Publisher: Nature Publishing Group\n\n\n\n
\n\n\n\n \n \n $\"Widespread$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n\n\n\n

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@article{wiggins_widespread_2022,\n\ttitle = {Widespread impact-generated porosity in early planetary crusts},\n\tvolume = {13},\n\tcopyright = {2022 The Author(s)},\n\tissn = {2041-1723},\n\turl = {https://www.nature.com/articles/s41467-022-32445-3},\n\tdoi = {10.1038/s41467-022-32445-3},\n\tabstract = {NASA’s Gravity Recovery and Interior Laboratory (GRAIL) spacecraft revealed the crust of the Moon is highly porous, with {\\textasciitilde}4\\% porosity at 20 km deep. The deep lying porosity discovered by GRAIL has been difficult to explain, with most current models only able to explain high porosity near the lunar surface (first few kilometers) or inside complex craters. Using hydrocode routines we simulated fracturing and generation of porosity by large impacts in lunar, martian, and Earth crust. Our simulations indicate impacts that produce 100–1000 km scale basins alone are capable of producing all observed porosity within the lunar crust. Simulations under the higher surface gravity of Mars and Earth suggest basin forming impacts can be a primary source of porosity and fracturing of ancient planetary crusts. Thus, we show that impacts could have supported widespread crustal fluid circulation, with important implications for subsurface habitable environments on early Earth and Mars.},\n\tlanguage = {en},\n\tnumber = {1},\n\turldate = {2022-09-01},\n\tjournal = {Nature Communications},\n\tauthor = {Wiggins, Sean E. and Johnson, Brandon C. and Collins, Gareth S. and Jay Melosh, H. and Marchi, Simone},\n\tmonth = aug,\n\tyear = {2022},\n\tnote = {Number: 1\nPublisher: Nature Publishing Group},\n\tkeywords = {Early solar system, Inner planets},\n\tpages = {4817},\n}\n\n

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\n \n\n \n \n Posiolova, L. V.; Lognonné, P.; Banerdt, W. B.; Clinton, J.; Collins, G. S.; Kawamura, T.; Ceylan, S.; Daubar, I. J.; Fernando, B.; Froment, M.; Giardini, D.; Malin, M. C.; Miljković, K.; Stähler, S. C.; Xu, Z.; Banks, M. E.; Beucler, É.; Cantor, B. A.; Charalambous, C.; Dahmen, N.; Davis, P.; Drilleau, M.; Dundas, C. M.; Durán, C.; Euchner, F.; Garcia, R. F.; Golombek, M.; Horleston, A.; Keegan, C.; Khan, A.; Kim, D.; Larmat, C.; Lorenz, R.; Margerin, L.; Menina, S.; Panning, M.; Pardo, C.; Perrin, C.; Pike, W. T.; Plasman, M.; Rajšić, A.; Rolland, L.; Rougier, E.; Speth, G.; Spiga, A.; Stott, A.; Susko, D.; Teanby, N. A.; Valeh, A.; Werynski, A.; Wójcicka, N.; and Zenhäusern, G.\n\n\n \n \n \n \n \n Largest recent impact craters on Mars: Orbital imaging and surface seismic co-investigation.\n \n \n \n \n\n\n \n\n\n\n Science, 378(6618): 412–417. October 2022.\n Publisher: American Association for the Advancement of Science\n\n\n\n
\n\n\n\n \n \n $\"Largest$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{posiolova_largest_2022,\n\ttitle = {Largest recent impact craters on {Mars}: {Orbital} imaging and surface seismic co-investigation},\n\tvolume = {378},\n\tshorttitle = {Largest recent impact craters on {Mars}},\n\turl = {https://www.science.org/doi/10.1126/science.abq7704},\n\tdoi = {10.1126/science.abq7704},\n\tabstract = {Two {\\textgreater}130-meter-diameter impact craters formed on Mars during the later half of 2021. These are the two largest fresh impact craters discovered by the Mars Reconnaissance Orbiter since operations started 16 years ago. The impacts created two of the largest seismic events (magnitudes greater than 4) recorded by InSight during its 3-year mission. The combination of orbital imagery and seismic ground motion enables the investigation of subsurface and atmospheric energy partitioning of the impact process on a planet with a thin atmosphere and the first direct test of martian deep-interior seismic models with known event distances. The impact at 35°N excavated blocks of water ice, which is the lowest latitude at which ice has been directly observed on Mars.},\n\tnumber = {6618},\n\turldate = {2022-11-09},\n\tjournal = {Science},\n\tauthor = {Posiolova, L. V. and Lognonné, P. and Banerdt, W. B. and Clinton, J. and Collins, G. S. and Kawamura, T. and Ceylan, S. and Daubar, I. J. and Fernando, B. and Froment, M. and Giardini, D. and Malin, M. C. and Miljković, K. and Stähler, S. C. and Xu, Z. and Banks, M. E. and Beucler, É. and Cantor, B. A. and Charalambous, C. and Dahmen, N. and Davis, P. and Drilleau, M. and Dundas, C. M. and Durán, C. and Euchner, F. and Garcia, R. F. and Golombek, M. and Horleston, A. and Keegan, C. and Khan, A. and Kim, D. and Larmat, C. and Lorenz, R. and Margerin, L. and Menina, S. and Panning, M. and Pardo, C. and Perrin, C. and Pike, W. T. and Plasman, M. and Rajšić, A. and Rolland, L. and Rougier, E. and Speth, G. and Spiga, A. and Stott, A. and Susko, D. and Teanby, N. A. and Valeh, A. and Werynski, A. and Wójcicka, N. and Zenhäusern, G.},\n\tmonth = oct,\n\tyear = {2022},\n\tnote = {Publisher: American Association for the Advancement of Science},\n\tpages = {412--417},\n}\n\n

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\n \n\n \n \n Stickle, A. M.; DeCoster, M. E.; Burger, C.; Caldwell, W. K.; Graninger, D.; Kumamoto, K. M.; Luther, R.; Ormö, J.; Raducan, S.; Rainey, E.; Schäfer, C. M.; Walker, J. D.; Zhang, Y.; Michel, P.; Owen, J. M.; Barnouin, O.; Cheng, A. F.; Chocron, S.; Collins, G. S.; Davison, T. M.; Dotto, E.; Ferrari, F.; Herreros, M. I.; Ivanovski, S. L.; Jutzi, M.; Lucchetti, A.; Martellato, E.; Pajola, M.; Plesko, C. S.; Syal, M. B.; Schwartz, S. R.; Sunshine, J. M.; and Wünnemann, K.\n\n\n \n \n \n \n \n Effects of Impact and Target Parameters on the Results of a Kinetic Impactor: Predictions for the Double Asteroid Redirection Test (DART) Mission.\n \n \n \n \n\n\n \n\n\n\n The Planetary Science Journal, 3(11): 248. November 2022.\n Publisher: IOP Publishing\n\n\n\n
\n\n\n\n \n \n $\"Effects$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{stickle_effects_2022,\n\ttitle = {Effects of {Impact} and {Target} {Parameters} on the {Results} of a {Kinetic} {Impactor}: {Predictions} for the {Double} {Asteroid} {Redirection} {Test} ({DART}) {Mission}},\n\tvolume = {3},\n\tissn = {2632-3338},\n\tshorttitle = {Effects of {Impact} and {Target} {Parameters} on the {Results} of a {Kinetic} {Impactor}},\n\turl = {https://iopscience.iop.org/article/10.3847/PSJ/ac91cc/meta},\n\tdoi = {10.3847/PSJ/ac91cc},\n\tlanguage = {en},\n\tnumber = {11},\n\turldate = {2022-11-30},\n\tjournal = {The Planetary Science Journal},\n\tauthor = {Stickle, Angela M. and DeCoster, Mallory E. and Burger, Christoph and Caldwell, Wendy K. and Graninger, Dawn and Kumamoto, Kathryn M. and Luther, Robert and Ormö, Jens and Raducan, Sabina and Rainey, Emma and Schäfer, Christoph M. and Walker, James D. and Zhang, Yun and Michel, Patrick and Owen, J. Michael and Barnouin, Olivier and Cheng, Andy F. and Chocron, Sidney and Collins, Gareth S. and Davison, Thomas M. and Dotto, Elisabetta and Ferrari, Fabio and Herreros, M. Isabel and Ivanovski, Stavro L. and Jutzi, Martin and Lucchetti, Alice and Martellato, Elena and Pajola, Maurizio and Plesko, Cathy S. and Syal, Megan Bruck and Schwartz, Stephen R. and Sunshine, Jessica M. and Wünnemann, Kai},\n\tmonth = nov,\n\tyear = {2022},\n\tnote = {Publisher: IOP Publishing},\n\tpages = {248},\n}\n\n

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\n \n\n \n \n Raducan, S. D.; and Jutzi, M.\n\n\n \n \n \n \n \n Global-scale Reshaping and Resurfacing of Asteroids by Small-scale Impacts, with Applications to the DART and Hera Missions.\n \n \n \n \n\n\n \n\n\n\n The Planetary Science Journal, 3(6): 128. June 2022.\n Publisher: IOP Publishing\n\n\n\n
\n\n\n\n \n \n $\"Global-scale$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{raducan_global-scale_2022,\n\ttitle = {Global-scale {Reshaping} and {Resurfacing} of {Asteroids} by {Small}-scale {Impacts}, with {Applications} to the {DART} and {Hera} {Missions}},\n\tvolume = {3},\n\tissn = {2632-3338},\n\turl = {https://iopscience.iop.org/article/10.3847/PSJ/ac67a7/meta},\n\tdoi = {10.3847/PSJ/ac67a7},\n\tlanguage = {en},\n\tnumber = {6},\n\turldate = {2022-06-08},\n\tjournal = {The Planetary Science Journal},\n\tauthor = {Raducan, Sabina D. and Jutzi, Martin},\n\tmonth = jun,\n\tyear = {2022},\n\tnote = {Publisher: IOP Publishing},\n\tpages = {128},\n}\n\n

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\n \n\n \n \n Raducan, S. D.; Jutzi, M.; Davison, T. M.; DeCoster, M. E.; Graninger, D. M.; Owen, J. M.; Stickle, A. M.; and Collins, G. S.\n\n\n \n \n \n \n \n Influence of the projectile geometry on the momentum transfer from a kinetic impactor and implications for the DART mission.\n \n \n \n \n\n\n \n\n\n\n International Journal of Impact Engineering, 162: 104147. April 2022.\n \n\n\n\n
\n\n\n\n \n \n $\"Influence$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 7 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{raducan_influence_2022,\n\ttitle = {Influence of the projectile geometry on the momentum transfer from a kinetic impactor and implications for the {DART} mission},\n\tvolume = {162},\n\tissn = {0734-743X},\n\turl = {https://www.sciencedirect.com/science/article/pii/S0734743X21003225},\n\tdoi = {10.1016/j.ijimpeng.2021.104147},\n\tabstract = {The DART spacecraft will impact Didymos’s secondary, Dimorphos, at the end of 2022 and cause a change in the orbital period of the secondary. For simplicity, most previous numerical simulations of the impact used a spherical projectile geometry to model the DART spacecraft. To investigate the effects of alternative, simple projectile geometries on the DART impact outcome we used the iSALE shock physics code in two and thee-dimensions to model vertical impacts of projectiles with a mass and speed equivalent to the nominal DART impact, into porous basalt targets. We found that the simple projectile geometries investigated here have minimal effects on the crater morphology and momentum enhancement. Projectile geometries modelled in two-dimensions that have similar surface areas at the point of impact, affect the crater radius and the crater volume by less than 5\\%. In the case of a more extreme projectile geometry (i.e., a rod, modelled in three-dimensions), the crater was elliptical and 50\\% shallower compared to the crater produced by a spherical projectile of the same momentum. The momentum enhancement factor in these test cases, commonly referred to as β, was within 7\\% for the 2D simulations and within 10\\% for the 3D simulations, of the value obtained for a uniform spherical projectile. The most prominent effects of projectile geometry are seen in the ejection velocity as a function of launch position and ejection angle of the fast ejecta that resides in the so-called ‘coupling zone’. These results will inform the LICIACube ejecta cone analysis.},\n\tlanguage = {en},\n\turldate = {2022-02-28},\n\tjournal = {International Journal of Impact Engineering},\n\tauthor = {Raducan, S. D. and Jutzi, M. and Davison, T. M. and DeCoster, M. E. and Graninger, D. M. and Owen, J. M. and Stickle, A. M. and Collins, G. S.},\n\tmonth = apr,\n\tyear = {2022},\n\tpages = {104147},\n}\n\n

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\n \n 2021\n \n \n (12)\n \n \n

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\n \n\n \n \n Wakita, S.; Johnson, B. C.; Denton, C. A.; and Davison, T. M.\n\n\n \n \n \n \n \n Jetting during oblique impacts of spherical impactors.\n \n \n \n \n\n\n \n\n\n\n Icarus, 360: 114365. May 2021.\n \n\n\n\n
\n\n\n\n \n \n $\"Jetting$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{wakita_jetting_2021,\n\ttitle = {Jetting during oblique impacts of spherical impactors},\n\tvolume = {360},\n\tissn = {0019-1035},\n\turl = {https://www.sciencedirect.com/science/article/pii/S0019103521000580},\n\tdoi = {10.1016/j.icarus.2021.114365},\n\tabstract = {During the early stages of an impact a small amount material may be jetted and ejected at speeds exceeding the impact velocity. Jetting is an important process for producing melt during relatively low velocity impacts. How impact angle affects the jetting process has yet to be fully understood. Here, we simulate jetting during oblique impacts using the iSALE shock physics code. Assuming both the target and impactor have the same composition (dunite), we examine the jetted material which exceeds the impact velocity. Our results show that oblique impacts always produce more jetted ejecta than vertical impacts, except for grazing impacts with impact angles {\\textless}15°. A 45°impact with an impact velocity of 3 km/s produces jetted material equal to ∼7\\% of the impactor mass. This is 6 times the jetted mass produced by a vertical impact with similar impact conditions. We also find that the origin of jetted ejecta depends on impact angle; for impact angles less than 45°, most of the jet is composed of impactor material, while at higher impact angles the jet is dominated by target material. Our findings are consistent with previous experimental work. In all cases, jetted materials are preferentially distributed downrange of the impactor.},\n\turldate = {2023-10-06},\n\tjournal = {Icarus},\n\tauthor = {Wakita, Shigeru and Johnson, Brandon C. and Denton, C. Adeene and Davison, Thomas M.},\n\tmonth = may,\n\tyear = {2021},\n\tkeywords = {Asteroids, Collisional physics, Impact processes},\n\tpages = {114365},\n}\n\n

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\n \n\n \n \n Rae, A. S. P.; Poelchau, M. H.; and Kenkmann, T.\n\n\n \n \n \n \n \n Stress and strain during shock metamorphism.\n \n \n \n \n\n\n \n\n\n\n Icarus, 370: 114687. December 2021.\n \n\n\n\n
\n\n\n\n \n \n $\"Stress$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 4 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{rae_stress_2021,\n\ttitle = {Stress and strain during shock metamorphism},\n\tvolume = {370},\n\tissn = {0019-1035},\n\turl = {https://www.sciencedirect.com/science/article/pii/S0019103521003432},\n\tdoi = {10.1016/j.icarus.2021.114687},\n\tabstract = {Shock metamorphism is the process by which rocks, and the minerals within them, transform during the passage of a shock wave. Shock effects, such as shatter cones, are critical for the identification of impact structures and have commonly been used to infer mechanical and structural information on the cratering process. To make these inferences, the mechanics of shock wave behavior must be understood. Here, we use numerical simulations to demonstrate how stresses act during shock metamorphism across all regions of the target that experience solid-state shock metamorphism. Furthermore, our numerical simulations predict the strains that are produced as a consequence of those stresses. The results show that the magnitude and orientation of stress and strain during shock metamorphism are variable throughout the target, both spatially and temporally, even between rocks that experience the same peak shock pressure. The provenance of a sample relative to the point of impact and the timing/mechanism of the formation of a shock effect must both be considered when making structural interpretations. The stress and strain magnitudes and orientations as functions of time and location presented in this study provide the constraints that enable a greater understanding of the formation of a variety of shock deformation effects. We demonstrate this with a case study of shatter cones at the Gosses Bluff impact structure. Our results provide a useful guide to assist geologists and petrologists in the interpretation of shock metamorphic effects.},\n\tlanguage = {en},\n\turldate = {2021-09-24},\n\tjournal = {Icarus},\n\tauthor = {Rae, Auriol S. P. and Poelchau, Michael H. and Kenkmann, Thomas},\n\tmonth = dec,\n\tyear = {2021},\n\tkeywords = {Deformation, Impact cratering, Shatter cones, Shock metamorphism, Strain, Stress},\n\tpages = {114687},\n}\n\n

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\n \n\n \n \n Raducan, S. D.; Davison, T. M.; and Collins, G. S.\n\n\n \n \n \n \n \n Ejecta distribution and momentum transfer from oblique impacts on asteroid surfaces.\n \n \n \n \n\n\n \n\n\n\n Icarus,114793. November 2021.\n \n\n\n\n
\n\n\n\n \n \n $\"Ejecta$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{raducan_ejecta_2021,\n\ttitle = {Ejecta distribution and momentum transfer from oblique impacts on asteroid surfaces},\n\tissn = {0019-1035},\n\turl = {https://www.sciencedirect.com/science/article/pii/S0019103521004425},\n\tdoi = {10.1016/j.icarus.2021.114793},\n\tabstract = {NASA’s Double Asteroid Redirection Test (DART) mission will impact its target asteroid, Dimorphos, at an oblique angle that will not be known prior to the impact. We computed iSALE-3D simulations of DART-like impacts on asteroid surfaces at different impact angles and found that the vertical momentum transfer efficiency, β, is similar for different impact angles, however, the imparted momentum is reduced as the impact angle decreases. It is expected that the momentum imparted from a 45∘ impact is reduced by up to 50\\% compared to a vertical impact. The direction of the ejected momentum is not normal to the surface, however it is observed to ‘straighten up’ with crater growth. iSALE-2D simulations of vertical impacts provide context for the iSALE-3D simulation results and show that the ejection angle varies with both target properties and with crater growth. While the ejection angle is relatively insensitive to the target porosity, it varies by up to 30∘ with target coefficient of internal friction. The simulation results presented in this paper can help constrain target properties from the DART crater ejecta cone, which will be imaged by the LICIACube. The results presented here represent the basis for an empirical scaling relationship for oblique impacts and can be used as a framework to determine an analytical approximation of the vertical component of the ejecta momentum, β−1, given known target properties.},\n\tlanguage = {en},\n\turldate = {2021-11-23},\n\tjournal = {Icarus},\n\tauthor = {Raducan, S. D. and Davison, T. M. and Collins, G. S.},\n\tmonth = nov,\n\tyear = {2021},\n\tkeywords = {DART, Impact cratering, Impact ejecta, Oblique impacts, Scaling laws},\n\tpages = {114793},\n}\n\n

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\n \n\n \n \n Halim, S. H.; Crawford, I. A.; Collins, G. S.; Joy, K. H.; and Davison, T. M.\n\n\n \n \n \n \n \n Assessing the survivability of biomarkers within terrestrial material impacting the lunar surface.\n \n \n \n \n\n\n \n\n\n\n Icarus, 354: 114026. January 2021.\n \n\n\n\n
\n\n\n\n \n \n $\"Assessing$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{halim_assessing_2021,\n\ttitle = {Assessing the survivability of biomarkers within terrestrial material impacting the lunar surface},\n\tvolume = {354},\n\tissn = {0019-1035},\n\turl = {https://www.sciencedirect.com/science/article/pii/S0019103520303870},\n\tdoi = {10.1016/j.icarus.2020.114026},\n\tabstract = {The history of organic and biological markers (biomarkers) on the Earth is effectively non-existent in the geological record {\\textgreater}3.8 Ga ago. Here, we investigate the potential for terrestrial material (i.e., terrestrial meteorites) to be transferred to the Moon by a large impact on Earth and subsequently survive impact with the lunar surface, using the iSALE shock physics code. Three-dimensional impact simulations show that a typical basin-forming impact on Earth can eject solid fragments equivalent to {\\textasciitilde}10−3 of an impactor mass at speeds sufficient to transfer from Earth to the Moon. Previous modelling of meteorite survivability has relied heavily upon the assumption that peak-shock pressures can be used as a proxy for gauging survival of projectiles and their possible biomarker constituents. Here, we show the importance of considering both pressure and temperature within the projectile, and the inclusion of both shock and shear heating, in assessing biomarker survival. Assuming that they survive launch from Earth, we show that some biomarker molecules within terrestrial meteorites are likely to survive impact with the Moon, especially at the lower end of the range of typical impact velocities for terrestrial meteorites (2.5 km s−1). The survival of larger biomarkers (e.g., microfossils) is also assessed, and we find limited, but significant, survival for low impact velocity and high target porosity scenarios. Thermal degradation of biomarkers shortly after impact depends heavily upon where the projectile material lands, whether it is buried or remains on the surface, and the related cooling timescales. Comparing sandstone and limestone projectiles shows similar temperature and pressure profiles for the same impact velocities, with limestone providing slightly more favourable conditions for biomarker survival.},\n\tlanguage = {en},\n\turldate = {2022-01-05},\n\tjournal = {Icarus},\n\tauthor = {Halim, Samuel H. and Crawford, Ian A. and Collins, Gareth S. and Joy, Katherine H. and Davison, Thomas M.},\n\tmonth = jan,\n\tyear = {2021},\n\tkeywords = {Biomarkers, Cratering, Impact-processes, Meteorites, Moon, surface},\n\tpages = {114026},\n}\n\n

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\n \n\n \n \n Rajšić, A.; Miljković, K.; Wójcicka, N.; Collins, G. S.; Onodera, K.; Kawamura, T.; Lognonné, P.; Wieczorek, M. A.; and Daubar, I. J.\n\n\n \n \n \n \n \n Numerical Simulations of the Apollo S-IVB Artificial Impacts on the Moon.\n \n \n \n \n\n\n \n\n\n\n Earth and Space Science, 8(12): e2021EA001887. 2021.\n _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2021EA001887\n\n\n\n
\n\n\n\n \n \n $\"Numerical$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{rajsic_numerical_2021,\n\ttitle = {Numerical {Simulations} of the {Apollo} {S}-{IVB} {Artificial} {Impacts} on the {Moon}},\n\tvolume = {8},\n\tissn = {2333-5084},\n\turl = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2021EA001887},\n\tdoi = {10.1029/2021EA001887},\n\tabstract = {The third stage of the Saturn IV rocket used in the five Apollo missions made craters on the Moon ∼30 m in diameter. Their initial impact conditions were known, so they can be considered controlled impacts. Here, we used the iSALE-2D shock physics code to numerically simulate the formation of these craters, and to calculate the vertical component of seismic moment (∼4 × 1010 Nm) and seismic efficiency (∼10−6) associated with these impacts. The irregular booster shape likely caused the irregular crater morphology observed. To investigate this, we modeled six projectile geometries, with footprint area between 3 and 105 m2, keeping the mass and velocity of the impactor constant. We showed that the crater depth and diameter decreased as the footprint area increased. The central mound observed in lunar impact sites could be a result of layering of the target and/or low density of the projectile. Understanding seismic signatures from impact events is important for planetary seismology. Calculating seismic parameters and validating them against controlled experiments in a planetary setting will help us understand the seismic data received, not only from the Moon, but also from the InSight Mission on Mars and future seismic missions.},\n\tlanguage = {en},\n\tnumber = {12},\n\turldate = {2022-02-21},\n\tjournal = {Earth and Space Science},\n\tauthor = {Rajšić, A. and Miljković, K. and Wójcicka, N. and Collins, G. S. and Onodera, K. and Kawamura, T. and Lognonné, P. and Wieczorek, M. A. and Daubar, I. J.},\n\tyear = {2021},\n\tnote = {\\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2021EA001887},\n\tkeywords = {Moon, artificial impacts, impact cratering, numerical modeling, seismic efficiency, seismic moment},\n\tpages = {e2021EA001887},\n}\n\n

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\n \n\n \n \n Crósta, A. P.; Silber, E. A.; Lopes, R. M. C.; Johnson, B. C.; Bjonnes, E.; Malaska, M. J.; Vance, S. D.; Sotin, C.; Solomonidou, A.; and Soderblom, J. M.\n\n\n \n \n \n \n \n Modeling the formation of Menrva impact crater on Titan: Implications for habitability.\n \n \n \n \n\n\n \n\n\n\n Icarus, 370: 114679. December 2021.\n \n\n\n\n
\n\n\n\n \n \n $\"Modeling$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 6 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{crosta_modeling_2021,\n\ttitle = {Modeling the formation of {Menrva} impact crater on {Titan}: {Implications} for habitability},\n\tvolume = {370},\n\tissn = {0019-1035},\n\tshorttitle = {Modeling the formation of {Menrva} impact crater on {Titan}},\n\turl = {https://www.sciencedirect.com/science/article/pii/S0019103521003365},\n\tdoi = {10.1016/j.icarus.2021.114679},\n\tabstract = {Titan is unique in the solar system: it is an ocean world, an icy world, an organic world, and has a dense atmosphere. It is a geologically active world as well, with ongoing exogenic processes, such as rainfall, sediment transportation and deposition, erosion, and possible endogenic processes, such as tectonism and cryovolcanism. This combination of an organic and an ocean world makes Titan a prime target for astrobiological research, as biosignatures may be present in its surface, in impact melt deposits and in cryovolcanic flows, as well as in deep ice and water ocean underneath the outer ice shell. Impact craters are important sites in this context, as they may have allowed an exchange of materials between Titan's layers, in particular between the surface, composed of organic sediments over icy bedrock, and the subsurface ocean. It is also possible that impacts may have favored the advance of prebiotic chemical reactions themselves, by providing thermal energy that would allow these reactions to proceed. To investigate possible exchange pathways between the subsurface water ocean and the organic-rich surface, we modeled the formation of the largest crater on Titan, Menrva, with a diameter of ca. 425 km. The premise is that, given a large enough impact event, the resulting crater could breach into Titan's ice shell and reach the subsurface ocean, creating pathways connecting the surface and the ocean. Materials from the deep subsurface ocean, including salts and potential biosignatures of putative subsurface biota, could be transported to the surface. Likewise, atmospherically derived organic surface materials could be directly inserted into the ocean, where they could undergo aqueous hydrolysis to form potential astrobiological building blocks, such as amino acids. To study the formation of a Menrva-like impact crater, we staged numerical simulations using the iSALE-2D shock physics code. We varied assumed ice shell thickness from 50 to 125 km and assumed thermal structure over a range consistent with geophysical data. We analyze the implications and potential contributions of impact cratering as a process that can facilitate the exchange of surface organics with liquid water. Our findings indicate that melt and partial melt of ice took place in the central zone, reaching ca. 65 km depth and ca. 60 km away from the center of the structure. Furthermore, a volume of ca. 102 km3 of ocean water could be traced to depths as shallow as 10 km. These results highlight the potential for a significant exchange of materials from the surface (organics and ice) and the subsurface (water ocean), particularly in the crater's central area. Our studies suggest that large hypervelocity impacts are a viable and likely key mechanism to create pathways between the underground water ocean and Titan's organic-rich surface layer and atmosphere.},\n\tlanguage = {en},\n\turldate = {2021-09-24},\n\tjournal = {Icarus},\n\tauthor = {Crósta, A. P. and Silber, E. A. and Lopes, R. M. C. and Johnson, B. C. and Bjonnes, E. and Malaska, M. J. and Vance, S. D. and Sotin, C. and Solomonidou, A. and Soderblom, J. M.},\n\tmonth = dec,\n\tyear = {2021},\n\tkeywords = {Cassini mission, Habitability, Impact crater, Menrva crater, Numerical modeling, Titan},\n\tpages = {114679},\n}\n\n

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\n Titan is unique in the solar system: it is an ocean world, an icy world, an organic world, and has a dense atmosphere. It is a geologically active world as well, with ongoing exogenic processes, such as rainfall, sediment transportation and deposition, erosion, and possible endogenic processes, such as tectonism and cryovolcanism. This combination of an organic and an ocean world makes Titan a prime target for astrobiological research, as biosignatures may be present in its surface, in impact melt deposits and in cryovolcanic flows, as well as in deep ice and water ocean underneath the outer ice shell. Impact craters are important sites in this context, as they may have allowed an exchange of materials between Titan's layers, in particular between the surface, composed of organic sediments over icy bedrock, and the subsurface ocean. It is also possible that impacts may have favored the advance of prebiotic chemical reactions themselves, by providing thermal energy that would allow these reactions to proceed. To investigate possible exchange pathways between the subsurface water ocean and the organic-rich surface, we modeled the formation of the largest crater on Titan, Menrva, with a diameter of ca. 425 km. The premise is that, given a large enough impact event, the resulting crater could breach into Titan's ice shell and reach the subsurface ocean, creating pathways connecting the surface and the ocean. Materials from the deep subsurface ocean, including salts and potential biosignatures of putative subsurface biota, could be transported to the surface. Likewise, atmospherically derived organic surface materials could be directly inserted into the ocean, where they could undergo aqueous hydrolysis to form potential astrobiological building blocks, such as amino acids. To study the formation of a Menrva-like impact crater, we staged numerical simulations using the iSALE-2D shock physics code. We varied assumed ice shell thickness from 50 to 125 km and assumed thermal structure over a range consistent with geophysical data. We analyze the implications and potential contributions of impact cratering as a process that can facilitate the exchange of surface organics with liquid water. Our findings indicate that melt and partial melt of ice took place in the central zone, reaching ca. 65 km depth and ca. 60 km away from the center of the structure. Furthermore, a volume of ca. 102 km3 of ocean water could be traced to depths as shallow as 10 km. These results highlight the potential for a significant exchange of materials from the surface (organics and ice) and the subsurface (water ocean), particularly in the crater's central area. Our studies suggest that large hypervelocity impacts are a viable and likely key mechanism to create pathways between the underground water ocean and Titan's organic-rich surface layer and atmosphere.\n

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\n \n\n \n \n Johnson, B. C.; Milliken, R. E.; Lewis, K. W.; and Collins, G. S.\n\n\n \n \n \n \n \n Impact generated porosity in Gale crater and implications for the density of sedimentary rocks in lower Aeolis Mons.\n \n \n \n \n\n\n \n\n\n\n Icarus, 366: 114539. September 2021.\n \n\n\n\n
\n\n\n\n \n \n $\"Impact$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{johnson_impact_2021,\n\ttitle = {Impact generated porosity in {Gale} crater and implications for the density of sedimentary rocks in lower {Aeolis} {Mons}},\n\tvolume = {366},\n\tissn = {0019-1035},\n\turl = {https://www.sciencedirect.com/science/article/pii/S0019103521002128},\n\tdoi = {10.1016/j.icarus.2021.114539},\n\tabstract = {Sedimentary rocks in Gale crater record important information about the climatic history and evolution of Mars. Recent gravity measurements and modeling indicate strata encountered by the Curiosity rover have a very low density (1680 ± 180 kg m−3) and thus unusually high porosity. Missing in these models, however, is the role of deeper crustal porosity on the observed gravity signatures. Here we simulate the impact formation of Gale crater and find that impact generated porosity results in a negative gravity anomaly that decreases in magnitude with distance from the basin center. Incorporating this expected post-impact gravity signature into models for the bulk density of strata in lower Mt. Sharp, we find a best-fit density of 2300 ± 130 kg m−3 for an impact into a target with no pre-impact porosity. Models incorporating pre-impact porosity result in densities that are up to 200 kg/m3 lower. These revised densities increase the maximum potential burial depth of rocks along the rover traverse, allowing for the possibility Gale crater may once have been filled with sediment.},\n\tlanguage = {en},\n\turldate = {2021-06-02},\n\tjournal = {Icarus},\n\tauthor = {Johnson, B. C. and Milliken, R. E. and Lewis, K. W. and Collins, G. S.},\n\tmonth = sep,\n\tyear = {2021},\n\tkeywords = {Gale crater, Gravity, Impact cratering, Mars},\n\tpages = {114539},\n}\n\n

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\n \n\n \n \n Fernando, B.; Wójcicka, N.; Froment, M.; Maguire, R.; Stähler, S. C.; Rolland, L.; Collins, G. S.; Karatekin, O.; Larmat, C.; Sansom, E. K.; Teanby, N. A.; Spiga, A.; Karakostas, F.; Leng, K.; Nissen-Meyer, T.; Kawamura, T.; Giardini, D.; Lognonné, P.; Banerdt, B.; and Daubar, I. J.\n\n\n \n \n \n \n \n Listening for the Landing: Seismic Detections of Perseverance's Arrival at Mars With InSight.\n \n \n \n \n\n\n \n\n\n\n Earth and Space Science, 8(4): e2020EA001585. 2021.\n _eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020EA001585\n\n\n\n
\n\n\n\n \n \n $\"Listening$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{fernando_listening_2021,\n\ttitle = {Listening for the {Landing}: {Seismic} {Detections} of {Perseverance}'s {Arrival} at {Mars} {With} {InSight}},\n\tvolume = {8},\n\tcopyright = {© 2021. The Authors. Earth and Space Science published by Wiley Periodicals LLC on behalf of American Geophysical Union.},\n\tissn = {2333-5084},\n\tshorttitle = {Listening for the {Landing}},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020EA001585},\n\tdoi = {https://doi.org/10.1029/2020EA001585},\n\tabstract = {The entry, descent, and landing (EDL) sequence of NASA's Mars 2020 Perseverance Rover will act as a seismic source of known temporal and spatial localization. We evaluate whether the signals produced by this event will be detectable by the InSight lander (3,452 km away), comparing expected signal amplitudes to noise levels at the instrument. Modeling is undertaken to predict the propagation of the acoustic signal (purely in the atmosphere), the seismoacoustic signal (atmosphere-to-ground coupled), and the elastodynamic seismic signal (in the ground only). Our results suggest that the acoustic and seismoacoustic signals, produced by the atmospheric shock wave from the EDL, are unlikely to be detectable due to the pattern of winds in the martian atmosphere and the weak air-to-ground coupling, respectively. However, the elastodynamic seismic signal produced by the impact of the spacecraft's cruise balance masses on the surface may be detected by InSight. The upper and lower bounds on predicted ground velocity at InSight are 2.0 × 10−14 and 1.3 × 10−10 m s−1. The upper value is above the noise floor at the time of landing 40\\% of the time on average. The large range of possible values reflects uncertainties in the current understanding of impact-generated seismic waves and their subsequent propagation and attenuation through Mars. Uncertainty in the detectability also stems from the indeterminate instrument noise level at the time of this future event. A positive detection would be of enormous value in constraining the seismic properties of Mars, and in improving our understanding of impact-generated seismic waves.},\n\tlanguage = {en},\n\tnumber = {4},\n\turldate = {2021-06-02},\n\tjournal = {Earth and Space Science},\n\tauthor = {Fernando, Benjamin and Wójcicka, Natalia and Froment, Marouchka and Maguire, Ross and Stähler, Simon C. and Rolland, Lucie and Collins, Gareth S. and Karatekin, Ozgur and Larmat, Carene and Sansom, Eleanor K. and Teanby, Nicholas A. and Spiga, Aymeric and Karakostas, Foivos and Leng, Kuangdai and Nissen-Meyer, Tarje and Kawamura, Taichi and Giardini, Domenico and Lognonné, Philippe and Banerdt, Bruce and Daubar, Ingrid J.},\n\tyear = {2021},\n\tnote = {\\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020EA001585},\n\tkeywords = {InSight, Mars, impacts, seismoacoustics, seismology},\n\tpages = {e2020EA001585},\n}\n\n

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\n \n\n \n \n Rajšić, A.; Miljković, K.; Collins, G. S.; Wünnemann, K.; Daubar, I. J.; Wójcicka, N.; and Wieczorek, M. A.\n\n\n \n \n \n \n \n Seismic Efficiency for Simple Crater Formation in the Martian Top Crust Analog.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 126(2): e2020JE006662. 2021.\n _eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JE006662\n\n\n\n
\n\n\n\n \n \n $\"Seismic$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 3 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{rajsic_seismic_2021,\n\ttitle = {Seismic {Efficiency} for {Simple} {Crater} {Formation} in the {Martian} {Top} {Crust} {Analog}},\n\tvolume = {126},\n\tcopyright = {© 2021. The Authors.},\n\tissn = {2169-9100},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JE006662},\n\tdoi = {https://doi.org/10.1029/2020JE006662},\n\tabstract = {The first seismometer operating on the surface of another planet was deployed by the NASA InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission to Mars. It gives us an opportunity to investigate the seismicity of Mars, including any seismic activity caused by small meteorite bombardment. Detectability of impact generated seismic signals is closely related to the seismic efficiency, defined as the fraction of the impactor's kinetic energy transferred into the seismic energy in a target medium. This work investigated the seismic efficiency of the Martian near surface associated with small meteorite impacts on Mars. We used the iSALE-2D (Impact-Simplified Arbitrary Lagrangian Eulerian) shock physics code to simulate the formation of the meter-size impact craters, and we used a recently formed 1.5 m diameter crater as a case study. The Martian crust was simulated as unfractured nonporous bedrock, fractured bedrock with 25\\% porosity, and highly porous regolith with 44\\% and 65\\% porosity. We used appropriate strength and porosity models defined in previous works, and we identified that the seismic efficiency is very sensitive to the speed of sound and elastic threshold in the target medium. We constrained the value of the impact-related seismic efficiency to be between the order of ∼10-7 to 10-6 for the regolith and ∼10-4 to 10-3 for the bedrock. For new impacts occurring on Mars, this work can help understand the near-surface properties of the Martian crust, and it contributes to the understanding of impact detectability via seismic signals as a function of the target media.},\n\tlanguage = {en},\n\tnumber = {2},\n\turldate = {2021-06-02},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Rajšić, A. and Miljković, K. and Collins, G. S. and Wünnemann, K. and Daubar, I. J. and Wójcicka, N. and Wieczorek, M. A.},\n\tyear = {2021},\n\tnote = {\\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JE006662},\n\tkeywords = {InSight mission, Mars, iSALE-2D code, impact cratering, numerical modeling, seismic efficiency},\n\tpages = {e2020JE006662},\n}\n\n

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\n \n\n \n \n Ogawa, R.; Nakamura, A. M.; Suzuki, A. I.; and Hasegawa, S.\n\n\n \n \n \n \n \n Crater shape as a possible record of the impact environment of metallic bodies: Effects of temperature, impact velocity and impactor density.\n \n \n \n \n\n\n \n\n\n\n Icarus, 362: 114410. July 2021.\n \n\n\n\n
\n\n\n\n \n \n $\"Crater$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 4 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{ogawa_crater_2021,\n\ttitle = {Crater shape as a possible record of the impact environment of metallic bodies: {Effects} of temperature, impact velocity and impactor density},\n\tvolume = {362},\n\tissn = {0019-1035},\n\tshorttitle = {Crater shape as a possible record of the impact environment of metallic bodies},\n\turl = {https://www.sciencedirect.com/science/article/pii/S0019103521000968},\n\tdoi = {10.1016/j.icarus.2021.114410},\n\tabstract = {Metallic bodies that were the cores of differentiated bodies are sources of iron meteorites and are considered to have formed early in the terrestrial planet region before migrating to the main asteroid belt. Surface temperatures and mutual collision velocities differ between the terrestrial planet region and the main asteroid belt. To investigate the dependence of crater shape on temperature, velocity and impactor density, we conducted impact experiments on room- and low-temperature iron meteorite and iron alloy targets (carbon steel SS400 and iron‑nickel alloy) with velocities of 0.8–7 km s−1. The projectiles were rock cylinders and metal spheres and cylinders. Oblique impact experiments were also conducted using stainless steel projectiles and SS400 steel targets which produced more prominent radial patterns downrange at room temperature than at low temperature. Crater diameters and depths were measured and compiled using non-dimensional parameter sets based on the π-group crater scaling relations. Two-dimensional numerical simulations were conducted using iSALE-2D code with the Johnson–Cook strength model. Both experimental and numerical results showed that the crater depth and diameter decreased with decreasing temperature, which strengthened the target, and with decreasing impact velocity. The decreasing tendency was more prominent for depth than for diameter, i.e., the depth/diameter ratio was smaller for the low temperature and low velocity conditions. The depth/diameter ratios of craters formed by rock projectiles were shallower than those of craters formed by metallic projectiles. Our results imply that the frequency distribution of the depth/diameter ratio for craters on the surface of metallic bodies may be used as a probe of the past impact environment of metallic bodies.},\n\tlanguage = {en},\n\turldate = {2021-06-02},\n\tjournal = {Icarus},\n\tauthor = {Ogawa, Ryo and Nakamura, Akiko M. and Suzuki, Ayako I. and Hasegawa, Sunao},\n\tmonth = jul,\n\tyear = {2021},\n\tkeywords = {Asteroids, Crater, Impact processes, Iron meteorite, Meteorites},\n\tpages = {114410},\n}\n\n

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\n \n\n \n \n Kurosawa, K.; Genda, H.; Azuma, S.; and Okazaki, K.\n\n\n \n \n \n \n \n The Role of Post-Shock Heating by Plastic Deformation During Impact Devolatilization of Calcite (CaCO3).\n \n \n \n \n\n\n \n\n\n\n Geophysical Research Letters, 48(7): e2020GL091130. 2021.\n _eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020GL091130\n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{kurosawa_role_2021,\n\ttitle = {The {Role} of {Post}-{Shock} {Heating} by {Plastic} {Deformation} {During} {Impact} {Devolatilization} of {Calcite} ({CaCO3})},\n\tvolume = {48},\n\tcopyright = {© 2021. American Geophysical Union. All Rights Reserved.},\n\tissn = {1944-8007},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL091130},\n\tdoi = {https://doi.org/10.1029/2020GL091130},\n\tabstract = {An accurate understanding of the relationship between the impact conditions and the degree of shock-induced thermal metamorphism in meteorites allows the impact environment in the early Solar System to be understood. A recent hydrocode has revealed that impact heating is much higher than previously thought. This is because plastic deformation of the shocked rocks causes further heating during decompression, which is termed post-shock heating. Here we compare impact simulations with laboratory experiments on the impact devolatilization of calcite to investigate whether the post-shock heating is also significant in natural samples. We calculated the mass of CO2 produced from the calcite, based on thermodynamics. We found that iSALE can reproduce the devolatilization behavior for rocks with the strength of calcite. In contrast, the calculated masses of CO2 at lower rock strengths are systematically smaller than the experimental values. Our results require a reassessment of the interpretation of thermal metamorphism in meteorites.},\n\tlanguage = {en},\n\tnumber = {7},\n\turldate = {2021-06-02},\n\tjournal = {Geophysical Research Letters},\n\tauthor = {Kurosawa, Kosuke and Genda, Hidenori and Azuma, Shintaro and Okazaki, Keishi},\n\tyear = {2021},\n\tnote = {\\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020GL091130},\n\tkeywords = {carbonates, hypervelocity impacts, impact devolatilization, impact heating, shock physics modeling, thermal metamorphism in meteorites},\n\tpages = {e2020GL091130},\n}\n\n

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\n \n\n \n \n Sato, M.; Kurosawa, K.; Kato, S.; Ushioda, M.; and Hasegawa, S.\n\n\n \n \n \n \n \n Shock Remanent Magnetization Intensity and Stability Distributions of Single-Domain Titanomagnetite-Bearing Basalt Sample Under the Pressure Range of 0.1–10 GPa.\n \n \n \n \n\n\n \n\n\n\n Geophysical Research Letters, 48(8): e2021GL092716. 2021.\n _eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2021GL092716\n\n\n\n
\n\n\n\n \n \n $\"Shock$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{sato_shock_2021,\n\ttitle = {Shock {Remanent} {Magnetization} {Intensity} and {Stability} {Distributions} of {Single}-{Domain} {Titanomagnetite}-{Bearing} {Basalt} {Sample} {Under} the {Pressure} {Range} of 0.1–10 {GPa}},\n\tvolume = {48},\n\tcopyright = {© 2021. American Geophysical Union. All Rights Reserved.},\n\tissn = {1944-8007},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021GL092716},\n\tdoi = {https://doi.org/10.1029/2021GL092716},\n\tabstract = {Knowledge of the shock remanent magnetization (SRM) property is crucial to interpret the spatial changes in magnetic anomalies observed over the impact crater. This study reports the spatial distributions of SRM intensity and stability of single-domain titanomagnetite-bearing basalt based on the SRM acquisition experiments using a two-stage light gas gun with Al projectiles, remanence measurements for divided subsamples, and impact simulations. The SRM properties systematically change with increasing pressure, and three distinctive aspects are recognized at different pressure ranges: (1) constant intensity below 0.1 GPa, (2) linear trend as intensity is proportional to pressure up to 1.1 GPa, and (3) constant intensity and increasing stability above 1.9 GPa. The SRM intensity and stability distributions suggest that the crustal rocks containing the single-domain titanomagnetite originally had an SRM intensity distribution according to the distance from the impact point, which changed depending on the remanence stability after the impact.},\n\tlanguage = {en},\n\tnumber = {8},\n\turldate = {2021-06-02},\n\tjournal = {Geophysical Research Letters},\n\tauthor = {Sato, Masahiko and Kurosawa, Kosuke and Kato, Shota and Ushioda, Masashi and Hasegawa, Sunao},\n\tyear = {2021},\n\tnote = {\\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2021GL092716},\n\tkeywords = {Impact cratering, magnetic anomaly, shock remanent magnetization, single-domain, titanomagnetite},\n\tpages = {e2021GL092716},\n}\n\n

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\n \n\n \n \n Wójcicka, N.; Collins, G. S.; Bastow, I. D.; Teanby, N. A.; Miljković, K.; Rajšić, A.; Daubar, I.; and Lognonné, P.\n\n\n \n \n \n \n \n The Seismic Moment and Seismic Efficiency of Small Impacts on Mars.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 125(10): e2020JE006540. 2020.\n _eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JE006540\n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{wojcicka_seismic_2020,\n\ttitle = {The {Seismic} {Moment} and {Seismic} {Efficiency} of {Small} {Impacts} on {Mars}},\n\tvolume = {125},\n\tcopyright = {©2020. The Authors.},\n\tissn = {2169-9100},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JE006540},\n\tdoi = {https://doi.org/10.1029/2020JE006540},\n\tabstract = {Since landing in late 2018, the InSight lander has been recording seismic signals on the surface of Mars. Despite nominal prelanding estimates of one to three meteorite impacts detected per Earth year, none have yet been identified seismically. To inform revised detectability estimates, we simulated numerically a suite of small impacts onto Martian regolith and characterized their seismic source properties. For the impactor size and velocity range most relevant for InSight, crater diameters are 1–30 m. We found that in this range scalar seismic moment is 106–1010 Nm and increases almost linearly with impact momentum. The ratio of horizontal to vertical seismic moment tensor components is ∼1, implying an almost isotropic P wave source, for vertical impacts. Seismic efficiencies are ∼10−6, dependent on the target crushing strength and impact velocity. Our predictions of relatively low seismic efficiency and seismic moment suggest that meteorite impact detectability on Mars is lower than previously assumed. Detection chances are best for impacts forming craters of diameter {\\textgreater}10 m.},\n\tlanguage = {en},\n\tnumber = {10},\n\turldate = {2020-11-16},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Wójcicka, N. and Collins, G. S. and Bastow, I. D. and Teanby, N. A. and Miljković, K. and Rajšić, A. and Daubar, I. and Lognonné, P.},\n\tyear = {2020},\n\tnote = {\\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JE006540},\n\tkeywords = {InSight, Mars, impacts, seismic efficiency, seismic moment},\n\tpages = {e2020JE006540},\n}\n\n

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\n \n\n \n \n Raducan, S. D.; Davison, T. M.; and Collins, G. S.\n\n\n \n \n \n \n \n Morphological Diversity of Impact Craters on Asteroid (16) Psyche: Insight From Numerical Models.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 125(9): e2020JE006466. 2020.\n _eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JE006466\n\n\n\n
\n\n\n\n \n \n $\"Morphological$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{raducan_morphological_2020,\n\ttitle = {Morphological {Diversity} of {Impact} {Craters} on {Asteroid} (16) {Psyche}: {Insight} {From} {Numerical} {Models}},\n\tvolume = {125},\n\tcopyright = {©2020. The Authors.},\n\tissn = {2169-9100},\n\tshorttitle = {Morphological {Diversity} of {Impact} {Craters} on {Asteroid} (16) {Psyche}},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JE006466},\n\tdoi = {https://doi.org/10.1029/2020JE006466},\n\tabstract = {The asteroid (16) Psyche, target of NASA's “Psyche” mission, is thought to be one of the most massive exposed iron cores in the solar system. Earth-based observations suggest that Psyche has a metal-rich surface; however, its internal structure cannot be determined from ground-based observations. Here we simulate impacts into a variety of possible target structures on Psyche and show the possible diversity in crater morphologies that the “Psyche” mission could encounter. If Psyche's interior is homogeneous, then the mission will find simple bowl-shaped craters, with a depth-diameter ratio diagnostic of rock or iron. Craters will be much deeper than those on other visited asteroids and possess much more spectacular rims if the surface is dominated by metallic iron. On the other hand, if Psyche has a layered structure, the spacecraft could find craters with more complex morphologies, such as concentric or flat-floored craters. Furthermore, if ferrovolcanism occurred on Psyche, then the morphology of craters less than 2 km in diameter could be even more exotic. Based on three to four proposed large craters on Psyche's surface, model size-frequency distributions suggest that if Psyche is indeed an exposed iron core, then the spacecraft will encounter a very old and evolved surface, that would be 4.5 Gyr old. For a rocky surface, then Psyche could be at least 3 Gyr old.},\n\tlanguage = {en},\n\tnumber = {9},\n\turldate = {2021-06-02},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Raducan, S. D. and Davison, T. M. and Collins, G. S.},\n\tyear = {2020},\n\tnote = {\\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JE006466},\n\tkeywords = {Psyche, asteroid, crater, impacts, simulations},\n\tpages = {e2020JE006466},\n}\n\n

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\n \n\n \n \n Raducan, S. D.; Davison, T. M.; and Collins, G. S.\n\n\n \n \n \n \n \n The effects of asteroid layering on ejecta mass-velocity distribution and implications for impact momentum transfer.\n \n \n \n \n\n\n \n\n\n\n Planetary and Space Science, 180: 104756. January 2020.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 3 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{raducan_effects_2020,\n\ttitle = {The effects of asteroid layering on ejecta mass-velocity distribution and implications for impact momentum transfer},\n\tvolume = {180},\n\tissn = {0032-0633},\n\turl = {http://www.sciencedirect.com/science/article/pii/S003206331930056X},\n\tdoi = {10.1016/j.pss.2019.104756},\n\tabstract = {Most bodies in the Solar System do not have a homogeneous structure. Understanding the outcome of an impact into regolith layers of different properties is especially important for NASA’s Double Asteroid Redirection Test (DART) and ESA’s Hera missions. Here we used the iSALE shock physics code to simulate the DART impact into three different target scenarios in the strength regime: a homogeneous porous half-space; layered targets with a porous weak layer overlying a stronger bedrock; and targets with exponentially decreasing porosity with depth. For each scenario we determined the sensitivity of crater morphology, ejecta mass-velocity distribution and momentum transferred from the impact for deflection, β−1, to target properties and structure. We found that for a homogeneous porous half-space, cohesion and porosity play a significant role and the DART impact is expected to produce a β−1 between 1 and 3. In a two-layer target scenario, the presence of a less porous, stronger lower layer close to the surface can cause both amplification and reduction of ejected mass and momentum relative to the homogeneous upper-layer case. For the case of DART, the momentum enhancement can change by up to 90\\%. Impacts into targets with an exponentially decreasing porosity with depth only produced an enhancement in the ejected mass and momentum for sharp decreases in porosity that occur within 6 m of the asteroid surface. Together with measurements of the DART crater by the Hera mission, these results can be used to test the predictive capabilities of numerical models of asteroid deflection.},\n\tlanguage = {en},\n\turldate = {2020-01-08},\n\tjournal = {Planetary and Space Science},\n\tauthor = {Raducan, S. D. and Davison, T. M. and Collins, G. S.},\n\tmonth = jan,\n\tyear = {2020},\n\tkeywords = {Ejecta, Impact cratering, Kinetic impactor, Layering, Numerical simulations},\n\tpages = {104756},\n}\n\n

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\n \n\n \n \n Stickle, A. M.; Bruck Syal, M.; Cheng, A. F.; Collins, G. S.; Davison, T. M.; Gisler, G.; Güldemeister, N.; Heberling, T.; Luther, R.; Michel, P.; Miller, P.; Owen, J. M.; Rainey, E. S. G.; Rivkin, A. S.; Rosch, T.; and Wünnemann, K.\n\n\n \n \n \n \n \n Benchmarking impact hydrocodes in the strength regime: Implications for modeling deflection by a kinetic impactor.\n \n \n \n \n\n\n \n\n\n\n Icarus, 338: 113446. March 2020.\n \n\n\n\n
\n\n\n\n \n \n $\"Benchmarking$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 3 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{stickle_benchmarking_2020,\n\ttitle = {Benchmarking impact hydrocodes in the strength regime: {Implications} for modeling deflection by a kinetic impactor},\n\tvolume = {338},\n\tissn = {0019-1035},\n\tshorttitle = {Benchmarking impact hydrocodes in the strength regime},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103519302222},\n\tdoi = {10.1016/j.icarus.2019.113446},\n\tabstract = {The Double Asteroid Redirection Test (DART) is a NASA-sponsored mission that will be the first direct test of the kinetic impactor technique for planetary defense. The DART spacecraft will impact into Didymos-B, the moon of the binary system 65803 Didymos, and the resulting period change will be measured from Earth. Impact simulations will be used to predict the crater size and momentum enhancement expected from the DART impact. Because the specific material properties (strength, porosity, internal structure) of the Didymos-B target are unknown, a wide variety of numerical simulations must be performed to better understand possible impact outcomes. This simulation campaign will involve a large parameter space being simulated using multiple different shock physics hydrocodes. In order to understand better the behaviors and properties of numerical simulation codes applicable to the DART impact, a benchmarking and validation program using different numerical codes to solve a set of standard problems was designed and implemented. The problems were designed to test the effects of material strength, porosity, damage models, and target geometry on the ejecta following an impact and thus the momentum transfer efficiency. Several important results were identified from comparing simulations across codes, including the effects of model resolution and porosity and strength model choice: 1) momentum transfer predictions almost uniformly exhibit a larger variation than predictions of crater size; 2) the choice of strength model, and the values used for material strength, are significantly more important in the prediction of crater size and momentum enhancement than variation between codes; 3) predictions for crater size and momentum enhancement tend to be similar (within 15‐20\\%) when similar strength models are used in different codes. These results will be used to better design a modeling plan for the DART mission as well as to better understand the potential results that may be expected due to unknown target properties. The DART impact simulation team will determine a specific desired material parameter set appropriate for the Didymos system that will be standardized (to the extent possible) across the different codes when making predictions for the DART mission. Some variation in predictions will still be expected, but that variation can be bracketed by the results shown in this study.},\n\tlanguage = {en},\n\turldate = {2020-04-06},\n\tjournal = {Icarus},\n\tauthor = {Stickle, Angela M. and Bruck Syal, Megan and Cheng, Andy F. and Collins, Gareth S. and Davison, Thomas M. and Gisler, Galen and Güldemeister, Nicole and Heberling, Tamra and Luther, Robert and Michel, Patrick and Miller, Paul and Owen, J. Michael and Rainey, Emma S. G. and Rivkin, Andrew S. and Rosch, Thomas and Wünnemann, Kai},\n\tmonth = mar,\n\tyear = {2020},\n\tkeywords = {Asteroids, Cratering, Impact processes},\n\tpages = {113446},\n}\n\n

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\n The Double Asteroid Redirection Test (DART) is a NASA-sponsored mission that will be the first direct test of the kinetic impactor technique for planetary defense. The DART spacecraft will impact into Didymos-B, the moon of the binary system 65803 Didymos, and the resulting period change will be measured from Earth. Impact simulations will be used to predict the crater size and momentum enhancement expected from the DART impact. Because the specific material properties (strength, porosity, internal structure) of the Didymos-B target are unknown, a wide variety of numerical simulations must be performed to better understand possible impact outcomes. This simulation campaign will involve a large parameter space being simulated using multiple different shock physics hydrocodes. In order to understand better the behaviors and properties of numerical simulation codes applicable to the DART impact, a benchmarking and validation program using different numerical codes to solve a set of standard problems was designed and implemented. The problems were designed to test the effects of material strength, porosity, damage models, and target geometry on the ejecta following an impact and thus the momentum transfer efficiency. Several important results were identified from comparing simulations across codes, including the effects of model resolution and porosity and strength model choice: 1) momentum transfer predictions almost uniformly exhibit a larger variation than predictions of crater size; 2) the choice of strength model, and the values used for material strength, are significantly more important in the prediction of crater size and momentum enhancement than variation between codes; 3) predictions for crater size and momentum enhancement tend to be similar (within 15‐20%) when similar strength models are used in different codes. These results will be used to better design a modeling plan for the DART mission as well as to better understand the potential results that may be expected due to unknown target properties. The DART impact simulation team will determine a specific desired material parameter set appropriate for the Didymos system that will be standardized (to the extent possible) across the different codes when making predictions for the DART mission. Some variation in predictions will still be expected, but that variation can be bracketed by the results shown in this study.\n

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\n \n\n \n \n Collins, G. S.; Patel, N.; Davison, T. M.; Rae, A. S. P.; Morgan, J. V.; and Gulick, S. P. S.\n\n\n \n \n \n \n \n A steeply-inclined trajectory for the Chicxulub impact.\n \n \n \n \n\n\n \n\n\n\n Nature Communications, 11(1): 1480. May 2020.\n Number: 1 Publisher: Nature Publishing Group\n\n\n\n
\n\n\n\n \n \n $\"A$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{collins_steeply-inclined_2020,\n\ttitle = {A steeply-inclined trajectory for the {Chicxulub} impact},\n\tvolume = {11},\n\tcopyright = {2020 The Author(s)},\n\tissn = {2041-1723},\n\turl = {https://www.nature.com/articles/s41467-020-15269-x},\n\tdoi = {10.1038/s41467-020-15269-x},\n\tabstract = {The environmental severity of large impacts on Earth is influenced by their impact trajectory. Impact direction and angle to the target plane affect the volume and depth of origin of vaporized target, as well as the trajectories of ejected material. The asteroid impact that formed the 66 Ma Chicxulub crater had a profound and catastrophic effect on Earth’s environment, but the impact trajectory is debated. Here we show that impact angle and direction can be diagnosed by asymmetries in the subsurface structure of the Chicxulub crater. Comparison of 3D numerical simulations of Chicxulub-scale impacts with geophysical observations suggests that the Chicxulub crater was formed by a steeply-inclined (45–60° to horizontal) impact from the northeast; several lines of evidence rule out a low angle ({\\textless}30°) impact. A steeply-inclined impact produces a nearly symmetric distribution of ejected rock and releases more climate-changing gases per impactor mass than either a very shallow or near-vertical impact.},\n\tlanguage = {en},\n\tnumber = {1},\n\turldate = {2020-06-11},\n\tjournal = {Nature Communications},\n\tauthor = {Collins, G. S. and Patel, N. and Davison, T. M. and Rae, A. S. P. and Morgan, J. V. and Gulick, S. P. S.},\n\tmonth = may,\n\tyear = {2020},\n\tnote = {Number: 1\nPublisher: Nature Publishing Group},\n\tpages = {1480},\n}\n\n

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\n \n\n \n \n Lyons, R. J.; Bowling, T. J.; Ciesla, F. J.; Davison, T. M.; and Collins, G. S.\n\n\n \n \n \n \n \n The effects of impacts on the cooling rates of iron meteorites.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 54(7): 1604–1618. 2019.\n _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/maps.13301\n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{lyons_effects_2019,\n\ttitle = {The effects of impacts on the cooling rates of iron meteorites},\n\tvolume = {54},\n\tcopyright = {© The Meteoritical Society, 2019.},\n\tissn = {1945-5100},\n\turl = {https://onlinelibrary.wiley.com/doi/abs/10.1111/maps.13301},\n\tdoi = {10.1111/maps.13301},\n\tabstract = {Iron meteorites provide a record of the thermal evolution of their parent bodies, with cooling rates inferred from the structures observed in the Widmanstätten pattern. Traditional planetesimal thermal models suggest that meteorite samples derived from the same iron core would have identical cooling rates, possibly providing constraints on the sizes and structures of their parent bodies. However, some meteorite groups exhibit a range of cooling rates or point to uncomfortably small parent bodies whose survival is difficult to reconcile with dynamical models. Together, these suggest that some meteorites are indicating a more complicated origin. To date, thermal models have largely ignored the effects that impacts would have on the thermal evolution of the iron meteorite parent bodies. Here we report numerical simulations investigating the effects that impacts at different times have on cooling rates of cores of differentiated planetesimals. We find that impacts that occur when the core is near or above its solidus, but the mantle has largely crystallized can expose iron near the surface of the body, leading to rapid and nonuniform cooling. The time period when a planetesimal can be affected in this way can range between 20 and 70 Myr after formation for a typical 100 km radius planetesimal. Collisions during this time would have been common, and thus played an important role in shaping the properties of iron meteorites.},\n\tlanguage = {en},\n\tnumber = {7},\n\turldate = {2020-04-07},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Lyons, Richard J. and Bowling, Timothy J. and Ciesla, Fred J. and Davison, Thomas M. and Collins, Gareth S.},\n\tyear = {2019},\n\tnote = {\\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/maps.13301},\n\tpages = {1604--1618},\n}\n\n

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\n \n\n \n \n Rae, A. S. P.; Collins, G. S.; Morgan, J. V.; Salge, T.; Christeson, G. L.; Leung, J.; Lofi, J.; Gulick, S. P. S.; Poelchau, M.; Riller, U.; Gebhardt, C.; Grieve, R. A. F.; and Osinski, G. R.\n\n\n \n \n \n \n \n Impact-Induced Porosity and Microfracturing at the Chicxulub Impact Structure.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 124(7): 1960–1978. 2019.\n _eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019JE005929\n\n\n\n
\n\n\n\n \n \n $\"Impact-Induced$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 3 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{rae_impact-induced_2019,\n\ttitle = {Impact-{Induced} {Porosity} and {Microfracturing} at the {Chicxulub} {Impact} {Structure}},\n\tvolume = {124},\n\tcopyright = {©2019. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JE005929},\n\tdoi = {10.1029/2019JE005929},\n\tabstract = {Porosity and its distribution in impact craters has an important effect on the petrophysical properties of impactites: seismic wave speeds and reflectivity, rock permeability, strength, and density. These properties are important for the identification of potential craters and the understanding of the process and consequences of cratering. The Chicxulub impact structure, recently drilled by the joint International Ocean Discovery Program and International Continental scientific Drilling Program Expedition 364, provides a unique opportunity to compare direct observations of impactites with geophysical observations and models. Here, we combine small-scale petrographic and petrophysical measurements with larger-scale geophysical measurements and numerical simulations of the Chicxulub impact structure. Our aim is to assess the cause of unusually high porosities within the Chicxulub peak ring and the capability of numerical impact simulations to predict the gravity signature and the distribution and texture of porosity within craters. We show that high porosities within the Chicxulub peak ring are primarily caused by shock-induced microfracturing. These fractures have preferred orientations, which can be predicted by considering the orientations of principal stresses during shock, and subsequent deformation during peak ring formation. Our results demonstrate that numerical impact simulations, implementing the Dynamic Collapse Model of peak ring formation, can accurately predict the distribution and orientation of impact-induced microfractures in large craters, which plays an important role in the geophysical signature of impact structures.},\n\tlanguage = {en},\n\tnumber = {7},\n\turldate = {2020-04-07},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Rae, Auriol S. P. and Collins, Gareth S. and Morgan, Joanna V. and Salge, Tobias and Christeson, Gail L. and Leung, Jody and Lofi, Johanna and Gulick, Sean P. S. and Poelchau, Michael and Riller, Ulrich and Gebhardt, Catalina and Grieve, Richard A. F. and Osinski, Gordon R.},\n\tyear = {2019},\n\tnote = {\\_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019JE005929},\n\tkeywords = {Chicxulub, cratering, fractures, porosity},\n\tpages = {1960--1978},\n}\n\n

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\n \n\n \n \n Raducan, S. D.; Davison, T. M.; Luther, R.; and Collins, G. S.\n\n\n \n \n \n \n \n The role of asteroid strength, porosity and internal friction in impact momentum transfer.\n \n \n \n \n\n\n \n\n\n\n Icarus, 329: 282–295. September 2019.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 3 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{raducan_role_2019,\n\ttitle = {The role of asteroid strength, porosity and internal friction in impact momentum transfer},\n\tvolume = {329},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103518305645},\n\tdoi = {10.1016/j.icarus.2019.03.040},\n\tabstract = {Earth is continually impacted by very small asteroids and debris, and a larger object, though uncommon, could produce a severe natural hazard. During impact crater formation the ballistic ejection of material out of the crater is a major process, which holds significance for an impact study into the deflection of asteroids. In this study we numerically simulate impacts into low-gravity, strength dominated asteroid surfaces using the iSALE shock physics code, and consider the Double Asteroid Redirection Test (DART) mission as a case study. We find that target cohesion, initial porosity, and internal friction coefficient greatly influence ejecta mass/velocity/launch-position distributions and hence the amount by which an asteroid can be deflected. Our results show that as the cohesion is decreased the ratio of ejected momentum to impactor momentum, β − 1, increases; β − 1 also increases as the initial porosity and internal friction coefficient of the asteroid surface decrease. Using nominal impactor parameters and reasonable estimates for the material properties of the Didymos binary asteroid, the DART target, our simulations show that the ejecta produced from the impact can enhance the deflection by a factor of 2 to 4. We use numerical impact simulations that replicate conditions in several laboratory experiments to demonstrate that our approach to quantify ejecta properties is consistent with impact experiments in analogous materials. Finally, we investigate the self-consistency between the crater size and ejection speed scaling relationships previously derived from the point-source approximation for impacts into the same target material.},\n\turldate = {2019-07-08},\n\tjournal = {Icarus},\n\tauthor = {Raducan, S. D. and Davison, T. M. and Luther, R. and Collins, G. S.},\n\tmonth = sep,\n\tyear = {2019},\n\tkeywords = {Asteroids, Ejecta, Impact cratering, Kinetic impactor, Numerical simulations},\n\tpages = {282--295},\n}\n\n

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\n \n\n \n \n Rae, A. S. P.; Collins, G. S.; Poelchau, M.; Riller, U.; Davison, T. M.; Grieve, R. A. F.; Osinski, G. R.; Morgan, J. V.; and Scientists, I. E. 3.\n\n\n \n \n \n \n \n Stress-Strain Evolution During Peak-Ring Formation: A Case Study of the Chicxulub Impact Structure.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 124(2): 396–417. 2019.\n \n\n\n\n
\n\n\n\n \n \n $\"Stress-Strain$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{rae_stress-strain_2019,\n\ttitle = {Stress-{Strain} {Evolution} {During} {Peak}-{Ring} {Formation}: {A} {Case} {Study} of the {Chicxulub} {Impact} {Structure}},\n\tvolume = {124},\n\tcopyright = {©2019. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\tshorttitle = {Stress-{Strain} {Evolution} {During} {Peak}-{Ring} {Formation}},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JE005821},\n\tdoi = {10.1029/2018JE005821},\n\tabstract = {Deformation is a ubiquitous process that occurs to rocks during impact cratering; thus, quantifying the deformation of those rocks can provide first-order constraints on the process of impact cratering. Until now, specific quantification of the conditions of stress and strain within models of impact cratering has not been compared to structural observations. This paper describes a methodology to analyze stress and strain within numerical impact models. This method is then used to predict deformation and its cause during peak-ring formation: a complex process that is not fully understood, requiring remarkable transient weakening and causing a significant redistribution of crustal rocks. The presented results are timely due to the recent Joint International Ocean Discovery Program and International Continental Scientific Drilling Program drilling of the peak ring within the Chicxulub crater, permitting direct comparison between the deformation history within numerical models and the structural history of rocks from a peak ring. The modeled results are remarkably consistent with observed deformation within the Chicxulub peak ring, constraining the following: (1) the orientation of rocks relative to their preimpact orientation; (2) total strain, strain rates, and the type of shear during each stage of cratering; and (3) the orientation and magnitude of principal stresses during each stage of cratering. The methodology and analysis used to generate these predictions is general and, therefore, allows numerical impact models to be constrained by structural observations of impact craters and for those models to produce quantitative predictions.},\n\tlanguage = {en},\n\tnumber = {2},\n\turldate = {2019-03-27},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Rae, Auriol S. P. and Collins, Gareth S. and Poelchau, Michael and Riller, Ulrich and Davison, Thomas M. and Grieve, Richard A. F. and Osinski, Gordon R. and Morgan, Joanna V. and Scientists, IODP-ICDP Expedition 364},\n\tyear = {2019},\n\tkeywords = {Chicxulub, deformation, impact cratering, peak ring, strain, stress},\n\tpages = {396--417},\n}\n\n

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\n \n\n \n \n Derrick, J. G.; Rutherford, M. E.; Chapman, D. J.; Davison, T. M.; Duarte, J. P. P.; Farbaniec, L.; Bland, P. A.; Eakins, D. E.; and Collins, G. S.\n\n\n \n \n \n \n \n Investigating shock processes in bimodal powder compaction through modelling and experiment at the mesoscale.\n \n \n \n \n\n\n \n\n\n\n International Journal of Solids and Structures, 163: 211–219. May 2019.\n \n\n\n\n
\n\n\n\n \n \n $\"Investigating$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{derrick_investigating_2019,\n\ttitle = {Investigating shock processes in bimodal powder compaction through modelling and experiment at the mesoscale},\n\tvolume = {163},\n\tissn = {0020-7683},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0020768318305213},\n\tdoi = {10.1016/j.ijsolstr.2018.12.025},\n\tabstract = {Impact-driven compaction is a proposed mechanism for the lithification of primordial bimodal granular mixtures from which many meteorites derive. We present a numerical-experimental mesoscale study that investigates the fundamental processes in shock compaction of this heterogeneous matter, using analog materials. Experiments were performed at the European Synchrotron Radiation Facility generating real-time, in-situ, X-ray radiographs of the shock’s passage in representative granular systems. Mesoscale simulations were performed using a shock physics code and set-ups that were geometrically identical to the experiments. We considered two scenarios: pure matrix, and matrix with a single chondrule. Good agreement was found between experiments and models in terms of shock position and post-shock compaction in the pure powder setup. When considering a single grain embedded in matrix we observed a spatial porosity anisotropy in its vicinity; the compaction was greater in the region immediately shockward of the grain, and less in its lee. We introduced the porosity vector, C, which points in the direction of lowest compaction across a chondrule. This direction-dependent observation may present a new way to decode the magnitude, and direction, of a single shock wave experienced by a meteorite in the past},\n\turldate = {2019-03-05},\n\tjournal = {International Journal of Solids and Structures},\n\tauthor = {Derrick, James G. and Rutherford, Michael E. and Chapman, David J. and Davison, Thomas M. and Duarte, Joao Piroto P. and Farbaniec, Lukasz and Bland, Phil A. and Eakins, Daniel E. and Collins, Gareth S.},\n\tmonth = may,\n\tyear = {2019},\n\tkeywords = {Chondritic meteorites, Granular media, Heterogeneous, Impact, Mesoscale modelling, Shock compaction, X-ray radiography},\n\tpages = {211--219},\n}\n\n

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\n \n\n \n \n Bowling, T. J.; Ciesla, F. J.; Davison, T. M.; Scully, J. E. C.; Castillo-Rogez, J. C.; Marchi, S.; and Johnson, B. C.\n\n\n \n \n \n \n \n Post-impact thermal structure and cooling timescales of Occator crater on asteroid 1 Ceres.\n \n \n \n \n\n\n \n\n\n\n Icarus, 320: 110–118. March 2019.\n \n\n\n\n
\n\n\n\n \n \n $\"Post-impact$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n\n\n\n

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@article{bowling_post-impact_2019,\n\tseries = {Occator {Crater} on {Ceres}},\n\ttitle = {Post-impact thermal structure and cooling timescales of {Occator} crater on asteroid 1 {Ceres}},\n\tvolume = {320},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103518300186},\n\tdoi = {10.1016/j.icarus.2018.08.028},\n\tabstract = {Occator crater is perhaps the most distinct surface feature observed by NASA's Dawn spacecraft on the Cerean surface. Contained within the crater are the highest albedo features on the planet, Cerealia Facula and Vinalia Faculae, and relatively smooth lobate flow deposits. We present hydrocode simulations of the formation of Occator crater, varying the water to rock ratio of our pre-impact Cerean surface. We find that at water to rock mass ratios up to 0.3, sufficient volumes of Occator's post-impact subsurface would be above the melting point of water to allow for the deposition of faculae-like deposits via impact-heat driven hydrothermal effusion of brines. This reservoir of hydrothermally viable material beneath the crater is composed of a mixture of impactor material and material uplifted from 10′s of kilometers beneath the pre-impact surface, which could sample a deep subsurface volatile reservoir, if present. Using a conductive cooling model, we estimate that the lifetime of hydrothermal activity within such a system, depending on choice of material constants, is between 0.4 and 4 Myr. Our results suggest that impact heating from the Occator forming impact provides a viable mechanism for the creation of the observed faculae, with the proviso that the faculae formed within a relatively short time window after the crater itself formed.},\n\turldate = {2019-03-26},\n\tjournal = {Icarus},\n\tauthor = {Bowling, Timothy J. and Ciesla, Fred J. and Davison, Thomas M. and Scully, Jennifer E. C. and Castillo-Rogez, Julie C. and Marchi, Simone and Johnson, Brandon C.},\n\tmonth = mar,\n\tyear = {2019},\n\tkeywords = {Asteroid Ceres, Asteroids Impact Processes},\n\tpages = {110--118},\n}\n\n

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\n \n\n \n \n Hopkins, R. T.; Osinski, G. R.; and Collins, G. S.\n\n\n \n \n \n \n \n Formation of Complex Craters in Layered Targets With Material Anisotropy.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 0(0). 2019.\n \n\n\n\n
\n\n\n\n \n \n $\"Formation$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{hopkins_formation_2019,\n\ttitle = {Formation of {Complex} {Craters} in {Layered} {Targets} {With} {Material} {Anisotropy}},\n\tvolume = {0},\n\tcopyright = {©2019. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JE005819},\n\tdoi = {10.1029/2018JE005819},\n\tabstract = {Meteorite impacts often occur in layered targets, where the strength of the target varies as a function of depth, but this complexity is often not represented in numerical impact simulations because of the high computational cost of resolving thin layers. To address this limitation, we developed a method to approximate the effect of multiple thin weak layers within a sedimentary sequence using a single material layer to represent the entire sequence. Our approach, implemented in the iSALE (impact-Simplified Arbitrary Lagrangian Eulerian) shock physics code, combines an anisotropic yield criterion with a cell-based method to track the orientation of layers. To demonstrate the efficacy of the method and constrain parameters of the anisotropic strength model required to replicate the effects of thin, weak layers, we compare results of simulations of an 20- to 25-km diameter complex crater on Earth using the new method to those from simulations that explicitly resolve multiple thin weak layers. We show that our approach allows for a reduction in computational cost, negating the need for an increase in spatial resolution to resolve thin layers in the target, while replicating crater formation and final morphology from the high-resolution models. In keeping with field observations, we also find that anisotropic layers may be responsible for a lack of central uplift expression observed at many craters formed in targets with thick sedimentary layers (e.g., the Haughton and Ries impact structures).},\n\tlanguage = {en},\n\tnumber = {0},\n\turldate = {2019-03-05},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Hopkins, Ryan T. and Osinski, Gordon R. and Collins, Gareth S.},\n\tyear = {2019},\n\tkeywords = {anisotropy, complex craters, impact cratering, shock-physics code},\n}\n\n

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\n \n\n \n \n Rutherford, M. E.; Derrick, J. G.; Chapman, D. J.; Collins, G. S.; and Eakins, D. E.\n\n\n \n \n \n \n \n Insights into local shockwave behavior and thermodynamics in granular materials from tomography-initialized mesoscale simulations.\n \n \n \n \n\n\n \n\n\n\n Journal of Applied Physics, 125(1): 015902. January 2019.\n \n\n\n\n
\n\n\n\n \n \n $\"Insights$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{rutherford_insights_2019,\n\ttitle = {Insights into local shockwave behavior and thermodynamics in granular           materials from tomography-initialized mesoscale simulations},\n\tvolume = {125},\n\tissn = {0021-8979},\n\turl = {https://aip.scitation.org/doi/10.1063/1.5048591},\n\tdoi = {10.1063/1.5048591},\n\tabstract = {Interpreting and tailoring the dynamic mechanical response of granular systems relies           upon understanding how the initial arrangement of grains influences the compaction           kinetics and thermodynamics. In this article, the influence of initial granular           arrangement on the dynamic compaction response of a bimodal powder system (soda-lime           distributed throughout a porous, fused silica matrix) was investigated through           continuum-level and mesoscale simulations incorporating real, as-tested microstructures           measured with X-ray tomography. By accounting for heterogeneities in the real powder           composition, continuum-level simulations were brought into significantly better agreement           with previously reported experimental data. Mesoscale simulations reproduced much of the           previously unexplained experimental data scatter, gave further evidence of low-impedance           mixture components dominating shock velocity dispersion, and crucially predicted the           unexpectedly high velocities observed experimentally during the early stages of           compaction. Moreover, only when the real microstructure was accounted for did simulations           predict that small fractions of the fused silica matrix material would be driven into the ββ{\\textless}math display="inline" overflow="scroll" altimg="eq-00001.gif"{\\textgreater} {\\textless}mi{\\textgreater}β{\\textless}/mi{\\textgreater} {\\textless}/math{\\textgreater}-quartz region of phase space. These results suggest that           using real microstructures in mesoscale simulations is a critical step in understanding           the full range of shock states achieved during dynamic granular compaction and           interpreting solid phase distributions found in real planetary bodies.},\n\tnumber = {1},\n\turldate = {2019-01-03},\n\tjournal = {Journal of Applied Physics},\n\tauthor = {Rutherford, M. E. and Derrick, J. G. and Chapman, D. J. and Collins, G. S. and Eakins, D. E.},\n\tmonth = jan,\n\tyear = {2019},\n\tpages = {015902},\n}\n\n

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\n \n 2018\n \n \n (9)\n \n \n

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\n \n\n \n \n Johnson, B. C.; Andrews‐Hanna, J. C.; Collins, G. S.; Freed, A. M.; Melosh, H. J.; and Zuber, M. T.\n\n\n \n \n \n \n \n Controls on the Formation of Lunar Multiring Basins.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 123(11): 3035–3050. 2018.\n \n\n\n\n
\n\n\n\n \n \n $\"Controls$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{johnson_controls_2018,\n\ttitle = {Controls on the {Formation} of {Lunar} {Multiring} {Basins}},\n\tvolume = {123},\n\tcopyright = {©2018. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JE005765},\n\tdoi = {10.1029/2018JE005765},\n\tabstract = {Multiring basins dominate the crustal structure, tectonics, and stratigraphy of the Moon. Understanding how these basins form is crucial for understanding the evolution of ancient planetary crusts. To understand how preimpact thermal structure and crustal thickness affect the formation of multiring basins, we simulate the formation of lunar basins and their rings under a range of target and impactor conditions. We find that ring locations, spacing, and offsets are sensitive to lunar thermal gradient (strength of the lithosphere), temperature of the deep lunar mantle (strength of the asthenosphere), and preimpact crustal thickness. We also explore the effect of impactor size on the formation of basin rings and reproduce the observed transition from peak-ring basins to multiring basins and reproduced many observed aspects of ring spacing and location. Our results are in broad agreement with the ring tectonic theory for the formation of basin rings and also suggest that ring tectonic theory applies to the rim scarp of smaller peak-ring basins.},\n\tlanguage = {en},\n\tnumber = {11},\n\turldate = {2019-07-08},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Johnson, Brandon C. and Andrews‐Hanna, Jeffrey C. and Collins, Gareth S. and Freed, Andrew M. and Melosh, H. J. and Zuber, Maria T.},\n\tyear = {2018},\n\tkeywords = {Moon, impact cratering, lunar geophysics, multiring basins},\n\tpages = {3035--3050},\n}\n\n

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\n \n\n \n \n Daubar, I.; Lognonné, P.; Teanby, N. A.; Miljkovic, K.; Stevanović, J.; Vaubaillon, J.; Kenda, B.; Kawamura, T.; Clinton, J.; Lucas, A.; Drilleau, M.; Yana, C.; Collins, G. S.; Banfield, D.; Golombek, M.; Kedar, S.; Schmerr, N.; Garcia, R.; Rodriguez, S.; Gudkova, T.; May, S.; Banks, M.; Maki, J.; Sansom, E.; Karakostas, F.; Panning, M.; Fuji, N.; Wookey, J.; van Driel, M.; Lemmon, M.; Ansan, V.; Böse, M.; Stähler, S.; Kanamori, H.; Richardson, J.; Smrekar, S.; and Banerdt, W. B.\n\n\n \n \n \n \n \n Impact-Seismic Investigations of the InSight Mission.\n \n \n \n \n\n\n \n\n\n\n Space Science Reviews, 214(8): 132. December 2018.\n \n\n\n\n
\n\n\n\n \n \n $\"Impact-Seismic$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{daubar_impact-seismic_2018,\n\ttitle = {Impact-{Seismic} {Investigations} of the {InSight} {Mission}},\n\tvolume = {214},\n\tissn = {1572-9672},\n\turl = {https://doi.org/10.1007/s11214-018-0562-x},\n\tdoi = {10.1007/s11214-018-0562-x},\n\tabstract = {Impact investigations will be an important aspect of the InSight mission. One of the scientific goals of the mission is a measurement of the current impact rate at Mars. Impacts will additionally inform the major goal of investigating the interior structure of Mars.In this paper, we review the current state of knowledge about seismic signals from impacts on the Earth, Moon, and laboratory experiments. We describe the generalized physical models that can be used to explain these signals. A discussion of the appropriate source time function for impacts is presented, along with spectral characteristics including the cutoff frequency and its dependence on impact momentum. Estimates of the seismic efficiency (ratio between seismic and impact energies) vary widely. Our preferred value for the seismic efficiency at Mars is 5×10−45×10−45 {\\textbackslash}times 10{\\textasciicircum}\\{- 4\\}, which we recommend using until we can measure it during the InSight mission, when seismic moments are not used directly. Effects of the material properties at the impact point and at the seismometer location are considered. We also discuss the processes by which airbursts and acoustic waves emanate from bolides, and the feasibility of detecting such signals.We then consider the case of impacts on Mars. A review is given of the current knowledge of present-day cratering on Mars: the current impact rate, characteristics of those impactors such as velocity and directions, and the morphologies of the craters those impactors create. Several methods of scaling crater size to impact energy are presented. The Martian atmosphere, although thin, will cause fragmentation of impactors, with implications for the resulting seismic signals.We also benchmark several different seismic modeling codes to be used in analysis of impact detections, and those codes are used to explore the seismic amplitude of impact-induced signals as a function of distance from the impact site. We predict a measurement of the current impact flux will be possible within the timeframe of the prime mission (one Mars year) with the detection of ∼ a few to several tens of impacts. However, the error bars on these predictions are large.Specific to the InSight mission, we list discriminators of seismic signals from impacts that will be used to distinguish them from marsquakes. We describe the role of the InSight Impacts Science Theme Group during mission operations, including a plan for possible night-time meteor imaging. The impacts detected by these methods during the InSight mission will be used to improve interior structure models, measure the seismic efficiency, and calculate the size frequency distribution of current impacts.},\n\tlanguage = {en},\n\tnumber = {8},\n\turldate = {2018-12-21},\n\tjournal = {Space Science Reviews},\n\tauthor = {Daubar, Ingrid and Lognonné, Philippe and Teanby, Nicholas A. and Miljkovic, Katarina and Stevanović, Jennifer and Vaubaillon, Jeremie and Kenda, Balthasar and Kawamura, Taichi and Clinton, John and Lucas, Antoine and Drilleau, Melanie and Yana, Charles and Collins, Gareth S. and Banfield, Don and Golombek, Matthew and Kedar, Sharon and Schmerr, Nicholas and Garcia, Raphael and Rodriguez, Sebastien and Gudkova, Tamara and May, Stephane and Banks, Maria and Maki, Justin and Sansom, Eleanor and Karakostas, Foivos and Panning, Mark and Fuji, Nobuaki and Wookey, James and van Driel, Martin and Lemmon, Mark and Ansan, Veronique and Böse, Maren and Stähler, Simon and Kanamori, Hiroo and Richardson, James and Smrekar, Suzanne and Banerdt, W. Bruce},\n\tmonth = dec,\n\tyear = {2018},\n\tkeywords = {Impact cratering, InSight, Mars, Seismology},\n\tpages = {132},\n}\n\n

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\n Impact investigations will be an important aspect of the InSight mission. One of the scientific goals of the mission is a measurement of the current impact rate at Mars. Impacts will additionally inform the major goal of investigating the interior structure of Mars.In this paper, we review the current state of knowledge about seismic signals from impacts on the Earth, Moon, and laboratory experiments. We describe the generalized physical models that can be used to explain these signals. A discussion of the appropriate source time function for impacts is presented, along with spectral characteristics including the cutoff frequency and its dependence on impact momentum. Estimates of the seismic efficiency (ratio between seismic and impact energies) vary widely. Our preferred value for the seismic efficiency at Mars is 5×10−45×10−45 \\times 10\\textasciicircum\\- 4\\, which we recommend using until we can measure it during the InSight mission, when seismic moments are not used directly. Effects of the material properties at the impact point and at the seismometer location are considered. We also discuss the processes by which airbursts and acoustic waves emanate from bolides, and the feasibility of detecting such signals.We then consider the case of impacts on Mars. A review is given of the current knowledge of present-day cratering on Mars: the current impact rate, characteristics of those impactors such as velocity and directions, and the morphologies of the craters those impactors create. Several methods of scaling crater size to impact energy are presented. The Martian atmosphere, although thin, will cause fragmentation of impactors, with implications for the resulting seismic signals.We also benchmark several different seismic modeling codes to be used in analysis of impact detections, and those codes are used to explore the seismic amplitude of impact-induced signals as a function of distance from the impact site. We predict a measurement of the current impact flux will be possible within the timeframe of the prime mission (one Mars year) with the detection of ∼ a few to several tens of impacts. However, the error bars on these predictions are large.Specific to the InSight mission, we list discriminators of seismic signals from impacts that will be used to distinguish them from marsquakes. We describe the role of the InSight Impacts Science Theme Group during mission operations, including a plan for possible night-time meteor imaging. The impacts detected by these methods during the InSight mission will be used to improve interior structure models, measure the seismic efficiency, and calculate the size frequency distribution of current impacts.\n

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\n \n\n \n \n Riller, U.; Poelchau, M. H.; Rae, A. S. P.; Schulte, F. M.; Collins, G. S.; Melosh, H. J.; Grieve, R. A. F.; Morgan, J. V.; Gulick, S. P. S.; Lofi, J.; Diaw, A.; McCall, N.; and Kring, D. A.\n\n\n \n \n \n \n \n Rock fluidization during peak-ring formation of large impact structures.\n \n \n \n \n\n\n \n\n\n\n Nature, 562(7728): 511–518. October 2018.\n \n\n\n\n
\n\n\n\n \n \n $\"Rock$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{riller_rock_2018,\n\ttitle = {Rock fluidization during peak-ring formation of large impact structures},\n\tvolume = {562},\n\tcopyright = {2018 Springer Nature Limited},\n\tissn = {1476-4687},\n\turl = {https://www.nature.com/articles/s41586-018-0607-z},\n\tdoi = {10.1038/s41586-018-0607-z},\n\tabstract = {Catastrophic rock weakening upon impact of a meteorite, and hence flow, is shown to be followed by regained rock strength that enabled the formation of the peak ring during cratering.},\n\tlanguage = {en},\n\tnumber = {7728},\n\turldate = {2018-10-25},\n\tjournal = {Nature},\n\tauthor = {Riller, Ulrich and Poelchau, Michael H. and Rae, Auriol S. P. and Schulte, Felix M. and Collins, Gareth S. and Melosh, H. Jay and Grieve, Richard A. F. and Morgan, Joanna V. and Gulick, Sean P. S. and Lofi, Johanna and Diaw, Abdoulaye and McCall, Naoma and Kring, David A.},\n\tmonth = oct,\n\tyear = {2018},\n\tpages = {511--518},\n}\n\n

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\n \n\n \n \n Derrick, J. G.; Rutherford, M. E.; Davison, T. M.; Chapman, D. J.; Eakins, D. E.; and Collins, G. S.\n\n\n \n \n \n \n \n Interrogating heterogeneous compaction of analogue materials at the mesoscale through numerical modeling and experiments.\n \n \n \n \n\n\n \n\n\n\n AIP Conference Proceedings, 1979(1): 110004. July 2018.\n \n\n\n\n
\n\n\n\n \n \n $\"Interrogating$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{derrick_interrogating_2018,\n\ttitle = {Interrogating heterogeneous compaction of analogue materials at the mesoscale through numerical modeling and experiments},\n\tvolume = {1979},\n\tissn = {0094-243X},\n\turl = {https://aip.scitation.org/doi/abs/10.1063/1.5044923},\n\tdoi = {10.1063/1.5044923},\n\tnumber = {1},\n\turldate = {2018-08-29},\n\tjournal = {AIP Conference Proceedings},\n\tauthor = {Derrick, James G. and Rutherford, Michael E. and Davison, Thomas M. and Chapman, David J. and Eakins, Daniel E. and Collins, Gareth S.},\n\tmonth = jul,\n\tyear = {2018},\n\tpages = {110004},\n}\n\n

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\n \n\n \n \n Luther, R.; Zhu, M.; Collins, G.; and Wünnemann, K.\n\n\n \n \n \n \n \n Effect of target properties and impact velocity on ejection dynamics and ejecta deposition.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 53(8): 1705–1732. August 2018.\n \n\n\n\n
\n\n\n\n \n \n $\"Effect$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{luther_effect_2018,\n\ttitle = {Effect of target properties and impact velocity on ejection dynamics and ejecta deposition},\n\tvolume = {53},\n\tcopyright = {© The Meteoritical Society, 2018.},\n\tissn = {1945-5100},\n\turl = {https://onlinelibrary.wiley.com/doi/abs/10.1111/maps.13143},\n\tdoi = {10.1111/maps.13143},\n\tabstract = {Impact craters are formed by the displacement and ejection of target material. Ejection angles and speeds during the excavation process depend on specific target properties. In order to quantify the influence of the constitutive properties of the target and impact velocity on ejection trajectories, we present the results of a systematic numerical parameter study. We have carried out a suite of numerical simulations of impact scenarios with different coefficients of friction (0.0–1.0), porosities (0–42\\%), and cohesions (0–150 MPa). Furthermore, simulations with varying pairs of impact velocity (1–20 km s−1) and projectile mass yielding craters of approximately equal volume are examined. We record ejection speed, ejection angle, and the mass of ejected material to determine parameters in scaling relationships, and to calculate the thickness of deposited ejecta by assuming analytical parabolic trajectories under Earth gravity. For the resulting deposits, we parameterize the thickness as a function of radial distance by a power law. We find that strength—that is, the coefficient of friction and target cohesion—has the strongest effect on the distribution of ejecta. In contrast, ejecta thickness as a function of distance is very similar for different target porosities and for varying impact velocities larger than 6 km s−1. We compare the derived ejecta deposits with observations from natural craters and experiments.},\n\tlanguage = {en},\n\tnumber = {8},\n\turldate = {2018-08-06},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Luther, Robert and Zhu, Meng-Hua and Collins, Gareth and Wünnemann, Kai},\n\tmonth = aug,\n\tyear = {2018},\n\tpages = {1705--1732},\n}\n\n

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\n \n\n \n \n Prieur, N. C.; Rolf, T.; Wünnemann, K.; and Werner, S. C.\n\n\n \n \n \n \n \n Formation of Simple Impact Craters in Layered Targets: Implications for Lunar Crater Morphology and Regolith Thickness.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 123(6): 1555–1578. June 2018.\n \n\n\n\n
\n\n\n\n \n \n $\"Formation$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{prieur_formation_2018,\n\ttitle = {Formation of {Simple} {Impact} {Craters} in {Layered} {Targets}: {Implications} for {Lunar} {Crater} {Morphology} and {Regolith} {Thickness}},\n\tvolume = {123},\n\tcopyright = {©2018. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\tshorttitle = {Formation of {Simple} {Impact} {Craters} in {Layered} {Targets}},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2017JE005463},\n\tdoi = {10.1029/2017JE005463},\n\tabstract = {Impact crater morphologies vary significantly across the lunar maria. Craters with diameter less than 400 m are closely related to variations in target properties (rock strength, porosity, and layering) as well as the impact velocity. Here we investigate target and impact conditions feasible for reproducing crater morphologies, such as normal, central-mound, flat-bottomed, and concentric craters, using numerical models of impact crater formation in two-layer targets under lunar conditions (i.e., average-impact velocity and gravity). Based on more than 1,000 numerical models, we observe that concentric craters can form with a strength contrast as low as factor of 2 between the layers as long as the difference in cohesion is larger than a value between 50 and 450 kPa (for an impact velocity of 12.7 km/s). Because of this small contrast, concentric craters do not serve as a good indication for the lunar regolith-mare interface. Crater morphology changes with crater diameter according to three different scenarios depending on layers' strengths and the impact velocity. For high-impact velocity or/and moderate material strength, normal crater morphology transitions directly to concentric morphology, while with large material strengths and/or low-impact velocity, craters change with size from normal to flat-bottomed and then to concentric morphology; only this latter pathway is consistent with previous laboratory results. Lunar regolith thicknesses estimated from crater morphologies can differ by up to 80\\% from previously inferred thicknesses. The transition from normal to flat-bottomed craters is found to be the most robust transition to infer the thickness of the surficial target layer.},\n\tlanguage = {en},\n\tnumber = {6},\n\turldate = {2018-08-06},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Prieur, N. C. and Rolf, T. and Wünnemann, K. and Werner, S. C.},\n\tmonth = jun,\n\tyear = {2018},\n\tkeywords = {Moon, crater morphology, impact crater modeling, layering, regolith thickness, simple impact craters},\n\tpages = {1555--1578},\n}\n\n

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\n \n\n \n \n Kurosawa, K.; and Genda, H.\n\n\n \n \n \n \n \n Effects of Friction and Plastic Deformation in Shock‐Comminuted Damaged Rocks on Impact Heating.\n \n \n \n \n\n\n \n\n\n\n Geophysical Research Letters, 45(2): 620–626. January 2018.\n \n\n\n\n
\n\n\n\n \n \n $\"Effects$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{kurosawa_effects_2018,\n\ttitle = {Effects of {Friction} and {Plastic} {Deformation} in {Shock}‐{Comminuted} {Damaged} {Rocks} on {Impact} {Heating}},\n\tvolume = {45},\n\tissn = {0094-8276},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL076285},\n\tdoi = {10.1002/2017GL076285},\n\tabstract = {Abstract Hypervelocity impacts cause significant heating of planetary bodies. Such events are recorded by a reset of 40Ar?36Ar ages and/or impact melts. Here we investigate the influence of friction and plastic deformation in shock?generated comminuted rocks on the degree of impact heating using the iSALE shock?physics code. We demonstrate that conversion from kinetic to internal energy in the targets with strength occurs during pressure release, and additional heating becomes significant for low?velocity impacts ({\\textless}10 km s?1). This additional heat reduces the impact?velocity thresholds required to heat the targets with the 0.1 projectile mass to temperatures for the onset of Ar loss and melting from 8 and 10 km s?1, respectively, for strengthless rocks to 2 and 6 km s?1 for typical rocks. Our results suggest that the impact conditions required to produce the unique features caused by impact heating span a much wider range than previously thought.},\n\tnumber = {2},\n\turldate = {2018-05-03},\n\tjournal = {Geophysical Research Letters},\n\tauthor = {Kurosawa, Kosuke and Genda, Hidenori},\n\tmonth = jan,\n\tyear = {2018},\n\tkeywords = {asteroids, impact heating, impact melts, numerical modeling, radiometric age},\n\tpages = {620--626},\n}\n\n

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\n \n\n \n \n Kurosawa, K.; Okamoto, T.; and Genda, H.\n\n\n \n \n \n \n \n Hydrocode modeling of the spallation process during hypervelocity impacts: Implications for the ejection of Martian meteorites.\n \n \n \n \n\n\n \n\n\n\n Icarus, 301: 219–234. February 2018.\n \n\n\n\n
\n\n\n\n \n \n $\"Hydrocode$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{kurosawa_hydrocode_2018,\n\ttitle = {Hydrocode modeling of the spallation process during hypervelocity impacts: {Implications} for the ejection of {Martian} meteorites},\n\tvolume = {301},\n\tissn = {0019-1035},\n\tshorttitle = {Hydrocode modeling of the spallation process during hypervelocity impacts},\n\turl = {http://www.sciencedirect.com/science/article/pii/S001910351730249X},\n\tdoi = {10.1016/j.icarus.2017.09.015},\n\tabstract = {Hypervelocity ejection of material by impact spallation is considered a plausible mechanism for material exchange between two planetary bodies. We have modeled the spallation process during vertical impacts over a range of impact velocities from 6 to 21 km/s using both grid- and particle-based hydrocode models. The Tillotson equations of state, which are able to treat the nonlinear dependence of density on pressure and thermal pressure in strongly shocked matter, were used to study the hydrodynamic–thermodynamic response after impacts. The effects of material strength and gravitational acceleration were not considered. A two-dimensional time-dependent pressure field within a 1.5-fold projectile radius from the impact point was investigated in cylindrical coordinates to address the generation of spalled material. A resolution test was also performed to reject ejected materials with peak pressures that were too low due to artificial viscosity. The relationship between ejection velocity veject and peak pressure Ppeak was also derived. Our approach shows that “late-stage acceleration” in an ejecta curtain occurs due to the compressible nature of the ejecta, resulting in an ejection velocity that can be higher than the ideal maximum of the resultant particle velocity after passage of a shock wave. We also calculate the ejecta mass that can escape from a planet like Mars (i.e., veject {\\textgreater} 5 km/s) that matches the petrographic constraints from Martian meteorites, and which occurs when Ppeak = 30–50 GPa. Although the mass of such ejecta is limited to 0.1–1 wt\\% of the projectile mass in vertical impacts, this is sufficient for spallation to have been a plausible mechanism for the ejection of Martian meteorites. Finally, we propose that impact spallation is a plausible mechanism for the generation of tektites.},\n\turldate = {2018-05-03},\n\tjournal = {Icarus},\n\tauthor = {Kurosawa, Kosuke and Okamoto, Takaya and Genda, Hidenori},\n\tmonth = feb,\n\tyear = {2018},\n\tkeywords = {Hydrocode modeling, Hypervelocity impact, Material ejection, Shock wave, Spallation},\n\tpages = {219--234},\n}\n\n

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\n \n\n \n \n Derrick, J. G.; LaJeunesse, J. W.; Davison, T. M.; Borg, J. P.; and Collins, G. S.\n\n\n \n \n \n \n \n Mesoscale simulations of shock compaction of a granular ceramic: effects of mesostructure and mixed-cell strength treatment.\n \n \n \n \n\n\n \n\n\n\n Modelling and Simulation in Materials Science and Engineering, 26(3): 035009. 2018.\n \n\n\n\n
\n\n\n\n \n \n $\"Mesoscale$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{derrick_mesoscale_2018,\n\ttitle = {Mesoscale simulations of shock compaction of a granular ceramic: effects of mesostructure and mixed-cell strength treatment},\n\tvolume = {26},\n\tissn = {0965-0393},\n\tshorttitle = {Mesoscale simulations of shock compaction of a granular ceramic},\n\turl = {http://stacks.iop.org/0965-0393/26/i=3/a=035009},\n\tdoi = {10.1088/1361-651X/aaab7e},\n\tabstract = {The shock response of granular materials is important in a variety of contexts but the precise dynamics of grains during compaction is poorly understood. Here we use 2D mesoscale numerical simulations of the shock compaction of granular tungsten carbide to investigate the effect of internal structure within the particle bed and ‘stiction’ between grains on the shock response. An increase in the average number of contacts with other particles, per particle, tends to shift the Hugoniot to higher shock velocities, lower particle velocities and lower densities. This shift is sensitive to inter-particle shear resistance. Eulerian shock physics codes approximate friction between, and interlocking of, grains with their treatment of mixed cell strength (stiction) and here we show that this has a significant effect on the shock response. When studying the compaction of particle beds it is not common to quantify the pre-compaction internal structure, yet our results suggest that such differences should be taken into account, either by using identical beds or by averaging results over multiple experiments.},\n\tlanguage = {en},\n\tnumber = {3},\n\turldate = {2018-02-23},\n\tjournal = {Modelling and Simulation in Materials Science and Engineering},\n\tauthor = {Derrick, J. G. and LaJeunesse, J. W. and Davison, T. M. and Borg, J. P. and Collins, G. S.},\n\tyear = {2018},\n\tpages = {035009},\n}\n\n

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\n \n\n \n \n Frank, E. A.; Potter, R. W. K.; Abramov, O.; James, P. B.; Klima, R. L.; Mojzsis, S. J.; and Nittler, L. R.\n\n\n \n \n \n \n \n Evaluating an impact origin for Mercury's high-magnesium region.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 122(3): 614–632. March 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Evaluating$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{frank_evaluating_2017,\n\ttitle = {Evaluating an impact origin for {Mercury}'s high-magnesium region},\n\tvolume = {122},\n\tcopyright = {©2017. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2016JE005244},\n\tdoi = {10.1002/2016JE005244},\n\tabstract = {During its four years in orbit around Mercury, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft's X-ray Spectrometer revealed a large geochemical terrane in the northern hemisphere that hosts the highest Mg/Si, S/Si, Ca/Si, and Fe/Si and lowest Al/Si ratios on the planet. Correlations with low topography, thin crust, and a sharp northern topographic boundary led to the proposal that this high-Mg region is the remnant of an ancient, highly degraded impact basin. Here we use a numerical modeling approach to explore the feasibility of this hypothesis and evaluate the results against multiple mission-wide data sets and resulting maps from MESSENGER. We find that an 3000 km diameter impact basin easily exhumes Mg-rich mantle material but that the amount of subsequent modification required to hide basin structure is incompatible with the strength of the geochemical anomaly, which is also present in maps of Gamma Ray and Neutron Spectrometer data. Consequently, the high-Mg region is more likely to be the product of high-temperature volcanism sourced from a chemically heterogeneous mantle than the remains of a large impact event.},\n\tlanguage = {en},\n\tnumber = {3},\n\turldate = {2018-08-06},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Frank, Elizabeth A. and Potter, Ross W. K. and Abramov, Oleg and James, Peter B. and Klima, Rachel L. and Mojzsis, Stephen J. and Nittler, Larry R.},\n\tmonth = mar,\n\tyear = {2017},\n\tkeywords = {MESSENGER, Mercury, geochemistry, impact},\n\tpages = {614--632},\n}\n\n

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\n \n\n \n \n Rutherford, M. E.; Chapman, D. J.; Derrick, J. G.; Patten, J. R. W.; Bland, P. A.; Rack, A.; Collins, G. S.; and Eakins, D. E.\n\n\n \n \n \n \n \n Probing the early stages of shock-induced chondritic meteorite formation at the mesoscale.\n \n \n \n \n\n\n \n\n\n\n Scientific Reports, 7: srep45206. May 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Probing$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{rutherford_probing_2017,\n\ttitle = {Probing the early stages of shock-induced chondritic meteorite formation at the mesoscale},\n\tvolume = {7},\n\tcopyright = {2017 Nature Publishing Group},\n\tissn = {2045-2322},\n\turl = {https://www.nature.com/articles/srep45206},\n\tdoi = {10.1038/srep45206},\n\tabstract = {Article},\n\tlanguage = {en},\n\turldate = {2017-07-04},\n\tjournal = {Scientific Reports},\n\tauthor = {Rutherford, Michael E. and Chapman, David J. and Derrick, James G. and Patten, Jack R. W. and Bland, Philip A. and Rack, Alexander and Collins, Gareth S. and Eakins, Daniel E.},\n\tmonth = may,\n\tyear = {2017},\n\tpages = {srep45206},\n}\n\n

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\n \n\n \n \n Silber, E. A.; and Johnson, B. C.\n\n\n \n \n \n \n \n Impact Crater Morphology and the Structure of Europa's Ice Shell.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 122(12): 2685–2701. December 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Impact$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{silber_impact_2017,\n\ttitle = {Impact {Crater} {Morphology} and the {Structure} of {Europa}'s {Ice} {Shell}},\n\tvolume = {122},\n\tcopyright = {©2017. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017JE005456},\n\tdoi = {10.1002/2017JE005456},\n\tabstract = {We performed numerical simulations of impact crater formation on Europa to infer the thickness and structure of its ice shell. The simulations were performed using iSALE to test both the conductive ice shell over ocean and the conductive lid over warm convective ice scenarios for a variety of conditions. The modeled crater depth-diameter is strongly dependent on the thermal gradient and temperature of the warm convective ice. Our results indicate that both a fully conductive (thin) shell and a conductive-convective (thick) shell can reproduce the observed crater depth-diameter and morphologies. For the conductive ice shell over ocean, the best fit is an approximately 8 km thick conductive ice shell. Depending on the temperature (255–265 K) and therefore strength of warm convective ice, the thickness of the conductive ice lid is estimated at 5–7 km. If central features within the crater, such as pits and domes, form during crater collapse, our simulations are in better agreement with the fully conductive shell (thin shell). If central features form well after the impact, however, our simulations suggest that a conductive-convective shell (thick shell) is more likely. Although our study does not provide a firm conclusion regarding the thickness of Europa's ice shell, our work indicates that Valhalla class multiring basins on Europa may provide robust constraints on the thickness of Europa's ice shell.},\n\tlanguage = {en},\n\tnumber = {12},\n\turldate = {2018-08-06},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Silber, Elizabeth A. and Johnson, Brandon C.},\n\tmonth = dec,\n\tyear = {2017},\n\tkeywords = {Europa, ice shell thickness, impact crater morphology, warm convective ice},\n\tpages = {2685--2701},\n}\n\n

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\n \n\n \n \n Martellato, E.; Vivaldi, V.; Massironi, M.; Cremonese, G.; Marzari, F.; Ninfo, A.; and Haruyama, J.\n\n\n \n \n \n \n \n Is the Linné impact crater morphology influenced by the rheological layering on the Moon's surface? Insights from numerical modeling.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 52(7): 1388–1411. July 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Is$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{martellato_is_2017,\n\ttitle = {Is the {Linné} impact crater morphology influenced by the rheological layering on the {Moon}'s surface? {Insights} from numerical modeling},\n\tvolume = {52},\n\tissn = {1945-5100},\n\tshorttitle = {Is the {Linné} impact crater morphology influenced by the rheological layering on the {Moon}'s surface?},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12892/abstract},\n\tdoi = {10.1111/maps.12892},\n\tabstract = {Linné is a simple crater, with a diameter of 2.23 km and a depth of 0.52 km, located in northwestern Mare Serenitatis. Recent high-resolution data acquired by the Lunar Reconnaissance Orbiter Camera revealed that the shape of this impact structure is best described by an inverted truncated-cone. We perform morphometric measurements, including slope and profile curvature, on the Digital Terrain Model of Linné, finding the possible presence of three subtle topographic steps, at the elevation of +20, −100, and −200 m relative to the target surface. The kink at −100 m might be related to the interface between two different rheological layers. Using the iSALE shock physics code, we numerically model the formation of Linné crater to derive hints on the possible impact conditions and target physical properties. In the initial setup, we adopt a basaltic projectile impacting the Moon with a speed of 18 km s−1. For the local surface, we consider either one or two layers, in order to test the influence of material properties or composite rheologies on the final crater morphology. The one-layer model shows that the largest variations in the crater shape take place when either the cohesion or the friction coefficient is varied. In particular, a cohesion of 10 kPa marks the threshold between conical- and parabolic-shaped craters. The two-layer model shows that the interface between the two layers would be exposed at the observed depth of 100 m when an intermediate value ({\\textasciitilde}200 m) for the upper fractured layer is set. We have also found that the truncated-cone morphology of Linné might originate from an incomplete collapse of the crater wall, as the breccia lens remains clustered along the crater walls, while the high-albedo deposit on the crater floor can be interpreted as a very shallow lens of fallout breccia. The modeling analysis allows us to derive important clues on the impactor size (under the assumption of a vertical impact and collision velocity equal to the mean value), and on the approximate, large-scale preimpact target properties. Observations suggest that these large-scale material properties likely include some important smaller scale variations, disclosed as subtle morphological steps in the crater walls. Furthermore, the modeling results allow advancing some hypotheses on the geological evolution of the Mare Serenitatis region where Linné crater is located (unit S14). We suggest that unit S14 has a thickness of at least a few hundreds of meters up to about 400 m.},\n\tlanguage = {en},\n\tnumber = {7},\n\turldate = {2018-01-09},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Martellato, Elena and Vivaldi, Valerio and Massironi, Matteo and Cremonese, Gabriele and Marzari, Francesco and Ninfo, Andrea and Haruyama, Junichi},\n\tmonth = jul,\n\tyear = {2017},\n\tpages = {1388--1411},\n}\n\n

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\n Linné is a simple crater, with a diameter of 2.23 km and a depth of 0.52 km, located in northwestern Mare Serenitatis. Recent high-resolution data acquired by the Lunar Reconnaissance Orbiter Camera revealed that the shape of this impact structure is best described by an inverted truncated-cone. We perform morphometric measurements, including slope and profile curvature, on the Digital Terrain Model of Linné, finding the possible presence of three subtle topographic steps, at the elevation of +20, −100, and −200 m relative to the target surface. The kink at −100 m might be related to the interface between two different rheological layers. Using the iSALE shock physics code, we numerically model the formation of Linné crater to derive hints on the possible impact conditions and target physical properties. In the initial setup, we adopt a basaltic projectile impacting the Moon with a speed of 18 km s−1. For the local surface, we consider either one or two layers, in order to test the influence of material properties or composite rheologies on the final crater morphology. The one-layer model shows that the largest variations in the crater shape take place when either the cohesion or the friction coefficient is varied. In particular, a cohesion of 10 kPa marks the threshold between conical- and parabolic-shaped craters. The two-layer model shows that the interface between the two layers would be exposed at the observed depth of 100 m when an intermediate value (~200 m) for the upper fractured layer is set. We have also found that the truncated-cone morphology of Linné might originate from an incomplete collapse of the crater wall, as the breccia lens remains clustered along the crater walls, while the high-albedo deposit on the crater floor can be interpreted as a very shallow lens of fallout breccia. The modeling analysis allows us to derive important clues on the impactor size (under the assumption of a vertical impact and collision velocity equal to the mean value), and on the approximate, large-scale preimpact target properties. Observations suggest that these large-scale material properties likely include some important smaller scale variations, disclosed as subtle morphological steps in the crater walls. Furthermore, the modeling results allow advancing some hypotheses on the geological evolution of the Mare Serenitatis region where Linné crater is located (unit S14). We suggest that unit S14 has a thickness of at least a few hundreds of meters up to about 400 m.\n

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\n \n\n \n \n Moreau, J.; Kohout, T.; and Wünnemann, K.\n\n\n \n \n \n \n \n Shock-darkening in ordinary chondrites: Determination of the pressure-temperature conditions by shock physics mesoscale modeling.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 52(11): 2375–2390. November 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Shock-darkening$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{moreau_shock-darkening_2017,\n\ttitle = {Shock-darkening in ordinary chondrites: {Determination} of the pressure-temperature conditions by shock physics mesoscale modeling},\n\tvolume = {52},\n\tcopyright = {© The Meteoritical Society,2017.},\n\tissn = {1945-5100},\n\tshorttitle = {Shock-darkening in ordinary chondrites},\n\turl = {https://onlinelibrary.wiley.com/doi/abs/10.1111/maps.12935},\n\tdoi = {10.1111/maps.12935},\n\tabstract = {We determined the shock-darkening pressure range in ordinary chondrites using the iSALE shock physics code. We simulated planar shock waves on a mesoscale in a sample layer at different nominal pressures. Iron and troilite grains were resolved in a porous olivine matrix in the sample layer. We used equations of state (Tillotson EoS and ANEOS) and basic strength and thermal properties to describe the material phases. We used Lagrangian tracers to record the peak shock pressures in each material unit. The post-shock temperatures (and the fractions of the tracers experiencing temperatures above the melting point) for each material were estimated after the passage of the shock wave and after the reflections of the shock at grain boundaries in the heterogeneous materials. The results showed that shock-darkening, associated with troilite melt and the onset of olivine melt, happened between 40 and 50 GPa with 52 GPa being the pressure at which all tracers in the troilite material reach the melting point. We demonstrate the difficulties of shock heating in iron and also the importance of porosity. Material impedances, grain shapes, and the porosity models available in the iSALE code are discussed. We also discuss possible not-shock-related triggers for iron melt.},\n\tlanguage = {en},\n\tnumber = {11},\n\turldate = {2018-05-15},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Moreau, J. and Kohout, T. and Wünnemann, K.},\n\tmonth = nov,\n\tyear = {2017},\n\tpages = {2375--2390},\n}\n\n

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\n \n\n \n \n Wakita, S.; Matsumoto, Y.; Oshino, S.; and Hasegawa, Y.\n\n\n \n \n \n \n \n Planetesimal Collisions as a Chondrule Forming Event.\n \n \n \n \n\n\n \n\n\n\n The Astrophysical Journal, 834(2): 125. 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Planetesimal$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{wakita_planetesimal_2017,\n\ttitle = {Planetesimal {Collisions} as a {Chondrule} {Forming} {Event}},\n\tvolume = {834},\n\tissn = {0004-637X},\n\turl = {http://stacks.iop.org/0004-637X/834/i=2/a=125},\n\tdoi = {10.3847/1538-4357/834/2/125},\n\tabstract = {Chondritic meteorites contain unique spherical materials named chondrules: sub-mm sized silicate grains once melted in a high temperature condition in the solar nebula. We numerically explore one of the chondrule forming processes—planetesimal collisions. Previous studies have found that impact jetting via protoplanet–planetesimal collisions can make chondrules with 1\\% of the impactors’ mass, when the impact velocity exceeds 2.5 km s −1 . Based on the mineralogical data of chondrules, undifferentiated planetesimals would be more suitable for chondrule-forming collisions than potentially differentiated protoplanets. We examine planetesimal–planetesimal collisions using a shock physics code and find two things: one is that planetesimal–planetesimal collisions produce nearly the same amount of chondrules as protoplanet–planetesimal collisions (∼1\\%). The other is that the amount of produced chondrules becomes larger as the impact velocity increases when two planetesimals collide with each other. We also find that progenitors of chondrules can originate from deeper regions of large targets (planetesimals or protoplanets) than small impactors (planetesimals). The composition of targets is therefore important, to fully account for the mineralogical data of currently sampled chondrules.},\n\tlanguage = {en},\n\tnumber = {2},\n\turldate = {2018-05-03},\n\tjournal = {The Astrophysical Journal},\n\tauthor = {Wakita, Shigeru and Matsumoto, Yuji and Oshino, Shoichi and Hasegawa, Yasuhiro},\n\tyear = {2017},\n\tpages = {125},\n}\n\n

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\n \n\n \n \n Davison, T. M.; Derrick, J. G.; Collins, G. S.; Bland, P. A.; Rutherford, M. E.; Chapman, D. J.; and Eakins, D. E.\n\n\n \n \n \n \n \n Impact-induced compaction of primitive solar system solids: The need for mesoscale modelling and experiments.\n \n \n \n \n\n\n \n\n\n\n Procedia Engineering, 204(Supplement C): 405–412. January 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Impact-induced$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{davison_impact-induced_2017,\n\tseries = {14th {Hypervelocity} {Impact} {Symposium} 2017},\n\ttitle = {Impact-induced compaction of primitive solar system solids: {The} need for mesoscale modelling and experiments},\n\tvolume = {204},\n\tissn = {1877-7058},\n\tshorttitle = {Impact-induced compaction of primitive solar system solids},\n\turl = {http://www.sciencedirect.com/science/article/pii/S187770581734362X},\n\tdoi = {10.1016/j.proeng.2017.09.801},\n\tabstract = {Primitive solar system solids were accreted as highly porous bimodal mixtures of mm-sized chondrules and sub-μm matrix grains. To understand the compaction and lithification of these materials by shock, it is necessary to investigate the process at the mesoscale; i.e., the scale of individual chondrules. Here we document simulations of hypervelocity compaction of primitive materials using the iSALE shock physics model. We compare the numerical methods employed here with shock compaction experiments involving bimodal mixtures of glass beads and silica powder and find good agreement in bulk material response between the experiments and models. The heterogeneous response to shock of bimodal porous mixtures with a composition more appropriate for primitive solids was subsequently investigated: strong temperature dichotomies between the chondrules and matrix were observed (non-porous chondrules remained largely cold, while the porous matrix saw temperature increases of 100’s K). Matrix compaction was heterogeneous, and post-shock porosity was found to be lower on the lee-side of chondrules. The strain in the matrix was shown to be higher near the chondrule rims, in agreement with observations from meteorites. Chondrule flattening in the direction of the shock increases with increasing impact velocity, with flattened chondrules oriented with their semi-minor axis parallel to the shock direction.},\n\tnumber = {Supplement C},\n\tjournal = {Procedia Engineering},\n\tauthor = {Davison, Thomas M. and Derrick, James G. and Collins, Gareth S. and Bland, Philip A. and Rutherford, Michael E. and Chapman, David J. and Eakins, Daniel E.},\n\tmonth = jan,\n\tyear = {2017},\n\tkeywords = {Mesoscale modeling, Numerical methods, Parent body processes, Planetary science, Shock compaction, chondrites},\n\tpages = {405--412},\n}\n\n

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\n \n\n \n \n Silber, E. A.; Osinski, G. R.; Johnson, B. C.; and Grieve, R. A. F.\n\n\n \n \n \n \n \n Effect of impact velocity and acoustic fluidization on the simple-to-complex transition of lunar craters.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 122(5): 2016JE005236. May 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Effect$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{silber_effect_2017,\n\ttitle = {Effect of impact velocity and acoustic fluidization on the simple-to-complex transition of lunar craters},\n\tvolume = {122},\n\tissn = {2169-9100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/2016JE005236/abstract},\n\tdoi = {10.1002/2016JE005236},\n\tabstract = {We use numerical modeling to investigate the combined effects of impact velocity and acoustic fluidization on lunar craters in the simple-to-complex transition regime. To investigate the full scope of the problem, we employed the two widely adopted Block-Model of acoustic fluidization scaling assumptions (scaling block size by impactor size and scaling by coupling parameter) and compared their outcomes. Impactor size and velocity were varied, such that large/slow and small/fast impactors would produce craters of the same diameter within a suite of simulations, ranging in diameter from 10 to 26 km, which straddles the simple-to-complex crater transition on the Moon. Our study suggests that the transition from simple to complex structures is highly sensitive to the choice of the time decay and viscosity constants in the Block-Model of acoustic fluidization. Moreover, the combination of impactor size and velocity plays a greater role than previously thought in the morphology of craters in the simple-to-complex size range. We propose that scaling of block size by impactor size is an appropriate choice for modeling simple-to-complex craters on planetary surfaces, including both varying and constant impact velocities, as the modeling results are more consistent with the observed morphology of lunar craters. This scaling suggests that the simple-to-complex transition occurs at a larger crater size, if higher impact velocities are considered, and is consistent with the observation that the simple-to-complex transition occurs at larger sizes on Mercury than Mars.},\n\tlanguage = {en},\n\tnumber = {5},\n\turldate = {2018-02-12},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Silber, Elizabeth A. and Osinski, Gordon R. and Johnson, Brandon C. and Grieve, Richard A. F.},\n\tmonth = may,\n\tyear = {2017},\n\tkeywords = {0545 Modeling, 5420 Impact phenomena, cratering, 6250 Moon, acoustic fluidization, lunar craters, numerical modeling, simple-to-complex transition},\n\tpages = {2016JE005236},\n}\n\n

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\n \n\n \n \n Watters, W. A.; Hundal, C. B.; Radford, A.; Collins, G. S.; and Tornabene, L. L.\n\n\n \n \n \n \n \n Dependence of secondary crater characteristics on downrange distance: High-resolution morphometry and simulations.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 122(8): 2017JE005295. August 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Dependence$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{watters_dependence_2017,\n\ttitle = {Dependence of secondary crater characteristics on downrange distance: {High}-resolution morphometry and simulations},\n\tvolume = {122},\n\tissn = {2169-9100},\n\tshorttitle = {Dependence of secondary crater characteristics on downrange distance},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/2017JE005295/abstract},\n\tdoi = {10.1002/2017JE005295},\n\tabstract = {On average, secondary impact craters are expected to deepen and become more symmetric as impact velocity (vi) increases with downrange distance (L). We have used high-resolution topography (1–2 m/pixel) to characterize the morphometry of secondary craters as a function of L for several well-preserved primary craters on Mars. The secondaries in this study (N = 2644) span a range of diameters (25 m ≤D≤400 m) and estimated impact velocities (0.4 km/s ≤vi≤2 km/s). The range of diameter-normalized rim-to-floor depth (d/D) broadens and reaches a ceiling of d/D≈0.22 at L≈280 km (vi= 1–1.2 km/s), whereas average rim height shows little dependence on vi for the largest craters (h/D≈0.02, D {\\textgreater} 60 m). Populations of secondaries that express the following morphometric asymmetries are confined to regions of differing radial extent: planform elongations (L{\\textless} 110–160 km), taller downrange rims (L {\\textless} 280 km), and cavities that are deeper uprange (L{\\textless} 450–500 km). Populations of secondaries with lopsided ejecta were found to extend to at least L ∼ 700 km. Impact hydrocode simulations with iSALE-2D for strong, intact projectile and target materials predict a ceiling for d/D versus L whose trend is consistent with our measurements. This study illuminates the morphometric transition from subsonic to hypervelocity cratering and describes the initial state of secondary crater populations. This has applications to understanding the chronology of planetary surfaces and the long-term evolution of small crater populations.},\n\tlanguage = {en},\n\tnumber = {8},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Watters, Wesley A. and Hundal, Carol B. and Radford, Arden and Collins, Gareth S. and Tornabene, Livio L.},\n\tmonth = aug,\n\tyear = {2017},\n\tkeywords = {5420 Impact phenomena, cratering, 5470 Surface materials and properties, 5494 Instruments and techniques, hydrocode simulations, impact cratering, secondary craters, surface processes},\n\tpages = {2017JE005295},\n}\n\n

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\n \n\n \n \n Collins, G. S.; Lynch, E.; McAdam, R.; and Davison, T. M.\n\n\n \n \n \n \n \n A numerical assessment of simple airblast models of impact airbursts.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science,1542–1560. 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"A$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{collins_numerical_2017,\n\ttitle = {A numerical assessment of simple airblast models of impact airbursts},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12873/abstract},\n\tdoi = {10.1111/maps.12873},\n\tabstract = {Asteroids and comets 10–100 m in size that collide with Earth disrupt dramatically in the atmosphere with an explosive transfer of energy, caused by extreme air drag. Such airbursts produce a strong blastwave that radiates from the meteoroid's trajectory and can cause damage on the surface. An established technique for predicting airburst blastwave damage is to treat the airburst as a static source of energy and to extrapolate empirical results of nuclear explosion tests using an energy-based scaling approach. Here we compare this approach to two more complex models using the iSALE shock physics code. We consider a moving-source airburst model where the meteoroid's energy is partitioned as two-thirds internal energy and one-third kinetic energy at the burst altitude, and a model in which energy is deposited into the atmosphere along the meteoroid's trajectory based on the pancake model of meteoroid disruption. To justify use of the pancake model, we show that it provides a good fit to the inferred energy release of the 2013 Chelyabinsk fireball. Predicted overpressures from all three models are broadly consistent at radial distances from ground zero that exceed three times the burst height. At smaller radial distances, the moving-source model predicts overpressures two times greater than the static-source model, whereas the cylindrical line-source model based on the pancake model predicts overpressures two times lower than the static-source model. Given other uncertainties associated with airblast damage predictions, the static-source approach provides an adequate approximation of the azimuthally averaged airblast for probabilistic hazard assessment.},\n\tlanguage = {en},\n\turldate = {2017-05-16},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Collins, Gareth S. and Lynch, Elliot and McAdam, Ronan and Davison, Thomas M.},\n\tyear = {2017},\n\tpages = {1542--1560},\n}\n\n

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\n \n\n \n \n Forman, L. V.; Bland, P. A.; Timms, N. E.; Daly, L.; Benedix, G. K.; Trimby, P. W.; Collins, G. S.; and Davison, T. M.\n\n\n \n \n \n \n \n Defining the mechanism for compaction of the CV chondrite parent body.\n \n \n \n \n\n\n \n\n\n\n Geology,G38864.1. April 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Defining$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{forman_defining_2017,\n\ttitle = {Defining the mechanism for compaction of the {CV} chondrite parent body},\n\tissn = {0091-7613, 1943-2682},\n\turl = {http://geology.gsapubs.org/content/early/2017/04/11/G38864.1},\n\tdoi = {10.1130/G38864.1},\n\tabstract = {The Allende meteorite, a relatively unaltered member of the CV carbonaceous chondrite group, contains primitive crystallographic textures that can inform our understanding of early Solar System planetary compaction. To test between models of porosity reduction on the CV parent body, complex microstructures within {\\textasciitilde}0.5-mm-diameter chondrules and {\\textasciitilde}10-μm-long matrix olivine grains were analyzed by electron backscatter diffraction (EBSD) techniques. The large area map presented is one of the most extensive EBSD maps to have been collected in application to extraterrestrial materials. Chondrule margins preferentially exhibit limited intragrain crystallographic misorientation due to localized crystal-plastic deformation. Crystallographic preferred orientations (CPOs) preserved by matrix olivine grains are strongly coupled to grain shape, most pronounced in shortest dimension {\\textless}a{\\textgreater}, yet are locally variable in orientation and strength. Lithostatic pressure within plausible chondritic model asteroids is not sufficient to drive compaction or create the observed microstructures if the aggregate was cold. Significant local variability in the orientation and intensity of compaction is also inconsistent with a global process. Detailed microstructures indicative of crystal-plastic deformation are consistent with brief heating events that were small in magnitude. When combined with a lack of sintered grains and the spatially heterogeneous CPO, ubiquitous hot isostatic pressing is unlikely to be responsible. Furthermore, Allende is the most metamorphosed CV chondrite, so if sintering occurred at all on the CV parent body it would be evident here. We conclude that the crystallographic textures observed reflect impact compaction and indicate shock-wave directionality. We therefore present some of the first significant evidence for shock compaction of the CV parent body.},\n\tlanguage = {en},\n\turldate = {2017-04-18},\n\tjournal = {Geology},\n\tauthor = {Forman, L. V. and Bland, P. A. and Timms, N. E. and Daly, L. and Benedix, G. K. and Trimby, P. W. and Collins, G. S. and Davison, T. M.},\n\tmonth = apr,\n\tyear = {2017},\n\tpages = {G38864.1},\n}\n\n

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\n \n\n \n \n Güldemeister, N.; and Wünnemann, K.\n\n\n \n \n \n \n \n Quantitative analysis of impact-induced seismic signals by numerical modeling.\n \n \n \n \n\n\n \n\n\n\n Icarus, 296: 15–27. November 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Quantitative$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{guldemeister_quantitative_2017,\n\ttitle = {Quantitative analysis of impact-induced seismic signals by numerical modeling},\n\tvolume = {296},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103516306017},\n\tdoi = {10.1016/j.icarus.2017.05.010},\n\tabstract = {We quantify the seismicity of impact events using a combined numerical and experimental approach. The objectives of this work are (1) the calibration of the numerical model by utilizing real-time measurements of the elastic wave velocity and pressure amplitudes in laboratory impact experiments; (2) the determination of seismic parameters, such as quality factor Q and seismic efficiency k, for materials of different porosity and water saturation by a systematic parameter study employing the calibrated numerical model. By means of “numerical experiments” we found that the seismic efficiency k decreases slightly with porosity from k=3.4×10−3 for nonporous quartzite to k=2.6×10−3 for 25\\% porous sandstone. If pores are completely or partly filled with water, we determined a seismic efficiency of k=8.2×10−5, which is approximately two orders of magnitude lower than in the nonporous case. By measuring the attenuation of the seismic wave with distance in our numerical experiments we determined the seismic quality factor Q to range between ∼35 for the solid quartzite and 80 for the porous dry targets. For water saturated target materials, Q is much lower, {\\textless}10. The obtained values are in the range of literature values. Translating the seismic efficiency into seismic magnitudes we show that the seismic magnitude of an impact event is about one order of magnitude smaller considering a water saturated target in comparison to a solid or porous target. Obtained seismic magnitudes decrease linearly with distance to the point of impact and are consistent with empirical data for distances closer to the point of impact. The seismic magnitude decreases more rapidly with distance for a water saturated material compared to a dry material.},\n\turldate = {2017-07-18},\n\tjournal = {Icarus},\n\tauthor = {Güldemeister, Nicole and Wünnemann, Kai},\n\tmonth = nov,\n\tyear = {2017},\n\tkeywords = {Impact hazard, Impact seismicity, Meteorite impacts, Seismic waves, numerical modeling},\n\tpages = {15--27},\n}\n\n

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\n \n\n \n \n Holm-Alwmark, S.; Rae, A. S. P.; Ferrière, L.; Alwmark, C.; and Collins, G. S.\n\n\n \n \n \n \n \n Combining shock barometry with numerical modeling: Insights into complex crater formation—The example of the Siljan impact structure (Sweden).\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science,Accepted. 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Combining$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{holm-alwmark_combining_2017,\n\ttitle = {Combining shock barometry with numerical modeling: {Insights} into complex crater formation—{The} example of the {Siljan} impact structure ({Sweden})},\n\tissn = {1945-5100},\n\tshorttitle = {Combining shock barometry with numerical modeling},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12955/abstract},\n\tdoi = {10.1111/maps.12955},\n\tabstract = {Siljan, central Sweden, is the largest known impact structure in Europe. It was formed at about 380 Ma, in the late Devonian period. The structure has been heavily eroded to a level originally located underneath the crater floor, and to date, important questions about the original size and morphology of Siljan remain unanswered. Here we present the results of a shock barometry study of quartz-bearing surface and drill core samples combined with numerical modeling using iSALE. The investigated 13 bedrock granitoid samples show that the recorded shock pressure decreases with increasing depth from 15 to 20 GPa near the (present) surface, to 10–15 GPa at 600 m depth. A best-fit model that is consistent with observational constraints relating to the present size of the structure, the location of the downfaulted sediments, and the observed surface and vertical shock barometry profiles is presented. The best-fit model results in a final crater (rim-to-rim) diameter of {\\textasciitilde}65 km. According to our simulations, the original Siljan impact structure would have been a peak-ring crater. Siljan was formed in a mixed target of Paleozoic sedimentary rocks overlaying crystalline basement. Our modeling suggests that, at the time of impact, the sedimentary sequence was approximately 3 km thick. Since then, there has been around 4 km of erosion of the structure.},\n\tlanguage = {en},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Holm-Alwmark, Sanna and Rae, Auriol S. P. and Ferrière, Ludovic and Alwmark, Carl and Collins, Gareth S.},\n\tyear = {2017},\n\tpages = {Accepted},\n}\n\n

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\n \n\n \n \n Luther, R.; Artemieva, N.; Ivanova, M.; Lorenz, C.; and Wünnemann, K.\n\n\n \n \n \n \n \n Snow carrots after the Chelyabinsk event and model implications for highly porous solar system objects.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 52(5): 979–999. May 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Snow$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{luther_snow_2017,\n\ttitle = {Snow carrots after the {Chelyabinsk} event and model implications for highly porous solar system objects},\n\tvolume = {52},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12831/abstract},\n\tdoi = {10.1111/maps.12831},\n\tabstract = {After the catastrophic disruption of the Chelyabinsk meteoroid, small fragments formed funnels in the snow layer covering the ground. We constrain the pre-impact characteristics of the fragments by simulating their atmospheric descent with the atmospheric entry model. Fragments resulting from catastrophic breakup may lose about 90\\% of their initial mass due to ablation and reach the snow vertically with a free-fall velocity in the range of 30–90 m s−1. The fall time of the fragments is much longer than their cooling time, and, as a consequence, fragments have the same temperature as the lower atmosphere, i.e., of about −20 °C. Then, we use the shock physics code iSALE to model the penetration of fragments into fluffy snow, the formation of a funnel and a zone of denser snow lining its walls. We examine the influence of several material parameters of snow and present our best-fit model by comparing funnel depth and funnel wall characteristics with observations. In addition, we suggest a viscous flow approximation to estimate funnel depth dependence on the meteorite mass. We discuss temperature gradient metamorphism as a possible mechanism which allows to fill the funnels with denser snow and to form the observed “snow carrots.” This natural experiment also helps us to calibrate the iSALE code for simulating impacts into highly porous matter in the solar system including tracks in the aerogel catchers of the Stardust mission and possible impact craters on the 67P/Churyumov-Gerasimenko comet observed recently by the Rosetta mission.},\n\tlanguage = {en},\n\tnumber = {5},\n\turldate = {2017-07-28},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Luther, Robert and Artemieva, Natalia and Ivanova, Marina and Lorenz, Cyril and Wünnemann, Kai},\n\tmonth = may,\n\tyear = {2017},\n\tpages = {979--999},\n}\n\n

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\n \n\n \n \n Muxworthy, A. R.; Bland, P. A.; Davison, T. M.; Moore, J.; Collins, G. S.; and Ciesla, F. J.\n\n\n \n \n \n \n \n Evidence for an impact-induced magnetic fabric in Allende, and exogenous alternatives to the core dynamo theory for Allende magnetization.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 52(10): 2132–2146. October 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Evidence$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{muxworthy_evidence_2017,\n\ttitle = {Evidence for an impact-induced magnetic fabric in {Allende}, and exogenous alternatives to the core dynamo theory for {Allende} magnetization},\n\tvolume = {52},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12918/abstract},\n\tdoi = {10.1111/maps.12918},\n\tabstract = {We conducted a paleomagnetic study of the matrix of Allende CV3 chondritic meteorite, isolating the matrix's primary remanent magnetization, measuring its magnetic fabric and estimating the ancient magnetic field intensity. A strong planar magnetic fabric was identified; the remanent magnetization of the matrix was aligned within this plane, suggesting a mechanism relating the magnetic fabric and remanence. The intensity of the matrix's remanent magnetization was found to be consistent and low ({\\textasciitilde}6 μT). The primary magnetic mineral was found to be pyrrhotite. Given the thermal history of Allende, we conclude that the remanent magnetization was formed during or after an impact event. Recent mesoscale impact modeling, where chondrules and matrix are resolved, has shown that low-velocity collisions can generate significant matrix temperatures, as pore-space compaction attenuates shock energy and dramatically increases the amount of heating. Nonporous chondrules are unaffected, and act as heat-sinks, so matrix temperature excursions are brief. We extend this work to model Allende, and show that a 1 km/s planar impact generates bulk porosity, matrix porosity, and fabric in our target that match the observed values. Bimodal mixtures of a highly porous matrix and nominally zero-porosity chondrules make chondrites uniquely capable of recording transient or unstable fields. Targets that have uniform porosity, e.g., terrestrial impact craters, will not record transient or unstable fields. Rather than a core dynamo, it is therefore possible that the origin of the magnetic field in Allende was the impact itself, or a nebula field recorded during transient impact heating.},\n\tlanguage = {en},\n\tnumber = {10},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Muxworthy, Adrian R. and Bland, Phillip A. and Davison, Thomas M. and Moore, James and Collins, Gareth S. and Ciesla, Fred J.},\n\tmonth = oct,\n\tyear = {2017},\n\tpages = {2132--2146},\n}\n\n

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\n \n\n \n \n Prieur, N. C.; Rolf, T.; Luther, R.; Wünnemann, K.; Xiao, Z.; and Werner, S. C.\n\n\n \n \n \n \n \n The effect of target properties on transient crater scaling for simple craters.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 122(8): 2017JE005283. August 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{prieur_effect_2017,\n\ttitle = {The effect of target properties on transient crater scaling for simple craters},\n\tvolume = {122},\n\tissn = {2169-9100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/2017JE005283/abstract},\n\tdoi = {10.1002/2017JE005283},\n\tabstract = {The effects of the coefficient of friction and porosity on impact cratering are not sufficiently considered in scaling laws that predict the crater size from a known impactor size, velocity, and mass. We carried out a systematic numerical study employing more than 1000 two-dimensional models of simple crater formation under lunar conditions in targets with varying properties. A simple numerical setup is used where targets are approximated as granular or brecciated materials, and any compression of porous materials results in permanent compaction. The results are found to be consistent with impact laboratory experiments for water, low-strength and low-porosity materials (e.g., wet sand), and sands. Using this assumption, we found that both the friction coefficient and porosity are important for estimating transient crater diameters as is the strength term in crater scaling laws, i.e., the effective strength. The effects of porosity and friction coefficient on impact cratering were parameterized and incorporated into π group scaling laws, and predict transient crater diameters within an accuracy of ±5\\% for targets with friction coefficients f ≥ 0.4 and porosities Φ = 0–30\\%. Moreover, 90 crater scaling relationships are made available and can be used to estimate transient crater diameters on various terrains and geological units with different coefficient of friction, porosity, and cohesion. The derived relationships are most robust for targets with Φ {\\textgreater} 10–15\\%, applicable for a lunar environment, and could therefore yield significant insights into the influence of target properties on cratering statistics.},\n\tlanguage = {en},\n\tnumber = {8},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Prieur, N. C. and Rolf, T. and Luther, R. and Wünnemann, K. and Xiao, Z. and Werner, S. C.},\n\tmonth = aug,\n\tyear = {2017},\n\tkeywords = {5420 Impact phenomena, cratering, 6250 Moon, CRATERING, Impact processes, Moon, target properties},\n\tpages = {2017JE005283},\n}\n\n

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\n \n\n \n \n Rae, A. S. P.; Collins, G. S.; Grieve, R. A. F.; Osinski, G. R.; and Morgan, J. V.\n\n\n \n \n \n \n \n Complex crater formation: Insights from combining observations of shock pressure distribution with numerical models at the West Clearwater Lake impact structure.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science,1330–1350. 2017.\n \n\n\n\n
\n\n\n\n \n \n $\"Complex$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{rae_complex_2017,\n\ttitle = {Complex crater formation: {Insights} from combining observations of shock pressure distribution with numerical models at the {West} {Clearwater} {Lake} impact structure},\n\tissn = {1945-5100},\n\tshorttitle = {Complex crater formation},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12825/abstract},\n\tdoi = {10.1111/maps.12825},\n\tabstract = {Large impact structures have complex morphologies, with zones of structural uplift that can be expressed topographically as central peaks and/or peak rings internal to the crater rim. The formation of these structures requires transient strength reduction in the target material and one of the proposed mechanisms to explain this behavior is acoustic fluidization. Here, samples of shock-metamorphosed quartz-bearing lithologies at the West Clearwater Lake impact structure, Canada, are used to estimate the maximum recorded shock pressures in three dimensions across the crater. These measurements demonstrate that the currently observed distribution of shock metamorphism is strongly controlled by the formation of the structural uplift. The distribution of peak shock pressures, together with apparent crater morphology and geological observations, is compared with numerical impact simulations to constrain parameters used in the block-model implementation of acoustic fluidization. The numerical simulations produce craters that are consistent with morphological and geological observations. The results show that the regeneration of acoustic energy must be an important feature of acoustic fluidization in crater collapse, and should be included in future implementations. Based on the comparison between observational data and impact simulations, we conclude that the West Clearwater Lake structure had an original rim (final crater) diameter of 35–40 km and has since experienced up to {\\textasciitilde}2 km of differential erosion.},\n\tlanguage = {en},\n\turldate = {2017-02-10},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Rae, A. S. P. and Collins, G. S. and Grieve, R. A. F. and Osinski, G. R. and Morgan, J. V.},\n\tyear = {2017},\n\tpages = {1330--1350},\n}\n\n

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\n \n\n \n \n Monteux, J.; and Arkani-Hamed, J.\n\n\n \n \n \n \n \n Scaling laws of impact induced shock pressure and particle velocity in planetary mantle.\n \n \n \n \n\n\n \n\n\n\n Icarus, 264: 246–256. January 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Scaling$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{monteux_scaling_2016,\n\ttitle = {Scaling laws of impact induced shock pressure and particle velocity in planetary mantle},\n\tvolume = {264},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103515004546},\n\tdoi = {10.1016/j.icarus.2015.09.040},\n\tabstract = {While major impacting bodies during accretion of a Mars type planet have very low velocities ({\\textless}10km/s), the characteristics of the shockwave propagation and, hence, the derived scaling laws are poorly known for these low velocity impacts. Here, we use iSALE-2D hydrocode simulations to calculate shock pressure and particle velocity in a Mars type body for impact velocities ranging from 4 to 10km/s. Large impactors of 100–400km in diameter, comparable to those impacted on Mars and created giant impact basins, are examined. To better represent the power law distribution of shock pressure and particle velocity as functions of distance from the impact site at the surface, we propose three distinct regions in the mantle: a near field regime, which extends to 1–3 times the projectile radius into the target, where the peak shock pressure and particle velocity decay very slowly with increasing distance, a mid field region, which extends to ∼4.5 times the impactor radius, where the pressure and particle velocity decay exponentially but moderately, and a more distant far field region where the pressure and particle velocity decay strongly with distance. These scaling laws are useful to determine impact heating of a growing proto-planet by numerous accreting bodies.},\n\turldate = {2018-08-06},\n\tjournal = {Icarus},\n\tauthor = {Monteux, J. and Arkani-Hamed, J.},\n\tmonth = jan,\n\tyear = {2016},\n\tkeywords = {Accretion, Impact processes, Interiors, Terrestrial planets, Thermal histories},\n\tpages = {246--256},\n}\n\n

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\n \n\n \n \n Johnson, B. C.; Blair, D. M.; Collins, G. S.; Melosh, H. J.; Freed, A. M.; Taylor, G. J.; Head, J. W.; Wieczorek, M. A.; Andrews-Hanna, J. C.; Nimmo, F.; Keane, J. T.; Miljković, K.; Soderblom, J. M.; and Zuber, M. T.\n\n\n \n \n \n \n \n Formation of the Orientale lunar multiring basin.\n \n \n \n \n\n\n \n\n\n\n Science, 354(6311): 441–444. October 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Formation$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{johnson_formation_2016,\n\ttitle = {Formation of the {Orientale} lunar multiring basin},\n\tvolume = {354},\n\tcopyright = {Copyright © 2016, American Association for the Advancement of Science},\n\tissn = {0036-8075, 1095-9203},\n\turl = {http://science.sciencemag.org/content/354/6311/441},\n\tdoi = {10.1126/science.aag0518},\n\tabstract = {titOn the origin of Orientale basinle\nOrientale basin is a major impact crater on the Moon, which is hard to see from Earth because it is right on the western edge of the lunar nearside. Relatively undisturbed by later events, Orientale serves as a prototype for understanding large impact craters throughout the solar system. Zuber et al. used the Gravity Recovery and Interior Laboratory (GRAIL) mission to map the gravitational field around the crater in great detail by flying the twin spacecraft as little as 2 km above the surface. Johnson et al. performed a sophisticated computer simulation of the impact and its subsequent evolution, designed to match the data from GRAIL. Together, these studies reveal how major impacts affect the lunar surface and will aid our understanding of other impacts on rocky planets and moons.\nScience, this issue pp. 438 and 441\nMultiring basins, large impact craters characterized by multiple concentric topographic rings, dominate the stratigraphy, tectonics, and crustal structure of the Moon. Using a hydrocode, we simulated the formation of the Orientale multiring basin, producing a subsurface structure consistent with high-resolution gravity data from the Gravity Recovery and Interior Laboratory (GRAIL) spacecraft. The simulated impact produced a transient crater, {\\textasciitilde}390 kilometers in diameter, that was not maintained because of subsequent gravitational collapse. Our simulations indicate that the flow of warm weak material at depth was crucial to the formation of the basin’s outer rings, which are large normal faults that formed at different times during the collapse stage. The key parameters controlling ring location and spacing are impactor diameter and lunar thermal gradients.\nA two-step isothermal process converts carbon dioxide and methane into carbon monoxide for chemical and fuel production\nA two-step isothermal process converts carbon dioxide and methane into carbon monoxide for chemical and fuel production},\n\tlanguage = {en},\n\tnumber = {6311},\n\turldate = {2016-10-31},\n\tjournal = {Science},\n\tauthor = {Johnson, Brandon C. and Blair, David M. and Collins, Gareth S. and Melosh, H. Jay and Freed, Andrew M. and Taylor, G. Jeffrey and Head, James W. and Wieczorek, Mark A. and Andrews-Hanna, Jeffrey C. and Nimmo, Francis and Keane, James T. and Miljković, Katarina and Soderblom, Jason M. and Zuber, Maria T.},\n\tmonth = oct,\n\tyear = {2016},\n\tpmid = {27789836},\n\tpages = {441--444},\n}\n\n

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\n \n\n \n \n Kendall, J. D.; and Melosh, H. J.\n\n\n \n \n \n \n \n Differentiated planetesimal impacts into a terrestrial magma ocean: Fate of the iron core.\n \n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 448: 24–33. August 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Differentiated$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{kendall_differentiated_2016,\n\ttitle = {Differentiated planetesimal impacts into a terrestrial magma ocean: {Fate} of the iron core},\n\tvolume = {448},\n\tissn = {0012-821X},\n\tshorttitle = {Differentiated planetesimal impacts into a terrestrial magma ocean},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0012821X16302217},\n\tdoi = {10.1016/j.epsl.2016.05.012},\n\tabstract = {The abundance of moderately siderophile elements (“iron-loving”; e.g. Co, Ni) in the Earth's mantle is 10 to 100 times larger than predicted by chemical equilibrium between silicate melt and iron at low pressure, but it does match expectation for equilibrium at high pressure and temperature. Recent studies of differentiated planetesimal impacts assume that planetesimal cores survive the impact intact as concentrated masses that passively settle from a zero initial velocity and undergo turbulent entrainment in a global magma ocean; under these conditions, cores greater than 10 km in diameter do not fully mix without a sufficiently deep magma ocean. We have performed hydrocode simulations that revise this assumption and yield a clearer picture of the impact process for differentiated planetesimals possessing iron cores with radius = 100 km that impact into magma oceans. The impact process strips away the silicate mantle of the planetesimal and then stretches the iron core, dispersing the liquid iron into a much larger volume of the underlying liquid silicate mantle. Lagrangian tracer particles track the initially intact iron core as the impact stretches and disperses the core. The final displacement distance of initially closest tracer pairs gives a metric of core stretching. The statistics of stretching imply mixing that separates the iron core into sheets, ligaments, and smaller fragments, on a scale of 10 km or less. The impact dispersed core fragments undergo further mixing through turbulent entrainment as the molten iron fragments rain through the magma ocean and settle deeper into the planet. Our results thus support the idea that iron in the cores of even large differentiated planetesimals can chemically equilibrate deep in a terrestrial magma ocean.},\n\turldate = {2016-08-23},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Kendall, Jordan D. and Melosh, H. J.},\n\tmonth = aug,\n\tyear = {2016},\n\tkeywords = {Accretion, differentiation, planetesimal dispersion, planetesimal impact, siderophile abundance},\n\tpages = {24--33},\n}\n\n

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\n \n\n \n \n Kowitz, A.; Güldemeister, N.; Schmitt, R. T.; Reimold, W.; Wünnemann, K.; and Holzwarth, A.\n\n\n \n \n \n \n \n Revision and recalibration of existing shock classifications for quartzose rocks using low-shock pressure (2.5–20 GPa) recovery experiments and mesoscale numerical modeling.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 51(10): 1741–1761. October 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Revision$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{kowitz_revision_2016,\n\ttitle = {Revision and recalibration of existing shock classifications for quartzose rocks using low-shock pressure (2.5–20 {GPa}) recovery experiments and mesoscale numerical modeling},\n\tvolume = {51},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12712/abstract},\n\tdoi = {10.1111/maps.12712},\n\tabstract = {A combination of shock recovery experiments and numerical modeling of shock deformation in the low-shock pressure range from 2.5 to 20 GPa for two dry sandstone types of different porosity, a completely water-saturated sandstone, and a well-indurated quartzite provides new insights into strongly heterogeneous distribution of different shock features. (1) For nonporous quartzo-feldspathic rocks, the traditional classification scheme (Stöffler ) is suitable with slight changes in pressure calibration. (2) For water-saturated quartzose rocks, a cataclastic texture (microbreccia) seems to be typical for the shock pressure range up to 20 GPa. This microbreccia does not show formation of PDFs but diaplectic quartz glass/SiO2 melt is formed at 20 GPa ({\\textasciitilde}1 vol\\%). (3) For porous quartzose rocks, the following sequence of shock features is observed with progressive increase in shock pressure (1) crushing of pores, (2) intense fracturing of quartz grains, and (3) increasing formation of diaplectic quartz glass/SiO2 melt replacing fracturing. The formation of diaplectic quartz glass/SiO2 melt, together with SiO2 high-pressure phases, is a continuous process that strongly depends on porosity. This experimental observation is confirmed by our concomitant numerical modeling. Recalibration of the shock classification scheme results in a porosity versus shock pressure diagram illustrating distinct boundaries for the different shock stages.},\n\tlanguage = {en},\n\tnumber = {10},\n\turldate = {2017-01-12},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Kowitz, Astrid and Güldemeister, Nicole and Schmitt, Ralf Thomas and Reimold, Wolf-Uwe and Wünnemann, Kai and Holzwarth, Andreas},\n\tmonth = oct,\n\tyear = {2016},\n\tpages = {1741--1761},\n}\n\n

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\n \n\n \n \n Kring, D. A.; Kramer, G. Y.; Collins, G. S.; Potter, R. W. K.; and Chandnani, M.\n\n\n \n \n \n \n \n Peak-ring structure and kinematics from a multi-disciplinary study of the Schrödinger impact basin.\n \n \n \n \n\n\n \n\n\n\n Nature Communications, 7: 13161. October 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Peak-ring$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{kring_peak-ring_2016,\n\ttitle = {Peak-ring structure and kinematics from a multi-disciplinary study of the {Schrödinger} impact basin},\n\tvolume = {7},\n\tissn = {2041-1723},\n\turl = {http://www.nature.com/doifinder/10.1038/ncomms13161},\n\tdoi = {10.1038/ncomms13161},\n\turldate = {2016-10-31},\n\tjournal = {Nature Communications},\n\tauthor = {Kring, David A. and Kramer, Georgiana Y. and Collins, Gareth S. and Potter, Ross W. K. and Chandnani, Mitali},\n\tmonth = oct,\n\tyear = {2016},\n\tpages = {13161},\n}\n\n

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\n \n\n \n \n Morgan, J. V.; Gulick, S. P. S.; Bralower, T.; Chenot, E.; Christeson, G.; Claeys, P.; Cockell, C.; Collins, G. S.; Coolen, M. J. L.; Ferrière, L.; Gebhardt, C.; Goto, K.; Jones, H.; Kring, D. A.; Ber, E. L.; Lofi, J.; Long, X.; Lowery, C.; Mellett, C.; Ocampo-Torres, R.; Osinski, G. R.; Perez-Cruz, L.; Pickersgill, A.; Poelchau, M.; Rae, A.; Rasmussen, C.; Rebolledo-Vieyra, M.; Riller, U.; Sato, H.; Schmitt, D. R.; Smit, J.; Tikoo, S.; Tomioka, N.; Urrutia-Fucugauchi, J.; Whalen, M.; Wittmann, A.; Yamaguchi, K. E.; and Zylberman, W.\n\n\n \n \n \n \n \n The formation of peak rings in large impact craters.\n \n \n \n \n\n\n \n\n\n\n Science, 354(6314): 878–882. November 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{morgan_formation_2016,\n\ttitle = {The formation of peak rings in large impact craters},\n\tvolume = {354},\n\tcopyright = {Copyright © 2016, American Association for the Advancement of Science},\n\tissn = {0036-8075, 1095-9203},\n\turl = {http://science.sciencemag.org/content/354/6314/878},\n\tdoi = {10.1126/science.aah6561},\n\tabstract = {Drilling into Chicxulub's formation\nThe Chicxulub impact crater, known for its link to the demise of the dinosaurs, also provides an opportunity to study rocks from a large impact structure. Large impact craters have “peak rings” that define a complex crater morphology. Morgan et al. looked at rocks from a drilling expedition through the peak rings of the Chicxulub impact crater (see the Perspective by Barton). The drill cores have features consistent with a model that postulates that a single over-heightened central peak collapsed into the multiple-peak-ring structure. The validity of this model has implications for far-ranging subjects, from how giant impacts alter the climate on Earth to the morphology of crater-dominated planetary surfaces.\nScience, this issue p. 878; see also p. 836\nLarge impacts provide a mechanism for resurfacing planets through mixing near-surface rocks with deeper material. Central peaks are formed from the dynamic uplift of rocks during crater formation. As crater size increases, central peaks transition to peak rings. Without samples, debate surrounds the mechanics of peak-ring formation and their depth of origin. Chicxulub is the only known impact structure on Earth with an unequivocal peak ring, but it is buried and only accessible through drilling. Expedition 364 sampled the Chicxulub peak ring, which we found was formed from uplifted, fractured, shocked, felsic basement rocks. The peak-ring rocks are cross-cut by dikes and shear zones and have an unusually low density and seismic velocity. Large impacts therefore generate vertical fluxes and increase porosity in planetary crust.\nRock samples from IODP/ICDP Expedition 364 support the dynamic collapse model for the formation of the Chicxulub crater.\nRock samples from IODP/ICDP Expedition 364 support the dynamic collapse model for the formation of the Chicxulub crater.},\n\tlanguage = {en},\n\tnumber = {6314},\n\turldate = {2016-11-18},\n\tjournal = {Science},\n\tauthor = {Morgan, Joanna V. and Gulick, Sean P. S. and Bralower, Timothy and Chenot, Elise and Christeson, Gail and Claeys, Philippe and Cockell, Charles and Collins, Gareth S. and Coolen, Marco J. L. and Ferrière, Ludovic and Gebhardt, Catalina and Goto, Kazuhisa and Jones, Heather and Kring, David A. and Ber, Erwan Le and Lofi, Johanna and Long, Xiao and Lowery, Christopher and Mellett, Claire and Ocampo-Torres, Rubén and Osinski, Gordon R. and Perez-Cruz, Ligia and Pickersgill, Annemarie and Poelchau, Michael and Rae, Auriol and Rasmussen, Cornelia and Rebolledo-Vieyra, Mario and Riller, Ulrich and Sato, Honami and Schmitt, Douglas R. and Smit, Jan and Tikoo, Sonia and Tomioka, Naotaka and Urrutia-Fucugauchi, Jaime and Whalen, Michael and Wittmann, Axel and Yamaguchi, Kosei E. and Zylberman, William},\n\tmonth = nov,\n\tyear = {2016},\n\tpages = {878--882},\n}\n\n

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\n \n\n \n \n Wünnemann, K.; Zhu, M.; and Stöffler, D.\n\n\n \n \n \n \n \n Impacts into quartz sand: Crater formation, shock metamorphism, and ejecta distribution in laboratory experiments and numerical models.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science,1762–1794. August 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Impacts$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{wunnemann_impacts_2016,\n\ttitle = {Impacts into quartz sand: {Crater} formation, shock metamorphism, and ejecta distribution in laboratory experiments and numerical models},\n\tissn = {1945-5100},\n\tshorttitle = {Impacts into quartz sand},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12710/abstract},\n\tdoi = {10.1111/maps.12710},\n\tabstract = {We investigated the ejection mechanics by a complementary approach of cratering experiments, including the microscopic analysis of material sampled from these experiments, and 2-D numerical modeling of vertical impacts. The study is based on cratering experiments in quartz sand targets performed at the NASA Ames Vertical Gun Range. In these experiments, the preimpact location in the target and the final position of ejecta was determined by using color-coded sand and a catcher system for the ejecta. The results were compared with numerical simulations of the cratering and ejection process to validate the iSALE shock physics code. In turn the models provide further details on the ejection velocities and angles. We quantify the general assumption that ejecta thickness decreases with distance according to a power-law and that the relative proportion of shocked material in the ejecta increase with distance. We distinguish three types of shock metamorphic particles (1) melt particles, (2) shock lithified aggregates, and (3) shock-comminuted grains. The agreement between experiment and model was excellent, which provides confidence that the models can predict ejection angles, velocities, and the degree of shock loading of material expelled from a crater accurately if impact parameters such as impact velocity, impactor size, and gravity are varied beyond the experimental limitations. This study is relevant for a quantitative assessment of impact gardening on planetary surfaces and the evolution of regolith layers on atmosphereless bodies.},\n\tlanguage = {en},\n\turldate = {2016-08-23},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Wünnemann, Kai and Zhu, Meng-Hua and Stöffler, Dieter},\n\tmonth = aug,\n\tyear = {2016},\n\tpages = {1762--1794},\n}\n\n

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\n \n\n \n \n Baker, D. M. H.; Head, J. W.; Collins, G. S.; and Potter, R. W. K.\n\n\n \n \n \n \n \n The formation of peak-ring basins: Working hypotheses and path forward in using observations to constrain models of impact-basin formation.\n \n \n \n \n\n\n \n\n\n\n Icarus, 273: 146–163. July 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{baker_formation_2016,\n\ttitle = {The formation of peak-ring basins: {Working} hypotheses and path forward in using observations to constrain models of impact-basin formation},\n\tvolume = {273},\n\tissn = {0019-1035},\n\tshorttitle = {The formation of peak-ring basins},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103515005527},\n\tdoi = {10.1016/j.icarus.2015.11.033},\n\tabstract = {Impact basins provide windows into the crustal structure and stratigraphy of planetary bodies; however, interpreting the stratigraphic origin of basin materials requires an understanding of the processes controlling basin formation and morphology. Peak-ring basins (exhibiting a rim crest and single interior ring of peaks) provide important insight into the basin-formation process, as they are transitional between complex craters with central peaks and larger multi-ring basins. New image and altimetry data from the Lunar Reconnaissance Orbiter as well as a suite of remote sensing datasets have permitted a reassessment of the origin of lunar peak-ring basins. We synthesize morphometric, spectroscopic, and gravity observations of lunar peak-ring basins and describe two working hypotheses for the formation of peak rings that involve interactions between inward collapsing walls of the transient cavity and large central uplifts of the crust and mantle. Major facets of our observations are then compared and discussed in the context of numerical simulations of peak-ring basin formation in order to plot a course for future model refinement and development.},\n\turldate = {2017-03-30},\n\tjournal = {Icarus},\n\tauthor = {Baker, David M. H. and Head, James W. and Collins, Gareth S. and Potter, Ross W. K.},\n\tmonth = jul,\n\tyear = {2016},\n\tkeywords = {CRATERING, Impact processes, Moon, Moon, surface},\n\tpages = {146--163},\n}\n\n

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\n \n\n \n \n Collins, G. S.; Elbeshausen, D.; Davison, T. M.; Wünnemann, K.; Ivanov, B.; and Melosh, H. J.\n\n\n \n \n \n \n \n iSALE-Dellen manual.\n \n \n \n \n\n\n \n\n\n\n Figshare,136 pages. July 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"iSALE-Dellen$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 5 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n\n\n\n

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@article{collins_isale-dellen_2016,\n\ttitle = {{iSALE}-{Dellen} manual},\n\turl = {https://figshare.com/articles/iSALE-Dellen_manual/3473690},\n\tdoi = {10.6084/m9.figshare.3473690},\n\tabstract = {Manual for the Dellen release of the iSALE shock physics code:\n\n\n\n\n\n\n\nA multi-material, multi-rheology shock physics code for simulating impact phenomena in two and three dimensions.},\n\turldate = {2016-07-15},\n\tjournal = {Figshare},\n\tauthor = {Collins, Gareth S. and Elbeshausen, Dirk and Davison, Thomas M. and Wünnemann, Kai and Ivanov, Boris and Melosh, H. Jay},\n\tmonth = jul,\n\tyear = {2016},\n\tkeywords = {Dellen, iSALE},\n\tpages = {136 pages},\n}\n\n

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\n \n\n \n \n Davison, T. M.; Collins, G. S.; and Bland, P. A.\n\n\n \n \n \n \n \n Mesoscale Modeling of Impact Compaction of Primitive Solar System Solids.\n \n \n \n \n\n\n \n\n\n\n The Astrophysical Journal, 821(1): 68. 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Mesoscale$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{davison_mesoscale_2016,\n\ttitle = {Mesoscale {Modeling} of {Impact} {Compaction} of {Primitive} {Solar} {System} {Solids}},\n\tvolume = {821},\n\tissn = {0004-637X},\n\turl = {http://stacks.iop.org/0004-637X/821/i=1/a=68},\n\tdoi = {10.3847/0004-637X/821/1/68},\n\tabstract = {We have developed a method for simulating the mesoscale compaction of early solar system solids in low-velocity impact events using the iSALE shock physics code. Chondrules are represented by non-porous disks, placed within a porous matrix. By simulating impacts into bimodal mixtures over a wide range of parameter space (including the chondrule-to-matrix ratio, the matrix porosity and composition, and the impact velocity), we have shown how each of these parameters influences the shock processing of heterogeneous materials. The temperature after shock processing shows a strong dichotomy: matrix temperatures are elevated much higher than the chondrules, which remain largely cold. Chondrules can protect some matrix from shock compaction, with shadow regions in the lee side of chondrules exhibiting higher porosity that elsewhere in the matrix. Using the results from this mesoscale modeling, we show how the ε − α porous-compaction model parameters depend on initial bulk porosity. We also show that the timescale for the temperature dichotomy to equilibrate is highly dependent on the porosity of the matrix after the shock, and will be on the order of seconds for matrix porosities of less than 0.1, and on the order of tens to hundreds of seconds for matrix porosities of ∼0.3–0.5. Finally, we have shown that the composition of the post-shock material is able to match the bulk porosity and chondrule-to-matrix ratios of meteorite groups such as carbonaceous chondrites and unequilibrated ordinary chondrites.},\n\tlanguage = {en},\n\tnumber = {1},\n\turldate = {2016-04-15},\n\tjournal = {The Astrophysical Journal},\n\tauthor = {Davison, Thomas M. and Collins, Gareth S. and Bland, Philip A.},\n\tyear = {2016},\n\tpages = {68},\n}\n\n

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\n \n\n \n \n Forman, L. V.; Bland, P. A.; Timms, N. E.; Collins, G. S.; Davison, T. M.; Ciesla, F. J.; Benedix, G. K.; Daly, L.; Trimby, P. W.; Yang, L.; and Ringer, S. P.\n\n\n \n \n \n \n \n Hidden secrets of deformation: Impact-induced compaction within a CV chondrite.\n \n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 452: 133–145. October 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Hidden$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{forman_hidden_2016,\n\ttitle = {Hidden secrets of deformation: {Impact}-induced compaction within a {CV} chondrite},\n\tvolume = {452},\n\tissn = {0012-821X},\n\tshorttitle = {Hidden secrets of deformation},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0012821X1630406X},\n\tdoi = {10.1016/j.epsl.2016.07.050},\n\tabstract = {The CV3 Allende is one of the most extensively studied meteorites in worldwide collections. It is currently classified as S1—essentially unshocked—using the classification scheme of Stöffler et al. (1991), however recent modelling suggests the low porosity observed in Allende indicates the body should have undergone compaction-related deformation. In this study, we detail previously undetected evidence of impact through use of Electron Backscatter Diffraction mapping to identify deformation microstructures in chondrules, AOAs and matrix grains. Our results demonstrate that forsterite-rich chondrules commonly preserve crystal-plastic microstructures (particularly at their margins); that low-angle boundaries in deformed matrix grains of olivine have a preferred orientation; and that disparities in deformation occur between chondrules, surrounding and non-adjacent matrix grains. We find heterogeneous compaction effects present throughout the matrix, consistent with a highly porous initial material. Given the spatial distribution of these crystal-plastic deformation microstructures, we suggest that this is evidence that Allende has undergone impact-induced compaction from an initially heterogeneous and porous parent body. We suggest that current shock classifications (Stöffler et al., 1991) relying upon data from chondrule interiors do not constrain the complete shock history of a sample.},\n\turldate = {2016-08-16},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Forman, L. V. and Bland, P. A. and Timms, N. E. and Collins, G. S. and Davison, T. M. and Ciesla, F. J. and Benedix, G. K. and Daly, L. and Trimby, P. W. and Yang, L. and Ringer, S. P.},\n\tmonth = oct,\n\tyear = {2016},\n\tkeywords = {Allende, Meteorite, compaction, crystallography, deformation, impact},\n\tpages = {133--145},\n}\n\n

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\n \n\n \n \n Johnson, B. C.; Collins, G. S.; Minton, D. A.; Bowling, T. J.; Simonson, B. M.; and Zuber, M. T.\n\n\n \n \n \n \n \n Spherule layers, crater scaling laws, and the population of ancient terrestrial impactors.\n \n \n \n \n\n\n \n\n\n\n Icarus, 271: 350–359. June 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Spherule$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{johnson_spherule_2016,\n\ttitle = {Spherule layers, crater scaling laws, and the population of ancient terrestrial impactors},\n\tvolume = {271},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103516000907},\n\tdoi = {10.1016/j.icarus.2016.02.023},\n\tabstract = {Ancient layers of impact spherules provide a record of Earth's early bombardment history. Here, we compare different bombardment histories to the spherule layer record and show that 3.2–3.5 Ga the flux of large impactors (10–100 km in diameter) was likely 20–40 times higher than today. The E-belt model of early Solar System dynamics suggests that an increased impactor flux during the Archean is the result of the destabilization of an inward extension of the main asteroid belt (Bottke et al., 2012). Here, we find that the nominal flux predicted by the E-belt model is 7–19 times too low to explain the spherule layer record. Moreover, rather than making most lunar basins younger than 4.1 Gyr old, the nominal E-belt model, coupled with a corrected crater diameter scaling law, only produces two lunar basins larger than 300 km in diameter. We also show that the spherule layer record when coupled with the lunar cratering record and careful consideration of crater scaling laws can constrain the size distribution of ancient terrestrial impactors. The preferred population is main-belt-like up to ∼50 km in diameter transitioning to a steep distribution going to larger sizes.},\n\turldate = {2016-04-05},\n\tjournal = {Icarus},\n\tauthor = {Johnson, Brandon C. and Collins, Gareth S. and Minton, David A. and Bowling, Timothy J. and Simonson, Bruce M. and Zuber, Maria T.},\n\tmonth = jun,\n\tyear = {2016},\n\tkeywords = {CRATERING, Earth, Moon, Near-Earth objects, Planetary dynamics},\n\tpages = {350--359},\n}\n\n

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\n \n\n \n \n Miljković, K.; Collins, G. S.; Wieczorek, M. A.; Johnson, B. C.; Soderblom, J. M.; Neumann, G. A.; and Zuber, M. T.\n\n\n \n \n \n \n \n Subsurface morphology and scaling of lunar impact basins.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 121(9): 2016JE005038. September 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Subsurface$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{miljkovic_subsurface_2016,\n\ttitle = {Subsurface morphology and scaling of lunar impact basins},\n\tvolume = {121},\n\tissn = {2169-9100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/2016JE005038/abstract},\n\tdoi = {10.1002/2016JE005038},\n\tabstract = {Impact bombardment during the first billion years after the formation of the Moon produced at least several tens of basins. The Gravity Recovery and Interior Laboratory (GRAIL) mission mapped the gravity field of these impact structures at significantly higher spatial resolution than previous missions, allowing for detailed subsurface and morphological analyses to be made across the entire globe. GRAIL-derived crustal thickness maps were used to define the regions of crustal thinning observed in centers of lunar impact basins, which represents a less unambiguous measure of a basin size than those based on topographic features. The formation of lunar impact basins was modeled numerically by using the iSALE-2D hydrocode, with a large range of impact and target conditions typical for the first billion years of lunar evolution. In the investigated range of impactor and target conditions, the target temperature had the dominant effect on the basin subsurface morphology. Model results were also used to update current impact scaling relationships applicable to the lunar setting (based on assumed target temperature). Our new temperature-dependent impact-scaling relationships provide estimates of impact conditions and transient crater diameters for the majority of impact basins mapped by GRAIL. As the formation of lunar impact basins is associated with the first {\\textasciitilde}700 Myr of the solar system evolution when the impact flux was considerably larger than the present day, our revised impact scaling relationships can aid further analyses and understanding of the extent of impact bombardment on the Moon and terrestrial planets in the early solar system.},\n\tlanguage = {en},\n\tnumber = {9},\n\turldate = {2016-12-20},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Miljković, K. and Collins, G. S. and Wieczorek, M. A. and Johnson, B. C. and Soderblom, J. M. and Neumann, G. A. and Zuber, M. T.},\n\tmonth = sep,\n\tyear = {2016},\n\tkeywords = {1221 Lunar and planetary geodesy and gravity, 5420 Impact phenomena, cratering, GRAIL, impact basin, lunar},\n\tpages = {2016JE005038},\n}\n\n

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\n \n\n \n \n Monteux, J.; Collins, G. S.; Tobie, G.; and Choblet, G.\n\n\n \n \n \n \n \n Consequences of large impacts on Enceladus’ core shape.\n \n \n \n \n\n\n \n\n\n\n Icarus, 264: 300–310. January 2016.\n \n\n\n\n
\n\n\n\n \n \n $\"Consequences$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{monteux_consequences_2016,\n\ttitle = {Consequences of large impacts on {Enceladus}’ core shape},\n\tvolume = {264},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103515004480},\n\tdoi = {10.1016/j.icarus.2015.09.034},\n\tabstract = {The intense activity on Enceladus suggests a differentiated interior consisting of a rocky core, an internal ocean and an icy mantle. However, topography and gravity data suggests large heterogeneity in the interior, possibly including significant core topography. In the present study, we investigated the consequences of collisions with large impactors on the core shape. We performed impact simulations using the code iSALE2D considering large differentiated impactors with radius ranging between 25 and 100 km and impact velocities ranging between 0.24 and 2.4 km/s. Our simulations showed that the main controlling parameters for the post-impact shape of Enceladus’ rock core are the impactor radius and velocity and to a lesser extent the presence of an internal water ocean and the porosity and strength of the rock core. For low energy impacts, the impactors do not pass completely through the icy mantle. Subsequent sinking and spreading of the impactor rock core lead to a positive core topographic anomaly. For moderately energetic impacts, the impactors completely penetrate through the icy mantle, inducing a negative core topography surrounded by a positive anomaly of smaller amplitude. The depth and lateral extent of the excavated area is mostly determined by the impactor radius and velocity. For highly energetic impacts, the rocky core is strongly deformed, and the full body is likely to be disrupted. Explaining the long-wavelength irregular shape of Enceladus’ core by impacts would imply multiple low velocity (\\&lt;2.4 km/s) collisions with deca-kilometric differentiated impactors, which is possible only after the LHB period.},\n\turldate = {2016-02-02},\n\tjournal = {Icarus},\n\tauthor = {Monteux, J. and Collins, G. S. and Tobie, G. and Choblet, G.},\n\tmonth = jan,\n\tyear = {2016},\n\tkeywords = {Accretion, CRATERING, Enceladus, Impact processes, Interiors},\n\tpages = {300--310},\n}\n\n

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\n \n\n \n \n Zhu, M.; Wünnemann, K.; and Potter, R. W. K.\n\n\n \n \n \n \n \n Numerical modeling of the ejecta distribution and formation of the Orientale basin on the Moon.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 120(12): 2118–2134. December 2015.\n \n\n\n\n
\n\n\n\n \n \n $\"Numerical$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{zhu_numerical_2015,\n\ttitle = {Numerical modeling of the ejecta distribution and formation of the {Orientale} basin on the {Moon}},\n\tvolume = {120},\n\tcopyright = {©2015. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2015JE004827},\n\tdoi = {10.1002/2015JE004827},\n\tabstract = {The formation and structure of the Orientale basin on the Moon has been extensively studied in the past; however, estimates of its transient crater size, excavated volume and depth, and ejecta distribution remain uncertain. Here we present a new numerical model to reinvestigate the formation and structure of Orientale basin and better constrain impact parameters such as impactor size and velocity. Unlike previous models, the observed ejecta distribution and ejecta thickness were used as the primary constraints to estimate transient crater size—the best measure of impact energy. Models were also compared to basin morphology and morphometry, and subsurface structures derived from high-resolution remote sensing observations and gravity data, respectively. The best fit model suggests a 100 km diameter impactor with a velocity of 12 km s−1 formed the Orientale basin on a relatively “cold” Moon. In this impact scenario the transient crater diameter is 400 km or 460 km depending on whether the crater is defined using the diameter of the excavation zone or the diameter of the growing cavity at the time of maximum crater volume, respectively. The volume of ejecta material is 4.70 × 106 km3, in agreement with recent estimates of the Orientale ejecta blanket thickness from remote sensing studies. The model also confirms the remote sensing spectroscopic observations that no mantle material was excavated and deposited at Orientale's rim.},\n\tlanguage = {en},\n\tnumber = {12},\n\turldate = {2018-08-06},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Zhu, Meng-Hua and Wünnemann, Kai and Potter, Ross W. K.},\n\tmonth = dec,\n\tyear = {2015},\n\tkeywords = {Moon, Orientale basin, numerical modeling},\n\tpages = {2118--2134},\n}\n\n

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\n \n\n \n \n Güldemeister, N.; Wünnemann, K.; and Poelchau, M.\n\n\n \n \n \n \n \n Scaling impact crater dimensions in cohesive rock by numerical modeling and laboratory experiments.\n \n \n \n \n\n\n \n\n\n\n In Osinski, G. R.; and Kring, D. A., editor(s), Large Meteorite Impacts and Planetary Evolution V. Geological Society of America, 2015.\n \n\n\n\n
\n\n\n\n \n \n $\"Scaling$ Paper\n \n \n\n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@incollection{guldemeister_scaling_2015,\n\ttitle = {Scaling impact crater dimensions in cohesive rock by numerical modeling and laboratory experiments},\n\tisbn = {978-0-8137-2518-5},\n\turl = {http://dx.doi.org/10.1130/2015.2518(02)},\n\tabstract = {Laboratory and numerical cratering experiments into sandstone and quartzite targets were carried out under conditions ranging from pure strength– to pure gravity–dominated crater formation. Numerical models were used to expand the process of crater formation beyond the strength-dominated laboratory impact experiments up to the gravity regime. We focused on the effect of strength and porosity on crater size and determined scaling parameters for two cohesive materials, sandstone and quartzite, over a range of crater sizes from the laboratory scale to large terrestrial craters. Crater volumes and diameters of experimental and modeling data were measured, and scaling laws were then used to determine μ values for these data in the strength and gravity regimes. These μ values range between 0.48 and 0.55 for sandstone and between 0.49 and 0.64 for quartzite. The scaled crater dimensions in numerical models agree quite well with experimental observations. An accurate definition of the strength parameter in pi-group scaling is crucial for predicting the crater size, in particular, in the transitional regime from strength to gravity scaling. We determined an effective strength value that accounts for the weakening of target material due to the accumulation of damage. Using the numerical models, we found an effective strength of 4.6 kPa for quartzite and 3.2 kPa for sandstone, which are almost five orders smaller than the quasi-static experimental strength values that only account for the intact state of the target material.},\n\turldate = {2017-07-28},\n\tbooktitle = {Large {Meteorite} {Impacts} and {Planetary} {Evolution} {V}},\n\tpublisher = {Geological Society of America},\n\tauthor = {Güldemeister, N. and Wünnemann, K. and Poelchau, M.H.},\n\teditor = {Osinski, Gordon R. and Kring, David A.},\n\tyear = {2015},\n}\n\n

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\n \n\n \n \n Milbury, C.; Johnson, B. C.; Melosh, H. J.; Collins, G. S.; Blair, D. M.; Soderblom, J. M.; Nimmo, F.; Bierson, C. J.; Phillips, R. J.; and Zuber, M. T.\n\n\n \n \n \n \n \n Preimpact porosity controls the gravity signature of lunar craters.\n \n \n \n \n\n\n \n\n\n\n Geophysical Research Letters, 42(22): 2015GL066198. November 2015.\n \n\n\n\n
\n\n\n\n \n \n $\"Preimpact$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{milbury_preimpact_2015,\n\ttitle = {Preimpact porosity controls the gravity signature of lunar craters},\n\tvolume = {42},\n\tissn = {1944-8007},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/2015GL066198/abstract},\n\tdoi = {10.1002/2015GL066198},\n\tabstract = {We model the formation of lunar complex craters and investigate the effect of preimpact porosity on their gravity signatures. We find that while preimpact target porosities less than {\\textasciitilde}7\\% produce negative residual Bouguer anomalies (BAs), porosities greater than {\\textasciitilde}7\\% produce positive anomalies whose magnitude is greater for impacted surfaces with higher initial porosity. Negative anomalies result from pore space creation due to fracturing and dilatant bulking, and positive anomalies result from destruction of pore space due to shock wave compression. The central BA of craters larger than {\\textasciitilde}215 km in diameter, however, are invariably positive because of an underlying central mantle uplift. We conclude that the striking differences between the gravity signatures of craters on the Earth and Moon are the result of the higher average porosity and variable porosity of the lunar crust.},\n\tlanguage = {en},\n\tnumber = {22},\n\turldate = {2016-02-02},\n\tjournal = {Geophysical Research Letters},\n\tauthor = {Milbury, C. and Johnson, B. C. and Melosh, H. J. and Collins, G. S. and Blair, D. M. and Soderblom, J. M. and Nimmo, F. and Bierson, C. J. and Phillips, R. J. and Zuber, M. T.},\n\tmonth = nov,\n\tyear = {2015},\n\tkeywords = {5417 Gravitational fields, 5470 Surface materials and properties, 5475 Tectonics, 8122 Dynamics: gravity and tectonics, 8135 Hydrothermal systems, GRAIL, Gravity Recovery and Interior Laboratory, Porosity, gravity, impact crater, lunar},\n\tpages = {2015GL066198},\n}\n\n

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\n \n\n \n \n Miljković, K.; Wieczorek, M. A.; Collins, G. S.; Solomon, S. C.; Smith, D. E.; and Zuber, M. T.\n\n\n \n \n \n \n \n Excavation of the lunar mantle by basin-forming impact events on the Moon.\n \n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 409: 243–251. January 2015.\n \n\n\n\n
\n\n\n\n \n \n $\"Excavation$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{miljkovic_excavation_2015,\n\ttitle = {Excavation of the lunar mantle by basin-forming impact events on the {Moon}},\n\tvolume = {409},\n\tissn = {0012-821X},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0012821X14006682},\n\tdoi = {10.1016/j.epsl.2014.10.041},\n\tabstract = {Global maps of crustal thickness on the Moon, derived from gravity measurements obtained by NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, have shown that the lunar crust is thinner than previously thought. Hyperspectral data obtained by the Kaguya mission have also documented areas rich in olivine that have been interpreted as material excavated from the mantle by some of the largest lunar impact events. Numerical simulations were performed with the iSALE-2D hydrocode to investigate the conditions under which mantle material may have been excavated during large impact events and where such material should be found. The results show that excavation of the mantle could have occurred during formation of the several largest impact basins on the nearside hemisphere as well as the Moscoviense basin on the farside hemisphere. Even though large areas in the central portions of these basins were later covered by mare basaltic lava flows, surficial lunar mantle deposits are predicted in areas external to these maria. Our results support the interpretation that the high olivine abundances detected by the Kaguya spacecraft could indeed be derived from the lunar mantle.},\n\turldate = {2014-11-28},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Miljković, Katarina and Wieczorek, Mark A. and Collins, Gareth S. and Solomon, Sean C. and Smith, David E. and Zuber, Maria T.},\n\tmonth = jan,\n\tyear = {2015},\n\tkeywords = {Moon, impact cratering, mantle},\n\tpages = {243--251},\n}\n\n

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\n \n\n \n \n Ormö, J.; Melero-Asensio, I.; Housen, K. R.; Wünnemann, K.; Elbeshausen, D.; and Collins, G. S.\n\n\n \n \n \n \n \n Scaling and reproducibility of craters produced at the Experimental Projectile Impact Chamber (EPIC), Centro de Astrobiología, Spain.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science,2067–2086. October 2015.\n \n\n\n\n
\n\n\n\n \n \n $\"Scaling$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{ormo_scaling_2015,\n\ttitle = {Scaling and reproducibility of craters produced at the {Experimental} {Projectile} {Impact} {Chamber} ({EPIC}), {Centro} de {Astrobiología}, {Spain}},\n\tcopyright = {© The Meteoritical Society, 2015.},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12560/abstract},\n\tdoi = {10.1111/maps.12560},\n\tabstract = {The Experimental Projectile Impact Chamber (EPIC) is a specially designed facility for the study of processes related to wet-target (e.g., “marine”) impacts. It consists of a 7 m wide, funnel-shaped test bed, and a 20.5 mm caliber compressed N2 gas gun. The target can be unconsolidated or liquid. The gas gun can launch 20 mm projectiles of various solid materials under ambient atmospheric pressure and at various angles from the horizontal. To test the functionality and quality of obtained results by EPIC, impacts were performed into dry beach sand targets with two different projectile materials; ceramic Al2O3 (max. velocity 290 m s−1) and Delrin (max. velocity 410 m s−1); 23 shots used a quarter-space setting (19 normal, 4 at 53° from horizontal) and 14 were in a half-space setting (13 normal, 1 at 53°). The experiments were compared with numerical simulations using the iSALE code. Differences were seen between the nondisruptive Al2O3 (ceramic) and the disruptive Delrin (polymer) projectiles in transient crater development. All final crater dimensions, when plotted in scaled form, agree reasonably well with the results of other studies of impacts into granular materials. We also successfully validated numerical models of vertical and oblique impacts in sand against the experimental results, as well as demonstrated that the EPIC quarter-space experiments are a reasonable approximation for half-space experiments. Altogether, the combined evaluation of experiments and numerical simulations support the usefulness of the EPIC in impact cratering studies.},\n\tlanguage = {en},\n\turldate = {2015-10-30},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Ormö, J. and Melero-Asensio, I. and Housen, K. R. and Wünnemann, K. and Elbeshausen, D. and Collins, G. S.},\n\tmonth = oct,\n\tyear = {2015},\n\tpages = {2067--2086},\n}\n\n

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\n \n\n \n \n Weiss, R.; Lynett, P.; and Wünnemann, K.\n\n\n \n \n \n \n \n The Eltanin impact and its tsunami along the coast of South America: Insights for potential deposits.\n \n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 409: 175–181. January 2015.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{weiss_eltanin_2015,\n\ttitle = {The {Eltanin} impact and its tsunami along the coast of {South} {America}: {Insights} for potential deposits},\n\tvolume = {409},\n\tissn = {0012-821X},\n\tshorttitle = {The {Eltanin} impact and its tsunami along the coast of {South} {America}},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0012821X14006773},\n\tdoi = {10.1016/j.epsl.2014.10.050},\n\tabstract = {The Eltanin impact occurred 2.15 million years ago in the Bellinghausen Sea in the southern Pacific. While a crater was not formed, evidence was left behind at the impact site to prove the impact origin. Previous studies suggest that a large tsunami formed, and sedimentary successions along the coast of South America have been attributed to the Eltanin impact tsunami. They are characterized by large clasts, often several meters in diameter. Our state-of-the-art numerical modeling of the impact process and its coupling with non-linear wave simulations allows for quantifying the initial wave characteristic and the propagation of tsunami-like waves over large distances. We find that the tsunami attenuates quickly with η ( r ) ∝ r − 1.2 resulting in maximum wave heights similar to those observed during the 2004 Sumatra and 2011 Tohoku-oki tsunamis. We compute a transport competence of the coastal flow and conclude that for the northernmost alleged tsunami deposits, especially for those in Hornitos, Chile, the transport competence is about two orders of magnitude too small to generate the observed deposits.},\n\turldate = {2014-12-02},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Weiss, Robert and Lynett, Patrick and Wünnemann, Kai},\n\tmonth = jan,\n\tyear = {2015},\n\tkeywords = {Eltanin impact, impact cratering, numerical simulations, tsunami modeling, tsunamis},\n\tpages = {175--181},\n}\n\n

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\n \n\n \n \n Asphaug, E.; Collins, G.; and Jutzi, M.\n\n\n \n \n \n \n Global Scale Impacts.\n \n \n \n\n\n \n\n\n\n In Michel, P.; Demeo, F. E.; and Bottke, W. F., editor(s), Asteroids IV, pages 661–678. University of Arizona Press, Tucson, Arizona, 2015.\n arXiv: 1504.02389\n\n\n\n
\n\n\n\n \n\n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n\n\n\n

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@incollection{asphaug_global_2015,\n\taddress = {Tucson, Arizona},\n\ttitle = {Global {Scale} {Impacts}},\n\tabstract = {Global scale impacts modify the physical or thermal state of a substantial fraction of a target asteroid. Specific effects include accretion, family formation, reshaping, mixing and layering, shock and frictional heating, fragmentation, material compaction, dilatation, stripping of mantle and crust, and seismic degradation. Deciphering the complicated record of global scale impacts, in asteroids and meteorites, will lead us to understand the original planet-forming process and its resultant populations, and their evolution in time as collisions became faster and fewer. We provide a brief overview of these ideas, and an introduction to models.},\n\tbooktitle = {Asteroids {IV}},\n\tpublisher = {University of Arizona Press},\n\tauthor = {Asphaug, Erik and Collins, Gareth and Jutzi, Martin},\n\teditor = {Michel, Patrick and Demeo, Francesca E. and Bottke, William F.},\n\tyear = {2015},\n\tnote = {arXiv: 1504.02389},\n\tkeywords = {Astrophysics - Earth and Planetary Astrophysics},\n\tpages = {661--678},\n}\n\n

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\n \n\n \n \n Potter, R. W. K.\n\n\n \n \n \n \n \n Investigating the onset of multi-ring impact basin formation.\n \n \n \n \n\n\n \n\n\n\n Icarus, 261: 91–99. November 2015.\n \n\n\n\n
\n\n\n\n \n \n $\"Investigating$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{potter_investigating_2015,\n\ttitle = {Investigating the onset of multi-ring impact basin formation},\n\tvolume = {261},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S001910351500353X},\n\tdoi = {10.1016/j.icarus.2015.08.009},\n\tabstract = {Multi-ring basins represent some of the largest, oldest, rarest and, therefore, least understood impact crater structures. Various theories have been put forward to explain their formation; there is currently, however, no consensus. Here, numerical modeling is used to investigate the onset of multi-ring basin formation on the Moon using two thermal profiles suitable for the lunar basin-forming epoch. Various multi-ring basin formation hypotheses are discussed, compared, and evaluated against target deformation and strain distribution in the models, as well as geological and geophysical observations. The mechanism that most closely resembles the numerical models in terms of basin formation and structure, as well as observations, appears to be the ring tectonic theory, whereby ring formation is dependent on transient cavities penetrating entirely through the Moon’s lithosphere into the asthenosphere below. The numerical models suggest that all lunar basins larger than Schrödinger (320 km diameter) should be capable of forming multiple rings, as their transient cavities penetrate into the asthenosphere for both thermal profiles. Additionally, the models demonstrate that the target’s thermal profile starts to influence basin formation and structure when impact energy exceeds that of the Schrödinger event.},\n\turldate = {2016-04-13},\n\tjournal = {Icarus},\n\tauthor = {Potter, Ross W. K.},\n\tmonth = nov,\n\tyear = {2015},\n\tkeywords = {CRATERING, Impact processes, Moon, interior, Moon, surface, Tectonics},\n\tpages = {91--99},\n}\n\n

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\n \n\n \n \n Potter, R. W. K.; Kring, D. A.; and Collins, G. S.\n\n\n \n \n \n \n \n Scaling of basin-sized impacts and the influence of target temperature.\n \n \n \n \n\n\n \n\n\n\n Geological Society of America Special Papers, 518: SPE518–06. September 2015.\n \n\n\n\n
\n\n\n\n \n \n $\"Scaling$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{potter_scaling_2015,\n\ttitle = {Scaling of basin-sized impacts and the influence of target temperature},\n\tvolume = {518},\n\tissn = {0072-1077,},\n\turl = {http://specialpapers.gsapubs.org/content/early/2015/09/17/2015.2518_06},\n\tdoi = {10.1130/2015.2518(06)},\n\tabstract = {We produce a set of scaling laws for basin-sized impacts using data from a suite of lunar basin numerical models. The results demonstrate the importance of pre-impact target temperature and thermal gradient, which are shown to greatly influence the modification phase of the impact cratering process. Impacts into targets with contrasting thermal properties also produce very different crustal and topographic profiles for impacts of the same energy. Thermal conditions do not, however, significantly influence the excavation stage of the cratering process; results demonstrate, as a consequence of gravity-dominated growth, that transient crater radii are generally within 5\\% of each other over a wide range of thermal gradients. Excavation depth-to-diameter ratios for the basin models ({\\textasciitilde}0.12) agree well with experimental, geological, and geophysical estimates, suggesting basins follow proportional scaling. This is further demonstrated by an agreement between the basin models and Pi-scaling laws based upon first principles and experimental data. The results of this work should also be applicable to basin-scale impacts on other silicate bodies, including the Hadean Earth.},\n\tlanguage = {en},\n\turldate = {2016-02-02},\n\tjournal = {Geological Society of America Special Papers},\n\tauthor = {Potter, Ross W. K. and Kring, David A. and Collins, Gareth S.},\n\tmonth = sep,\n\tyear = {2015},\n\tpages = {SPE518--06},\n}\n\n

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\n \n\n \n \n Williams, D. A.; O'Brien, D. P.; Schenk, P. M.; Denevi, B. W.; Carsenty, U.; Marchi, S.; Scully, J. E. C.; Jaumann, R.; De Sanctis, M. C.; Palomba, E.; Ammannito, E.; Longobardo, A.; Magni, G.; Frigeri, A.; Russell, C. T.; Raymond, C. A.; Davison, T. M.; and Team, D. S.\n\n\n \n \n \n \n \n Lobate and flow-like features on asteroid Vesta.\n \n \n \n \n\n\n \n\n\n\n Planetary and Space Science, 103: 24–35. November 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"Lobate$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{williams_lobate_2014,\n\ttitle = {Lobate and flow-like features on asteroid {Vesta}},\n\tvolume = {103},\n\tissn = {0032-0633},\n\turl = {http://www.sciencedirect.com/science/article/pii/S003206331300158X},\n\tdoi = {10.1016/j.pss.2013.06.017},\n\tabstract = {We studied high-resolution images of asteroid Vesta's surface ({\\textasciitilde}70 and 20–25 m/pixel) obtained during the High- and Low-Altitude Mapping Orbits (HAMO, LAMO) of NASA's Dawn mission to assess the formation mechanisms responsible for a variety of lobate, flow-like features observed across the surface. We searched for evidence of volcanic flows, based on prior mathematical modeling and the well-known basaltic nature of Vesta's crust, but no unequivocal morphologic evidence of ancient volcanic activity has thus far been identified. Rather, we find that all lobate, flow-like features on Vesta appear to be related either to impact or erosional processes. Morphologically distinct lobate features occur in and around impact craters, and most of these are interpreted as impact ejecta flows, or possibly flows of impact melt. Estimates of melt production from numerical models and scaling laws suggests that large craters like Marcia ({\\textasciitilde}60 km diameter) could have potentially produced impact melt volumes ranging from tens of millions of cubic meters to a few tens of cubic kilometers, which are relatively small volumes compared to similar-sized lunar craters, but which are consistent with putative impact melt features observed in Dawn images. There are also examples of lobate flows that trend downhill both inside and outside of crater rims and basin scarps, which are interpreted as the result of gravity-driven mass movements (slumps and landslides).},\n\turldate = {2014-12-04},\n\tjournal = {Planetary and Space Science},\n\tauthor = {Williams, D. A. and O'Brien, D. P. and Schenk, P. M. and Denevi, B. W. and Carsenty, U. and Marchi, S. and Scully, J. E. C. and Jaumann, R. and De Sanctis, Maria Cristina and Palomba, E. and Ammannito, E. and Longobardo, A. and Magni, G. and Frigeri, A. and Russell, C. T. and Raymond, C. A. and Davison, T. M. and Dawn Science Team},\n\tmonth = nov,\n\tyear = {2014},\n\tkeywords = {Asteroids, Dawn, Vesta, \\_tablet, impact cratering},\n\tpages = {24--35},\n}\n\n

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\n \n\n \n \n Miljković, K.; Collins, G. S.; and Bland, P. A.\n\n\n \n \n \n \n \n Reply to comment on: “Supportive comment on: “Morphology and population of binary asteroid impact craters”, by K. Miljković, G.S. Collins, S. Mannick and P.A. Bland – An updated assessment”.\n \n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 405: 285–286. November 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"Reply$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n\n\n\n

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@article{miljkovic_reply_2014,\n\ttitle = {Reply to comment on: “{Supportive} comment on: “{Morphology} and population of binary asteroid impact craters”, by {K}. {Miljković}, {G}.{S}. {Collins}, {S}. {Mannick} and {P}.{A}. {Bland} – {An} updated assessment”},\n\tvolume = {405},\n\tissn = {0012-821X},\n\tshorttitle = {Reply to comment on},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0012821X14005329},\n\tdoi = {10.1016/j.epsl.2014.08.026},\n\tabstract = {In Miljković et al. (2013) we resolved the apparent contradiction that while 15\\% of the Near Earth Asteroid (impactor) population are binaries, only 2–4\\% of craters formed on Earth and Mars (target planet) are doublet craters. Using 3D hydrocode simulations to explore the physics of binary impacts, we showed that only 2\\% of binary asteroid impacts produced well-separated doublets, while the rest covered morphologies ranging from overlapping to elliptical or even circular. We then generated a complete classification dataset to aid in the identification of the (sometimes subtle) morphological characteristics consistent with a binary asteroid impact. We thank Schmieder et al. (2013) for providing additional detailed geochronological constraints which indicate that our lower bound of 2\\% doublet craters on Earth may in fact be ≤1.5\\%.},\n\turldate = {2014-11-28},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Miljković, Katarina and Collins, Gareth S. and Bland, Philip A.},\n\tmonth = nov,\n\tyear = {2014},\n\tkeywords = {crater population, doublet craters},\n\tpages = {285--286},\n}\n\n

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\n \n\n \n \n Davison, T. M.; Ciesla, F. J.; Collins, G. S.; and Elbeshausen, D.\n\n\n \n \n \n \n \n The effect of impact obliquity on shock heating in planetesimal collisions.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 49(12): 2252–2265. December 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{davison_effect_2014,\n\ttitle = {The effect of impact obliquity on shock heating in planetesimal collisions},\n\tvolume = {49},\n\tcopyright = {© The Meteoritical Society, 2014.},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12394/abstract},\n\tdoi = {10.1111/maps.12394},\n\tabstract = {Collisions between planetesimals in the early solar system were a common and fundamental process. Most collisions occurred at an oblique incidence angle, yet the influence of impact angle on heating in collisions is not fully understood. We have conducted a series of shock physics simulations to quantify oblique heating processes, and find that both impact angle and target curvature are important in quantifying the amount of heating in a collision. We find an expression to estimate the heating in an oblique collision compared to that in a vertical incidence collision. We have used this expression to quantify heating in the Rhealsilvia-forming impact on Vesta, and find that there is slightly more heating in a 45° impact than in a vertical impact. Finally, we apply these results to Monte Carlo simulations of collisional processes in the early solar system, and determine the overall effect of impact obliquity from the range of impacts that occurred on a meteorite parent body. For those bodies that survived 100 Myr without disruption, it is not necessary to account for the natural variation in impact angle, as the amount of heating was well approximated by a fixed impact angle of 45°. However, for disruptive impacts, this natural variation in impact angle should be accounted for, as around a quarter of bodies were globally heated by at least 100 K in a variable-angle model, an order of magnitude higher than under an assumption of a fixed angle of 45°.},\n\tlanguage = {en},\n\tnumber = {12},\n\turldate = {2015-09-02},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Davison, Thomas M. and Ciesla, Fred J. and Collins, Gareth S. and Elbeshausen, Dirk},\n\tmonth = dec,\n\tyear = {2014},\n\tpages = {2252--2265},\n}\n\n

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\n \n\n \n \n Bland, P. A.; Collins, G. S.; Davison, T. M.; Abreu, N. M.; Ciesla, F. J.; Muxworthy, A. R.; and Moore, J.\n\n\n \n \n \n \n \n Pressure–temperature evolution of primordial solar system solids during impact-induced compaction.\n \n \n \n \n\n\n \n\n\n\n Nature Communications, 5. December 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"Pressure–temperature$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n\n\n\n

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@article{bland_pressuretemperature_2014,\n\ttitle = {Pressure–temperature evolution of primordial solar system solids during impact-induced compaction},\n\tvolume = {5},\n\tcopyright = {© 2014 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.},\n\turl = {http://www.nature.com/ncomms/2014/141203/ncomms6451/full/ncomms6451.html},\n\tdoi = {10.1038/ncomms6451},\n\tabstract = {Prior to becoming chondritic meteorites, primordial solids were a poorly consolidated mix of mm-scale igneous inclusions (chondrules) and high-porosity sub-μm dust (matrix). We used high-resolution numerical simulations to track the effect of impact-induced compaction on these materials. Here we show that impact velocities as low as 1.5 km s−1 were capable of heating the matrix to {\\textgreater}1,000 K, with pressure–temperature varying by {\\textgreater}10 GPa and {\\textgreater}1,000 K over {\\textasciitilde}100 μm. Chondrules were unaffected, acting as heat-sinks: matrix temperature excursions were brief. As impact-induced compaction was a primary and ubiquitous process, our new understanding of its effects requires that key aspects of the chondrite record be re-evaluated: palaeomagnetism, petrography and variability in shock level across meteorite groups. Our data suggest a lithification mechanism for meteorites, and provide a ‘speed limit’ constraint on major compressive impacts that is inconsistent with recent models of solar system orbital architecture that require an early, rapid phase of main-belt collisional evolution.},\n\tlanguage = {en},\n\turldate = {2014-12-05},\n\tjournal = {Nature Communications},\n\tauthor = {Bland, P. A. and Collins, G. S. and Davison, T. M. and Abreu, N. M. and Ciesla, F. J. and Muxworthy, A. R. and Moore, J.},\n\tmonth = dec,\n\tyear = {2014},\n\tkeywords = {Earth sciences, Planetary sciences},\n}\n\n

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\n \n\n \n \n Bray, V. J.; Collins, G. S.; Morgan, J. V.; Melosh, H. J.; and Schenk, P. M.\n\n\n \n \n \n \n \n Hydrocode simulation of Ganymede and Europa cratering trends – How thick is Europa’s crust?.\n \n \n \n \n\n\n \n\n\n\n Icarus, 231: 394–406. March 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"Hydrocode$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{bray_hydrocode_2014,\n\ttitle = {Hydrocode simulation of {Ganymede} and {Europa} cratering trends – {How} thick is {Europa}’s crust?},\n\tvolume = {231},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103513005186},\n\tdoi = {10.1016/j.icarus.2013.12.009},\n\tabstract = {One of the continuing debates of outer Solar System research centers on the thickness of Europa’s ice crust, as it affects both the habitability and accessibility of its sub-surface ocean. Here we use hydrocode modeling of the impact process in layered ice and water targets and comparison to Europan cratering trends and Galileo-derived topographic profiles to investigate the crustal thickness. Full or partial penetration of the ice crust by an impactor occurred in simulations in which the ice thickness was less than 14 times the projectile radius. Craters produced in these thin-shell simulations were consistently smaller than for larger ice thicknesses, which will complicate inference of large impactor population sizes. Simulations in which the resultant crater was 3 times the ice layer thickness resulted in summit-pit morphology. This work supports that summit pit craters noted on both rocky and icy bodies, can be created by the presence of a weaker layer at depth. We suggest that floor pits, seen only on ice-rich bodies, require a different formation mechanism to summit pits.\nPristine craters formed in a target with high heat flow were shallower than for the same impact into a target of lesser heat flow, suggesting that the ‘starting’ crater morphology for viscous relaxation, isostatic readjustments and erosion rate studies is different for craters formed in times of different heat flow. We find that the crater depth–diameter trend of Europa can only be recreated when simulating impact into an upper brittle ice layer of 7 km depth, with a corresponding geothermal gradient of 0.025 K/m. As this ice thickness estimate is below ∼10 km, results from this work suggest that convective overturn of the surface ice may occur, or have occurred, on Europa making the development of indigenous life a possibility.},\n\turldate = {2014-03-27},\n\tjournal = {Icarus},\n\tauthor = {Bray, Veronica J. and Collins, Gareth S. and Morgan, Joanna V. and Melosh, H. Jay and Schenk, Paul M.},\n\tmonth = mar,\n\tyear = {2014},\n\tkeywords = {Astrobiology, CRATERING, Europa, Ganymede, Impact processes},\n\tpages = {394--406},\n}\n\n

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\n \n\n \n \n Collins, G. S.\n\n\n \n \n \n \n \n Numerical simulations of impact crater formation with dilatancy.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets,2014JE004708. December 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"Numerical$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{collins_numerical_2014,\n\ttitle = {Numerical simulations of impact crater formation with dilatancy},\n\tcopyright = {©2014. The Authors., This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.},\n\tissn = {2169-9100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/2014JE004708/abstract},\n\tdoi = {10.1002/2014JE004708},\n\tabstract = {Impact-induced fracturing creates porosity that is responsible for many aspects of the geophysical signature of an impact crater. This paper describes a simple model of dilatancy—the creation of porosity in a shearing geological material—and its implementation in the iSALE shock physics code. The model is used to investigate impact-induced dilatancy during simple and complex crater formation on Earth. Simulations of simple crater formation produce porosity distributions consistent with observations. Dilatancy model parameters appropriate for low-quality rock masses give the best agreement with observation; more strongly dilatant behavior would require substantial postimpact porosity reduction. The tendency for rock to dilate less when shearing under high pressure is an important property of the model. Pressure suppresses impact-induced dilatancy: in the shock wave, at depth beneath the crater floor, and in the convergent subcrater flow that forms the central uplift. Consequently, subsurface porosity distribution is a strong function of crater size, which is reflected in the inferred gravity anomaly. The Bouguer gravity anomaly for simulated craters smaller than 25 km is a broad low with a magnitude proportional to the crater radius; larger craters exhibit a central gravity high within a suppressed gravity low. Lower crustal pressures on the Moon relative to Earth imply that impact-induced dilatancy is more effective on the Moon than Earth for the same size impact in an initially nonporous target. This difference may be mitigated by the presence of porosity in the lunar crust.},\n\tlanguage = {en},\n\turldate = {2014-12-16},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Collins, G. S.},\n\tmonth = dec,\n\tyear = {2014},\n\tkeywords = {1219 Gravity anomalies and Earth structure, 1221 Lunar and planetary geodesy and gravity, 5420 Impact phenomena, cratering, dilatancy, gravity anomaly, impact cratering, numerical modeling},\n\tpages = {2014JE004708},\n}\n\n

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\n \n\n \n \n Freed, A. M.; Johnson, B. C.; Blair, D. M.; Melosh, H. J.; Neumann, G. A.; Phillips, R. J.; Solomon, S. C.; Wieczorek, M. A.; and Zuber, M. T.\n\n\n \n \n \n \n \n The formation of lunar mascon basins from impact to contemporary form.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 119(11): 2014JE004657. November 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{freed_formation_2014,\n\ttitle = {The formation of lunar mascon basins from impact to contemporary form},\n\tvolume = {119},\n\tissn = {2169-9100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/2014JE004657/abstract},\n\tdoi = {10.1002/2014JE004657},\n\tabstract = {Positive free-air gravity anomalies associated with large lunar impact basins represent a superisostatic mass concentration or “mascon.” High-resolution lunar gravity data from the Gravity Recovery and Interior Laboratory spacecraft reveal that these mascons are part of a bulls-eye pattern in which the central positive anomaly is surrounded by an annulus of negative anomalies, which in turn is surrounded by an outer annulus of positive anomalies. To understand the origin of this gravity pattern, we modeled numerically the entire evolution of basin formation from impact to contemporary form. With a hydrocode, we simulated impact excavation and collapse and show that during the major basin-forming era, the preimpact crust and mantle were sufficiently weak to enable a crustal cap to flow back over and cover the mantle exposed by the impact within hours. With hydrocode results as initial conditions, we simulated subsequent cooling and viscoelastic relaxation of topography using a finite element model, focusing on the mare-free Freundlich-Sharonov and mare-infilled Humorum basins. By constraining these models with measured free-air and Bouguer gravity anomalies as well as surface topography, we show that lunar basins evolve by isostatic adjustment from an initially subisostatic state following the collapse stage. The key to the development of a superisostatic inner basin center is its mechanical coupling to the outer basin that rises in response to subisostatic stresses, enabling the inner basin to rise above isostatic equilibrium. Our calculations relate basin size to impactor diameter and velocity, and they constrain the preimpact lunar thermal structure, crustal thickness, viscoelastic rheology, and, for the Humorum basin, the thickness of its postimpact mare fill.},\n\tlanguage = {en},\n\tnumber = {11},\n\turldate = {2015-05-14},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Freed, Andrew M. and Johnson, Brandon C. and Blair, David M. and Melosh, H. J. and Neumann, Gregory A. and Phillips, Roger J. and Solomon, Sean C. and Wieczorek, Mark A. and Zuber, Maria T.},\n\tmonth = nov,\n\tyear = {2014},\n\tkeywords = {5420 Impact phenomena, cratering, 5460 Physical properties of materials, 5714 Gravitational fields, 6250 Moon, basins, gravity, impact, lunar, mascons},\n\tpages = {2014JE004657},\n}\n\n

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\n \n\n \n \n Johnson, B. C.; Bowling, T. J.; and Melosh, H. J.\n\n\n \n \n \n \n \n Jetting during vertical impacts of spherical projectiles.\n \n \n \n \n\n\n \n\n\n\n Icarus, 238: 13–22. August 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"Jetting$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{johnson_jetting_2014,\n\ttitle = {Jetting during vertical impacts of spherical projectiles},\n\tvolume = {238},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103514002474},\n\tdoi = {10.1016/j.icarus.2014.05.003},\n\tabstract = {The extreme pressures reached during jetting, a process by which material is squirted out from the contact point of two colliding objects, causes melting and vaporization at low impact velocities. Jetting is a major source of melting in shocked porous material, a potential source of tektites, a possible origin of chondrules, and even a conceivable origin of the Moon. Here, in an attempt to quantify the importance of jetting, we present numerical simulation of jetting during the vertical impacts of spherical projectiles on both flat and curved targets. We find that impacts on curved targets result in more jetted material but that higher impact velocities result in less jetted material. For an aluminum impactor striking a flat Al target at 2 km/s we find that 3.4\\% of a projectile mass is jetted while 8.3\\% is jetted for an impact between two equal sized Al spheres. Our results indicate that the theory of jetting during the collision of thin plates can be used to predict the conditions when jetting will occur. However, we find current analytic models do not make accurate predictions of the amount of jetted mass. Our work indicates that the amount of jetted mass is independent of model resolution as long as some jetted material is resolved. This is the result of lower velocity material dominating the mass of the jet.},\n\turldate = {2014-07-09},\n\tjournal = {Icarus},\n\tauthor = {Johnson, B. C. and Bowling, T. J. and Melosh, H. J.},\n\tmonth = aug,\n\tyear = {2014},\n\tkeywords = {CRATERING, Collisional physics, Impact processes},\n\tpages = {13--22},\n}\n\n

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\n \n\n \n \n Johnson, B. C.; and Melosh, H. J.\n\n\n \n \n \n \n \n Formation of melt droplets, melt fragments, and accretionary impact lapilli during a hypervelocity impact.\n \n \n \n \n\n\n \n\n\n\n Icarus, 228: 347–363. January 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"Formation$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{johnson_formation_2014,\n\ttitle = {Formation of melt droplets, melt fragments, and accretionary impact lapilli during a hypervelocity impact},\n\tvolume = {228},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S001910351300451X},\n\tdoi = {10.1016/j.icarus.2013.10.022},\n\tabstract = {We present a model that describes the formation of melt droplets, melt fragments, and accretionary impact lapilli during a hypervelocity impact. Using the iSALE hydrocode, coupled to the ANEOS equation of state for silica, we create high-resolution two-dimensional impact models to track the motion of impact ejecta. We then estimate the size of the ejecta products using simple analytical expressions and information derived from our hydrocode models. Ultimately, our model makes predictions of how the size of the ejecta products depends on impactor size, impact velocity, and ejection velocity. In general, we find that larger impactor sizes result in larger ejecta products and higher ejection velocities result in smaller ejecta product sizes. We find that a 10 km diameter impactor striking at a velocity of 20 km/s creates millimeter scale melt droplets comparable to the melt droplets found in the Chicxulub ejecta curtain layer. Our model also predicts that melt droplets, melt fragments, and accretionary impact lapilli should be found together in well preserved ejecta curtain layers and that all three ejecta products can form even on airless bodies that lack significant volatile content. This prediction agrees with observations of ejecta from the Sudbury and Chicxulub impacts as well as the presence of accretionary impact lapilli in lunar breccia.},\n\turldate = {2015-06-16},\n\tjournal = {Icarus},\n\tauthor = {Johnson, B. C. and Melosh, H. J.},\n\tmonth = jan,\n\tyear = {2014},\n\tkeywords = {CRATERING, Earth, Impact processes},\n\tpages = {347--363},\n}\n\n

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\n \n\n \n \n Marchi, S.; Bottke, W. F.; Elkins-Tanton, L. T.; Bierhaus, M.; Wuennemann, K.; Morbidelli, A.; and Kring, D. A.\n\n\n \n \n \n \n \n Widespread mixing and burial of Earth's Hadean crust by asteroid impacts.\n \n \n \n \n\n\n \n\n\n\n Nature, 511(7511): 578–582. July 2014.\n \n\n\n\n
\n\n\n\n \n \n $\"Widespread$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n\n\n\n

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@article{marchi_widespread_2014,\n\ttitle = {Widespread mixing and burial of {Earth}'s {Hadean} crust by asteroid impacts},\n\tvolume = {511},\n\tissn = {0028-0836},\n\turl = {http://www.nature.com/nature/journal/v511/n7511/full/nature13539.html?WT.ec_id=NATURE-20140731},\n\tdoi = {10.1038/nature13539},\n\tlanguage = {en},\n\tnumber = {7511},\n\turldate = {2014-07-31},\n\tjournal = {Nature},\n\tauthor = {Marchi, S. and Bottke, W. F. and Elkins-Tanton, L. T. and Bierhaus, M. and Wuennemann, K. and Morbidelli, A. and Kring, D. A.},\n\tmonth = jul,\n\tyear = {2014},\n\tkeywords = {Inner planets, geophysics},\n\tpages = {578--582},\n}\n\n\n\n\n

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\n \n\n \n \n Artemieva, N. A.; Wünnemann, K.; Krien, F.; Reimold, W. U.; and Stöffler, D.\n\n\n \n \n \n \n \n Ries crater and suevite revisited—Observations and modeling Part II: Modeling.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 48(4): 590–627. April 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Ries$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{artemieva_ries_2013,\n\ttitle = {Ries crater and suevite revisited—{Observations} and modeling {Part} {II}: {Modeling}},\n\tvolume = {48},\n\tcopyright = {© The Meteoritical Society, 2013.},\n\tissn = {1945-5100},\n\tshorttitle = {Ries crater and suevite revisited—{Observations} and modeling {Part} {II}},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12085/abstract},\n\tdoi = {10.1111/maps.12085},\n\tabstract = {We present the results of numerical modeling of the formation of the Ries crater utilizing the two hydrocodes SOVA and iSALE. These standard models allow us to reproduce crater shape, size, and morphology, and composition and extension of the continuous ejecta blanket. Some of these results cannot, however, be readily reconciled with observations: the impact plume above the crater consists mainly of molten and vaporized sedimentary rocks, containing very little material in comparison with the ejecta curtain; at the end of the modification stage, the crater floor is covered by a thick layer of impact melt with a total volume of 6–11 km3; the thickness of true fallback material from the plume inside the crater does not exceed a couple of meters; ejecta from all stratigraphic units of the target are transported ballistically; no separation of sedimentary and crystalline rocks—as observed between suevites and Bunte Breccia at Ries—is noted. We also present numerical results quantifying the existing geological hypotheses of Ries ejecta emplacement from an impact plume, by melt flow, or by a pyroclastic density current. The results show that none of these mechanisms is consistent with physical constraints and/or observations. Finally, we suggest a new hypothesis of suevite formation and emplacement by postimpact interaction of hot impact melt with water or volatile-rich sedimentary rocks.},\n\tlanguage = {en},\n\tnumber = {4},\n\turldate = {2014-07-17},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Artemieva, N. A. and Wünnemann, K. and Krien, F. and Reimold, W. U. and Stöffler, D.},\n\tmonth = apr,\n\tyear = {2013},\n\tpages = {590--627},\n}\n\n

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\n \n\n \n \n Bowling, T. J.; Johnson, B. C.; Melosh, H. J.; Ivanov, B. A.; O'Brien, D. P.; Gaskell, R.; and Marchi, S.\n\n\n \n \n \n \n \n Antipodal terrains created by the Rheasilvia basin forming impact on asteroid 4 Vesta.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 118(9): 1821–1834. September 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Antipodal$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{bowling_antipodal_2013,\n\ttitle = {Antipodal terrains created by the {Rheasilvia} basin forming impact on asteroid 4 {Vesta}},\n\tvolume = {118},\n\tcopyright = {©2013. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/jgre.20123/abstract},\n\tdoi = {10.1002/jgre.20123},\n\tabstract = {The Rheasilvia impact on asteroid 4 Vesta may have been sufficiently large to create disrupted terrains at the impact antipode. This paper investigates the amount of deformation expected at the Rheasilvia antipode using numerical models of sufficient resolution to directly observe terrain modification and material displacements following the arrival of impact stresses. We find that the magnitude and mode of deformation expected at the impact antipode is strongly dependent on both the sound speed and porosity of Vesta's mantle, as well as the strength of the Vestan core. In the case of low mantle porosities and high core strengths, we predict the existence of a topographic high (a peak) caused by the collection of spalled and uplifted material at the antipode. Observations by NASA's Dawn spacecraft cannot provide definite evidence that large amounts of deformation occurred at the Rheasilvia antipode, largely due to the presence of younger large impact craters in the region. However, a deficiency of small craters near the antipodal point suggests that some degree of deformation did occur.},\n\tlanguage = {en},\n\tnumber = {9},\n\turldate = {2015-03-02},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Bowling, T. J. and Johnson, B. C. and Melosh, H. J. and Ivanov, B. A. and O'Brien, D. P. and Gaskell, R. and Marchi, S.},\n\tmonth = sep,\n\tyear = {2013},\n\tkeywords = {4 Vesta, 5420 Impact phenomena, cratering, 5460 Physical properties of materials, 5470 Surface materials and properties, 6205 Asteroids, Asteroid, Rheasilvia, antipode, impact, shock physics},\n\tpages = {1821--1834},\n}\n\n

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\n \n\n \n \n Davison, T. M.; O'Brien, D. P.; Ciesla, F. J.; and Collins, G. S.\n\n\n \n \n \n \n \n The early impact histories of meteorite parent bodies.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 48(10): 1894–1918. October 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{davison_early_2013,\n\ttitle = {The early impact histories of meteorite parent bodies},\n\tvolume = {48},\n\tcopyright = {© The Meteoritical Society, 2013.},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12193/abstract},\n\tdoi = {10.1111/maps.12193},\n\tabstract = {We have developed a statistical framework that uses collisional evolution models, shock physics modeling, and scaling laws to determine the range of plausible collisional histories for individual meteorite parent bodies. It is likely that those parent bodies that were not catastrophically disrupted sustained hundreds of impacts on their surfaces—compacting, heating, and mixing the outer layers; it is highly unlikely that many parent bodies escaped without any impacts processing the outer few kilometers. The first 10–20 Myr were the most important time for impacts, both in terms of the number of impacts and the increase of specific internal energy due to impacts. The model has been applied to evaluate the proposed impact histories of several meteorite parent bodies: up to 10 parent bodies that were not disrupted in the first 100 Myr experienced a vaporizing collision of the type necessary to produce the metal inclusions and chondrules on the CB chondrite parent; around 1–5\\% of bodies that were catastrophically disrupted after 12 Myr sustained impacts at times that match the heating events recorded on the IAB/winonaite parent body; more than 75\\% of 100 km radius parent bodies, which survived past 100 Myr without being disrupted, sustained an impact that excavates to the depth required for mixing in the outer layers of the H-chondrite parent body; and to protect the magnetic field on the CV chondrite parent body, the crust would have had to have been thick (approximately 20 km) to prevent it being punctured by impacts.},\n\tlanguage = {en},\n\tnumber = {10},\n\turldate = {2014-04-04},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Davison, Thomas M. and O'Brien, David P. and Ciesla, Fred J. and Collins, Gareth S.},\n\tmonth = oct,\n\tyear = {2013},\n\tpages = {1894--1918},\n}\n\n

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\n \n\n \n \n Elbeshausen, D.; Wünnemann, K.; and Collins, G. S.\n\n\n \n \n \n \n \n The transition from circular to elliptical impact craters.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 118(11): 2013JE004477. November 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{elbeshausen_transition_2013,\n\ttitle = {The transition from circular to elliptical impact craters},\n\tvolume = {118},\n\tcopyright = {©2013. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/2013JE004477/abstract},\n\tdoi = {10.1002/2013JE004477},\n\tabstract = {Elliptical impact craters are rare among the generally symmetric shape of impact structures on planetary surfaces. Nevertheless, a better understanding of the formation of these craters may significantly contribute to our overall understanding of hypervelocity impact cratering. The existence of elliptical craters raises a number of questions: Why do some impacts result in a circular crater whereas others form elliptical shapes? What conditions promote the formation of elliptical craters? How does the formation of elliptical craters differ from those of circular craters? Is the formation process comparable to those of elliptical craters formed at subsonic speeds? How does crater formation work at the transition from circular to elliptical craters? By conducting more than 800 three-dimensional (3-D) hydrocode simulations, we have investigated these questions in a quantitative manner. We show that the threshold angle for elliptical crater generation depends on cratering efficiency. We have analyzed and quantified the influence of projectile size and material strength (cohesion and coefficient of internal friction) independently from each other. We show that elliptical craters are formed by shock-induced excavation, the same process that forms circular craters and reveal that the transition from circular to elliptical craters is characterized by the dominance of two processes: A directed and momentum-controlled energy transfer in the beginning and a subsequent symmetric, nearly instantaneous energy release.},\n\tlanguage = {en},\n\tnumber = {11},\n\turldate = {2014-08-12},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Elbeshausen, Dirk and Wünnemann, Kai and Collins, Gareth S.},\n\tmonth = nov,\n\tyear = {2013},\n\tkeywords = {1932 High-performance computing, 4302 Geological, 4314 Mathematical and computer modeling, 4475 Scaling: spatial and temporal, 5420 Impact phenomena, cratering, crater formation, elliptical craters, equivalent depth of burst, hydrocode simulations, impact explosion analogy},\n\tpages = {2013JE004477},\n}\n\n

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\n \n\n \n \n Miljković, K.; Wieczorek, M. A.; Collins, G. S.; Laneuville, M.; Neumann, G. A.; Melosh, H. J.; Solomon, S. C.; Phillips, R. J.; Smith, D. E.; and Zuber, M. T.\n\n\n \n \n \n \n \n Asymmetric Distribution of Lunar Impact Basins Caused by Variations in Target Properties.\n \n \n \n \n\n\n \n\n\n\n Science, 342(6159): 724–726. November 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Asymmetric$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{miljkovic_asymmetric_2013,\n\ttitle = {Asymmetric {Distribution} of {Lunar} {Impact} {Basins} {Caused} by {Variations} in {Target} {Properties}},\n\tvolume = {342},\n\tissn = {0036-8075, 1095-9203},\n\turl = {http://www.sciencemag.org/content/342/6159/724},\n\tdoi = {10.1126/science.1243224},\n\tabstract = {Maps of crustal thickness derived from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission revealed more large impact basins on the nearside hemisphere of the Moon than on its farside. The enrichment in heat-producing elements and prolonged volcanic activity on the lunar nearside hemisphere indicate that the temperature of the nearside crust and upper mantle was hotter than that of the farside at the time of basin formation. Using the iSALE-2D hydrocode to model impact basin formation, we found that impacts on the hotter nearside would have formed basins with up to twice the diameter of similar impacts on the cooler farside hemisphere. The size distribution of lunar impact basins is thus not representative of the earliest inner solar system impact bombardment.\nWhich Side of the Moon?\nThe far- and nearsides of the Moon are geologically different. Using high-precision crustal thickness maps derived from NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, Miljković et al. (p. 724) show that the distribution of lunar impact basins is also highly asymmetrical. Numerical simulations of impact basin formation coupled with three-dimensional simulations of the Moon's asymmetric thermal evolution suggest that lateral variations in temperature within the Moon's crust have a large effect on the final size of an impact basin.},\n\tlanguage = {en},\n\tnumber = {6159},\n\turldate = {2014-01-17},\n\tjournal = {Science},\n\tauthor = {Miljković, Katarina and Wieczorek, Mark A. and Collins, Gareth S. and Laneuville, Matthieu and Neumann, Gregory A. and Melosh, H. Jay and Solomon, Sean C. and Phillips, Roger J. and Smith, David E. and Zuber, Maria T.},\n\tmonth = nov,\n\tyear = {2013},\n\tpmid = {24202170},\n\tpages = {724--726},\n}\n\n

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\n \n\n \n \n Potter, R. W. K.; and Collins, G. S.\n\n\n \n \n \n \n \n Numerical modeling of asteroid survivability and possible scenarios for the Morokweng crater-forming impact.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 48(5): 744–757. May 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Numerical$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{potter_numerical_2013,\n\ttitle = {Numerical modeling of asteroid survivability and possible scenarios for the {Morokweng} crater-forming impact},\n\tvolume = {48},\n\tcopyright = {© The Meteoritical Society, 2013.},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12098/abstract},\n\tdoi = {10.1111/maps.12098},\n\tabstract = {The fate of the impactor is an important aspect of the impact-cratering process. Defining impactor material as surviving if it remains solid (i.e., does not melt or vaporize) during crater formation, previous numerical modeling and experiments have shown that survivability decreases with increasing impact velocity, impact angle (with respect to the horizontal), and target density. Here, we show that in addition to these, impactor survivability depends on the porosity and shape of the impactor. Increasing impactor porosity decreases impactor survivability, while prolate-shaped (polar axis {\\textgreater} equatorial axis) impactors survive impact more so than spherical and oblate-shaped (polar axis {\\textless} equatorial axis) impactors. These results are used to produce a relatively simple equation, which can be used to estimate the impactor fraction shocked to a given pressure as a function of these parameters. By applying our findings to the Morokweng crater-forming impact, we suggest impact scenarios that explain the high meteoritic content and presence of unmolten fossil meteorites within the Morokweng crater. In addition to previous suggestions of a low-velocity and/or high-angled impact, this work suggests that an elongated and/or low porosity impactor may also help explain the anomalously high survivability of the Morokweng impactor.},\n\tlanguage = {en},\n\tnumber = {5},\n\turldate = {2014-08-12},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Potter, Ross W. K. and Collins, Gareth S.},\n\tmonth = may,\n\tyear = {2013},\n\tpages = {744--757},\n}\n\n

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\n \n\n \n \n Potter, R. W. K.; Kring, D. A.; Collins, G. S.; Kiefer, W. S.; and McGovern, P. J.\n\n\n \n \n \n \n \n Numerical modeling of the formation and structure of the Orientale impact basin.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 118(5): 963–979. May 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Numerical$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{potter_numerical_2013-1,\n\ttitle = {Numerical modeling of the formation and structure of the {Orientale} impact basin},\n\tvolume = {118},\n\tcopyright = {©2013. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/jgre.20080/abstract},\n\tdoi = {10.1002/jgre.20080},\n\tabstract = {The Orientale impact basin is the youngest and best-preserved lunar multi-ring basin and has, thus, been the focus of studies investigating basin-forming processes and final structures. A consensus about how multi-ring basins form, however, remains elusive. Here we numerically model the Orientale basin-forming impact with the aim of resolving some of the uncertainties associated with this basin. By using two thermal profiles estimating lunar conditions at the time of Orientale's formation and constraining the numerical models with crustal structures inferred from gravity data, we provide estimates for Orientale's impact energy (2–9  × 1025 J), impactor size (50–80 km diameter), transient crater size (∼320–480 km), excavation depth (40–55 km), and impact melt volume (∼106 km3). We also analyze the distribution and deformation of target material and compare our model results and Orientale observations with the Chicxulub crater to investigate similarities between these two impact structures.},\n\tlanguage = {en},\n\tnumber = {5},\n\turldate = {2014-07-21},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Potter, Ross W. K. and Kring, David A. and Collins, Gareth S. and Kiefer, Walter S. and McGovern, Patrick J.},\n\tmonth = may,\n\tyear = {2013},\n\tkeywords = {0545 Modeling, 5420 Impact phenomena, cratering, 6205 Asteroids, 6250 Moon, Chicxulub, Orientale, basin formation, impact basins, late heavy bombardment, lunar cataclysm},\n\tpages = {963--979},\n}\n\n

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\n \n\n \n \n Weiss, R.; Krastel, S.; Anasetti, A.; and Wünnemann, K.\n\n\n \n \n \n \n \n Constraining the characteristics of tsunami waves from deformable submarine slides.\n \n \n \n \n\n\n \n\n\n\n Geophysical Journal International, 194(1): 316–321. July 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Constraining$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{weiss_constraining_2013,\n\ttitle = {Constraining the characteristics of tsunami waves from deformable submarine slides},\n\tvolume = {194},\n\tissn = {0956-540X},\n\turl = {https://academic.oup.com/gji/article/194/1/316/645010/Constraining-the-characteristics-of-tsunami-waves},\n\tdoi = {10.1093/gji/ggt094},\n\tabstract = {As a marine hazard, submarine slope failures have the potential to directly destroy offshore infrastructure, and, if a tsunami is generated, it also endangers the life of those who live and work at the coastline. The hazard and risk from tsunamis generated by submarine mass failure is difficult to quantify and evaluate due to the problems to constrain the characteristics of the triggered submarine landslide, which introduces unquantifiable uncertainty to hazard assessments based on numerical modelling. To lower the uncertainty, we present a method that determines material parameters for the slide body to constrain the generated tsunami waves. Our method employs the distribution of landslide run-out masses and their comparison with simulations. It assumes that the slide material can be approximated by bulk values during the slide motion. To demonstrate our method, we make use of Valdes slide run-out masses off the Chilean coast.},\n\tnumber = {1},\n\turldate = {2017-10-10},\n\tjournal = {Geophysical Journal International},\n\tauthor = {Weiss, Robert and Krastel, Sebastian and Anasetti, Andreas and Wünnemann, Kai},\n\tmonth = jul,\n\tyear = {2013},\n\tpages = {316--321},\n}\n\n

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\n \n\n \n \n Ciesla, F. J.; Davison, T. M.; Collins, G. S.; and O'Brien, D. P.\n\n\n \n \n \n \n \n Thermal consequences of impacts in the early solar system.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 48(12): 2559–2576. December 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Thermal$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{ciesla_thermal_2013,\n\ttitle = {Thermal consequences of impacts in the early solar system},\n\tvolume = {48},\n\tcopyright = {© The Meteoritical Society, 2013.},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12236/abstract},\n\tdoi = {10.1111/maps.12236},\n\tabstract = {Collisions between planetesimals were common during the first approximately 100 Myr of solar system formation. Such collisions have been suggested to be responsible for thermal processing seen in some meteorites, although previous work has demonstrated that such events could not be responsible for the global thermal evolution of a meteorite parent body. At this early epoch in solar system history, however, meteorite parent bodies would have been heated or retained heat from the decay of short-lived radionuclides, most notably 26Al. The postimpact structure of an impacted body is shown here to be a strong function of the internal temperature structure of the target body. We calculate the temperature–time history of all mass in these impacted bodies, accounting for their heating in an onion-shell–structured body prior to the collision event and then allowing for the postimpact thermal evolution as heat from both radioactivities and the impact is diffused through the resulting planetesimal and radiated to space. The thermal histories of materials in these bodies are compared with what they would be in an unimpacted, onion-shell body. We find that while collisions in the early solar system led to the heating of a target body around the point of impact, a greater amount of mass had its cooling rates accelerated as a result of the flow of heated materials to the surface during the cratering event.},\n\tlanguage = {en},\n\tnumber = {12},\n\turldate = {2014-04-04},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Ciesla, Fred J. and Davison, Thomas M. and Collins, Gareth S. and O'Brien, David P.},\n\tmonth = dec,\n\tyear = {2013},\n\tpages = {2559--2576},\n}\n\n

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\n \n\n \n \n Güldemeister, N.; Wünnemann, K.; Durr, N.; and Hiermaier, S.\n\n\n \n \n \n \n \n Propagation of impact-induced shock waves in porous sandstone using mesoscale modeling.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 48(1): 115–133. January 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Propagation$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{guldemeister_propagation_2013,\n\ttitle = {Propagation of impact-induced shock waves in porous sandstone using mesoscale modeling},\n\tvolume = {48},\n\tcopyright = {© The Meteoritical Society, 2012},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2012.01430.x/abstract},\n\tdoi = {10.1111/j.1945-5100.2012.01430.x},\n\tabstract = {Generation and propagation of shock waves by meteorite impact is significantly affected by material properties such as porosity, water content, and strength. The objective of this work was to quantify processes related to the shock-induced compaction of pore space by numerical modeling, and compare the results with data obtained in the framework of the Multidisciplinary Experimental and Modeling Impact Research Network (MEMIN) impact experiments. We use mesoscale models resolving the collapse of individual pores to validate macroscopic (homogenized) approaches describing the bulk behavior of porous and water-saturated materials in large-scale models of crater formation, and to quantify localized shock amplification as a result of pore space crushing. We carried out a suite of numerical models of planar shock wave propagation through a well-defined area (the “sample”) of porous and/or water-saturated material. The porous sample is either represented by a homogeneous unit where porosity is treated as a state variable (macroscale model) and water content by an equation of state for mixed material (ANEOS) or by a defined number of individually resolved pores (mesoscale model). We varied porosity and water content and measured thermodynamic parameters such as shock wave velocity and particle velocity on meso- and macroscales in separate simulations. The mesoscale models provide additional data on the heterogeneous distribution of peak shock pressures as a consequence of the complex superposition of reflecting rarefaction waves and shock waves originating from the crushing of pores. We quantify the bulk effect of porosity, the reduction in shock pressure, in terms of Hugoniot data as a function of porosity, water content, and strength of a quartzite matrix. We find a good agreement between meso-, macroscale models and Hugoniot data from shock experiments. We also propose a combination of a porosity compaction model (ε–α model) that was previously only used for porous materials and the ANEOS for water-saturated quartzite (all pore space is filled with water) to describe the behavior of partially water-saturated material during shock compression. Localized amplification of shock pressures results from pore collapse and can reach as much as four times the average shock pressure in the porous sample. This may explain the often observed localized high shock pressure phases next to more or less unshocked grains in impactites and meteorites.},\n\tlanguage = {en},\n\tnumber = {1},\n\turldate = {2015-03-25},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Güldemeister, Nicole and Wünnemann, Kai and Durr, Nathanael and Hiermaier, Stefan},\n\tmonth = jan,\n\tyear = {2013},\n\tpages = {115--133},\n}\n\n

\n

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\n Generation and propagation of shock waves by meteorite impact is significantly affected by material properties such as porosity, water content, and strength. The objective of this work was to quantify processes related to the shock-induced compaction of pore space by numerical modeling, and compare the results with data obtained in the framework of the Multidisciplinary Experimental and Modeling Impact Research Network (MEMIN) impact experiments. We use mesoscale models resolving the collapse of individual pores to validate macroscopic (homogenized) approaches describing the bulk behavior of porous and water-saturated materials in large-scale models of crater formation, and to quantify localized shock amplification as a result of pore space crushing. We carried out a suite of numerical models of planar shock wave propagation through a well-defined area (the “sample”) of porous and/or water-saturated material. The porous sample is either represented by a homogeneous unit where porosity is treated as a state variable (macroscale model) and water content by an equation of state for mixed material (ANEOS) or by a defined number of individually resolved pores (mesoscale model). We varied porosity and water content and measured thermodynamic parameters such as shock wave velocity and particle velocity on meso- and macroscales in separate simulations. The mesoscale models provide additional data on the heterogeneous distribution of peak shock pressures as a consequence of the complex superposition of reflecting rarefaction waves and shock waves originating from the crushing of pores. We quantify the bulk effect of porosity, the reduction in shock pressure, in terms of Hugoniot data as a function of porosity, water content, and strength of a quartzite matrix. We find a good agreement between meso-, macroscale models and Hugoniot data from shock experiments. We also propose a combination of a porosity compaction model (ε–α model) that was previously only used for porous materials and the ANEOS for water-saturated quartzite (all pore space is filled with water) to describe the behavior of partially water-saturated material during shock compression. Localized amplification of shock pressures results from pore collapse and can reach as much as four times the average shock pressure in the porous sample. This may explain the often observed localized high shock pressure phases next to more or less unshocked grains in impactites and meteorites.\n

\n\n\n

\n \n\n \n \n Kowitz, A.; Güldemeister, N.; Reimold, W. U.; Schmitt, R. T.; and Wünnemann, K.\n\n\n \n \n \n \n \n Diaplectic quartz glass and SiO2 melt experimentally generated at only 5 GPa shock pressure in porous sandstone: Laboratory observations and meso-scale numerical modeling.\n \n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 384: 17–26. December 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Diaplectic$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{kowitz_diaplectic_2013,\n\ttitle = {Diaplectic quartz glass and {SiO2} melt experimentally generated at only 5 {GPa} shock pressure in porous sandstone: {Laboratory} observations and meso-scale numerical modeling},\n\tvolume = {384},\n\tissn = {0012-821X},\n\tshorttitle = {Diaplectic quartz glass and {SiO2} melt experimentally generated at only 5 {GPa} shock pressure in porous sandstone},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0012821X13005323},\n\tdoi = {10.1016/j.epsl.2013.09.021},\n\tabstract = {A combination of shock recovery experiments and numerical modeling of shock deformation in the low pressure range from 2.5 to 17.5 GPa in dry, porous Seeberger sandstone provides new, significant insights with respect to the heterogeneous nature of shock distribution in such important, upper crustal material, for which to date no pressure-calibrated scheme for shock metamorphism exists. We found that pores are already completely closed at 2.5 GPa shock pressure. Whole quartz grains or parts of them are transformed to diaplectic quartz glass and/or SiO2 melt starting already at 5 GPa, whereas these effects are not observed below shock pressures of 30–35 and ∼45 GPa, respectively, in shock experiments with quartz single crystals. The appearance of diaplectic glass or melt is not restricted to the zone directly below the impacted surface but is related to the occurrence of pores in a much broader zone. The combined amount of these phases increases distinctly with increasing shock pressure from 0.03 vol.\\% at 5 GPa to ∼80 vol.\\% at 17.5 GPa. In accordance with a previous shock classification for silica phases in naturally shocked Coconino sandstone from Meteor Crater that was based on varied slopes of the Coconino sandstone Hugoniot curve, our observations allow us to construct a shock pressure classification for porous sandstone consistent with shock stages 1b–4 of the progressive shock metamorphism classification of Kieffer (1971).\n\nNumerical modeling at the meso-scale provides the explanation for the discrepancy of shock deformation in porous material and single-crystal quartz, in keeping with our experimental results. It confirms that pore space is completely collapsed at low nominal pressure and demonstrates that pore space collapse results in localized pressure amplification that can exceed 4 times the initial pressure. This provides an explanation for the formation of diaplectic quartz glass and lechatelierite as observed in the low-shock-pressure experiments. The numerical models predict an amount of SiO2 melt similar to that observed in the shock experiments. This also shows that numerical models are essential to provide information beyond experimental capabilities.},\n\turldate = {2014-10-23},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Kowitz, A. and Güldemeister, N. and Reimold, W. U. and Schmitt, R. T. and Wünnemann, K.},\n\tmonth = dec,\n\tyear = {2013},\n\tkeywords = {diaplectic quartz glass, meso-scale modeling, pore collapse, shock effects, shock metamorphism, silica melt},\n\tpages = {17--26},\n}\n\n

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\n A combination of shock recovery experiments and numerical modeling of shock deformation in the low pressure range from 2.5 to 17.5 GPa in dry, porous Seeberger sandstone provides new, significant insights with respect to the heterogeneous nature of shock distribution in such important, upper crustal material, for which to date no pressure-calibrated scheme for shock metamorphism exists. We found that pores are already completely closed at 2.5 GPa shock pressure. Whole quartz grains or parts of them are transformed to diaplectic quartz glass and/or SiO2 melt starting already at 5 GPa, whereas these effects are not observed below shock pressures of 30–35 and ∼45 GPa, respectively, in shock experiments with quartz single crystals. The appearance of diaplectic glass or melt is not restricted to the zone directly below the impacted surface but is related to the occurrence of pores in a much broader zone. The combined amount of these phases increases distinctly with increasing shock pressure from 0.03 vol.% at 5 GPa to ∼80 vol.% at 17.5 GPa. In accordance with a previous shock classification for silica phases in naturally shocked Coconino sandstone from Meteor Crater that was based on varied slopes of the Coconino sandstone Hugoniot curve, our observations allow us to construct a shock pressure classification for porous sandstone consistent with shock stages 1b–4 of the progressive shock metamorphism classification of Kieffer (1971). Numerical modeling at the meso-scale provides the explanation for the discrepancy of shock deformation in porous material and single-crystal quartz, in keeping with our experimental results. It confirms that pore space is completely collapsed at low nominal pressure and demonstrates that pore space collapse results in localized pressure amplification that can exceed 4 times the initial pressure. This provides an explanation for the formation of diaplectic quartz glass and lechatelierite as observed in the low-shock-pressure experiments. The numerical models predict an amount of SiO2 melt similar to that observed in the shock experiments. This also shows that numerical models are essential to provide information beyond experimental capabilities.\n

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\n \n\n \n \n Melosh, H. J.; Freed, A. M.; Johnson, B. C.; Blair, D. M.; Andrews-Hanna, J. C.; Neumann, G. A.; Phillips, R. J.; Smith, D. E.; Solomon, S. C.; Wieczorek, M. A.; and Zuber, M. T.\n\n\n \n \n \n \n \n The Origin of Lunar Mascon Basins.\n \n \n \n \n\n\n \n\n\n\n Science, 340(6140): 1552–1555. June 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{melosh_origin_2013,\n\ttitle = {The {Origin} of {Lunar} {Mascon} {Basins}},\n\tvolume = {340},\n\tissn = {0036-8075, 1095-9203},\n\turl = {http://www.sciencemag.org/content/340/6140/1552},\n\tdoi = {10.1126/science.1235768},\n\tabstract = {High-resolution gravity data from the Gravity Recovery and Interior Laboratory spacecraft have clarified the origin of lunar mass concentrations (mascons). Free-air gravity anomalies over lunar impact basins display bull’s-eye patterns consisting of a central positive (mascon) anomaly, a surrounding negative collar, and a positive outer annulus. We show that this pattern results from impact basin excavation and collapse followed by isostatic adjustment and cooling and contraction of a voluminous melt pool. We used a hydrocode to simulate the impact and a self-consistent finite-element model to simulate the subsequent viscoelastic relaxation and cooling. The primary parameters controlling the modeled gravity signatures of mascon basins are the impactor energy, the lunar thermal gradient at the time of impact, the crustal thickness, and the extent of volcanic fill.\nLunar Mascons Explained\nThe origin of lunar mass concentrations (or mascons), which appear as prominent bull's-eye patterns on gravitational maps of both the near- and far side of the Moon, has been a mystery since they were originally detected in 1968. Using state-of-the-art simulation codes, Melosh et al. (p. 1552, published online 30 May; see the Perspective by Montesi) developed a model to explain the formation of mascons, linking the processes of impact cratering, tectonic deformation, and volcanic extrusion.},\n\tlanguage = {en},\n\tnumber = {6140},\n\turldate = {2014-07-21},\n\tjournal = {Science},\n\tauthor = {Melosh, H. J. and Freed, Andrew M. and Johnson, Brandon C. and Blair, David M. and Andrews-Hanna, Jeffrey C. and Neumann, Gregory A. and Phillips, Roger J. and Smith, David E. and Solomon, Sean C. and Wieczorek, Mark A. and Zuber, Maria T.},\n\tmonth = jun,\n\tyear = {2013},\n\tpmid = {23722426},\n\tpages = {1552--1555},\n}\n\n

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\n \n\n \n \n Miljković, K.; Collins, G. S.; Mannick, S.; and Bland, P. A.\n\n\n \n \n \n \n \n Morphology and population of binary asteroid impact craters.\n \n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 363(0): 121–132. February 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Morphology$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{miljkovic_morphology_2013,\n\ttitle = {Morphology and population of binary asteroid impact craters},\n\tvolume = {363},\n\tissn = {0012-821X},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0012821X12007194},\n\tdoi = {10.1016/j.epsl.2012.12.033},\n\tabstract = {Observational data show that in the Near Earth Asteroid (NEA) region 15\\% of asteroids are binary. However, the observed number of plausible doublet craters is 2–4\\% on Earth and 2–3\\% on Mars. This discrepancy between the percentage of binary asteroids and doublets on Earth and Mars may imply that not all binary systems form a clearly distinguishable doublet crater owing to insufficient separation between the binary components at the point of impact. We simulate the crater morphology formed in close binary asteroid impacts in a planetary environment and the range of possible crater morphologies includes: single (circular or elliptical) craters, overlapping (tear-drop or peanut shaped) craters, as well as clearly distinct, doublet craters. While the majority of binary asteroids impacting Earth or Mars should form a single, circular crater, about one in four are expected to form elongated or overlapping impact craters and one in six are expected to be doublets. This implies that doublets are formed in approximately 2\\% of all asteroid impacts on Earth and that elongated or overlapping binary impact craters are under-represented in the terrestrial crater record. The classification of a complete range of binary asteroid impact crater structures provides a template for binary asteroid impact crater morphologies, which can help in identifying planetary surface features observed by remote sensing.},\n\tnumber = {0},\n\turldate = {2013-01-25},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Miljković, Katarina and Collins, Gareth S. and Mannick, Sahil and Bland, Philip A.},\n\tmonth = feb,\n\tyear = {2013},\n\tkeywords = {binary asteroids, crater morphology, crater population, doublets},\n\tpages = {121--132},\n}\n\n

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\n \n\n \n \n Potter, R. W. K.; Kring, D. A.; and Collins, G. S.\n\n\n \n \n \n \n \n Quantifying the attenuation of structural uplift beneath large lunar craters.\n \n \n \n \n\n\n \n\n\n\n Geophysical Research Letters, 40(21): 5615–5620. 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Quantifying$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{potter_quantifying_2013,\n\ttitle = {Quantifying the attenuation of structural uplift beneath large lunar craters},\n\tvolume = {40},\n\tcopyright = {©2013. American Geophysical Union. All Rights Reserved.},\n\tissn = {1944-8007},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1002/2013GL057829/abstract},\n\tdoi = {10.1002/2013GL057829},\n\tabstract = {Terrestrial crater observations and laboratory experiments demonstrate that target material beneath complex impact craters is uplifted relative to its preimpact position. Current estimates suggest maximum uplift is one tenth of the final crater diameter for terrestrial complex craters and one tenth to one fifth for lunar central peak craters. These latter values are derived from an analytical model constrained by observations from small craters and may not be applicable to larger complex craters and basins. Here, using numerical modeling, we produce a set of relatively simple analytical equations that estimate the maximum amount of structural uplift and quantify the attenuation of uplift with depth beneath large lunar craters.},\n\tlanguage = {en},\n\tnumber = {21},\n\turldate = {2014-03-13},\n\tjournal = {Geophysical Research Letters},\n\tauthor = {Potter, Ross W. K. and Kring, David A. and Collins, Gareth S.},\n\tyear = {2013},\n\tkeywords = {Moon, complex craters, impact basins, numerical modeling, structural uplift},\n\tpages = {5615--5620},\n}\n\n

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\n \n\n \n \n Yue, Z.; Johnson, B. C.; Minton, D. A.; Melosh, H. J.; Di, K.; Hu, W.; and Liu, Y.\n\n\n \n \n \n \n \n Projectile remnants in central peaks of lunar impact craters.\n \n \n \n \n\n\n \n\n\n\n Nature Geoscience, 6(6): 435–437. June 2013.\n \n\n\n\n
\n\n\n\n \n \n $\"Projectile$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{yue_projectile_2013,\n\ttitle = {Projectile remnants in central peaks of lunar impact craters},\n\tvolume = {6},\n\tcopyright = {© 2013 Nature Publishing Group},\n\tissn = {1752-0894},\n\turl = {http://www.nature.com/ngeo/journal/v6/n6/abs/ngeo1828.html},\n\tdoi = {10.1038/ngeo1828},\n\tabstract = {The projectiles responsible for the formation of large impact craters are often assumed to melt or vaporize during the impact, so that only geochemical traces or small fragments remain in the final crater. In high-speed oblique impacts, some projectile material may survive, but this material is scattered far down-range from the impact site. Unusual minerals, such as magnesium-rich spinel and olivine, observed in the central peaks of many lunar craters are therefore attributed to the excavation of layers below the lunar surface. Yet these minerals are abundant in many asteroids, meteorites and chondrules. Here we use a numerical model to simulate the formation of impact craters and to trace the fate of the projectile material. We find that for vertical impact velocities below about 12 km s−1, the projectile may both survive the impact and be swept back into the central peak of the final crater as it collapses, although it would be fragmented and strongly deformed. We conclude that some unusual minerals observed in the central peaks of many lunar impact craters could be exogenic in origin and may not be indigenous to the Moon.},\n\tlanguage = {en},\n\tnumber = {6},\n\turldate = {2014-09-18},\n\tjournal = {Nature Geoscience},\n\tauthor = {Yue, Z. and Johnson, B. C. and Minton, D. A. and Melosh, H. J. and Di, K. and Hu, W. and Liu, Y.},\n\tmonth = jun,\n\tyear = {2013},\n\tpages = {435--437},\n}\n\n

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\n \n\n \n \n Collins, G.; Wuennemann, K.; Artemieva, N.; and Pierazzo, E.\n\n\n \n \n \n \n Numerical modelling of impact processes.\n \n \n \n\n\n \n\n\n\n In Impact Cratering: Processes and Products, pages 254–270. Wiley-Blackwell, 2012.\n \n\n\n\n
\n\n\n\n \n\n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@incollection{collins_numerical_2012,\n\ttitle = {Numerical modelling of impact processes},\n\tisbn = {978-1-4051-9829-5},\n\tbooktitle = {Impact {Cratering}: {Processes} and {Products}},\n\tpublisher = {Wiley-Blackwell},\n\tauthor = {Collins, G.S. and Wuennemann, K. and Artemieva, N. and Pierazzo, E.},\n\tyear = {2012},\n\tpages = {254--270},\n}\n\n

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\n \n\n \n \n Collins, G. S.; Melosh, H. J.; and Osinski, G. R.\n\n\n \n \n \n \n \n The Impact-Cratering Process.\n \n \n \n \n\n\n \n\n\n\n Elements, 8(1): 25–30. February 2012.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 4 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{collins_impact-cratering_2012,\n\ttitle = {The {Impact}-{Cratering} {Process}},\n\tvolume = {8},\n\tissn = {1811-5209, 1811-5217},\n\turl = {http://elements.geoscienceworld.org/content/8/1/25},\n\tdoi = {10.2113/gselements.8.1.25},\n\tabstract = {Impact cratering is an important and unique geologic process. The high speeds, forces and temperatures involved are quite unlike conventional endogenic processes, and the environmental consequences can be catastrophic. Kilometre-scale craters are excavated and collapse in minutes, in some cases distributing debris around the globe and exhuming deeply buried strata. In the process, rocks are deformed, broken, heated and transformed in unique ways. Elevated temperatures in the crust may persist for millennia, and important chemical reactions are promoted by the extreme environment of the impact plume. Released gases may cause long-term perturbations to the climate, and impact-related phosphorus reduction may have played a role in the origin of life on Earth.},\n\tlanguage = {en},\n\tnumber = {1},\n\turldate = {2014-01-23},\n\tjournal = {Elements},\n\tauthor = {Collins, Gareth S. and Melosh, H. Jay and Osinski, Gordon R.},\n\tmonth = feb,\n\tyear = {2012},\n\tkeywords = {crater collapse, ejecta, impact crater, shock wave},\n\tpages = {25--30},\n}\n\n

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\n \n\n \n \n Davison, T. M.; Ciesla, F. J.; and Collins, G. S.\n\n\n \n \n \n \n \n Post-Impact Thermal Evolution of Porous Planetesimals.\n \n \n \n \n\n\n \n\n\n\n Geochimica et Cosmochimica Acta, 95: 252–269. 2012.\n \n\n\n\n
\n\n\n\n \n \n $\"Post-Impact$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{davison_post-impact_2012,\n\ttitle = {Post-{Impact} {Thermal} {Evolution} of {Porous} {Planetesimals}},\n\tvolume = {95},\n\tissn = {0016-7037},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0016703712004486?v=s5},\n\tdoi = {10.1016/j.gca.2012.08.001},\n\tabstract = {Impacts between planetesimals have largely been ruled out as a heat source in the early Solar System, by calculations that show them to be an inefficient heat source and unlikely to cause global heating. However, the long-term, localized thermal effects of impacts on planetesimals have never been fully quantified. Here, we simulate a range of impact scenarios between planetesimals to determine the post-impact thermal histories of the parent bodies, and hence the importance of impact heating in the thermal evolution of planetesimals. We find on a local scale that heating material to petrologic type 6 is achievable for a range of impact velocities and initial porosities, and impact melting is possible in porous material at a velocity of \\&gt; 4 km/s. Burial of heated impactor material beneath the impact crater is common, insulating that material and allowing the parent body to retain the heat for extended periods (∼ millions of years). Cooling rates at 773 K are typically 1 - 1000 K/Ma, matching a wide range of measurements of metallographic cooling rates from chondritic materials. While the heating presented here is localized to the impact site, multiple impacts over the lifetime of a parent body are likely to have occurred. Moreover, as most meteorite samples are on the centimeter to meter scale, the localized effects of impact heating cannot be ignored.},\n\turldate = {2012-08-17},\n\tjournal = {Geochimica et Cosmochimica Acta},\n\tauthor = {Davison, Thomas M. and Ciesla, Fred J. and Collins, Gareth S.},\n\tyear = {2012},\n\tpages = {252--269},\n}\n\n

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\n \n\n \n \n Johnson, B. C.; and Melosh, H. J.\n\n\n \n \n \n \n \n Impact spherules as a record of an ancient heavy bombardment of Earth.\n \n \n \n \n\n\n \n\n\n\n Nature, 485(7396): 75–77. May 2012.\n \n\n\n\n
\n\n\n\n \n \n $\"Impact$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{johnson_impact_2012,\n\ttitle = {Impact spherules as a record of an ancient heavy bombardment of {Earth}},\n\tvolume = {485},\n\tcopyright = {© 2012 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.},\n\tissn = {0028-0836},\n\turl = {http://www.nature.com/nature/journal/v485/n7396/full/nature10982.html},\n\tdoi = {10.1038/nature10982},\n\tabstract = {Impact craters are the most obvious indication of asteroid impacts, but craters on Earth are quickly obscured or destroyed by surface weathering and tectonic processes. Earth/'s impact history is inferred therefore either from estimates of the present-day impactor flux as determined by observations of near-Earth asteroids, or from the Moon/'s incomplete impact chronology. Asteroids hitting Earth typically vaporize a mass of target rock comparable to the projectile/'s mass. As this vapour expands in a large plume or fireball, it cools and condenses into molten droplets called spherules. For asteroids larger than about ten kilometres in diameter, these spherules are deposited in a global layer. Spherule layers preserved in the geologic record accordingly provide information about an impact even when the source crater cannot be found. Here we report estimates of the sizes and impact velocities of the asteroids that created global spherule layers. The impact chronology from these spherule layers reveals that the impactor flux was significantly higher 3.5 billion years ago than it is now. This conclusion is consistent with a gradual decline of the impactor flux after the Late Heavy Bombardment.},\n\tlanguage = {en},\n\tnumber = {7396},\n\turldate = {2014-01-16},\n\tjournal = {Nature},\n\tauthor = {Johnson, B. C. and Melosh, H. J.},\n\tmonth = may,\n\tyear = {2012},\n\tkeywords = {Earth sciences, Geology, Planetary sciences, geophysics},\n\tpages = {75--77},\n}\n\n

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\n \n\n \n \n Potter, R.; Collins, G.; Kiefer, W.; McGovern, P.; and Kring, D.\n\n\n \n \n \n \n \n Constraining the size of the South Pole-Aitken basin impact.\n \n \n \n \n\n\n \n\n\n\n Icarus, 220(2): 730–743. August 2012.\n \n\n\n\n
\n\n\n\n \n \n $\"Constraining$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{potter_constraining_2012,\n\ttitle = {Constraining the size of the {South} {Pole}-{Aitken} basin impact},\n\tvolume = {220},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S001910351200214X},\n\tdoi = {10.1016/j.icarus.2012.05.032},\n\tabstract = {The South Pole-Aitken (SPA) basin is the largest and oldest definitive impact structure on the Moon. To understand how this immense basin formed, we conducted a suite of SPA-scale numerical impact simulations varying impactor size, impact velocity, and lithospheric thermal gradient. We compared our model results to observational SPA basin data to constrain a best-fit scenario for the SPA basin-forming impact. Our results show that the excavation depth-to-diameter ratio for SPA-scale impacts is constant for all impact scenarios and is consistent with analytical and geological estimates of excavation depth in smaller craters, suggesting that SPA-scale impacts follow proportional scaling. Steep near-surface thermal gradients and high internal temperatures greatly affected the basin-forming process, basin structure and impact-generated melt volume. In agreement with previous numerical studies of SPA-scale impacts, crustal material is entirely removed from the basin center which is instead occupied by a large melt pool of predominantly mantle composition. Differentiation of the melt pool is needed to be consistent with observational data. Assuming differentiation of the thick impact-generated melt sheet occurred, and using observational basin data as constraints, we find the best-fit impact scenario for the formation of the South Pole-Aitken basin to be an impact with an energy of ∼4\\&\\#xa0;×\\&\\#xa0;1026\\&\\#xa0;J (our specific model considered an impactor 170\\&\\#xa0;km in diameter, striking at 10\\&\\#xa0;km/s).},\n\tnumber = {2},\n\turldate = {2012-07-12},\n\tjournal = {Icarus},\n\tauthor = {Potter, R.W.K. and Collins, G.S. and Kiefer, W.S. and McGovern, P.J. and Kring, D.A.},\n\tmonth = aug,\n\tyear = {2012},\n\tkeywords = {CRATERING, Collisional physics, Impact processes, Moon},\n\tpages = {730--743},\n}\n\n

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\n \n\n \n \n Bray, V. J.; Schenk, P. M.; Jay Melosh, H.; Morgan, J. V.; and Collins, G. S.\n\n\n \n \n \n \n \n Ganymede crater dimensions – Implications for central peak and central pit formation and development.\n \n \n \n \n\n\n \n\n\n\n Icarus, 217(1): 115–129. January 2012.\n \n\n\n\n
\n\n\n\n \n \n $\"Ganymede$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{bray_ganymede_2012,\n\ttitle = {Ganymede crater dimensions – {Implications} for central peak and central pit formation and development},\n\tvolume = {217},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103511003976},\n\tdoi = {10.1016/j.icarus.2011.10.004},\n\tabstract = {The morphology of impact craters on the icy Galilean satellites differs from craters on rocky bodies. The differences are thought due to the relative weakness of ice and the possible presence of sub-surface water layers. Digital elevation models constructed from Galileo images were used to measure a range of dimensions of craters on the dark and bright terrains of Ganymede. Measurements were made from multiple profiles across each crater, so that natural variation in crater dimensions could be assessed and averaged scaling trends constructed. The additional depth, slope and volume information reported in this work has enabled study of central peak formation and development, and allowed a quantitative assessment of the various theories for central pit formation. We note a possible difference in the size-morphology progression between small craters on icy and silicate bodies, where central peaks occur in small craters before there is any slumping of the crater rim, which is the opposite to the observed sequence on the Moon. Conversely, our crater dimension analyses suggest that the size-morphology progression of large lunar craters from central peak to peak-ring is mirrored on Ganymede, but that the peak-ring is subsequently modified to a central pit morphology. Pit formation may occur via the collapse of surface material into a void left by the gradual release of impact-induced volatiles or the drainage of impact melt into sub-crater fractures.},\n\tnumber = {1},\n\turldate = {2012-02-27},\n\tjournal = {Icarus},\n\tauthor = {Bray, Veronica J. and Schenk, Paul M. and Jay Melosh, H. and Morgan, Joanna V. and Collins, Gareth S.},\n\tmonth = jan,\n\tyear = {2012},\n\tkeywords = {CRATERING, Ganymede, Impact processes},\n\tpages = {115--129},\n}\n\n

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\n \n\n \n \n Miljkovic, K.; Collins, G. S; Chapman, D. J.; Patel, M. R; and Proud, W.\n\n\n \n \n \n \n \n High-velocity impacts in porous solar system materials.\n \n \n \n \n\n\n \n\n\n\n AIP Conference Proceedings, 1426(1): 871–874. March 2012.\n \n\n\n\n
\n\n\n\n \n \n $\"High-velocity$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{miljkovic_high-velocity_2012,\n\ttitle = {High-velocity impacts in porous solar system materials},\n\tvolume = {1426},\n\tissn = {0094243X},\n\turl = {http://proceedings.aip.org/resource/2/apcpcs/1426/1/871_1?ver=pdfcov},\n\tdoi = {doi:10.1063/1.3686416},\n\tabstract = {High-velocity impacts on planetary surfaces are common events in the solar system. The conse-quences of such impacts depend, in part, on the properties of the target solar system body, such as surface strength, porosity and gravity. Bodies in the solar system exhibit a range of material properties, hence it is difficult to specify a general material model. Experimental investigations of impacts onto solar system sur- faces often use sand as an analogue material and hydrocode simulations of impact often assume a sand-like equation of state (EoS) and strength model, which is valid only for a limited range of porosities. To simu- late impact on smaller bodies in the solar system, such as asteroids, comets or smaller planetary satellites, requires a more appropriate material model. We compare iSALE-2D hydrocode simulations of impacts in porous granular materials with results from laboratory impact experiments made by [1] to test and refine a general-purpose material model applicable for a wide range of porous materials in the solar system.},\n\tnumber = {1},\n\turldate = {2012-04-16},\n\tjournal = {AIP Conference Proceedings},\n\tauthor = {Miljkovic, Katarina and Collins, Gareth S and Chapman, David James and Patel, Manish R and Proud, William},\n\tmonth = mar,\n\tyear = {2012},\n\tpages = {871--874},\n}\n\n

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\n \n\n \n \n Potter, R. W. K.; Kring, D. A.; Collins, G. S.; Kiefer, W. S.; and McGovern, P. J.\n\n\n \n \n \n \n \n Estimating transient crater size using the crustal annular bulge: Insights from numerical modeling of lunar basin-scale impacts.\n \n \n \n \n\n\n \n\n\n\n Geophysical Research Letters, 39(18): L18203. September 2012.\n \n\n\n\n
\n\n\n\n \n \n $\"Estimating$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{potter_estimating_2012,\n\ttitle = {Estimating transient crater size using the crustal annular bulge: {Insights} from numerical modeling of lunar basin-scale impacts},\n\tvolume = {39},\n\tcopyright = {© 2008 American Geophysical Union},\n\tissn = {0094-8276},\n\tshorttitle = {Estimating transient crater size using the crustal annular bulge},\n\turl = {http://www.agu.org/pubs/crossref/2012/2012GL052981.shtml},\n\tdoi = {10.1029/2012GL052981},\n\tabstract = {The transient crater is an important impact cratering concept. Its volume and diameter can be used to predict impact energy and momentum, impact melt volume, and maximum depth and volume of ejected material. Transient crater sizes are often estimated using scaling laws based on final crater rim diameters. However, crater rim estimates, especially for lunar basins, can be controversial. Here, we use numerical modeling of lunar basin-scale impacts to produce a new, alternative method for estimating transient crater radius using the annular bulge of crust observed beneath most lunar basins. Using target thermal conditions appropriate for the lunar Imbrian and Nectarian periods, we find this relationship to be dependent on lunar crust and upper mantle temperatures. This result is potentially important when analyzing lunar basin subsurface structures inferred from the GRAIL mission.},\n\tlanguage = {English},\n\tnumber = {18},\n\turldate = {2012-10-08},\n\tjournal = {Geophysical Research Letters},\n\tauthor = {Potter, R. W. K. and Kring, D. A. and Collins, G. S. and Kiefer, W. S. and McGovern, P. J.},\n\tmonth = sep,\n\tyear = {2012},\n\tpages = {L18203},\n}\n\n

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\n\n\n\n\n\n

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\n \n 2011\n \n \n (5)\n \n \n

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\n \n \n

\n \n\n \n \n Collins, G.; Melosh, H.; and Wünnemann, K.\n\n\n \n \n \n \n \n Improvements to the ɛ-α porous compaction model for simulating impacts into high-porosity solar system objects.\n \n \n \n \n\n\n \n\n\n\n International Journal of Impact Engineering, 38(6): 434–439. June 2011.\n \n\n\n\n
\n\n\n\n \n \n $\"Improvements$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{collins_improvements_2011,\n\ttitle = {Improvements to the ɛ-α porous compaction model for simulating impacts into high-porosity solar system objects},\n\tvolume = {38},\n\tissn = {0734-743X},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0734743X10001594},\n\tdoi = {10.1016/j.ijimpeng.2010.10.013},\n\tnumber = {6},\n\tjournal = {International Journal of Impact Engineering},\n\tauthor = {Collins, G.S. and Melosh, H.J. and Wünnemann, K.},\n\tmonth = jun,\n\tyear = {2011},\n\tkeywords = {Hydrocode modeling, impact cratering, porosity, solar system},\n\tpages = {434--439},\n}\n\n

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\n\n\n

\n \n\n \n \n Collins, G.; Elbeshausen, D.; Davison, T.; Robbins, S.; and Hynek, B.\n\n\n \n \n \n \n \n The size-frequency distribution of elliptical impact craters.\n \n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 310(1-2): 1–8. October 2011.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

\n

@article{collins_size-frequency_2011,\n\ttitle = {The size-frequency distribution of elliptical impact craters},\n\tvolume = {310},\n\tissn = {0012821X},\n\turl = {http://elsevier-apps.sciverse.com/GoogleMaps/index.jsp?doi=10.1016/j.epsl.2011.07.023},\n\tdoi = {10.1016/j.epsl.2011.07.023},\n\tnumber = {1-2},\n\turldate = {2011-12-20},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Collins, G.S. and Elbeshausen, D. and Davison, T.M. and Robbins, S.J. and Hynek, B.M.},\n\tmonth = oct,\n\tyear = {2011},\n\tpages = {1--8},\n}\n\n

\n

\n\n\n\n

\n\n\n

\n \n\n \n \n Davison, T. M; Collins, G. S; Elbeshausen, D.; Wünnemann, K.; and Kearsley, A.\n\n\n \n \n \n \n \n Numerical modeling of oblique hypervelocity impacts on strong ductile targets.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 46(10): 1510–1524. October 2011.\n \n\n\n\n
\n\n\n\n \n \n $\"Numerical$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

\n

@article{davison_numerical_2011,\n\ttitle = {Numerical modeling of oblique hypervelocity impacts on strong ductile targets},\n\tvolume = {46},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2011.01246.x/abstract},\n\tdoi = {10.1111/j.1945-5100.2011.01246.x},\n\tabstract = {Abstract– The majority of meteorite impacts occur at oblique incidence angles. However, many of the effects of obliquity on impact crater size and morphology are poorly understood. Laboratory experiments and numerical models have shown that crater size decreases with impact angle, the along-range crater profile becomes asymmetric at low incidence angles, and below a certain threshold angle the crater planform becomes elliptical. Experimental results at approximately constant impact velocity suggest that the elliptical threshold angle depends on target material properties. Herein, we test the hypothesis that the threshold for oblique crater asymmetry depends on target material strength. Three-dimensional numerical modeling offers a unique opportunity to study the individual effects of both impact angle and target strength; however, a systematic study of these two parameters has not previously been performed. In this work, the three-dimensional shock physics code iSALE-3D is validated against laboratory experiments of impacts into a strong, ductile target material. Digital elevation models of craters formed in laboratory experiments were created from stereo pairs of scanning electron microscope images, allowing the size and morphology to be directly compared with the iSALE-3D craters. The simulated craters show excellent agreement with both the crater size and morphology of the laboratory experiments. iSALE-3D is also used to investigate the effect of target strength on oblique incidence impact cratering. We find that the elliptical threshold angle decreases with decreasing target strength, and hence with increasing cratering efficiency. Our simulations of impacts on ductile targets also support the prediction from Chapman and McKinnon (1986) that cratering efficiency depends on only the vertical component of the velocity vector.},\n\tlanguage = {en},\n\tnumber = {10},\n\turldate = {2012-01-12},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Davison, Thomas M and Collins, Gareth S and Elbeshausen, Dirk and Wünnemann, Kai and Kearsley, Anton},\n\tmonth = oct,\n\tyear = {2011},\n\tpages = {1510--1524},\n}\n\n

\n

\n\n\n\n\n\n

\n\n\n

\n \n\n \n \n Morgan, J. V.; Warner, M. R.; Collins, G. S.; Grieve, R. a. F.; Christeson, G. L.; Gulick, S. P. S.; and Barton, P. J.\n\n\n \n \n \n \n \n Full waveform tomographic images of the peak ring at the Chicxulub impact crater.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research, 116(B6): B06303. June 2011.\n \n\n\n\n
\n\n\n\n \n \n $\"Full$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

\n

@article{morgan_full_2011,\n\ttitle = {Full waveform tomographic images of the peak ring at the {Chicxulub} impact crater},\n\tvolume = {116},\n\tcopyright = {© 2008 American Geophysical Union},\n\tissn = {0148-0227},\n\turl = {http://www.agu.org/pubs/crossref/2011/2010JB008015.shtml},\n\tdoi = {10.1029/2010JB008015},\n\tabstract = {Peak rings are a feature of large impact craters on the terrestrial planets and are generally believed to be formed from deeply buried rocks that are uplifted during crater formation. The precise lithology and kinematics of peak ring formation, however, remains unclear. Previous work has revealed a suite of bright inward dipping reflectors beneath the peak ring at the Chicxulub impact crater and that the peak ring was formed from rocks with a relatively low seismic velocity. New two-dimensional, full waveform tomographic velocity images show that the uppermost lithology of the peak ring is formed from a thin (∼100–200 m thick) layer of low-velocity (∼3000–3200 m/s) rocks. This low-velocity layer is most likely composed of highly porous, allogenic impact breccias. Our models also show that the change in velocity between lithologies within and outside the peak ring is more abrupt than previously realized and occurs close to the location of the dipping reflectors. Across the peak ring, velocity appears to correlate well with predicted shock pressures from a dynamic model of crater formation, where the rocks that form the peak ring originate from an uplifted basement that has been subjected to high shock pressures (10–50 GPa) and lie above downthrown sedimentary rocks that have been subjected to shock pressures of {\\textless}5 GPa. These observations suggest that low velocities within the peak ring may be related to shock effects and that the dipping reflectors underneath the peak ring might represent the boundary between highly shocked basement and weakly shocked sediments.},\n\tlanguage = {English},\n\tnumber = {B6},\n\turldate = {2012-12-20},\n\tjournal = {Journal of Geophysical Research},\n\tauthor = {Morgan, J. V. and Warner, M. R. and Collins, G. S. and Grieve, R. a. F. and Christeson, G. L. and Gulick, S. P. S. and Barton, P. J.},\n\tmonth = jun,\n\tyear = {2011},\n\tpages = {B06303},\n}\n\n

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\n\n\n\n\n\n

\n\n\n

\n \n\n \n \n Wünnemann, K.; Nowka, D.; Collins, G.S.; Elbeshausen, D.; and Bierhaus, M.\n\n\n \n \n \n \n \n Scaling of impact crater formation on planetary surfaces – insights from numerical modeling.\n \n \n \n \n\n\n \n\n\n\n In Proceedings of the 11th Hypervelocity Impact Symposium 2010, pages 828, Freiburg, Germany, 2011. Fraunhofer Verlag, Stuttgart\n \n\n\n\n
\n\n\n\n \n \n $\"Scaling$ Paper\n \n \n\n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

\n

@inproceedings{wunnemann_scaling_2011,\n\taddress = {Freiburg, Germany},\n\ttitle = {Scaling of impact crater formation on planetary surfaces – insights from numerical modeling},\n\tisbn = {3-8396-0280-7},\n\turl = {https://www.researchgate.net/publication/257609508_Scaling_of_impact_crater_formation_on_planetary_surfaces--Insights_from_numerical_modeling},\n\tabstract = {We conducted a suite of more than 150 numerical models of crater formation in targets with different material properties. The study aims to determine important scaling parameters used in scaling laws that predict the crater diameter  as  a  function  of  impact  velocity,  gravity,  density  of  the  projectile  and  target,  projectile  size,  and  a number of material properties such as the coefficient of friction, cohesion, and porosity. We focus on large-scale craters on planetary surfaces where crater growth is primarily limited by gravity. However, our models show that the resistance against plastic deformation affects the size of the transient crater over a broad range of size-scales of impact events. Generally it can be said the higher the coefficient of friction, the more porous the target, and the larger the cohesive strength the smaller the resulting crater. We provide estimates of scaling parameters applicable for materials of different friction, porosity, and cohesion. By means of the famous Barringer Crater in Arizona we demonstrate the effect of target properties on the size of the projectile required to form a crater of given size.},\n\tbooktitle = {Proceedings of the 11th {Hypervelocity} {Impact} {Symposium} 2010},\n\tpublisher = {Fraunhofer Verlag, Stuttgart},\n\tauthor = {Wünnemann, K. and {Nowka, D.} and {Collins, G.S.} and {Elbeshausen, D.} and {Bierhaus, M.}},\n\tyear = {2011},\n\tpages = {828},\n}\n\n

\n

\n\n\n\n\n\n

\n

\n \n 2010\n \n \n (2)\n \n \n

\n

\n \n \n

\n \n\n \n \n Davison, T. M; Collins, G. S; and Ciesla, F. J\n\n\n \n \n \n \n Numerical modelling of heating in porous planetesimal collisions.\n \n \n \n\n\n \n\n\n\n Icarus, 208(1): 468–481. 2010.\n \n\n\n\n
\n\n\n\n \n\n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

\n

@article{davison_numerical_2010,\n\ttitle = {Numerical modelling of heating in porous planetesimal collisions},\n\tvolume = {208},\n\tnumber = {1},\n\tjournal = {Icarus},\n\tauthor = {Davison, T. M and Collins, G. S and Ciesla, F. J},\n\tyear = {2010},\n\tkeywords = {Collisional physics, Planetary formation, Planetesimals, impact processes},\n\tpages = {468--481},\n}\n\n

\n

\n\n\n\n

\n\n\n

\n \n\n \n \n Wünnemann, K.; Collins, G. S.; and Weiss, R.\n\n\n \n \n \n \n \n Impact of a cosmic body into Earth's ocean and the generation of large water waves: Insight from numerical modeling.\n \n \n \n \n\n\n \n\n\n\n Reviews of Geophysics, 48: 26 PP.. December 2010.\n \n\n\n\n
\n\n\n\n \n \n $\"Impact$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

\n

@article{wunnemann_impact_2010,\n\ttitle = {Impact of a cosmic body into {Earth}'s ocean and the generation of large water waves: {Insight} from numerical modeling},\n\tvolume = {48},\n\tshorttitle = {Impact of a cosmic body into {Earth}'s ocean and the generation of large water waves},\n\turl = {http://www.agu.org/pubs/crossref/2010/2009RG000308.shtml},\n\tdoi = {201010.1029/2009RG000308},\n\turldate = {2012-01-12},\n\tjournal = {Reviews of Geophysics},\n\tauthor = {Wünnemann, K. and Collins, G. S. and Weiss, R.},\n\tmonth = dec,\n\tyear = {2010},\n\tpages = {26 PP.},\n}\n\n

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\n\n\n\n\n\n

\n

\n \n 2009\n \n \n (3)\n \n \n

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\n \n \n

\n \n\n \n \n Christeson, G. L.; Collins, G. S.; Morgan, J. V.; Gulick, S. P.; Barton, P. J.; and Warner, M. R.\n\n\n \n \n \n \n \n Mantle deformation beneath the Chicxulub impact crater.\n \n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 284(1–2): 249–257. June 2009.\n \n\n\n\n
\n\n\n\n \n \n $\"Mantle$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

\n

@article{christeson_mantle_2009,\n\ttitle = {Mantle deformation beneath the {Chicxulub} impact crater},\n\tvolume = {284},\n\tissn = {0012-821X},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0012821X09002635},\n\tdoi = {10.1016/j.epsl.2009.04.033},\n\tnumber = {1–2},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Christeson, Gail L. and Collins, Gareth S. and Morgan, Joanna V. and Gulick, Sean P.S. and Barton, Penny J. and Warner, Michael R.},\n\tmonth = jun,\n\tyear = {2009},\n\tkeywords = {CRATER, Moho, chicxulub, terrestrial impact},\n\tpages = {249--257},\n}\n\n

\n

\n\n\n\n

\n\n\n

\n \n\n \n \n Elbeshausen, D.; Wünnemann, K.; and Collins, G. S\n\n\n \n \n \n \n Scaling of oblique impacts in frictional targets: Implications for crater size and formation mechanisms.\n \n \n \n\n\n \n\n\n\n Icarus, 204(2): 716–731. 2009.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

\n

@article{elbeshausen_scaling_2009,\n\ttitle = {Scaling of oblique impacts in frictional targets: {Implications} for crater size and formation mechanisms},\n\tvolume = {204},\n\tdoi = {10.1016/j.icarus.2009.07.018},\n\tnumber = {2},\n\tjournal = {Icarus},\n\tauthor = {Elbeshausen, Dirk and Wünnemann, Kai and Collins, Gareth S},\n\tyear = {2009},\n\tkeywords = {Cratering, Earth, Geologic processes, Meteorites, impact processes},\n\tpages = {716--731},\n}\n\n

\n

\n\n\n\n

\n\n\n

\n \n\n \n \n Kenkmann, T.; Collins, G.; Wittmann, A.; Wünnemann, K.; Reimold, W.; and Melosh, H.\n\n\n \n \n \n \n \n A model for the formation of the Chesapeake Bay impact crater as revealed by drilling and numerical simulation.\n \n \n \n \n\n\n \n\n\n\n Geological Society of America Special Papers, 458: 571 –585. January 2009.\n \n\n\n\n
\n\n\n\n \n \n $\"A$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

\n

@article{kenkmann_model_2009,\n\ttitle = {A model for the formation of the {Chesapeake} {Bay} impact crater as revealed by drilling and numerical simulation},\n\tvolume = {458},\n\turl = {http://specialpapers.gsapubs.org/content/458/571.abstract},\n\tdoi = {10.1130/2009.2458(25)},\n\tabstract = {The combination of petrographic analysis of drill core from the recent International Continental Scientific Drilling Program (ICDP)–U.S Geological Survey (USGS) drilling project and results from numerical simulations provides new constraints for reconstructing the kinematic history and duration of different stages of the Chesa-peake Bay impact event. The numerical model, in good qualitative agreement with previous seismic data across the crater, is also roughly consistent with the stratigraphy of the new borehole. From drill core observations and modeling, the following conclusions can be drawn: (1) The lack of a shock metamorphic overprint of cored basement lithologies suggests that the drill core might not have reached the parautochthonous shocked crater floor but merely cored basement blocks that slumped off the rim of the original cavity into the crater during crater modification. (2) The sequence of polymict lithic breccia, suevite, and impact melt rock (1397–1551 m) must have been deposited prior to the arrival of the 950-m-thick resurge and avalanche-delivered beds and blocks within 5–7 min after impact. (3) This short period for transportation and deposition of impactites may suggest that the majority of the impactites of the Eyreville core never left the transient crater and was emplaced by ground surge. This is in accordance with observations of impact breccia fabrics. However, the uppermost part of the suevite section contains a pronounced component of airborne material. (4) Limited amounts of shock-deformed debris and melt fragments also occur throughout the Exmore beds. Shard-enriched intervals in the upper Exmore beds indicate that some material interpreted to be part of the hot ejecta plume was incorporated and dispersed into the upper resurge deposits. This suggests that collapse of the ejecta plume was contemporaneous with the major resurge event(s). Modeling indicates that the resurge flow should have been concluded some 20 min after impact; hence, this also likely marked the end of the major episode of deposition from the ejecta plume.},\n\turldate = {2012-01-12},\n\tjournal = {Geological Society of America Special Papers},\n\tauthor = {Kenkmann, T. and Collins, G.S. and Wittmann, A. and Wünnemann, K. and Reimold, W.U. and Melosh, H.J.},\n\tmonth = jan,\n\tyear = {2009},\n\tpages = {571 --585},\n}\n\n

\n

\n\n\n

\n The combination of petrographic analysis of drill core from the recent International Continental Scientific Drilling Program (ICDP)–U.S Geological Survey (USGS) drilling project and results from numerical simulations provides new constraints for reconstructing the kinematic history and duration of different stages of the Chesa-peake Bay impact event. The numerical model, in good qualitative agreement with previous seismic data across the crater, is also roughly consistent with the stratigraphy of the new borehole. From drill core observations and modeling, the following conclusions can be drawn: (1) The lack of a shock metamorphic overprint of cored basement lithologies suggests that the drill core might not have reached the parautochthonous shocked crater floor but merely cored basement blocks that slumped off the rim of the original cavity into the crater during crater modification. (2) The sequence of polymict lithic breccia, suevite, and impact melt rock (1397–1551 m) must have been deposited prior to the arrival of the 950-m-thick resurge and avalanche-delivered beds and blocks within 5–7 min after impact. (3) This short period for transportation and deposition of impactites may suggest that the majority of the impactites of the Eyreville core never left the transient crater and was emplaced by ground surge. This is in accordance with observations of impact breccia fabrics. However, the uppermost part of the suevite section contains a pronounced component of airborne material. (4) Limited amounts of shock-deformed debris and melt fragments also occur throughout the Exmore beds. Shard-enriched intervals in the upper Exmore beds indicate that some material interpreted to be part of the hot ejecta plume was incorporated and dispersed into the upper resurge deposits. This suggests that collapse of the ejecta plume was contemporaneous with the major resurge event(s). Modeling indicates that the resurge flow should have been concluded some 20 min after impact; hence, this also likely marked the end of the major episode of deposition from the ejecta plume.\n

\n\n\n

\n\n\n\n\n\n

\n

\n \n 2008\n \n \n (6)\n \n \n

\n

\n \n \n

\n \n\n \n \n Osinski, G. R; Grieve, R. a. F; Collins, G. S; Marion, C.; and Sylvester, P.\n\n\n \n \n \n \n \n The effect of target lithology on the products of impact melting.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 43(12): 1939–1954. December 2008.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

\n

@article{osinski_effect_2008,\n\ttitle = {The effect of target lithology on the products of impact melting},\n\tvolume = {43},\n\tissn = {1945-5100},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2008.tb00654.x/abstract},\n\tdoi = {10.1111/j.1945-5100.2008.tb00654.x},\n\tabstract = {Abstract— Impact cratering is an important geological process on the terrestrial planets and rocky and icy moons of the outer solar system. Impact events generate pressures and temperatures that can melt a substantial volume of the target; however, there remains considerable discussion as to the effect of target lithology on the generation of impact melts. Early studies showed that for impacts into crystalline targets, coherent impact melt rocks or “sheets” are formed with these rocks often displaying classic igneous structures (e.g., columnar jointing) and textures. For impact structures containing some amount of sedimentary rocks in the target sequence, a wide range of impact-generated lithologies have been described, although it has generally been suggested that impact melt is either lacking or is volumetrically minor. This is surprising given theoretical constraints, which show that as much melt should be produced during impacts into sedimentary targets. The question then arises: where has all the melt gone? The goal of this synthesis is to explore the effect of target lithology on the products of impact melting. A comparative study of the similarly sized Haughton, Mistastin, and Ries impact structures, suggests that the fundamental processes of impact melting are basically the same in sedimentary and crystalline targets, regardless of target properties. Furthermore, using advanced microbeam analytical techniques, it is apparent that, for the structures under consideration here, a large proportion of the melt is retained within the crater (as crater-fill impactites) for impacts into sedimentary-bearing target rocks. Thus, it is suggested that the basic products are genetically equivalent but they just appear different. That is, it is the textural, chemical and physical properties of the products that vary.},\n\tlanguage = {en},\n\tnumber = {12},\n\turldate = {2012-01-12},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Osinski, G. R and Grieve, R. a. F and Collins, G. S and Marion, C. and Sylvester, P.},\n\tmonth = dec,\n\tyear = {2008},\n\tpages = {1939--1954},\n}\n\n

\n

\n\n\n\n\n\n

\n\n\n

\n \n\n \n \n Wünnemann, K.; Collins, G. S; and Osinski, G. R\n\n\n \n \n \n \n Numerical modelling of impact melt production in porous rocks.\n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 269(3-4): 530–539. 2008.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

\n

@article{wunnemann_numerical_2008,\n\ttitle = {Numerical modelling of impact melt production in porous rocks},\n\tvolume = {269},\n\tdoi = {10.1016/j.epsl.2008.03.007},\n\tnumber = {3-4},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Wünnemann, K. and Collins, G. S and Osinski, G. R},\n\tyear = {2008},\n\tkeywords = {impact cratering, impact melt scaling, porosity, shock melting, shock metamorphism},\n\tpages = {530--539},\n}\n\n

\n

\n\n\n\n

\n\n\n

\n \n\n \n \n Bray, V. J; Collins, G. S; Morgan, J. V; and Schenk, P. M\n\n\n \n \n \n \n \n The effect of target properties on crater morphology: Comparison of central peak craters on the Moon and Ganymede.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 43(12): 1979–1992. December 2008.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

\n

@article{bray_effect_2008,\n\ttitle = {The effect of target properties on crater morphology: {Comparison} of central peak craters on the {Moon} and {Ganymede}},\n\tvolume = {43},\n\tissn = {1945-5100},\n\tshorttitle = {The effect of target properties on crater morphology},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2008.tb00656.x/abstract},\n\tdoi = {10.1111/j.1945-5100.2008.tb00656.x},\n\tabstract = {Abstract— We examine the morphology of central peak craters on the Moon and Ganymede in order to investigate differences in the near-surface properties of these bodies. We have extracted topographic profiles across craters on Ganymede using Galileo images, and use these data to compile scaling trends. Comparisons between lunar and Ganymede craters show that crater depth, wall slope and amount of central uplift are all affected by material properties. We observe no major differences between similar-sized craters in the dark and bright terrain of Ganymede, suggesting that dark terrain does not contain enough silicate material to significantly increase the strength of the surface ice. Below crater diameters of ˜12 km, central peak craters on Ganymede and simple craters on the Moon have similar rim heights, indicating comparable amounts of rim collapse. This suggests that the formation of central peaks at smaller crater diameters on Ganymede than the Moon is dominated by enhanced central floor uplift rather than rim collapse. Crater wall slope trends are similar on the Moon and Ganymede, indicating that there is a similar trend in material weakening with increasing crater size, and possibly that the mechanism of weakening during impact is analogous in icy and rocky targets. We have run a suite of numerical models to simulate the formation of central peak craters on Ganymede and the Moon. Our modeling shows that the same styles of strength model can be applied to ice and rock, and that the strength model parameters do not differ significantly between materials.},\n\tlanguage = {en},\n\tnumber = {12},\n\turldate = {2012-01-12},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Bray, Veronica J and Collins, Gareth S and Morgan, Joanna V and Schenk, Paul M},\n\tmonth = dec,\n\tyear = {2008},\n\tpages = {1979--1992},\n}\n\n

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\n \n\n \n \n Collins, G. S; Kenkmann, T.; Osinski, G. R; and Wünnemann, K.\n\n\n \n \n \n \n \n Mid‐sized complex crater formation in mixed crystalline‐sedimentary targets: Insight from modeling and observation.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 43(12): 1955–1977. December 2008.\n \n\n\n\n
\n\n\n\n \n \n $\"Mid‐sized$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{collins_midsized_2008,\n\ttitle = {Mid‐sized complex crater formation in mixed crystalline‐sedimentary targets: {Insight} from modeling and observation},\n\tvolume = {43},\n\tissn = {1945-5100},\n\tshorttitle = {Mid‐sized complex crater formation in mixed crystalline‐sedimentary targets},\n\turl = {http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2008.tb00655.x/abstract},\n\tdoi = {10.1111/j.1945-5100.2008.tb00655.x},\n\tabstract = {Abstract— Large impact crater formation is an important geologic process that is not fully understood. The current paradigm for impact crater formation is based on models and observations of impacts in homogeneous targets. Real targets are rarely uniform; for example, the majority of Earth's surface is covered by sedimentary rocks and/or a water layer. The ubiquity of layering across solar system bodies makes it important to understand the effect target properties have on the cratering process. To advance understanding of the mechanics of crater collapse, and the effect of variations in target properties on crater formation, the first “Bridging the Gap” workshop recommended that geological observation and numerical modeling focussed on mid-sized (15–30 km diameter) craters on Earth. These are large enough to be complex; small enough to be mapped, surveyed and modelled at high resolution; and numerous enough for the effects of target properties to be potentially disentangled from the effects of other variables. In this paper, we compare observations and numerical models of three 18–26 km diameter craters formed in different target lithology: Ries, Germany; Haughton, Canada; and El'gygytgyn, Russia. Based on the first-order assumption that the impact energy was the same in all three impacts we performed numerical simulations of each crater to construct a simple quantitative model for mid-sized complex crater formation in a subaerial, mixed crystalline-sedimentary target. We compared our results with interpreted geological profiles of Ries and Haughton, based on detailed new and published geological mapping and published geophysical surveys. Our combined observational and numerical modeling work suggests that the major structural differences between each crater can be explained by the difference in thickness of the pre-impact sedimentary cover in each case. We conclude that the presence of an inner ring at Ries, and not at Haughton, is because basement rocks that are stronger than the overlying sediments are sufficiently close to the surface that they are uplifted and overturned during excavation and remain as an uplifted ring after modification and post-impact erosion. For constant impact energy, transient and final crater diameters increase with increasing sediment thickness.},\n\tlanguage = {en},\n\tnumber = {12},\n\turldate = {2012-01-12},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Collins, G. S and Kenkmann, T. and Osinski, G. R and Wünnemann, K.},\n\tmonth = dec,\n\tyear = {2008},\n\tpages = {1955--1977},\n}\n\n

\n

\n\n\n

\n Abstract— Large impact crater formation is an important geologic process that is not fully understood. The current paradigm for impact crater formation is based on models and observations of impacts in homogeneous targets. Real targets are rarely uniform; for example, the majority of Earth's surface is covered by sedimentary rocks and/or a water layer. The ubiquity of layering across solar system bodies makes it important to understand the effect target properties have on the cratering process. To advance understanding of the mechanics of crater collapse, and the effect of variations in target properties on crater formation, the first “Bridging the Gap” workshop recommended that geological observation and numerical modeling focussed on mid-sized (15–30 km diameter) craters on Earth. These are large enough to be complex; small enough to be mapped, surveyed and modelled at high resolution; and numerous enough for the effects of target properties to be potentially disentangled from the effects of other variables. In this paper, we compare observations and numerical models of three 18–26 km diameter craters formed in different target lithology: Ries, Germany; Haughton, Canada; and El'gygytgyn, Russia. Based on the first-order assumption that the impact energy was the same in all three impacts we performed numerical simulations of each crater to construct a simple quantitative model for mid-sized complex crater formation in a subaerial, mixed crystalline-sedimentary target. We compared our results with interpreted geological profiles of Ries and Haughton, based on detailed new and published geological mapping and published geophysical surveys. Our combined observational and numerical modeling work suggests that the major structural differences between each crater can be explained by the difference in thickness of the pre-impact sedimentary cover in each case. We conclude that the presence of an inner ring at Ries, and not at Haughton, is because basement rocks that are stronger than the overlying sediments are sufficiently close to the surface that they are uplifted and overturned during excavation and remain as an uplifted ring after modification and post-impact erosion. For constant impact energy, transient and final crater diameters increase with increasing sediment thickness.\n

\n\n\n

\n \n\n \n \n Collins, G. S; Morgan, J. V; Barton, P.; Christeson, G. L; Gulick, S.; Urrutia-Fucugauchi, J.; Warner, M. R; and Wünnemann, K.\n\n\n \n \n \n \n Dynamic modeling suggests terrace zone asymmetry in the Chicxulub crater is caused by target heterogeneity.\n \n \n \n\n\n \n\n\n\n Earth and Planetary Science Letters, 270: 221–230. 2008.\n \n\n\n\n
\n\n\n\n \n\n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{collins_dynamic_2008,\n\ttitle = {Dynamic modeling suggests terrace zone asymmetry in the {Chicxulub} crater is caused by target heterogeneity},\n\tvolume = {270},\n\tjournal = {Earth and Planetary Science Letters},\n\tauthor = {Collins, G. S and Morgan, J. V and Barton, P. and Christeson, G. L and Gulick, S. and Urrutia-Fucugauchi, J. and Warner, M. R and Wünnemann, K.},\n\tyear = {2008},\n\tpages = {221--230},\n}\n\n

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\n \n\n \n \n Pierazzo, E.; Artemieva, N.; Asphaug, E.; Baldwin, E. C; Cazamias, J.; Coker, R.; Collins, G. S; Crawford, D.; Elbeshausen, D.; Holsapple, K. A; Housen, K. R; Korycansky, D. G; and Wunnemann, K.\n\n\n \n \n \n \n Validation of numerical codes for impact and explosion cratering.\n \n \n \n\n\n \n\n\n\n Meteoritics and Planetary Science, 43(12): 1917–1938. 2008.\n \n\n\n\n
\n\n\n\n \n\n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{pierazzo_validation_2008,\n\ttitle = {Validation of numerical codes for impact and explosion cratering},\n\tvolume = {43},\n\tnumber = {12},\n\tjournal = {Meteoritics and Planetary Science},\n\tauthor = {Pierazzo, E. and Artemieva, N. and Asphaug, E. and Baldwin, E. C and Cazamias, J. and Coker, R. and Collins, G. S and Crawford, D. and Elbeshausen, D. and Holsapple, K. A and Housen, K. R and Korycansky, D. G and Wunnemann, K.},\n\tyear = {2008},\n\tpages = {1917--1938},\n}\n\n

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\n \n 2007\n \n \n (1)\n \n \n

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\n \n\n \n \n Davison, T.; and Collins, G. S.\n\n\n \n \n \n \n \n The effect of the oceans on the terrestrial crater size-frequency distribution: Insight from numerical modeling.\n \n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 42(11): 1915–1927. 2007.\n \n\n\n\n
\n\n\n\n \n \n $\"The$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{davison_effect_2007,\n\ttitle = {The effect of the oceans on the terrestrial crater size-frequency distribution: {Insight} from numerical modeling},\n\tvolume = {42},\n\tissn = {1945-5100},\n\turl = {http://dx.doi.org/10.1111/j.1945-5100.2007.tb00550.x},\n\tdoi = {10.1111/j.1945-5100.2007.tb00550.x},\n\tnumber = {11},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Davison, T. and Collins, G. S.},\n\tyear = {2007},\n\tpages = {1915--1927},\n}\n\n

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\n \n 2006\n \n \n (2)\n \n \n

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\n \n\n \n \n Goldin, T. J; Wünnemann, K.; Melosh, H. J; and Collins, G. S\n\n\n \n \n \n \n Hydrocode modeling of the Sierra Madera impact structure.\n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 41(12): 1947–1958. 2006.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{goldin_hydrocode_2006,\n\ttitle = {Hydrocode modeling of the {Sierra} {Madera} impact structure},\n\tvolume = {41},\n\tdoi = {10.1111/j.1945-5100.2006.tb00462.x},\n\tnumber = {12},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Goldin, T. J and Wünnemann, K. and Melosh, H. J and Collins, G. S},\n\tyear = {2006},\n\tpages = {1947--1958},\n}\n\n

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\n \n\n \n \n Wünnemann, K.; Collins, G. S.; and Melosh, H. J.\n\n\n \n \n \n \n \n A strain-based porosity model for use in hydrocode simulations of impacts and implications for transient crater growth in porous targets.\n \n \n \n \n\n\n \n\n\n\n Icarus, 180(2): 514–527. February 2006.\n \n\n\n\n
\n\n\n\n \n \n $\"A$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{wunnemann_strain-based_2006,\n\ttitle = {A strain-based porosity model for use in hydrocode simulations of impacts and implications for transient crater growth in porous targets},\n\tvolume = {180},\n\tissn = {0019-1035},\n\turl = {http://www.sciencedirect.com/science/article/pii/S0019103505004124},\n\tdoi = {10.1016/j.icarus.2005.10.013},\n\tabstract = {Numerical modelling of impact cratering has reached a high degree of sophistication; however, the treatment of porous materials still poses a large problem in hydrocode calculations. We present a novel approach for dealing with porous compaction in numerical modelling of impact crater formation. In contrast to previous attempts (e.g., P-alpha model, snowplow model), our model accounts for the collapse of pore space by assuming that the compaction function depends upon volumetric strain rather than pressure. Our new ɛ-alpha model requires only four input parameters and each has a physical meaning. The model is simple and intuitive and shows good agreement with a wide variety of experimental data, ranging from static compaction tests to highly dynamic impact experiments. Our major objective in developing the model is to investigate the effect of porosity and internal friction on transient crater formation. We present preliminary numerical model results that suggest that both porosity and internal friction play an important role in limiting crater growth over a large range in gravity-scaled source size.},\n\tnumber = {2},\n\turldate = {2014-07-17},\n\tjournal = {Icarus},\n\tauthor = {Wünnemann, K. and Collins, G. S. and Melosh, H. J.},\n\tmonth = feb,\n\tyear = {2006},\n\tkeywords = {CRATERING, Collisional physics, Impact processes, Surfacescomets},\n\tpages = {514--527},\n}\n\n

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\n \n 2005\n \n \n (2)\n \n \n

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\n \n\n \n \n Collins, G. S; and Wünnemann, K.\n\n\n \n \n \n \n How big was the Chesapeake Bay impact? Insight from numerical modeling.\n \n \n \n\n\n \n\n\n\n Geology, 33(12): 925–928. 2005.\n undefined How big was the Chesapeake Bay impact? Insight from numerical modeling\n\n\n\n
\n\n\n\n \n\n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{collins_how_2005,\n\ttitle = {How big was the {Chesapeake} {Bay} impact? {Insight} from numerical modeling},\n\tvolume = {33},\n\tnumber = {12},\n\tjournal = {Geology},\n\tauthor = {Collins, G. S and Wünnemann, K.},\n\tyear = {2005},\n\tnote = {undefined\nHow big was the Chesapeake Bay impact? Insight from numerical modeling},\n\tpages = {925--928},\n}\n\n

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\n \n\n \n \n Turtle, E.; Pierazzo, E.; Collins, G.; Osinski, G.; Melosh, H.; Morgan, J.; and Reimold, W.\n\n\n \n \n \n \n \n Impact structures: What does crater diameter mean?.\n \n \n \n \n\n\n \n\n\n\n Geological Society of America Special Papers, 384: 1 –24. January 2005.\n \n\n\n\n
\n\n\n\n \n \n $\"Impact$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{turtle_impact_2005,\n\ttitle = {Impact structures: {What} does crater diameter mean?},\n\tvolume = {384},\n\tshorttitle = {Impact structures},\n\turl = {http://specialpapers.gsapubs.org/content/384/1.abstract},\n\tdoi = {10.1130/0-8137-2384-1.1},\n\tabstract = {The diameter of an impact crater is one of the most basic and important parameters used in energy scaling and numerical modeling of the cratering process. However, within the impact and geological communities and literature, there is considerable confusion about crater sizes due to the occurrence of a variety of concentric features, any of which might be interpreted as defining a crater's diameter. The disparate types of data available for different craters make the use of consistent metrics difficult, especially when comparing terrestrial to extraterrestrial craters. Furthermore, assessment of the diameters of terrestrial craters can be greatly complicated due to post-impact modification by erosion and tectonic activity. We analyze the terminology used to describe crater geometry and size and attempt to clarify the confusion over what exactly the term “crater diameter” means, proposing a consistent terminology to help avert future ambiguities. We discuss several issues of crater-size in the context of four large terrestrial examples for which crater diameters have been disputed (Chicxulub, Sudbury, Vredefort, and Chesapeake Bay) with the aim of moving toward consistent application of terminology.},\n\turldate = {2012-01-12},\n\tjournal = {Geological Society of America Special Papers},\n\tauthor = {Turtle, E.P. and Pierazzo, E. and Collins, G.S. and Osinski, G.R. and Melosh, H.J. and Morgan, J.V. and Reimold, W.U.},\n\tmonth = jan,\n\tyear = {2005},\n\tpages = {1 --24},\n}\n\n

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\n \n 2004\n \n \n (1)\n \n \n

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\n \n\n \n \n Collins, G. S; Melosh, H. J; and Ivanov, B. A\n\n\n \n \n \n \n Modeling damage and deformation in impact simulations.\n \n \n \n\n\n \n\n\n\n Meteoritics & Planetary Science, 39(2): 217–231. 2004.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n \n \n abstract \n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\n\n\n

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@article{collins_modeling_2004,\n\ttitle = {Modeling damage and deformation in impact simulations},\n\tvolume = {39},\n\tdoi = {10.1111/j.1945-5100.2004.tb00337.x},\n\tabstract = {Numerical modeling is a powerful tool for investigating the formation of large impact craters but is one that must be validated with observational evidence. Quantitative analysis of damage and deformation in the target surrounding an impact event provides a promising means of validation for numerical models of terrestrial impact craters, particularly in cases where the final pristine crater morphology is ambiguous or unknown. In this paper, we discuss the aspects of the behavior of brittle materials important for the accurate simulation of damage and deformation surrounding an impact event and the care required to interpret the results. We demonstrate this with an example simulation of an impact into a terrestrial, granite target that produces a 10 km-diameter transient crater. The results of the simulation are shown in terms of damage (a scalar quantity that reflects the totality of fragmentation) and plastic strain, both total plastic strain (the accumulated amount of permanent shear deformation, regardless of the sense of shear) and net plastic strain (the amount of permanent shear deformation where the sense of shear is accounted for). Damage and plastic strain are both greatest close to the impact site and decline with radial distance. However, the reversal in flow patterns from the downward and outward excavation flow to the inward and upward collapse flow implies that net plastic strains may be significantly lower than total plastic strains. Plastic strain in brittle rocks is very heterogeneous; however, continuum modeling requires that the deformation of the target during an impact event be described in terms of an average strain that applies over a large volume of rock (large compared to the spacing between individual zones of sliding). This paper demonstrates that model predictions of smooth average strain are entirely consistent with an actual strain concentrated along very narrow zones. Furthermore, we suggest that model predictions of total accumulated strain should correlate with observable variations in bulk density and seismic velocity.},\n\tnumber = {2},\n\tjournal = {Meteoritics \\& Planetary Science},\n\tauthor = {Collins, G. S and Melosh, H. J and Ivanov, B. A},\n\tyear = {2004},\n\tkeywords = {chicxulub crater, collapse, compression, failure, friction, mechanics, peak-ring formation, rock, shear, strength},\n\tpages = {217--231},\n}\n\n

\n

\n\n\n

\n Numerical modeling is a powerful tool for investigating the formation of large impact craters but is one that must be validated with observational evidence. Quantitative analysis of damage and deformation in the target surrounding an impact event provides a promising means of validation for numerical models of terrestrial impact craters, particularly in cases where the final pristine crater morphology is ambiguous or unknown. In this paper, we discuss the aspects of the behavior of brittle materials important for the accurate simulation of damage and deformation surrounding an impact event and the care required to interpret the results. We demonstrate this with an example simulation of an impact into a terrestrial, granite target that produces a 10 km-diameter transient crater. The results of the simulation are shown in terms of damage (a scalar quantity that reflects the totality of fragmentation) and plastic strain, both total plastic strain (the accumulated amount of permanent shear deformation, regardless of the sense of shear) and net plastic strain (the amount of permanent shear deformation where the sense of shear is accounted for). Damage and plastic strain are both greatest close to the impact site and decline with radial distance. However, the reversal in flow patterns from the downward and outward excavation flow to the inward and upward collapse flow implies that net plastic strains may be significantly lower than total plastic strains. Plastic strain in brittle rocks is very heterogeneous; however, continuum modeling requires that the deformation of the target during an impact event be described in terms of an average strain that applies over a large volume of rock (large compared to the spacing between individual zones of sliding). This paper demonstrates that model predictions of smooth average strain are entirely consistent with an actual strain concentrated along very narrow zones. Furthermore, we suggest that model predictions of total accumulated strain should correlate with observable variations in bulk density and seismic velocity.\n

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\n \n 2003\n \n \n (2)\n \n \n

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\n \n\n \n \n Collins, G. S.; and Melosh, H. J.\n\n\n \n \n \n \n \n Acoustic fluidization and the extraordinary mobility of sturzstroms.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research, 108: 14. October 2003.\n \n\n\n\n
\n\n\n\n \n \n $\"Acoustic$ Paper\n \n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n \n \n 2 downloads\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{collins_acoustic_2003,\n\ttitle = {Acoustic fluidization and the extraordinary mobility of sturzstroms},\n\tvolume = {108},\n\turl = {http://www.agu.org/pubs/crossref/2003/2003JB002465.shtml},\n\tdoi = {200310.1029/2003JB002465},\n\turldate = {2012-01-12},\n\tjournal = {Journal of Geophysical Research},\n\tauthor = {Collins, Gareth S. and Melosh, H. Jay},\n\tmonth = oct,\n\tyear = {2003},\n\tpages = {14},\n}\n\n

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\n\n\n\n

\n\n\n

\n \n\n \n \n Pierazzo, E.; and Collins, G. S\n\n\n \n \n \n \n A brief introduction to hydrocode modelling of impact cratering.\n \n \n \n\n\n \n\n\n\n In Dypvik, H.; Burchell, M.; and Claeys, P., editor(s), Cratering in Marine Environments and on Ice, pages 340. Springer, Berlin, 2003.\n undefined A brief introduction to hydrocode modelling of impact cratering\n\n\n\n
\n\n\n\n \n\n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@incollection{pierazzo_brief_2003,\n\taddress = {Berlin},\n\ttitle = {A brief introduction to hydrocode modelling of impact cratering},\n\tbooktitle = {Cratering in {Marine} {Environments} and on {Ice}},\n\tpublisher = {Springer},\n\tauthor = {Pierazzo, E. and Collins, G. S},\n\teditor = {Dypvik, H. and Burchell, M. and Claeys, P.},\n\tyear = {2003},\n\tnote = {undefined\nA brief introduction to hydrocode modelling of impact cratering},\n\tpages = {340},\n}\n\n

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\n \n 2002\n \n \n (1)\n \n \n

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\n \n\n \n \n Collins, G. S; Melosh, H. J; Morgan, J. V; and Warner, M. R\n\n\n \n \n \n \n Hydrocode Simulations of Chicxulub Crater Collapse and Peak-ring Formation.\n \n \n \n\n\n \n\n\n\n Icarus, 157: 24–33. 2002.\n \n\n\n\n
\n\n\n\n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n \n \n 1 download\n \n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{collins_hydrocode_2002,\n\ttitle = {Hydrocode {Simulations} of {Chicxulub} {Crater} {Collapse} and {Peak}-ring {Formation}},\n\tvolume = {157},\n\tdoi = {10.1006/icar.2002.6822},\n\tjournal = {Icarus},\n\tauthor = {Collins, G. S and Melosh, H. J and Morgan, J. V and Warner, M. R},\n\tyear = {2002},\n\tpages = {24--33},\n}\n\n

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\n \n 2000\n \n \n (1)\n \n \n

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\n \n\n \n \n Morgan, J. V; Warner, M. R; Collins, G. S; Melosh, H. J; and Christeson, G. L\n\n\n \n \n \n \n Peak ring formation in large impact craters.\n \n \n \n\n\n \n\n\n\n Earth Planet. Sci. Lett., 183(3-4): 347–354. 2000.\n undefined Peak ring formation in large impact craters Earth Planet. Sci. Lett.\n\n\n\n
\n\n\n\n \n\n \n \n doi\n \n \n\n \n link\n \n \n\n bibtex\n \n\n \n\n \n\n \n \n \n \n \n \n \n\n \n \n \n\n\n\n

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@article{morgan_peak_2000,\n\ttitle = {Peak ring formation in large impact craters},\n\tvolume = {183},\n\tdoi = {10.1016/S0012-821X(00)00307-1},\n\tnumber = {3-4},\n\tjournal = {Earth Planet. Sci. Lett.},\n\tauthor = {Morgan, J. V and Warner, M. R and Collins, G. S and Melosh, H. J and Christeson, G. L},\n\tyear = {2000},\n\tnote = {undefined\nPeak ring formation in large impact craters\nEarth Planet. Sci. Lett.},\n\tpages = {347--354},\n}\n\n

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\n \n undefined\n \n \n (1)\n \n \n

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\n \n\n \n \n Zhu, M.; Wünnemann, K.; Potter, R. W. K.; Kleine, T.; and Morbidelli, A.\n\n\n \n \n \n \n \n Are the Moon's Nearside-Farside Asymmetries the Result of a Giant Impact?.\n \n \n \n \n\n\n \n\n\n\n Journal of Geophysical Research: Planets, 0(0). .\n \n\n\n\n
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@article{zhu_are_nodate,\n\ttitle = {Are the {Moon}'s {Nearside}-{Farside} {Asymmetries} the {Result} of a {Giant} {Impact}?},\n\tvolume = {0},\n\tcopyright = {©2019. American Geophysical Union. All Rights Reserved.},\n\tissn = {2169-9100},\n\turl = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JE005826},\n\tdoi = {10.1029/2018JE005826},\n\tabstract = {The Moon exhibits striking geological asymmetries in elevation, crustal thickness, and composition between its nearside and farside. Although several scenarios have been proposed to explain these asymmetries, their origin remains debated. Recent remote sensing observations suggest that (1) the crust on the farside highlands consists of two layers: a primary anorthositic layer with thickness of 30-50 km and on top a more mafic-rich layer 10 km thick and (2) the nearside exhibits a large area of low-Ca pyroxene that has been interpreted to have an impact origin. These observations support the idea that the lunar nearside-farside asymmetries may be the result of a giant impact. Here using quantitative numerical modeling, we test the hypothesis that a giant impact on the early Moon can explain the striking differences in elevation, crustal thickness, and composition between the nearside and farside of the Moon. We find that a large impactor, impacting the current nearside with a low velocity, can form a mega-basin and reproduce the characteristics of the crustal asymmetry and structures comparable to those observed on the current Moon, including the nearside lowlands and the farside's mafic-rich layer on top of a primordial anorthositic crust. Our model shows that the excavated deep-seated KREEP (potassium, rare earth elements, and phosphorus) material, deposited close to the basin rim, slumps back into the basin and covers the entire basin floor; subsequent large impacts can transport the shallow KREEP material to the surface, resulting in its observed distribution. In addition, our model suggests that prior to the asymmetry-forming impact, the Moon may have had an 182W anomaly compared to the immediate post-giant impact Earth's mantle, as predicted if the Moon was created through a giant collision with the proto-Earth.},\n\tlanguage = {en},\n\tnumber = {0},\n\turldate = {2019-08-20},\n\tjournal = {Journal of Geophysical Research: Planets},\n\tauthor = {Zhu, Meng-Hua and Wünnemann, Kai and Potter, Ross W. K. and Kleine, Thorsten and Morbidelli, Alessandro},\n\tkeywords = {Giant impact, KREEP, Moon's asymmetries, Nearside's lowlands},\n}\n\n

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