iSALE.bib

@article{collins_modeling_2004,
	title = {Modeling damage and deformation in impact simulations},
	volume = {39},
	doi = {10.1111/j.1945-5100.2004.tb00337.x},
	abstract = {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.},
	number = {2},
	journal = {Meteoritics \& Planetary Science},
	author = {Collins, G. S and Melosh, H. J and Ivanov, B. A},
	year = {2004},
	keywords = {chicxulub crater, collapse, compression, failure, friction, mechanics, peak-ring formation, rock, shear, strength},
	pages = {217--231}
}

@article{collins_hydrocode_2002,
	title = {Hydrocode {Simulations} of {Chicxulub} {Crater} {Collapse} and {Peak}-ring {Formation}},
	volume = {157},
	doi = {10.1006/icar.2002.6822},
	journal = {Icarus},
	author = {Collins, G. S and Melosh, H. J and Morgan, J. V and Warner, M. R},
	year = {2002},
	pages = {24--33},
	file = {CollinsEtAl2002.pdf:/Users/gsc/Zotero/storage/95FFPK67/CollinsEtAl2002.pdf:application/pdf}
}

@article{collins_dynamic_2008,
	title = {Dynamic modeling suggests terrace zone asymmetry in the {Chicxulub} crater is caused by target heterogeneity},
	volume = {270},
	journal = {Earth and Planetary Science Letters},
	author = {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.},
	year = {2008},
	note = {undefined
Dynamic modeling suggests terrace zone asymmetry in the Chicxulub crater is caused by target heterogeneity
file://localhost/Users/gsc/Work/PDF\%20Library/CollinsEtAl2008b.pdf},
	pages = {221--230},
	file = {Collins et al. - 2008 - Dynamic modeling suggests terrace zone asymmetry i.pdf:/Users/gsc/Zotero/storage/VP68XB4X/Collins et al. - 2008 - Dynamic modeling suggests terrace zone asymmetry i.pdf:application/pdf}
}

@article{collins_how_2005,
	title = {How big was the {Chesapeake} {Bay} impact? {Insight} from numerical modeling},
	volume = {33},
	number = {12},
	journal = {Geology},
	author = {Collins, G. S and Wünnemann, K.},
	year = {2005},
	note = {undefined
How big was the Chesapeake Bay impact? Insight from numerical modeling},
	pages = {925--928},
	file = {CollinsWunnemann2005.pdf:/Users/gsc/Zotero/storage/XEGXAI6E/CollinsWunnemann2005.pdf:application/pdf}
}

@article{miljkovic_high-velocity_2012,
	title = {High-velocity impacts in porous solar system materials},
	volume = {1426},
	issn = {0094243X},
	url = {http://proceedings.aip.org/resource/2/apcpcs/1426/1/871_1?ver=pdfcov},
	doi = {doi:10.1063/1.3686416},
	abstract = {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.},
	number = {1},
	urldate = {2012-04-16},
	journal = {AIP Conference Proceedings},
	author = {Miljkovic, Katarina and Collins, Gareth S and Chapman, David James and Patel, Manish R and Proud, William},
	month = mar,
	year = {2012},
	pages = {871--874},
	file = {AIP Journal Snapshot:/Users/gsc/Zotero/storage/4WRKBJWR/871_1.html:text/html;Miljkovic et al. - 2012 - High-velocity impacts in porous solar system mater.pdf:/Users/gsc/Zotero/storage/TQTJ7SWS/Miljkovic et al. - 2012 - High-velocity impacts in porous solar system mater.pdf:application/pdf}
}

@article{davison_numerical_2010,
	title = {Numerical modelling of heating in porous planetesimal collisions},
	volume = {208},
	number = {1},
	journal = {Icarus},
	author = {Davison, T. M and Collins, G. S and Ciesla, F. J},
	year = {2010},
	note = {undefined
Numerical modelling of heating in porous planetesimal collisions
0019-1035
doi: DOI: 10.1016/j.icarus.2010.01.034
http://www.sciencedirect.com/science/article/B6WGF-4YC2XJY-2/2/3a16f15454e505ec37c58ca1d7e2de68
file://localhost/Users/gsc/Work/PDF\%20Library/DavisonEtAl2010.pdf},
	keywords = {Collisional physics, impact processes, Planetary formation, Planetesimals},
	pages = {468--481},
	file = {DavisonEtAl2010.pdf:/Users/gsc/Zotero/storage/S8PE7AAQ/DavisonEtAl2010.pdf:application/pdf}
}

@article{elbeshausen_scaling_2009,
	title = {Scaling of oblique impacts in frictional targets: {Implications} for crater size and formation mechanisms},
	volume = {204},
	doi = {10.1016/j.icarus.2009.07.018},
	number = {2},
	journal = {Icarus},
	author = {Elbeshausen, Dirk and Wünnemann, Kai and Collins, Gareth S},
	year = {2009},
	note = {undefined
Scaling of oblique impacts in frictional targets: Implications for crater size and formation mechanisms
0019-1035
doi: DOI: 10.1016/j.icarus.2009.07.018
http://www.sciencedirect.com/science/article/B6WGF-4WV780N-1/2/7ccc15b4941e4c65f170fda69f8214fc
file://localhost/Users/gsc/Work/PDF\%20Library/ElbeshausenEtAl2009.pdf},
	keywords = {Cratering, Earth, Geologic processes, impact processes, Meteorites},
	pages = {716--731},
	file = {ElbeshausenEtAl2009.pdf:/Users/gsc/Zotero/storage/7J5QTU3H/ElbeshausenEtAl2009.pdf:application/pdf}
}

@article{goldin_hydrocode_2006,
	title = {Hydrocode modeling of the {Sierra} {Madera} impact structure},
	volume = {41},
	doi = {10.1111/j.1945-5100.2006.tb00462.x},
	number = {12},
	journal = {Meteoritics \& Planetary Science},
	author = {Goldin, T. J and Wünnemann, K. and Melosh, H. J and Collins, G. S},
	year = {2006},
	note = {undefined
Hydrocode modeling of the Sierra Madera impact structure
file://localhost/Users/gsc/Work/PDF\%20Library/GoldinEtAl2006.pdf},
	pages = {1947--1958},
	file = {GoldinEtAl2006.pdf:/Users/gsc/Zotero/storage/SGE6I4BU/GoldinEtAl2006.pdf:application/pdf}
}

@article{morgan_peak_2000,
	title = {Peak ring formation in large impact craters},
	volume = {183},
	doi = {10.1016/S0012-821X(00)00307-1},
	number = {3-4},
	journal = {Earth Planet. Sci. Lett.},
	author = {Morgan, J. V and Warner, M. R and Collins, G. S and Melosh, H. J and Christeson, G. L},
	year = {2000},
	note = {undefined
Peak ring formation in large impact craters
Earth Planet. Sci. Lett.},
	pages = {347--354}
}

@article{pierazzo_validation_2008,
	title = {Validation of numerical codes for impact and explosion cratering},
	volume = {43},
	number = {12},
	journal = {Meteoritics and Planetary Science},
	author = {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.},
	year = {2008},
	note = {undefined
Validation of numerical codes for impact and explosion cratering
file://localhost/Users/gsc/Work/PDF\%20Library/PierazzoEtAl2008.pdf},
	pages = {1917--1938}
}

@incollection{pierazzo_brief_2003,
	address = {Berlin},
	title = {A brief introduction to hydrocode modelling of impact cratering},
	booktitle = {Cratering in {Marine} {Environments} and on {Ice}},
	publisher = {Springer},
	author = {Pierazzo, E. and Collins, G. S},
	editor = {Dypvik, H. and Burchell, M. and Claeys, P.},
	year = {2003},
	note = {undefined
A brief introduction to hydrocode modelling of impact cratering},
	pages = {340}
}

@article{yue_projectile_2013,
	title = {Projectile remnants in central peaks of lunar impact craters},
	volume = {6},
	copyright = {© 2013 Nature Publishing Group},
	issn = {1752-0894},
	url = {http://www.nature.com/ngeo/journal/v6/n6/abs/ngeo1828.html},
	doi = {10.1038/ngeo1828},
	abstract = {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.},
	language = {en},
	number = {6},
	urldate = {2014-09-18},
	journal = {Nature Geoscience},
	author = {Yue, Z. and Johnson, B. C. and Minton, D. A. and Melosh, H. J. and Di, K. and Hu, W. and Liu, Y.},
	month = jun,
	year = {2013},
	pages = {435--437},
	file = {ngeo1828-s1.pdf:/Users/gsc/Zotero/storage/PG84DRUJ/ngeo1828-s1.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/CQ2G6HS9/ngeo1828.html:text/html;Yue et al. - 2013 - Projectile remnants in central peaks of lunar impa.pdf:/Users/gsc/Zotero/storage/VT5X497R/Yue et al. - 2013 - Projectile remnants in central peaks of lunar impa.pdf:application/pdf}
}

@article{wunnemann_numerical_2008,
	title = {Numerical modelling of impact melt production in porous rocks},
	volume = {269},
	doi = {10.1016/j.epsl.2008.03.007},
	number = {3-4},
	journal = {Earth and Planetary Science Letters},
	author = {Wünnemann, K. and Collins, G. S and Osinski, G. R},
	year = {2008},
	keywords = {impact cratering, impact melt scaling, porosity, shock melting, shock metamorphism},
	pages = {530--539},
	file = {WunnemannEtAl2008.pdf:/Users/gsc/Zotero/storage/9RBZ5ICH/WunnemannEtAl2008.pdf:application/pdf}
}

@article{davison_effect_2007,
	title = {The effect of the oceans on the terrestrial crater size-frequency distribution: {Insight} from numerical modeling},
	volume = {42},
	issn = {1945-5100},
	url = {http://dx.doi.org/10.1111/j.1945-5100.2007.tb00550.x},
	doi = {10.1111/j.1945-5100.2007.tb00550.x},
	number = {11},
	journal = {Meteoritics \& Planetary Science},
	author = {Davison, T. and Collins, G. S.},
	year = {2007},
	pages = {1915--1927},
	file = {DavisonCollins2007.pdf:/Users/gsc/Box Sync/PDF Library/DavisonCollins2007.pdf:application/pdf}
}

@article{collins_size-frequency_2011,
	title = {The size-frequency distribution of elliptical impact craters},
	volume = {310},
	issn = {0012821X},
	url = {http://elsevier-apps.sciverse.com/GoogleMaps/index.jsp?doi=10.1016/j.epsl.2011.07.023},
	doi = {10.1016/j.epsl.2011.07.023},
	number = {1-2},
	urldate = {2011-12-20},
	journal = {Earth and Planetary Science Letters},
	author = {Collins, G.S. and Elbeshausen, D. and Davison, T.M. and Robbins, S.J. and Hynek, B.M.},
	month = oct,
	year = {2011},
	pages = {1--8},
	file = {Collins et al. - 2011 - The size-frequency distribution of elliptical impa.pdf:/Users/gsc/Zotero/storage/SWCJZJDD/Collins et al. - 2011 - The size-frequency distribution of elliptical impa.pdf:application/pdf;Supplementary Geospatial Data:/Users/gsc/Zotero/storage/WBFZU34R/index.html:text/html}
}

@article{collins_improvements_2011,
	title = {Improvements to the ɛ-α porous compaction model for simulating impacts into high-porosity solar system objects},
	volume = {38},
	issn = {0734-743X},
	url = {http://www.sciencedirect.com/science/article/pii/S0734743X10001594},
	doi = {10.1016/j.ijimpeng.2010.10.013},
	number = {6},
	journal = {International Journal of Impact Engineering},
	author = {Collins, G.S. and Melosh, H.J. and Wünnemann, K.},
	month = jun,
	year = {2011},
	keywords = {Hydrocode modeling, impact cratering, porosity, solar system},
	pages = {434--439},
	file = {CollinsEtAl_porosity_2011.pdf:/Users/gsc/Zotero/storage/ESW7A6Q8/CollinsEtAl_porosity_2011.pdf:application/pdf}
}

@article{wunnemann_impact_2010,
	title = {Impact of a cosmic body into {Earth}'s ocean and the generation of large water waves: {Insight} from numerical modeling},
	volume = {48},
	shorttitle = {Impact of a cosmic body into {Earth}'s ocean and the generation of large water waves},
	url = {http://www.agu.org/pubs/crossref/2010/2009RG000308.shtml},
	doi = {201010.1029/2009RG000308},
	urldate = {2012-01-12},
	journal = {Reviews of Geophysics},
	author = {Wünnemann, K. and Collins, G. S. and Weiss, R.},
	month = dec,
	year = {2010},
	pages = {26 PP.}
}

@article{christeson_mantle_2009,
	title = {Mantle deformation beneath the {Chicxulub} impact crater},
	volume = {284},
	issn = {0012-821X},
	url = {http://www.sciencedirect.com/science/article/pii/S0012821X09002635},
	doi = {10.1016/j.epsl.2009.04.033},
	number = {1–2},
	journal = {Earth and Planetary Science Letters},
	author = {Christeson, Gail L. and Collins, Gareth S. and Morgan, Joanna V. and Gulick, Sean P.S. and Barton, Penny J. and Warner, Michael R.},
	month = jun,
	year = {2009},
	keywords = {chicxulub, CRATER, Moho, terrestrial impact},
	pages = {249--257},
	file = {Christeson et al. - 2009 - Mantle deformation beneath the Chicxulub impact cr.pdf:/Users/gsc/Zotero/storage/TGM7KTW3/Christeson et al. - 2009 - Mantle deformation beneath the Chicxulub impact cr.pdf:application/pdf}
}

@article{collins_midsized_2008,
	title = {Mid‐sized complex crater formation in mixed crystalline‐sedimentary targets: {Insight} from modeling and observation},
	volume = {43},
	issn = {1945-5100},
	shorttitle = {Mid‐sized complex crater formation in mixed crystalline‐sedimentary targets},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2008.tb00655.x/abstract},
	doi = {10.1111/j.1945-5100.2008.tb00655.x},
	abstract = {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.},
	language = {en},
	number = {12},
	urldate = {2012-01-12},
	journal = {Meteoritics \& Planetary Science},
	author = {Collins, G. S and Kenkmann, T. and Osinski, G. R and Wünnemann, K.},
	month = dec,
	year = {2008},
	pages = {1955--1977},
	file = {Collins et al. - 2008 - Mid‐sized complex crater formation in mixed crysta.pdf:/Users/gsc/Zotero/storage/TQWAGXJS/Collins et al. - 2008 - Mid‐sized complex crater formation in mixed crysta.pdf:application/pdf}
}

@article{bray_effect_2008,
	title = {The effect of target properties on crater morphology: {Comparison} of central peak craters on the {Moon} and {Ganymede}},
	volume = {43},
	issn = {1945-5100},
	shorttitle = {The effect of target properties on crater morphology},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2008.tb00656.x/abstract},
	doi = {10.1111/j.1945-5100.2008.tb00656.x},
	abstract = {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.},
	language = {en},
	number = {12},
	urldate = {2012-01-12},
	journal = {Meteoritics \& Planetary Science},
	author = {Bray, Veronica J and Collins, Gareth S and Morgan, Joanna V and Schenk, Paul M},
	month = dec,
	year = {2008},
	pages = {1979--1992},
	file = {Bray et al. - 2008 - The effect of target properties on crater morpholo.pdf:/Users/gsc/Zotero/storage/GQSQ88TT/Bray et al. - 2008 - The effect of target properties on crater morpholo.pdf:application/pdf}
}

@article{osinski_effect_2008,
	title = {The effect of target lithology on the products of impact melting},
	volume = {43},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2008.tb00654.x/abstract},
	doi = {10.1111/j.1945-5100.2008.tb00654.x},
	abstract = {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.},
	language = {en},
	number = {12},
	urldate = {2012-01-12},
	journal = {Meteoritics \& Planetary Science},
	author = {Osinski, G. R and Grieve, R. a. F and Collins, G. S and Marion, C. and Sylvester, P.},
	month = dec,
	year = {2008},
	pages = {1939--1954},
	file = {Wiley Full Text PDF:/Users/gsc/Zotero/storage/9TVAKZNX/Osinski et al. - 2008 - The effect of target lithology on the products of .pdf:application/pdf}
}

@article{kenkmann_model_2009,
	title = {A model for the formation of the {Chesapeake} {Bay} impact crater as revealed by drilling and numerical simulation},
	volume = {458},
	url = {http://specialpapers.gsapubs.org/content/458/571.abstract},
	doi = {10.1130/2009.2458(25)},
	abstract = {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.},
	urldate = {2012-01-12},
	journal = {Geological Society of America Special Papers},
	author = {Kenkmann, T. and Collins, G.S. and Wittmann, A. and Wünnemann, K. and Reimold, W.U. and Melosh, H.J.},
	month = jan,
	year = {2009},
	pages = {571 --585},
	file = {Snapshot:/Users/gsc/Zotero/storage/A42RX4DX/571.html:text/html}
}

@article{turtle_impact_2005,
	title = {Impact structures: {What} does crater diameter mean?},
	volume = {384},
	shorttitle = {Impact structures},
	url = {http://specialpapers.gsapubs.org/content/384/1.abstract},
	doi = {10.1130/0-8137-2384-1.1},
	abstract = {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.},
	urldate = {2012-01-12},
	journal = {Geological Society of America Special Papers},
	author = {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.},
	month = jan,
	year = {2005},
	pages = {1 --24},
	file = {Snapshot:/Users/gsc/Zotero/storage/3W7HTFIZ/1.html:text/html}
}

@article{collins_acoustic_2003,
	title = {Acoustic fluidization and the extraordinary mobility of sturzstroms},
	volume = {108},
	url = {http://www.agu.org/pubs/crossref/2003/2003JB002465.shtml},
	doi = {200310.1029/2003JB002465},
	urldate = {2012-01-12},
	journal = {Journal of Geophysical Research},
	author = {Collins, Gareth S. and Melosh, H. Jay},
	month = oct,
	year = {2003},
	pages = {14}
}

@article{davison_numerical_2011,
	title = {Numerical modeling of oblique hypervelocity impacts on strong ductile targets},
	volume = {46},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2011.01246.x/abstract},
	doi = {10.1111/j.1945-5100.2011.01246.x},
	abstract = {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.},
	language = {en},
	number = {10},
	urldate = {2012-01-12},
	journal = {Meteoritics \& Planetary Science},
	author = {Davison, Thomas M and Collins, Gareth S and Elbeshausen, Dirk and Wünnemann, Kai and Kearsley, Anton},
	month = oct,
	year = {2011},
	pages = {1510--1524},
	file = {Davison et al. - 2011 - Numerical modeling of oblique hypervelocity impact.pdf:/Users/gsc/Zotero/storage/PTWBSWGX/Davison et al. - 2011 - Numerical modeling of oblique hypervelocity impact.pdf:application/pdf}
}

@article{bray_ganymede_2012,
	title = {Ganymede crater dimensions – {Implications} for central peak and central pit formation and development},
	volume = {217},
	issn = {0019-1035},
	url = {http://www.sciencedirect.com/science/article/pii/S0019103511003976},
	doi = {10.1016/j.icarus.2011.10.004},
	abstract = {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.},
	number = {1},
	urldate = {2012-02-27},
	journal = {Icarus},
	author = {Bray, Veronica J. and Schenk, Paul M. and Jay Melosh, H. and Morgan, Joanna V. and Collins, Gareth S.},
	month = jan,
	year = {2012},
	keywords = {CRATERING, Ganymede, Impact processes},
	pages = {115--129},
	file = {Bray et al. - 2012 - Ganymede crater dimensions – Implications for cent.pdf:/Users/gsc/Zotero/storage/CHJ8G5N6/Bray et al. - 2012 - Ganymede crater dimensions – Implications for cent.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/SS2QBA6F/Bray et al. - 2012 - Ganymede crater dimensions – Implications for cent.html:text/html}
}

@article{potter_constraining_2012,
	title = {Constraining the size of the {South} {Pole}-{Aitken} basin impact},
	volume = {220},
	issn = {0019-1035},
	url = {http://www.sciencedirect.com/science/article/pii/S001910351200214X},
	doi = {10.1016/j.icarus.2012.05.032},
	abstract = {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).},
	number = {2},
	urldate = {2012-07-12},
	journal = {Icarus},
	author = {Potter, R.W.K. and Collins, G.S. and Kiefer, W.S. and McGovern, P.J. and Kring, D.A.},
	month = aug,
	year = {2012},
	keywords = {Collisional physics, CRATERING, Impact processes, Moon},
	pages = {730--743},
	file = {Potter et al. - 2012 - Constraining the size of the South Pole-Aitken bas.pdf:/Users/gsc/Zotero/storage/4NTFTJZT/Potter et al. - 2012 - Constraining the size of the South Pole-Aitken bas.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/U7SBT2DS/S001910351200214X.html:text/html}
}

@article{davison_post-impact_2012,
	title = {Post-{Impact} {Thermal} {Evolution} of {Porous} {Planetesimals}},
	volume = {95},
	issn = {0016-7037},
	url = {http://www.sciencedirect.com/science/article/pii/S0016703712004486?v=s5},
	doi = {10.1016/j.gca.2012.08.001},
	abstract = {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 \> 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.},
	urldate = {2012-08-17},
	journal = {Geochimica et Cosmochimica Acta},
	author = {Davison, Thomas M. and Ciesla, Fred J. and Collins, Gareth S.},
	year = {2012},
	pages = {252--269},
	file = {ScienceDirect Snapshot:/Users/gsc/Zotero/storage/AXF7GTP4/S0016703712004486.html:text/html}
}

@article{potter_estimating_2012,
	title = {Estimating transient crater size using the crustal annular bulge: {Insights} from numerical modeling of lunar basin-scale impacts},
	volume = {39},
	copyright = {© 2008 American Geophysical Union},
	issn = {0094-8276},
	shorttitle = {Estimating transient crater size using the crustal annular bulge},
	url = {http://www.agu.org/pubs/crossref/2012/2012GL052981.shtml},
	doi = {10.1029/2012GL052981},
	abstract = {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.},
	language = {English},
	number = {18},
	urldate = {2012-10-08},
	journal = {Geophysical Research Letters},
	author = {Potter, R. W. K. and Kring, D. A. and Collins, G. S. and Kiefer, W. S. and McGovern, P. J.},
	month = sep,
	year = {2012},
	pages = {L18203},
	file = {Potter et al. - 2012 - Estimating transient crater size using the crustal.pdf:/Users/gsc/Zotero/storage/7NUCJ5ZU/Potter et al. - 2012 - Estimating transient crater size using the crustal.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/QGCJTJFT/2012GL052981.html:text/html}
}

@article{morgan_full_2011,
	title = {Full waveform tomographic images of the peak ring at the {Chicxulub} impact crater},
	volume = {116},
	copyright = {© 2008 American Geophysical Union},
	issn = {0148-0227},
	url = {http://www.agu.org/pubs/crossref/2011/2010JB008015.shtml},
	doi = {10.1029/2010JB008015},
	abstract = {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.},
	language = {English},
	number = {B6},
	urldate = {2012-12-20},
	journal = {Journal of Geophysical Research},
	author = {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.},
	month = jun,
	year = {2011},
	pages = {B06303},
	file = {Morgan et al. - 2011 - Full waveform tomographic images of the peak ring .pdf:/Users/gsc/Zotero/storage/CQCT54T4/Morgan et al. - 2011 - Full waveform tomographic images of the peak ring .pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/NTGUFPJT/2010JB008015.html:text/html}
}

@article{miljkovic_morphology_2013,
	title = {Morphology and population of binary asteroid impact craters},
	volume = {363},
	issn = {0012-821X},
	url = {http://www.sciencedirect.com/science/article/pii/S0012821X12007194},
	doi = {10.1016/j.epsl.2012.12.033},
	abstract = {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.},
	number = {0},
	urldate = {2013-01-25},
	journal = {Earth and Planetary Science Letters},
	author = {Miljković, Katarina and Collins, Gareth S. and Mannick, Sahil and Bland, Philip A.},
	month = feb,
	year = {2013},
	keywords = {binary asteroids, crater morphology, crater population, doublets},
	pages = {121--132},
	file = {Miljković et al. - 2013 - Morphology and population of binary asteroid impac.pdf:/Users/gsc/Zotero/storage/KHPX37GX/Miljković et al. - 2013 - Morphology and population of binary asteroid impac.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/WRZB9TFC/S0012821X12007194.html:text/html}
}

@incollection{collins_numerical_2012,
	title = {Numerical modelling of impact processes},
	isbn = {978-1-4051-9829-5},
	booktitle = {Impact {Cratering}: {Processes} and {Products}},
	publisher = {Wiley-Blackwell},
	author = {Collins, G.S. and Wuennemann, K. and Artemieva, N. and Pierazzo, E.},
	year = {2012},
	pages = {254--270}
}

@article{johnson_impact_2012,
	title = {Impact spherules as a record of an ancient heavy bombardment of {Earth}},
	volume = {485},
	copyright = {© 2012 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.},
	issn = {0028-0836},
	url = {http://www.nature.com/nature/journal/v485/n7396/full/nature10982.html},
	doi = {10.1038/nature10982},
	abstract = {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.},
	language = {en},
	number = {7396},
	urldate = {2014-01-16},
	journal = {Nature},
	author = {Johnson, B. C. and Melosh, H. J.},
	month = may,
	year = {2012},
	keywords = {Earth sciences, Geology, geophysics, Planetary sciences},
	pages = {75--77},
	file = {Johnson and Melosh - 2012 - Impact spherules as a record of an ancient heavy b.pdf:/Users/gsc/Zotero/storage/WI3T3BAX/Johnson and Melosh - 2012 - Impact spherules as a record of an ancient heavy b.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/I3Q74UWG/nature10982.html:text/html}
}

@article{miljkovic_asymmetric_2013,
	title = {Asymmetric {Distribution} of {Lunar} {Impact} {Basins} {Caused} by {Variations} in {Target} {Properties}},
	volume = {342},
	issn = {0036-8075, 1095-9203},
	url = {http://www.sciencemag.org/content/342/6159/724},
	doi = {10.1126/science.1243224},
	abstract = {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.
Which Side of the Moon?
The 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.},
	language = {en},
	number = {6159},
	urldate = {2014-01-17},
	journal = {Science},
	author = {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.},
	month = nov,
	year = {2013},
	pmid = {24202170},
	pages = {724--726},
	file = {Miljković et al. - 2013 - Asymmetric Distribution of Lunar Impact Basins Cau.pdf:/Users/gsc/Zotero/storage/P8ASCR5U/Miljković et al. - 2013 - Asymmetric Distribution of Lunar Impact Basins Cau.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/HRHF9CI4/724.html:text/html}
}

@article{collins_impact-cratering_2012,
	title = {The {Impact}-{Cratering} {Process}},
	volume = {8},
	issn = {1811-5209, 1811-5217},
	url = {http://elements.geoscienceworld.org/content/8/1/25},
	doi = {10.2113/gselements.8.1.25},
	abstract = {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.},
	language = {en},
	number = {1},
	urldate = {2014-01-23},
	journal = {Elements},
	author = {Collins, Gareth S. and Melosh, H. Jay and Osinski, Gordon R.},
	month = feb,
	year = {2012},
	keywords = {crater collapse, ejecta, impact crater, shock wave},
	pages = {25--30},
	file = {Collins et al. - 2012 - The Impact-Cratering Process.pdf:/Users/gsc/Zotero/storage/SVUFTPZN/Collins et al. - 2012 - The Impact-Cratering Process.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/9QXMC2SV/25.html:text/html}
}

@article{potter_quantifying_2013,
	title = {Quantifying the attenuation of structural uplift beneath large lunar craters},
	volume = {40},
	copyright = {©2013. American Geophysical Union. All Rights Reserved.},
	issn = {1944-8007},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/2013GL057829/abstract},
	doi = {10.1002/2013GL057829},
	abstract = {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.},
	language = {en},
	number = {21},
	urldate = {2014-03-13},
	journal = {Geophysical Research Letters},
	author = {Potter, Ross W. K. and Kring, David A. and Collins, Gareth S.},
	year = {2013},
	keywords = {complex craters, impact basins, Moon, numerical modeling, structural uplift},
	pages = {5615--5620},
	file = {Potter et al. - 2013 - Quantifying the attenuation of structural uplift b.pdf:/Users/gsc/Zotero/storage/ZNX98IZW/Potter et al. - 2013 - Quantifying the attenuation of structural uplift b.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/S3WUZ8X5/full.html:text/html}
}

@article{bray_hydrocode_2014,
	title = {Hydrocode simulation of {Ganymede} and {Europa} cratering trends – {How} thick is {Europa}’s crust?},
	volume = {231},
	issn = {0019-1035},
	url = {http://www.sciencedirect.com/science/article/pii/S0019103513005186},
	doi = {10.1016/j.icarus.2013.12.009},
	abstract = {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.
Pristine 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.},
	urldate = {2014-03-27},
	journal = {Icarus},
	author = {Bray, Veronica J. and Collins, Gareth S. and Morgan, Joanna V. and Melosh, H. Jay and Schenk, Paul M.},
	month = mar,
	year = {2014},
	keywords = {Astrobiology, CRATERING, Europa, Ganymede, Impact processes},
	pages = {394--406},
	file = {Bray et al. - 2014 - Hydrocode simulation of Ganymede and Europa crater.pdf:/Users/gsc/Zotero/storage/UQ4ZXCHH/Bray et al. - 2014 - Hydrocode simulation of Ganymede and Europa crater.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/7S8XVXRN/S0019103513005186.html:text/html}
}

@article{ciesla_thermal_2013,
	title = {Thermal consequences of impacts in the early solar system},
	volume = {48},
	copyright = {© The Meteoritical Society, 2013.},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12236/abstract},
	doi = {10.1111/maps.12236},
	abstract = {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.},
	language = {en},
	number = {12},
	urldate = {2014-04-04},
	journal = {Meteoritics \& Planetary Science},
	author = {Ciesla, Fred J. and Davison, Thomas M. and Collins, Gareth S. and O'Brien, David P.},
	month = dec,
	year = {2013},
	pages = {2559--2576},
	file = {Ciesla et al. - 2013 - Thermal consequences of impacts in the early solar.pdf:/Users/gsc/Zotero/storage/7S9PSFKH/Ciesla et al. - 2013 - Thermal consequences of impacts in the early solar.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/D5NNFTAA/abstract.html:text/html}
}

@article{davison_early_2013,
	title = {The early impact histories of meteorite parent bodies},
	volume = {48},
	copyright = {© The Meteoritical Society, 2013.},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12193/abstract},
	doi = {10.1111/maps.12193},
	abstract = {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.},
	language = {en},
	number = {10},
	urldate = {2014-04-04},
	journal = {Meteoritics \& Planetary Science},
	author = {Davison, Thomas M. and O'Brien, David P. and Ciesla, Fred J. and Collins, Gareth S.},
	month = oct,
	year = {2013},
	pages = {1894--1918},
	file = {Davison et al. - 2013 - The early impact histories of meteorite parent bod.pdf:/Users/gsc/Zotero/storage/TRTH2AEF/Davison et al. - 2013 - The early impact histories of meteorite parent bod.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/4HUS2KZK/abstract.html:text/html}
}

@article{johnson_jetting_2014,
	title = {Jetting during vertical impacts of spherical projectiles},
	volume = {238},
	issn = {0019-1035},
	url = {http://www.sciencedirect.com/science/article/pii/S0019103514002474},
	doi = {10.1016/j.icarus.2014.05.003},
	abstract = {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.},
	urldate = {2014-07-09},
	journal = {Icarus},
	author = {Johnson, B. C. and Bowling, T. J. and Melosh, H. J.},
	month = aug,
	year = {2014},
	keywords = {Collisional physics, CRATERING, Impact processes},
	pages = {13--22},
	file = {Johnson et al. - 2014 - Jetting during vertical impacts of spherical proje.pdf:/Users/gsc/Zotero/storage/43EBXH6A/Johnson et al. - 2014 - Jetting during vertical impacts of spherical proje.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/Q6JUSUQH/S0019103514002474.html:text/html}
}

@article{artemieva_ries_2013,
	title = {Ries crater and suevite revisited—{Observations} and modeling {Part} {II}: {Modeling}},
	volume = {48},
	copyright = {© The Meteoritical Society, 2013.},
	issn = {1945-5100},
	shorttitle = {Ries crater and suevite revisited—{Observations} and modeling {Part} {II}},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12085/abstract},
	doi = {10.1111/maps.12085},
	abstract = {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.},
	language = {en},
	number = {4},
	urldate = {2014-07-17},
	journal = {Meteoritics \& Planetary Science},
	author = {Artemieva, N. A. and Wünnemann, K. and Krien, F. and Reimold, W. U. and Stöffler, D.},
	month = apr,
	year = {2013},
	pages = {590--627},
	file = {Artemieva et al. - 2013 - Ries crater and suevite revisited—Observations and.pdf:/Users/gsc/Zotero/storage/B3DTVSHN/Artemieva et al. - 2013 - Ries crater and suevite revisited—Observations and.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/RW9PA7KJ/abstract.html:text/html}
}

@article{wunnemann_strain-based_2006,
	title = {A strain-based porosity model for use in hydrocode simulations of impacts and implications for transient crater growth in porous targets},
	volume = {180},
	issn = {0019-1035},
	url = {http://www.sciencedirect.com/science/article/pii/S0019103505004124},
	doi = {10.1016/j.icarus.2005.10.013},
	abstract = {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.},
	number = {2},
	urldate = {2014-07-17},
	journal = {Icarus},
	author = {Wünnemann, K. and Collins, G. S. and Melosh, H. J.},
	month = feb,
	year = {2006},
	keywords = {Collisional physics, CRATERING, Impact processes, Surfacescomets},
	pages = {514--527},
	file = {ScienceDirect Snapshot:/Users/gsc/Zotero/storage/DPUZETXB/S0019103505004124.html:text/html;Wünnemann et al. - 2006 - A strain-based porosity model for use in hydrocode.pdf:/Users/gsc/Zotero/storage/7PV6527P/Wünnemann et al. - 2006 - A strain-based porosity model for use in hydrocode.pdf:application/pdf}
}

@article{melosh_origin_2013,
	title = {The {Origin} of {Lunar} {Mascon} {Basins}},
	volume = {340},
	issn = {0036-8075, 1095-9203},
	url = {http://www.sciencemag.org/content/340/6140/1552},
	doi = {10.1126/science.1235768},
	abstract = {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.
Lunar Mascons Explained
The 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.},
	language = {en},
	number = {6140},
	urldate = {2014-07-21},
	journal = {Science},
	author = {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.},
	month = jun,
	year = {2013},
	pmid = {23722426},
	pages = {1552--1555},
	file = {Melosh et al. - 2013 - The Origin of Lunar Mascon Basins.pdf:/Users/gsc/Zotero/storage/28F64FJJ/Melosh et al. - 2013 - The Origin of Lunar Mascon Basins.pdf:application/pdf;Melosh-SM.pdf:/Users/gsc/Zotero/storage/INMG5ITM/Melosh-SM.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/BUWZJ5RW/1552.html:text/html}
}

@article{potter_numerical_2013,
	title = {Numerical modeling of the formation and structure of the {Orientale} impact basin},
	volume = {118},
	copyright = {©2013. American Geophysical Union. All Rights Reserved.},
	issn = {2169-9100},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/jgre.20080/abstract},
	doi = {10.1002/jgre.20080},
	abstract = {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.},
	language = {en},
	number = {5},
	urldate = {2014-07-21},
	journal = {Journal of Geophysical Research: Planets},
	author = {Potter, Ross W. K. and Kring, David A. and Collins, Gareth S. and Kiefer, Walter S. and McGovern, Patrick J.},
	month = may,
	year = {2013},
	keywords = {0545 Modeling, 5420 Impact phenomena, cratering, 6205 Asteroids, 6250 Moon, basin formation, Chicxulub, impact basins, late heavy bombardment, lunar cataclysm, Orientale},
	pages = {963--979},
	file = {Potter et al. - 2013 - Numerical modeling of the formation and structure .pdf:/Users/gsc/Zotero/storage/5WNGB62P/Potter et al. - 2013 - Numerical modeling of the formation and structure .pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/TCF5495S/abstract.html:text/html}
}

@article{marchi_widespread_2014,
	title = {Widespread mixing and burial of {Earth}/'s {Hadean} crust by asteroid impacts},
	volume = {511},
	copyright = {© 2014 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.},
	issn = {0028-0836},
	url = {http://www.nature.com/nature/journal/v511/n7511/full/nature13539.html?WT.ec_id=NATURE-20140731},
	doi = {10.1038/nature13539},
	abstract = {The history of the Hadean Earth ([sim]4.0-4.5 billion years ago) is poorly understood because few known rocks are older than [sim]3.8 billion years old. The main constraints from this era come from ancient submillimetre zircon grains. Some of these zircons date back to [sim]4.4 billion years ago when the Moon, and presumably the Earth, was being pummelled by an enormous flux of extraterrestrial bodies. The magnitude and exact timing of these early terrestrial impacts, and their effects on crustal growth and evolution, are unknown. Here we provide a new bombardment model of the Hadean Earth that has been calibrated using existing lunar and terrestrial data. We find that the surface of the Hadean Earth was widely reprocessed by impacts through mixing and burial by impact-generated melt. This model may explain the age distribution of Hadean zircons and the absence of early terrestrial rocks. Existing oceans would have repeatedly boiled away into steam atmospheres as a result of large collisions as late as about 4 billion years ago.},
	language = {en},
	number = {7511},
	urldate = {2014-07-31},
	journal = {Nature},
	author = {Marchi, S. and Bottke, W. F. and Elkins-Tanton, L. T. and Bierhaus, M. and Wuennemann, K. and Morbidelli, A. and Kring, D. A.},
	month = jul,
	year = {2014},
	keywords = {geophysics, Inner planets},
	pages = {578--582},
	file = {Marchi et al. - 2014 - Widespread mixing and burial of Earth's Hadean cr.pdf:/Users/gsc/Zotero/storage/88Q4URFR/Marchi et al. - 2014 - Widespread mixing and burial of Earth's Hadean cr.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/KNRXAXN3/nature13539.html:text/html}
}

@article{elbeshausen_transition_2013,
	title = {The transition from circular to elliptical impact craters},
	volume = {118},
	copyright = {©2013. American Geophysical Union. All Rights Reserved.},
	issn = {2169-9100},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/2013JE004477/abstract},
	doi = {10.1002/2013JE004477},
	abstract = {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.},
	language = {en},
	number = {11},
	urldate = {2014-08-12},
	journal = {Journal of Geophysical Research: Planets},
	author = {Elbeshausen, Dirk and Wünnemann, Kai and Collins, Gareth S.},
	month = nov,
	year = {2013},
	keywords = {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},
	pages = {2013JE004477},
	file = {Elbeshausen et al. - 2013 - The transition from circular to elliptical impact .pdf:/Users/gsc/Zotero/storage/9IGD8QSB/Elbeshausen et al. - 2013 - The transition from circular to elliptical impact .pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/7HSM8K9B/abstract.html:text/html}
}

@article{potter_numerical_2013-1,
	title = {Numerical modeling of asteroid survivability and possible scenarios for the {Morokweng} crater-forming impact},
	volume = {48},
	copyright = {© The Meteoritical Society, 2013.},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12098/abstract},
	doi = {10.1111/maps.12098},
	abstract = {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.},
	language = {en},
	number = {5},
	urldate = {2014-08-12},
	journal = {Meteoritics \& Planetary Science},
	author = {Potter, Ross W. K. and Collins, Gareth S.},
	month = may,
	year = {2013},
	pages = {744--757},
	file = {Potter and Collins - 2013 - Numerical modeling of asteroid survivability and p.pdf:/Users/gsc/Zotero/storage/ZJF6XN2T/Potter and Collins - 2013 - Numerical modeling of asteroid survivability and p.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/DZZF3WCA/abstract.html:text/html}
}

@article{kowitz_diaplectic_2013,
	title = {Diaplectic quartz glass and {SiO}2 melt experimentally generated at only 5 {GPa} shock pressure in porous sandstone: {Laboratory} observations and meso-scale numerical modeling},
	volume = {384},
	issn = {0012-821X},
	shorttitle = {Diaplectic quartz glass and {SiO}2 melt experimentally generated at only 5 {GPa} shock pressure in porous sandstone},
	url = {http://www.sciencedirect.com/science/article/pii/S0012821X13005323},
	doi = {10.1016/j.epsl.2013.09.021},
	abstract = {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.},
	urldate = {2014-10-23},
	journal = {Earth and Planetary Science Letters},
	author = {Kowitz, A. and Güldemeister, N. and Reimold, W. U. and Schmitt, R. T. and Wünnemann, K.},
	month = dec,
	year = {2013},
	keywords = {diaplectic quartz glass, meso-scale modeling, pore collapse, shock effects, shock metamorphism, silica melt},
	pages = {17--26},
	file = {Kowitz et al. - 2013 - Diaplectic quartz glass and SiO2 melt experimental.pdf:/Users/gsc/Zotero/storage/JEVJQU7H/Kowitz et al. - 2013 - Diaplectic quartz glass and SiO2 melt experimental.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/P2VFFHIV/S0012821X13005323.html:text/html}
}

@article{miljkovic_excavation_2015,
	title = {Excavation of the lunar mantle by basin-forming impact events on the {Moon}},
	volume = {409},
	issn = {0012-821X},
	url = {http://www.sciencedirect.com/science/article/pii/S0012821X14006682},
	doi = {10.1016/j.epsl.2014.10.041},
	abstract = {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.},
	urldate = {2014-11-28},
	journal = {Earth and Planetary Science Letters},
	author = {Miljković, Katarina and Wieczorek, Mark A. and Collins, Gareth S. and Solomon, Sean C. and Smith, David E. and Zuber, Maria T.},
	month = jan,
	year = {2015},
	keywords = {impact cratering, mantle, Moon},
	pages = {243--251},
	file = {Miljković et al. - 2015 - Excavation of the lunar mantle by basin-forming im.pdf:/Users/gsc/Zotero/storage/729M7345/Miljković et al. - 2015 - Excavation of the lunar mantle by basin-forming im.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/UKTKTHB4/S0012821X14006682.html:text/html}
}

@article{miljkovic_reply_2014,
	title = {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”},
	volume = {405},
	issn = {0012-821X},
	shorttitle = {Reply to comment on},
	url = {http://www.sciencedirect.com/science/article/pii/S0012821X14005329},
	doi = {10.1016/j.epsl.2014.08.026},
	abstract = {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\%.},
	urldate = {2014-11-28},
	journal = {Earth and Planetary Science Letters},
	author = {Miljković, Katarina and Collins, Gareth S. and Bland, Philip A.},
	month = nov,
	year = {2014},
	keywords = {crater population, doublet craters},
	pages = {285--286},
	file = {Miljković et al. - 2014 - Reply to comment on “Supportive comment on “Morp.pdf:/Users/gsc/Zotero/storage/HRUV2PXA/Miljković et al. - 2014 - Reply to comment on “Supportive comment on “Morp.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/3JWN5DDQ/S0012821X14005329.html:text/html}
}

@article{weiss_eltanin_2015,
	title = {The {Eltanin} impact and its tsunami along the coast of {South} {America}: {Insights} for potential deposits},
	volume = {409},
	issn = {0012-821X},
	shorttitle = {The {Eltanin} impact and its tsunami along the coast of {South} {America}},
	url = {http://www.sciencedirect.com/science/article/pii/S0012821X14006773},
	doi = {10.1016/j.epsl.2014.10.050},
	abstract = {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.},
	urldate = {2014-12-02},
	journal = {Earth and Planetary Science Letters},
	author = {Weiss, Robert and Lynett, Patrick and Wünnemann, Kai},
	month = jan,
	year = {2015},
	keywords = {Eltanin impact, impact cratering, numerical simulations, tsunami modeling, tsunamis},
	pages = {175--181},
	file = {ScienceDirect Snapshot:/Users/gsc/Zotero/storage/DBMXUVRD/S0012821X14006773.html:text/html;Weiss et al. - 2015 - The Eltanin impact and its tsunami along the coast.pdf:/Users/gsc/Zotero/storage/RKUNSSA2/Weiss et al. - 2015 - The Eltanin impact and its tsunami along the coast.pdf:application/pdf}
}

@article{bland_pressuretemperature_2014,
	title = {Pressure–temperature evolution of primordial solar system solids during impact-induced compaction},
	volume = {5},
	copyright = {© 2014 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.},
	url = {http://www.nature.com/ncomms/2014/141203/ncomms6451/full/ncomms6451.html},
	doi = {10.1038/ncomms6451},
	abstract = {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.},
	language = {en},
	urldate = {2014-12-05},
	journal = {Nature Communications},
	author = {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.},
	month = dec,
	year = {2014},
	keywords = {Earth sciences, Planetary sciences},
	file = {Bland et al. - 2014 - Pressure–temperature evolution of primordial solar.pdf:/Users/gsc/Zotero/storage/2AVGZ2GC/Bland et al. - 2014 - Pressure–temperature evolution of primordial solar.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/BBA58WTM/ncomms6451.html:text/html}
}

@article{collins_numerical_2014,
	title = {Numerical simulations of impact crater formation with dilatancy},
	copyright = {©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.},
	issn = {2169-9100},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/2014JE004708/abstract},
	doi = {10.1002/2014JE004708},
	abstract = {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.},
	language = {en},
	urldate = {2014-12-16},
	journal = {Journal of Geophysical Research: Planets},
	author = {Collins, G. S.},
	month = dec,
	year = {2014},
	keywords = {1219 Gravity anomalies and Earth structure, 1221 Lunar and planetary geodesy and gravity, 5420 Impact phenomena, cratering, dilatancy, gravity anomaly, impact cratering, numerical modeling},
	pages = {2014JE004708},
	file = {Collins - 2014 - Numerical simulations of impact crater formation w.pdf:/Users/gsc/Zotero/storage/JKQKRTNR/Collins - 2014 - Numerical simulations of impact crater formation w.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/3CAQ2ZP8/abstract.html:text/html}
}

@article{johnson_formation_2014,
	title = {Formation of melt droplets, melt fragments, and accretionary impact lapilli during a hypervelocity impact},
	volume = {228},
	issn = {0019-1035},
	url = {http://www.sciencedirect.com/science/article/pii/S001910351300451X},
	doi = {10.1016/j.icarus.2013.10.022},
	abstract = {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.},
	urldate = {2015-06-16},
	journal = {Icarus},
	author = {Johnson, B. C. and Melosh, H. J.},
	month = jan,
	year = {2014},
	keywords = {CRATERING, Earth, Impact processes},
	pages = {347--363},
	file = {Johnson and Melosh - 2014 - Formation of melt droplets, melt fragments, and ac.pdf:/Users/gsc/Zotero/storage/7HT957BB/Johnson and Melosh - 2014 - Formation of melt droplets, melt fragments, and ac.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/3XA95WUN/S001910351300451X.html:text/html}
}

@article{bowling_antipodal_2013,
	title = {Antipodal terrains created by the {Rheasilvia} basin forming impact on asteroid 4 {Vesta}},
	volume = {118},
	copyright = {©2013. American Geophysical Union. All Rights Reserved.},
	issn = {2169-9100},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/jgre.20123/abstract},
	doi = {10.1002/jgre.20123},
	abstract = {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.},
	language = {en},
	number = {9},
	urldate = {2015-03-02},
	journal = {Journal of Geophysical Research: Planets},
	author = {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.},
	month = sep,
	year = {2013},
	keywords = {4 Vesta, 5420 Impact phenomena, cratering, 5460 Physical properties of materials, 5470 Surface materials and properties, 6205 Asteroids, antipode, Asteroid, impact, Rheasilvia, shock physics},
	pages = {1821--1834},
	file = {Bowling et al. - 2013 - Antipodal terrains created by the Rheasilvia basin.pdf:/Users/gsc/Zotero/storage/DBBVIDA8/Bowling et al. - 2013 - Antipodal terrains created by the Rheasilvia basin.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/PTCZGWG9/abstract.html:text/html}
}

@article{guldemeister_propagation_2013,
	title = {Propagation of impact-induced shock waves in porous sandstone using mesoscale modeling},
	volume = {48},
	copyright = {© The Meteoritical Society, 2012},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2012.01430.x/abstract},
	doi = {10.1111/j.1945-5100.2012.01430.x},
	abstract = {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.},
	language = {en},
	number = {1},
	urldate = {2015-03-25},
	journal = {Meteoritics \& Planetary Science},
	author = {Güldemeister, Nicole and Wünnemann, Kai and Durr, Nathanael and Hiermaier, Stefan},
	month = jan,
	year = {2013},
	pages = {115--133},
	file = {Güldemeister et al. - 2013 - Propagation of impact-induced shock waves in porou.pdf:/Users/gsc/Zotero/storage/QI3ACWX8/Güldemeister et al. - 2013 - Propagation of impact-induced shock waves in porou.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/RRQZ2BNA/abstract.html:text/html}
}

@article{freed_formation_2014,
	title = {The formation of lunar mascon basins from impact to contemporary form},
	volume = {119},
	issn = {2169-9100},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/2014JE004657/abstract},
	doi = {10.1002/2014JE004657},
	abstract = {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.},
	language = {en},
	number = {11},
	urldate = {2015-05-14},
	journal = {Journal of Geophysical Research: Planets},
	author = {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.},
	month = nov,
	year = {2014},
	keywords = {5420 Impact phenomena, cratering, 5460 Physical properties of materials, 5714 Gravitational fields, 6250 Moon, basins, gravity, impact, lunar, mascons},
	pages = {2014JE004657},
	file = {Freed et al. - 2014 - The formation of lunar mascon basins from impact t.pdf:/Users/gsc/Zotero/storage/E8AZDEPX/Freed et al. - 2014 - The formation of lunar mascon basins from impact t.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/VG5RAIEV/abstract.html:text/html}
}

@article{davison_effect_2014,
	title = {The effect of impact obliquity on shock heating in planetesimal collisions},
	volume = {49},
	copyright = {© The Meteoritical Society, 2014.},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12394/abstract},
	doi = {10.1111/maps.12394},
	abstract = {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°.},
	language = {en},
	number = {12},
	urldate = {2015-09-02},
	journal = {Meteoritics \& Planetary Science},
	author = {Davison, Thomas M. and Ciesla, Fred J. and Collins, Gareth S. and Elbeshausen, Dirk},
	month = dec,
	year = {2014},
	pages = {2252--2265},
	file = {Davison et al. - 2014 - The effect of impact obliquity on shock heating in.pdf:/Users/gsc/Zotero/storage/5UNDNTE7/Davison et al. - 2014 - The effect of impact obliquity on shock heating in.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/5UTX3KGM/abstract.html:text/html}
}

@article{ormo_scaling_2015,
	title = {Scaling and reproducibility of craters produced at the {Experimental} {Projectile} {Impact} {Chamber} ({EPIC}), {Centro} de {Astrobiología}, {Spain}},
	copyright = {© The Meteoritical Society, 2015.},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12560/abstract},
	doi = {10.1111/maps.12560},
	abstract = {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.},
	language = {en},
	urldate = {2015-10-30},
	journal = {Meteoritics \& Planetary Science},
	author = {Ormö, J. and Melero-Asensio, I. and Housen, K. R. and Wünnemann, K. and Elbeshausen, D. and Collins, G. S.},
	month = oct,
	year = {2015},
	pages = {2067--2086},
	file = {Ormö et al. - 2015 - Scaling and reproducibility of craters produced at.pdf:/Users/gsc/Zotero/storage/9NFPS9G6/Ormö et al. - 2015 - Scaling and reproducibility of craters produced at.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/FCBTMDHS/abstract.html:text/html}
}

@article{milbury_preimpact_2015,
	title = {Preimpact porosity controls the gravity signature of lunar craters},
	volume = {42},
	issn = {1944-8007},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/2015GL066198/abstract},
	doi = {10.1002/2015GL066198},
	abstract = {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.},
	language = {en},
	number = {22},
	urldate = {2016-02-02},
	journal = {Geophysical Research Letters},
	author = {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.},
	month = nov,
	year = {2015},
	keywords = {5417 Gravitational fields, 5470 Surface materials and properties, 5475 Tectonics, 8122 Dynamics: gravity and tectonics, 8135 Hydrothermal systems, GRAIL, gravity, Gravity Recovery and Interior Laboratory, impact crater, lunar, Porosity},
	pages = {2015GL066198},
	file = {Milbury et al. - 2015 - Preimpact porosity controls the gravity signature .pdf:/Users/gsc/Zotero/storage/FAEC2HPA/Milbury et al. - 2015 - Preimpact porosity controls the gravity signature .pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/WFSH7NNH/abstract.html:text/html}
}

@article{potter_scaling_2015,
	title = {Scaling of basin-sized impacts and the influence of target temperature},
	volume = {518},
	issn = {0072-1077,},
	url = {http://specialpapers.gsapubs.org/content/early/2015/09/17/2015.2518_06},
	doi = {10.1130/2015.2518(06)},
	abstract = {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.},
	language = {en},
	urldate = {2016-02-02},
	journal = {Geological Society of America Special Papers},
	author = {Potter, Ross W. K. and Kring, David A. and Collins, Gareth S.},
	month = sep,
	year = {2015},
	pages = {SPE518--06},
	file = {Potteretal2015_GSA_BasinScaling.pdf:/Users/gsc/Zotero/storage/P29CW84P/Potteretal2015_GSA_BasinScaling.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/QPKT49BA/2015.2518_06.html:text/html}
}

@article{monteux_consequences_2016,
	title = {Consequences of large impacts on {Enceladus}’ core shape},
	volume = {264},
	issn = {0019-1035},
	url = {http://www.sciencedirect.com/science/article/pii/S0019103515004480},
	doi = {10.1016/j.icarus.2015.09.034},
	abstract = {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 (\<2.4 km/s) collisions with deca-kilometric differentiated impactors, which is possible only after the LHB period.},
	urldate = {2016-02-02},
	journal = {Icarus},
	author = {Monteux, J. and Collins, G. S. and Tobie, G. and Choblet, G.},
	month = jan,
	year = {2016},
	keywords = {Accretion, CRATERING, Enceladus, Impact processes, Interiors},
	pages = {300--310},
	file = {Monteux et al. - 2016 - Consequences of large impacts on Enceladus’ core s.pdf:/Users/gsc/Zotero/storage/9R3RU789/Monteux et al. - 2016 - Consequences of large impacts on Enceladus’ core s.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/JBQN7J4S/S0019103515004480.html:text/html}
}

@article{johnson_spherule_2016,
	title = {Spherule layers, crater scaling laws, and the population of ancient terrestrial impactors},
	volume = {271},
	issn = {0019-1035},
	url = {http://www.sciencedirect.com/science/article/pii/S0019103516000907},
	doi = {10.1016/j.icarus.2016.02.023},
	abstract = {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.},
	urldate = {2016-04-05},
	journal = {Icarus},
	author = {Johnson, Brandon C. and Collins, Gareth S. and Minton, David A. and Bowling, Timothy J. and Simonson, Bruce M. and Zuber, Maria T.},
	month = jun,
	year = {2016},
	keywords = {CRATERING, Earth, Moon, Near-Earth objects, Planetary dynamics},
	pages = {350--359},
	file = {Johnson et al. - 2016 - Spherule layers, crater scaling laws, and the popu.pdf:/Users/gsc/Zotero/storage/6X8IHMC6/Johnson et al. - 2016 - Spherule layers, crater scaling laws, and the popu.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/AI3Z5TZQ/S0019103516000907.html:text/html}
}

@inproceedings{wunnemann_scaling_2011,
	address = {Freiburg, Germany},
	title = {Scaling of impact crater formation on planetary surfaces – insights from numerical modeling},
	isbn = {3-8396-0280-7},
	url = {https://www.researchgate.net/publication/257609508_Scaling_of_impact_crater_formation_on_planetary_surfaces--Insights_from_numerical_modeling},
	abstract = {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.},
	booktitle = {Proceedings of the 11th {Hypervelocity} {Impact} {Symposium} 2010},
	publisher = {Fraunhofer Verlag, Stuttgart},
	author = {Wünnemann, K. and {Nowka, D.} and {Collins, G.S.} and {Elbeshausen, D.} and {Bierhaus, M.}},
	year = {2011},
	pages = {828}
}

@incollection{asphaug_global_2015,
	address = {Tucson, Arizona},
	title = {Global {Scale} {Impacts}},
	abstract = {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.},
	booktitle = {Asteroids {IV}},
	publisher = {University of Arizona Press},
	author = {Asphaug, Erik and Collins, Gareth and Jutzi, Martin},
	editor = {Michel, Patrick and Demeo, Francesca E. and Bottke, William F.},
	year = {2015},
	note = {arXiv: 1504.02389},
	keywords = {Astrophysics - Earth and Planetary Astrophysics},
	pages = {661--678},
	file = {arXiv.org Snapshot:/Users/gsc/Zotero/storage/7RUM239W/1504.html:text/html;Asphaug et al. - 2015 - Global Scale Impacts.pdf:/Users/gsc/Zotero/storage/BGZM257T/Asphaug et al. - 2015 - Global Scale Impacts.pdf:application/pdf}
}

@article{potter_investigating_2015,
	title = {Investigating the onset of multi-ring impact basin formation},
	volume = {261},
	issn = {0019-1035},
	url = {http://www.sciencedirect.com/science/article/pii/S001910351500353X},
	doi = {10.1016/j.icarus.2015.08.009},
	abstract = {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.},
	urldate = {2016-04-13},
	journal = {Icarus},
	author = {Potter, Ross W. K.},
	month = nov,
	year = {2015},
	keywords = {CRATERING, Impact processes, Moon, interior, Moon, surface, Tectonics},
	pages = {91--99},
	file = {ScienceDirect Full Text PDF:/Users/gsc/Zotero/storage/I4PN3RK8/Potter - 2015 - Investigating the onset of multi-ring impact basin.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/3DSNNVQ3/S001910351500353X.html:text/html}
}

@article{davison_mesoscale_2016,
	title = {Mesoscale {Modeling} of {Impact} {Compaction} of {Primitive} {Solar} {System} {Solids}},
	volume = {821},
	issn = {0004-637X},
	url = {http://stacks.iop.org/0004-637X/821/i=1/a=68},
	doi = {10.3847/0004-637X/821/1/68},
	abstract = {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.},
	language = {en},
	number = {1},
	urldate = {2016-04-15},
	journal = {The Astrophysical Journal},
	author = {Davison, Thomas M. and Collins, Gareth S. and Bland, Philip A.},
	year = {2016},
	pages = {68},
	file = {Davison et al. - 2016 - Mesoscale Modeling of Impact Compaction of Primiti.pdf:/Users/gsc/Zotero/storage/72W8F3D3/Davison et al. - 2016 - Mesoscale Modeling of Impact Compaction of Primiti.pdf:application/pdf}
}

@article{forman_hidden_2016,
	title = {Hidden secrets of deformation: {Impact}-induced compaction within a {CV} chondrite},
	volume = {452},
	issn = {0012-821X},
	shorttitle = {Hidden secrets of deformation},
	url = {http://www.sciencedirect.com/science/article/pii/S0012821X1630406X},
	doi = {10.1016/j.epsl.2016.07.050},
	abstract = {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.},
	urldate = {2016-08-16},
	journal = {Earth and Planetary Science Letters},
	author = {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.},
	month = oct,
	year = {2016},
	keywords = {Allende, compaction, crystallography, deformation, impact, Meteorite},
	pages = {133--145},
	file = {Forman et al. - 2016 - Hidden secrets of deformation Impact-induced comp.pdf:/Users/gsc/Zotero/storage/FIBUN4VF/Forman et al. - 2016 - Hidden secrets of deformation Impact-induced comp.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/3E8QFCA7/S0012821X1630406X.html:text/html}
}

@article{collins_isale-dellen_2016,
	title = {{iSALE}-{Dellen} manual},
	url = {https://figshare.com/articles/iSALE-Dellen_manual/3473690},
	doi = {10.6084/m9.figshare.3473690},
	abstract = {Manual for the Dellen release of the iSALE shock physics code:







A multi-material, multi-rheology shock physics code for simulating impact phenomena in two and three dimensions.},
	urldate = {2016-07-15},
	journal = {Figshare},
	author = {Collins, Gareth S. and Elbeshausen, Dirk and Davison, Thomas M. and Wünnemann, Kai and Ivanov, Boris and Melosh, H. Jay},
	month = jul,
	year = {2016},
	keywords = {Dellen, iSALE},
	pages = {136 pages}
}

@article{wunnemann_impacts_2016,
	title = {Impacts into quartz sand: {Crater} formation, shock metamorphism, and ejecta distribution in laboratory experiments and numerical models},
	issn = {1945-5100},
	shorttitle = {Impacts into quartz sand},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12710/abstract},
	doi = {10.1111/maps.12710},
	abstract = {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.},
	language = {en},
	urldate = {2016-08-23},
	journal = {Meteoritics \& Planetary Science},
	author = {Wünnemann, Kai and Zhu, Meng-Hua and Stöffler, Dieter},
	month = aug,
	year = {2016},
	pages = {1762--1794},
	file = {Snapshot:/Users/gsc/Zotero/storage/6E5TG9RN/abstract.html:text/html;Wünnemann et al. - 2016 - Impacts into quartz sand Crater formation, shock .pdf:/Users/gsc/Zotero/storage/N8XJXSN2/Wünnemann et al. - 2016 - Impacts into quartz sand Crater formation, shock .pdf:application/pdf}
}

@article{kendall_differentiated_2016,
	title = {Differentiated planetesimal impacts into a terrestrial magma ocean: {Fate} of the iron core},
	volume = {448},
	issn = {0012-821X},
	shorttitle = {Differentiated planetesimal impacts into a terrestrial magma ocean},
	url = {http://www.sciencedirect.com/science/article/pii/S0012821X16302217},
	doi = {10.1016/j.epsl.2016.05.012},
	abstract = {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.},
	urldate = {2016-08-23},
	journal = {Earth and Planetary Science Letters},
	author = {Kendall, Jordan D. and Melosh, H. J.},
	month = aug,
	year = {2016},
	keywords = {Accretion, differentiation, planetesimal dispersion, planetesimal impact, siderophile abundance},
	pages = {24--33},
	file = {Kendall and Melosh - 2016 - Differentiated planetesimal impacts into a terrest.pdf:/Users/gsc/Zotero/storage/EEAUQ27R/Kendall and Melosh - 2016 - Differentiated planetesimal impacts into a terrest.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/C9NPZASP/S0012821X16302217.html:text/html}
}

@article{kring_peak-ring_2016,
	title = {Peak-ring structure and kinematics from a multi-disciplinary study of the {Schrödinger} impact basin},
	volume = {7},
	issn = {2041-1723},
	url = {http://www.nature.com/doifinder/10.1038/ncomms13161},
	doi = {10.1038/ncomms13161},
	urldate = {2016-10-31},
	journal = {Nature Communications},
	author = {Kring, David A. and Kramer, Georgiana Y. and Collins, Gareth S. and Potter, Ross W. K. and Chandnani, Mitali},
	month = oct,
	year = {2016},
	pages = {13161},
	file = {Kring et al. - 2016 - Peak-ring structure and kinematics from a multi-di.pdf:/Users/gsc/Zotero/storage/WNPU62FD/Kring et al. - 2016 - Peak-ring structure and kinematics from a multi-di.pdf:application/pdf}
}

@article{johnson_formation_2016,
	title = {Formation of the {Orientale} lunar multiring basin},
	volume = {354},
	copyright = {Copyright © 2016, American Association for the Advancement of Science},
	issn = {0036-8075, 1095-9203},
	url = {http://science.sciencemag.org/content/354/6311/441},
	doi = {10.1126/science.aag0518},
	abstract = {titOn the origin of Orientale basinle
Orientale 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.
Science, this issue pp. 438 and 441
Multiring 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.
A two-step isothermal process converts carbon dioxide and methane into carbon monoxide for chemical and fuel production
A two-step isothermal process converts carbon dioxide and methane into carbon monoxide for chemical and fuel production},
	language = {en},
	number = {6311},
	urldate = {2016-10-31},
	journal = {Science},
	author = {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.},
	month = oct,
	year = {2016},
	pmid = {27789836},
	pages = {441--444},
	file = {Johnson et al. - 2016 - Formation of the Orientale lunar multiring basin.pdf:/Users/gsc/Zotero/storage/VH3ZKG8T/Johnson et al. - 2016 - Formation of the Orientale lunar multiring basin.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/Z524WTSC/441.html:text/html}
}

@article{morgan_formation_2016,
	title = {The formation of peak rings in large impact craters},
	volume = {354},
	copyright = {Copyright © 2016, American Association for the Advancement of Science},
	issn = {0036-8075, 1095-9203},
	url = {http://science.sciencemag.org/content/354/6314/878},
	doi = {10.1126/science.aah6561},
	abstract = {Drilling into Chicxulub's formation
The 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.
Science, this issue p. 878; see also p. 836
Large 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.
Rock samples from IODP/ICDP Expedition 364 support the dynamic collapse model for the formation of the Chicxulub crater.
Rock samples from IODP/ICDP Expedition 364 support the dynamic collapse model for the formation of the Chicxulub crater.},
	language = {en},
	number = {6314},
	urldate = {2016-11-18},
	journal = {Science},
	author = {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},
	month = nov,
	year = {2016},
	pages = {878--882},
	file = {Morgan et al. - 2016 - The formation of peak rings in large impact crater.pdf:/Users/gsc/Zotero/storage/V5EP37XG/Morgan et al. - 2016 - The formation of peak rings in large impact crater.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/V2EBPUIR/878.html:text/html}
}

@article{miljkovic_subsurface_2016,
	title = {Subsurface morphology and scaling of lunar impact basins},
	volume = {121},
	issn = {2169-9100},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/2016JE005038/abstract},
	doi = {10.1002/2016JE005038},
	abstract = {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.},
	language = {en},
	number = {9},
	urldate = {2016-12-20},
	journal = {Journal of Geophysical Research: Planets},
	author = {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.},
	month = sep,
	year = {2016},
	keywords = {1221 Lunar and planetary geodesy and gravity, 5420 Impact phenomena, cratering, GRAIL, impact basin, lunar},
	pages = {2016JE005038},
	file = {Miljković et al. - 2016 - Subsurface morphology and scaling of lunar impact .pdf:/Users/gsc/Zotero/storage/3E2FBSTE/Miljković et al. - 2016 - Subsurface morphology and scaling of lunar impact .pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/82B5U76D/abstract\;jsessionid=80B7CCA19A2D24A1E28987C06E164984.html:text/html}
}

@article{kowitz_revision_2016,
	title = {Revision and recalibration of existing shock classifications for quartzose rocks using low-shock pressure (2.5–20 {GPa}) recovery experiments and mesoscale numerical modeling},
	volume = {51},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12712/abstract},
	doi = {10.1111/maps.12712},
	abstract = {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.},
	language = {en},
	number = {10},
	urldate = {2017-01-12},
	journal = {Meteoritics \& Planetary Science},
	author = {Kowitz, Astrid and Güldemeister, Nicole and Schmitt, Ralf Thomas and Reimold, Wolf-Uwe and Wünnemann, Kai and Holzwarth, Andreas},
	month = oct,
	year = {2016},
	pages = {1741--1761},
	file = {Kowitz et al. - 2016 - Revision and recalibration of existing shock class.pdf:/Users/gsc/Zotero/storage/ZD844EZB/Kowitz et al. - 2016 - Revision and recalibration of existing shock class.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/B4NJQRQZ/abstract.html:text/html}
}

@article{rae_complex_2017,
	title = {Complex crater formation: {Insights} from combining observations of shock pressure distribution with numerical models at the {West} {Clearwater} {Lake} impact structure},
	issn = {1945-5100},
	shorttitle = {Complex crater formation},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12825/abstract},
	doi = {10.1111/maps.12825},
	abstract = {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.},
	language = {en},
	urldate = {2017-02-10},
	journal = {Meteoritics \& Planetary Science},
	author = {Rae, A. S. P. and Collins, G. S. and Grieve, R. A. F. and Osinski, G. R. and Morgan, J. V.},
	year = {2017},
	pages = {1330--1350},
	file = {Rae et al. - 2017 - Complex crater formation Insights from combining .pdf:/Users/gsc/Zotero/storage/9REKMC72/Rae et al. - 2017 - Complex crater formation Insights from combining .pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/CI392V8E/abstract.html:text/html}
}

@article{baker_formation_2016,
	title = {The formation of peak-ring basins: {Working} hypotheses and path forward in using observations to constrain models of impact-basin formation},
	volume = {273},
	issn = {0019-1035},
	shorttitle = {The formation of peak-ring basins},
	url = {http://www.sciencedirect.com/science/article/pii/S0019103515005527},
	doi = {10.1016/j.icarus.2015.11.033},
	abstract = {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.},
	urldate = {2017-03-30},
	journal = {Icarus},
	author = {Baker, David M. H. and Head, James W. and Collins, Gareth S. and Potter, Ross W. K.},
	month = jul,
	year = {2016},
	keywords = {CRATERING, Impact processes, Moon, Moon, surface},
	pages = {146--163},
	file = {Baker et al. - 2016 - The formation of peak-ring basins Working hypothe.pdf:/Users/gsc/Zotero/storage/T2RQJ2H4/Baker et al. - 2016 - The formation of peak-ring basins Working hypothe.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/HWIUCGWR/S0019103515005527.html:text/html}
}

@article{forman_defining_2017,
	title = {Defining the mechanism for compaction of the {CV} chondrite parent body},
	issn = {0091-7613, 1943-2682},
	url = {http://geology.gsapubs.org/content/early/2017/04/11/G38864.1},
	doi = {10.1130/G38864.1},
	abstract = {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.},
	language = {en},
	urldate = {2017-04-18},
	journal = {Geology},
	author = {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.},
	month = apr,
	year = {2017},
	pages = {G38864.1},
	file = {Snapshot:/Users/gsc/Zotero/storage/CG9G9QMB/G38864.1.html:text/html}
}

@article{collins_numerical_2017,
	title = {A numerical assessment of simple airblast models of impact airbursts},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12873/abstract},
	doi = {10.1111/maps.12873},
	abstract = {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.},
	language = {en},
	urldate = {2017-05-16},
	journal = {Meteoritics \& Planetary Science},
	author = {Collins, Gareth S. and Lynch, Elliot and McAdam, Ronan and Davison, Thomas M.},
	year = {2017},
	pages = {1542--1560},
	file = {Collins et al. - 2017 - A numerical assessment of simple airblast models o.pdf:/Users/gsc/Zotero/storage/ETCBC2TX/Collins et al. - 2017 - A numerical assessment of simple airblast models o.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/TAR39TWD/abstract.html:text/html}
}

@article{guldemeister_quantitative_2017,
	title = {Quantitative analysis of impact-induced seismic signals by numerical modeling},
	volume = {296},
	issn = {0019-1035},
	url = {http://www.sciencedirect.com/science/article/pii/S0019103516306017},
	doi = {10.1016/j.icarus.2017.05.010},
	abstract = {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.},
	urldate = {2017-07-18},
	journal = {Icarus},
	author = {Güldemeister, Nicole and Wünnemann, Kai},
	month = nov,
	year = {2017},
	keywords = {Impact hazard, Impact seismicity, Meteorite impacts, numerical modeling, Seismic waves},
	pages = {15--27},
	file = {Güldemeister and Wünnemann - 2017 - Quantitative analysis of impact-induced seismic si.pdf:/Users/gsc/Zotero/storage/AET537P5/Güldemeister and Wünnemann - 2017 - Quantitative analysis of impact-induced seismic si.pdf:application/pdf;ScienceDirect Snapshot:/Users/gsc/Zotero/storage/3FZEBQHV/S0019103516306017.html:text/html}
}

@article{luther_snow_2017,
	title = {Snow carrots after the {Chelyabinsk} event and model implications for highly porous solar system objects},
	volume = {52},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12831/abstract},
	doi = {10.1111/maps.12831},
	abstract = {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.},
	language = {en},
	number = {5},
	urldate = {2017-07-28},
	journal = {Meteoritics \& Planetary Science},
	author = {Luther, Robert and Artemieva, Natalia and Ivanova, Marina and Lorenz, Cyril and Wünnemann, Kai},
	month = may,
	year = {2017},
	pages = {979--999},
	file = {Snapshot:/Users/gsc/Zotero/storage/E2PIGQBT/abstract.html:text/html}
}

@incollection{guldemeister_scaling_2015,
	title = {Scaling impact crater dimensions in cohesive rock by numerical modeling and laboratory experiments},
	isbn = {978-0-8137-2518-5},
	url = {http://dx.doi.org/10.1130/2015.2518(02)},
	abstract = {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.},
	urldate = {2017-07-28},
	booktitle = {Large {Meteorite} {Impacts} and {Planetary} {Evolution} {V}},
	publisher = {Geological Society of America},
	author = {Güldemeister, N. and Wünnemann, K. and Poelchau, M.H.},
	editor = {Osinski, Gordon R. and Kring, David A.},
	year = {2015}
}

@article{muxworthy_evidence_2017,
	title = {Evidence for an impact-induced magnetic fabric in {Allende}, and exogenous alternatives to the core dynamo theory for {Allende} magnetization},
	volume = {52},
	issn = {1945-5100},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12918/abstract},
	doi = {10.1111/maps.12918},
	abstract = {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.},
	language = {en},
	number = {10},
	journal = {Meteoritics \& Planetary Science},
	author = {Muxworthy, Adrian R. and Bland, Phillip A. and Davison, Thomas M. and Moore, James and Collins, Gareth S. and Ciesla, Fred J.},
	month = oct,
	year = {2017},
	pages = {2132--2146},
	file = {Muxworthy et al. - 2017 - Evidence for an impact-induced magnetic fabric in .pdf:/Users/gsc/Zotero/storage/59J7A4XG/Muxworthy et al. - 2017 - Evidence for an impact-induced magnetic fabric in .pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/ITXWWVXC/abstract\;jsessionid=9C98E788FC2C2E74920A1B8C6ABA54DC.html:text/html}
}

@article{watters_dependence_2017,
	title = {Dependence of secondary crater characteristics on downrange distance: {High}-resolution morphometry and simulations},
	volume = {122},
	issn = {2169-9100},
	shorttitle = {Dependence of secondary crater characteristics on downrange distance},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/2017JE005295/abstract},
	doi = {10.1002/2017JE005295},
	abstract = {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.},
	language = {en},
	number = {8},
	journal = {Journal of Geophysical Research: Planets},
	author = {Watters, Wesley A. and Hundal, Carol B. and Radford, Arden and Collins, Gareth S. and Tornabene, Livio L.},
	month = aug,
	year = {2017},
	keywords = {5420 Impact phenomena, cratering, 5470 Surface materials and properties, 5494 Instruments and techniques, hydrocode simulations, impact cratering, secondary craters, surface processes},
	pages = {2017JE005295},
	file = {Snapshot:/Users/gsc/Zotero/storage/EPUMMSNV/abstract.html:text/html;Watters et al. - 2017 - Dependence of secondary crater characteristics on .pdf:/Users/gsc/Zotero/storage/E5MRE2KJ/Watters et al. - 2017 - Dependence of secondary crater characteristics on .pdf:application/pdf}
}

@article{holm-alwmark_combining_2017,
	title = {Combining shock barometry with numerical modeling: {Insights} into complex crater formation—{The} example of the {Siljan} impact structure ({Sweden})},
	issn = {1945-5100},
	shorttitle = {Combining shock barometry with numerical modeling},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/maps.12955/abstract},
	doi = {10.1111/maps.12955},
	abstract = {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.},
	language = {en},
	journal = {Meteoritics \& Planetary Science},
	author = {Holm-Alwmark, Sanna and Rae, Auriol S. P. and Ferrière, Ludovic and Alwmark, Carl and Collins, Gareth S.},
	year = {2017},
	pages = {Accepted},
	file = {Holm-Alwmark et al. - Combining shock barometry with numerical modeling.pdf:/Users/gsc/Zotero/storage/QJ8G38QQ/Holm-Alwmark et al. - Combining shock barometry with numerical modeling.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/7ZJW5JB2/abstract.html:text/html}
}

@article{weiss_constraining_2013,
	title = {Constraining the characteristics of tsunami waves from deformable submarine slides},
	volume = {194},
	issn = {0956-540X},
	url = {https://academic.oup.com/gji/article/194/1/316/645010/Constraining-the-characteristics-of-tsunami-waves},
	doi = {10.1093/gji/ggt094},
	abstract = {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.},
	number = {1},
	urldate = {2017-10-10},
	journal = {Geophysical Journal International},
	author = {Weiss, Robert and Krastel, Sebastian and Anasetti, Andreas and Wünnemann, Kai},
	month = jul,
	year = {2013},
	pages = {316--321},
	file = {Snapshot:/Users/gsc/Zotero/storage/TWKWFIR2/Constraining-the-characteristics-of-tsunami-waves.html:text/html;Weiss et al. - 2013 - Constraining the characteristics of tsunami waves .pdf:/Users/gsc/Zotero/storage/SV9GMR6E/Weiss et al. - 2013 - Constraining the characteristics of tsunami waves .pdf:application/pdf}
}

@article{prieur_effect_2017,
	title = {The effect of target properties on transient crater scaling for simple craters},
	volume = {122},
	issn = {2169-9100},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/2017JE005283/abstract},
	doi = {10.1002/2017JE005283},
	abstract = {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.},
	language = {en},
	number = {8},
	journal = {Journal of Geophysical Research: Planets},
	author = {Prieur, N. C. and Rolf, T. and Luther, R. and Wünnemann, K. and Xiao, Z. and Werner, S. C.},
	month = aug,
	year = {2017},
	keywords = {5420 Impact phenomena, cratering, 6250 Moon, CRATERING, Impact processes, Moon, target properties},
	pages = {2017JE005283},
	file = {Prieur et al. - 2017 - The effect of target properties on transient crate.pdf:/Users/gsc/Zotero/storage/SIXFGF39/Prieur et al. - 2017 - The effect of target properties on transient crate.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/BQHTS33E/abstract.html:text/html}
}

@article{silber_effect_2017,
	title = {Effect of impact velocity and acoustic fluidization on the simple-to-complex transition of lunar craters},
	volume = {122},
	issn = {2169-9100},
	url = {http://onlinelibrary.wiley.com/doi/10.1002/2016JE005236/abstract},
	doi = {10.1002/2016JE005236},
	abstract = {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.},
	language = {en},
	number = {5},
	urldate = {2018-02-12},
	journal = {Journal of Geophysical Research: Planets},
	author = {Silber, Elizabeth A. and Osinski, Gordon R. and Johnson, Brandon C. and Grieve, Richard A. F.},
	month = may,
	year = {2017},
	keywords = {0545 Modeling, 5420 Impact phenomena, cratering, 6250 Moon, acoustic fluidization, lunar craters, numerical modeling, simple-to-complex transition},
	pages = {2016JE005236},
	file = {Silber et al. - 2017 - Effect of impact velocity and acoustic fluidizatio.pdf:/Users/gsc/Zotero/storage/J4P6VM6A/Silber et al. - 2017 - Effect of impact velocity and acoustic fluidizatio.pdf:application/pdf;Snapshot:/Users/gsc/Zotero/storage/YR443FZK/abstract.html:text/html}
}