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@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},