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Damage and rock-volatile mixture effects on impact crater formation

O'Keefe, John D. and Stewart, Sarah T. and Lainhart, Michael E. and Ahrens, Thomas J. (2001) Damage and rock-volatile mixture effects on impact crater formation. International Journal of Impact Engineering, 26 (1-10). pp. 543-553. ISSN 0734-743X. doi:10.1016/S0734-743X(01)00112-9.

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We explored simple geologic strength and material response models to determine which have the capability to simulate impact-induced faulting, complicated ejecta patterns and complex crater shapes. This led us to develop models for material damage, dilatancy, and inhomogeneous materials (mixtures). We found that a strength degradation (damage) model was necessary to produce faulting in homogeneous materials. Both normal and thrust ring faults may occur and extend relatively deeply into the planet during the transient cavity radial expansion. The maximum depth of fault development is about the depth of maximum penetration by the projectile. Dilatancy in geologic materials may reduce the final bulk density compared to the pristine state because of irreversible fracturing. When we include the effects of dilatancy, the radial position of faulting is displaced because of greater upward motions. In addition, the late time crater profile is shallower and the expression of features such as central peaks and rings may be more pronounced. Both damage and rock-ice mixtures effect the distribution of ejecta. The excavation flow field within the heavily damaged region is similar to flow fields in Mohr-Coulomb materials with no zero-pressure strength. In the outer, less damaged zone within the excavation cavity, the material trajectories collapse back into the crater. This effect creates a zone of reduced ejecta emplacement near the edge of the final crater. In the case of rock-ice mixtures, energy is preferentially deposited in the more compressible volatile component and the ejecta pattern is dependent upon the location of shock-induced phase changes in the volatile material.

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Additional Information:© 2001 Elsevier Science Ltd. We thank the reviewers for their thoughtful comments. In addition we appreciate the readily given assistance of Gene Hertel of Sandia Laboratories in the use of CTH. This research was supported under NASA Goddard grant NAG5-8915. Contribution number 8714. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125.
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Subject Keywords:impact; shock damage; dilatancy; crater faults; ejecta; thermal fracturing; complex craters
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Caltech Division of Geological and Planetary Sciences8714
Issue or Number:1-10
Record Number:CaltechAUTHORS:20141023-080006635
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Official Citation:John D. O'Keefe, Sarah T. Stewart, Michael E. Lainhart, Thomas J. Ahrens, Damage and rock-volatile mixture effects on impact crater formation, International Journal of Impact Engineering, Volume 26, Issues 1–10, December 2001, Pages 543-553, ISSN 0734-743X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50713
Deposited By: Tony Diaz
Deposited On:23 Oct 2014 16:15
Last Modified:10 Nov 2021 18:59

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