HR: 16:00h
AN: MR54A-01 INVITED [Abstracts]
TI: The Effect of Material Properties on the Impact Cratering Process
AU: * Pierazzo, E
EM: betty@psi.edu
AF: Planetary Science Institute, 1700 E. Fort Lowell Road,
Suite 106, Tucson, AZ 85719, United States
AU: Ivanov, B
EM: ivanov@lpl.arizona.edu
AF: Institute for Dynamics of Geospheres, Russian Academy of Sci., Leninsky Prospect 38/6,
Moscow, 117939, Russian Federation
AU: Artemieva, N
EM: artemeva@psi.edu
AF: Planetary Science Institute, 1700 E. Fort Lowell Road,
Suite 106, Tucson, AZ 85719, United States
AU: Artemieva, N
EM: artemeva@psi.edu
AF: Institute for Dynamics of Geospheres, Russian Academy of Sci., Leninsky Prospect 38/6,
Moscow, 117939, Russian Federation
AB:
The cratering process is strongly affected by the physical and chemical properties of target material, including
porosity, volatile content and natural mixtures of diverse rocks. On Earth craters in water-saturated sediments are
larger than their energy-equivalents in dry soils, which, in turn, are larger than their energy-equivalents in
crystalline rocks. On Mars, the distinctly lobate outer boundary (and sometimes several overlapping sets of flow
lobes) of impact crater ejecta blankets suggests mobilization of subsurface volatiles, in contrast to evidence from
the much drier Moon and Mercury, where craters are surrounded by ballistically emplaced ejecta. A thorough
understanding of the behavior and influence of material characteristics on the impact process is crucial for using
impact cratering as a tool to better understand the physical, geological, and biogeochemical processes on a
given planetary body. The presence of volatiles, namely water, in the target may affect shock propagation and
consequently target melting and the final crater morphology. When the target is a mixture of materials with very
different impedance, as is the case for rocks and water, the shock wave propagation may be affected by the
interaction of the original shock wave with shocks reflected at material boundaries. Single- and multiple-shocked
materials experiencing the same peak shock pressure will reach substantially different thermodynamic states,
with the multiple-shocked material having lower shock temperature and shock entropy. As a result, for mixtures of
materials with very different impedances the maximum shock pressure alone may not be the best criterion for
estimating melting and vaporization. Water vaporization may also influence the ejection process by affecting the
amount and dispersion of shocked ejecta. We carried out a series of numerical studies to investigate the effect of
water and/or ice in the target on the cratering process. Initial results indicate that there is no single incipient and
complete shock pressure for shock melting of ice in permafrost. These values depend on dry rock porosity and
on the amount and shape of the water/ice inclusions. Neglecting to properly address target properties in
numerical models may ultimately limit our understanding of the cratering process and result in predictions that
are in disagreement with observations.
DE: 5199 General or miscellaneous
DE: 5420 Impact phenomena, cratering (6022, 8136)
DE: 5460 Physical properties of materials
DE: 5470 Surface materials and properties
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting