Effects of lithologies on impact cratering: continuation of Numerical Modeling of Known Terrestrial Craters.

The study of crater populations is an important tool for understanding the geologic history of planetary surfaces (e.g., McGill, 1977). Impact cratering modifies locally and temporally the physical and thermal state of target and ejects and distributes material in various physical states (melted, shocked, pulverized, etc.) over a wide region around the excavated crater. At the same time, the physical and chemical properties of target material, including porosity, volatile content and natural mixtures of diverse rocks strongly affect the cratering process. 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 biochemical processes on a given planetary body. Numerical simulations, and to a somewhat lesser degree, due to scaling limitations, laboratory experiments are the best tools for such an undertaking. Over the past two grant cycles we have accumulated valuable experience in understanding the influence of target properties on the impact process by modeling the formation of specific terrestrial craters. In the process, we have significantly improved our numerical codes (SOVA and SALEB)and material models. Overall, current material and hydrodynamic models allow us to reproduce the main features of crater morphology versus impact size. At the same time, our results indicate that there are still limitations in the models that must be improved for an accurate reproduction of impact events.