CAMCS
Planetary Impact
Radial and concentric faults, lineaments and grooves have all been identified in association with impact craters on planets and asteroids. These, along with excavated blocks and ejecta, are often the direct result of dynamic fracture that occurs during the cratering process. Explanations of these observations all derive from simulations of the large-scale impact cratering process coupled with assumptions on planetary and asteroidal structure. The tremendous importance of impact processes in determining the evolution of planetary surfaces and the related collisional evolution of the asteroids has resulted in a significant amount of work on various parts of this problem. However, simulations of these impact processes are limited by the availability of appropriate material models that account for dynamic failure mechanisms. It is our global objective, within this proposed research program, to use recent advances in dynamic failure mechanics to provide material models that incorporate dynamic failure processes and that are appropriate for large-scale planetary impact. As a specific result, we will provide advanced fracture models that will improve predictions of fracture and fragmentation during large-scale planetary impact processes, particularly in the intermediate strain rate regime where current models are inaccurate.
A significant part of the material volume involved in impact cratering (e.g. of an asteroid onto a planet or icy satellite) sees strain rates that are very different from the extreme strain rates associated with the contact and compression domain; these strain rates can range from 0.01 to 1000 s-1 over very large process volumes. In this domain, massive failure of the pre-shocked materials dominates the impact processes. Current models of material behavior and fragmentation have difficulty handling this regime, because of the coupling between massive failure processes, strength, energetics and dynamics. We propose to address this regime: understanding this regime will enable robust modeling of asteroidal and planetary impacts.
Scientific and Program Objectives
We bring together expertise in dynamic failure mechanics and planetary science to investigate the material behavior and failure processes associated with large scale impacts and intermediate strain rates. Our specific scientific objectives are the following:
- Develop experimentally verified models for the failure of geophysical materials at the intermediate strain rates in planetary scale impact events. This will be the largest task within this program.
- Implement a selection of the models into a computational simulation approach for planetary impact problems, and consider scaling implications
- Examine the observational implications of the advanced failure models that we develop with recourse to existing data.