ICME Overview for Impact Cratering of Olivine
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ICME Overview for Impact Cratering of Olivine
Background Information
Impact cratering occurs in three stages -- contact and compression, excavation, and modification[1]. The contact and compression stage begins when the projectile makes contact with the surface of the target, which can occur at velocities anywhere between 11.2 and 72.8 km/s on Earth. The projectile pushes target material out of its path as it is slowed by the material's resistance. The target material is strongly compressed creating shockwaves that propagate away from the impact zone at a large fractin of the projectile velocity. Pressures generated during this early stage of impact cratering reach hundreds of GPa's, so both projectile and target materials may mel or vaporize upon unloading, at which point the contact and compression stage concludes and the excavation stage begins. During the excavation stage, the target material unloads, creating a rarefaction wave that begins to move the material, initiating the excavation that opens a crater several times the diameter of the projectile. Once the crater has been fully excavated, so begins the modification stage, in which loose debris slides down the crater walls and pools at the bottom.
Atomistics
Atomic scale calculations can be performed to determine the elastic modulus and the dependence of bond mobility on strain rate can be determined.
Microscale
Material in the compressed region will be exposed to very high temperatures, which will cause olivine to become ductile and dislocation density will become the driving force for crack growth as a result of the forces of the impact and subsequent shockwave.
Mesoscale
Material near the region of impact will be subjected to a very rapid compression followed by unloading that causes a phase change in the form of melting and subsequent recrystallization.
Macroscale
Finite element analysis of the model can be performed to analyze the consequences of a meteoric impact such as crater diameter and depth.
References
- ↑ H.J. Melosh, "Impact Cratering: A Geologic Process", Oxford University Press, New York, NY, 1989.
