Effects of Friction and Plastic Deformation in Shock-Comminuted Damaged Rocks on Impact Heating

Hypervelocity impacts cause significant heating of planetary bodies. Such events are recorded by a reset of Ar-40-Ar-36 ages and/or impact melts. Here we investigate the influence of friction and plastic deformation in shock-generated comminuted rocks on the degree of impact heating using the iSALE shock-physics code. We demonstrate that conversion from kinetic to internal energy in the targets with strength occurs during pressure release, and additional heating becomes significant for low-velocity impacts (<10 km s(-1)). This additional heat reduces the impact-velocity thresholds required to heat the targets with the 0.1 projectile mass to temperatures for the onset of Ar loss and melting from 8 and 10 km s(-1), respectively, for strengthless rocks to 2 and 6 km s(-1) for typical rocks. Our results suggest that the impact conditions required to produce the unique features caused by impact heating span a much wider range than previously thought.