Impact experiments on ice

Abstract

The results of cratering and fragmentation experiments on pure ice are reported. The projectiles used are cylindrical aluminum, poly‐carbonate, teflon, and pyrophyllite fired at velocities between 110 m/sec and 680 m/sec, with kinetic energies at impact between 2 and 500 joules. Crater diameters (pit diameters) in the ice were about two times larger than craters in the same energy range in basalts. The ratios of (pit diameter)/(spall diameter) are about three and the ratios of (depth of crater)/(spall diameter) are between 0.1 and 0.3 which are close to the depth/diameter ratios observed in basalts. The crater diameter in ice is also well expressed as a single function of the ‘late‐stage effective energy’ defined recently by Mizutani et al. [1983]. The specific energy for complete destruction of ice target is about 50 J/kg which is two orders of magnitude smaller than that of basalt. The present experimental data on cratering and fragmentation of ice show that the impacts associated with the largest craters on Callisto and Mimas must have severely fractured the whole satellites, and that those giant impacts with the kinetic energy of 10 23 to 10 27 joules probably affected significantly the evolution of the satellites.