Hypervelocity impact cratering on water ice targets at temperatures ranging from 100 K to 253 K

Surface temperatures on the icy satellites decrease substantially with distance from the Sun. Some of the main surface features on these bodies are hypervelocity impact craters. Understanding the influence of ice temperature on impact crater morphology is thus important. Previous laboratory impact crater data on water (H2O) ice targets was mostly at relatively high temperatures (255 K) and studies at low temperatures are limited. In addition, the few low-temperature studies have been at much lower velocities than those considered hypervelocity. They are thus not representative of impact craters on icy satellites. Accordingly data is presented here studying the dependence on target temperature for hypervelocity impact cratering on H2O ice at velocities of 5 km s(-1) using spherical, 1 mm diameter aluminium projectiles. In this study, the ice target temperature ranged from 100 K to 253 K. Results for crater diameter, depths and volume are given along with ratios of these data. The results showed strong dependencies with temperature for all the above parameters. The strongest dependencies were from crater depth and volume. However, not all these properties vary in the same way with temperature. As the temperature of the ice increased, volume and depth increased, but crater diameter decreased. While the overall size scale of the laboratory studies (mm-cm dimensions) is still not appropriate to planetary scales (m-km), the general behavior as a function of target temperature has been established.