Impact crater formed on sintered snow surface simulating porous icy bodies

To improve the scaling parameter controlling the impact crater formation in the strength regime, we conducted impact experiments on sintered snow targets with the dynamic strength continuously changed from 20 to 200 kPa, and the largest crater size formed on small icy satellites was considered by using the revised scaling parameter. Ice and snow projectiles were impacted on a snow surface with 36% porosity at an impact velocity from 31 m s−1 to 150 m s−1. The snow target was sintered at the temperature from −5 °C to −18 °C, and the snow dynamic strength was changed with the sintering duration at each temperature. We found that the mass ejected from the crater normalized by the projectile mass, πV  , was related to the ratio of the dynamic strength to the impact pressure, πY∗, as follows: πV=0.01πY∗-1.2, where the impact pressure was indicated by P = ρtC0tvi/2 with the target density of ρt, when the impact velocity, vi, was much smaller than the bulk sound velocity C0t (typically 1.8 km s−1 in our targets). The ratio of the largest crater diameter to the diameter of the target body, dmax/D, was estimated by calculating the crater diameter at the impact condition for catastrophic disruption and then compared to the observed dmax/D of jovian and saturnian small satellites, in order to discuss the formation condition of these large dmax/D in the strength regime.

► We made impact-cratering experiments on sintered snow at 31–150 m s−1. ► Snow targets had the dynamic strength (Y) from 20 kPa to 200 kPa. ► A scaling parameter of crater formation in the strength regime (πY∗) was improved. ► πY∗ was the ratio of Y   to shock induced pressure at the impact point. ► The πY∗ was used to estimate the largest crater size on small icy bodies.