Radar Attenuation for Subsurface Sounding on Enceladus: Effects of a Thermally Insulating Porous Ice Layer.

Byrne, W.P.; Plesa, A.-C.; Rückriemen-Bez, T.; Hussmann, H.; Benedikter, A.

Abstract

Saturn's moon Enceladus is thought to possess habitable conditions due to the presence of a global ocean, potential water-rock interactions at the ocean's base, and its ocean composition derived from sampling active plumes at the south pole. The thin (35 km) and cold ice shell of this small moon in the outer solar system is expected to allow the direct detection of the ice-ocean interface using low-frequency radar sounder instruments. Here we investigate the two-way radar attenuation in Enceladus' ice shell, focusing on the effect of a porous icy layer generated by Enceladus' jet activity. Our results show that in regions with a thin (or absent) porous surface layer, total ice shell penetration is possible. In regions covered by thick and strongly insulating porous surface layers, however, as little as 2% of the ice shell can be penetrated. Nevertheless, a thick porous surface layer leads to high subsurface temperatures promoting the formation of brines at shallow depth that can be detected by future radar measurements.