Dielectric Characterization of Ice/Na2SO4·10H2O Mixtures: Implications for Radar Investigations of Icy Satellites

Abstract

Jupiter satellites will be the object of study of future ESA and NASA missions: JUICE and Europa. In particular these missions have been motivated to understand the geological activity from the subsurface to the surface and also to constrain the minimal thickness of the ice shell. In fact, both missions will host a radar on board: JUICE will investigate the subsurface through RIME, an ice penetrating radar sounder operating on a single frequency band, centered at 9 MHz, that should be able to penetrate up to 9 km (depending on the crust properties) below the frozen surface, with a vertical resolution of up to 30 meters in the ice, while REASON is a dual frequency radar (9 and 60 MHz) that will be hosted on Europa mission. The performance of both radars depends on the dielectric behavior of the icy crusts, which in turn are related to the temperature and chemical constituents of the icy shells. In this context, we have performed a series of dielectric measurements as a function of frequency on different sodium sulfate decahydrate mixtures cooled down to typical temperatures of Jovian satellites. Our objective is to evaluate the effective penetration capability of low-frequency sounder radars in detecting subsurface structures characterized by variations in the electrical properties of the ice. The results of this experimental activity revealed that these salty ice analogs showed a decrease in attenuation with the temperature drop, increasing the radar signal possibilities to penetrate inside the satellite