Electromagnetic characterization of saline mixture for shallow radar exploration

Abstract

The first recognition of the Jupiter system, performed by the Voyager spacecraft, suggested the possibility of an ocean of liquid water beneath the ice shell two of Jupiter's moons, Ganymede and Europa. In addition, the Galileo mission detected in the icy shell the presence of impurities like magnesium and sodium sulfates, and sulfuric and hydrochloric acids. JUICE - JUpiter ICy moons Explorer will investigate the potentially habitable zones in the Ganymede, Europa and Callisto moons. In particular a radar sounder (RIME) operating at 9 MHz, optimized for the penetration of the icy shell, will provide the subsurface survey up to a depth of about 9 km. The performance of RIME depends on the electromagnetic properties of the icy shells, which in turn are related to the impurity contents and temperature. In this scenario, we have performed measurements of dielectric properties of ice doped with MgSO4, Na2SO4. The tests were performed as a function of frequency from 20 Hz to 1 MHz and temperature down to 100 K. The electromagnetic behaviour of saline-ices have shown that the attenuation coefficient becomes very small when the temperature decreases.