Electromagnetic characterization of saline/acid ice mixture for shallow radar exploration

The aim of this work is the estimation of the electromagnetic parameters of the icy geomaterials present in Jovian satellite crusts. 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 of the two 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 chloridric 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 , H2SO4 and HCl. The tests were performed as a function of frequency from 20 Hz to 30 MHz and temperature down to 100 K. In particular, the dielectric properties of the ice samples were measured using a capacitive cell and LCR meters. The values of real and imaginary parts of dielectric permittivity allow us to estimate velocity and attenuation of radar signals versus salts and acids content, to optimize the JUICE mission data analysis.