Constraining the thermophysical structure and composition of Europa’s ice shell through radar detection of eutectic interfaces

Recently launched missions, NASA’s Europa Clipper and ESA’s JUpiter ICy moons Explorer (JUICE), are equipped with ice-penetrating radar sounders for the purpose of studying Europa’s subsurface ice shell and global ocean. Detection of a eutectic interface within Europa’s ice shell may offer a direct measurement on the amount and distribution of brine at its lowest thermodynamically stable temperature. We explore how a potential radar detection of a eutectic interface may help constrain ice shell thickness, thermal structure, and compositional chemistry. We find that the role of bulk ice shell salinity in eutectic detection differs significantly across different binary endmember compositions, NaCl and MgSO₄, as well as multi-ion compositions of ice shell chemistry. We additionally find that the geometric distribution of eutectic brine impacts radar detectability, and we further discuss the prospects of detecting vertically and laterally extended hydrological features such as dikes, sills, or perched lakes.