Investigating the Thermodynamics and Seismic Profile of the Europan Hydrosphere through Pure-Water Modeling and Saltwater Experiments

Europa is a prime candidate for the search for life beyond Earth due to its theorized subsurface liquid-water ocean. We perform a computational analysis of the thermodynamic properties for a pure-water Europan hydrosphere using a Python programming framework called SeaFreeze, creating four models of the ice shell assuming surface temperatures of 50K and 140K and ice shell thicknesses of 3km and 30km. We observe mostly linear trends for density and p- and s-wave velocities with respect to depth. Assuming a colder surface temperature of 50K introduces an inversion curve near the surface for density, indicating that temperature affects the models more than pressure. We also experimentally investigate the phase diagram of NaCl-water solutions up to 20% NaCl by weight. By measuring the freezing temperatures of these solutions at varying pressures (0MPa-80MPa), we find that increasing both the salt concentration and pressure decreases the freezing point. We expect that adding NaCl to the pure-water models would flatten the linear trends. Future work includes further comparisons between the models and saltwater experiments, exploring the phase diagram of different solutes (e.g., MgSO4), and extending the models through Europa’s subsurface ocean layer.