Heat storage in ocean worlds: The role of slurries

Abstract

ABSTRACT Several icy moons of the Solar system, such as Europa, harbor global oceans below their surfaces. It is conceivable that a number of exoplanetary bodies may also possess them. The presence of aqueous layers, partially or totally liquid, highly influences the bulk physical properties of these bodies, particularly the thermal state, and consequently, the geological activity and the potential habitability over time. In this work, we obtained experimental data to characterize the thermal budgets of aqueous environments in planetary bodies depending on the main solute composition, and we quantified the heat associated with water-rich materials’ phase transitions occurring during planetary evolution. We measured the heat capacity (Cp) and the sensible heat values of aqueous systems at several concentrations of sulfate, carbonate, chloride, ammonia, and methanol at low temperatures, and we calculated the latent heat associated with the phase transitions. Raman spectroscopy allowed us to identify the phases related to the Cp and enthalpy (ΔH) variations. We applied thermal functions to estimate the energy involved in the generation of oceans and other endogenous processes, recognizing the impact of heat transfer by both ice and brine slurries. Likewise, we calculated the heat associated with the formation of local liquid lenses, particularly below Europa’s surface, which is suggested by the presence of geological features such as Thera Macula. We propose that the calorimetric properties of the slurries of the studied salt- and volatile-systems may sustain the potential habitability of icy moons and support the formation of certain surface features, in particular due to the high latent heat density and the promotion of the exothermic local growth of ice blocks that can separate from the remaining liquid.