On the pressure dependence of salty aqueous eutectics

The eutectic is fundamental to multicomponent systems, defining the lowest temperature at which a given liquid phase is stable. Although binary aqueous eutectics have been broadly characterized at atmospheric pressure, eutectic data at high pressure are scarce, leaving critical gaps both in the data available for modeling and in our understanding of how eutectic equilibria may evolve with pressure. In this work, we deploy a simple, high-throughput, isochoric freezing method to measure the pressure dependences of five binary aqueous eutectics, chosen for their importance in compositional modeling of the distant icy planets deemed most likely to harbor life. Our data reveal that the pressure dependence of all the eutectics measured herein can be approximated by the pressure dependence of the ice Ih melting curve, providing a key rule of thumb for future analysis, and we further demonstrate multiple methods by which additional thermophysical properties of these high-pressure eutectics may be extracted from the measured pressure-temperature coordinates.