On the pressure dependence of salty aqueous eutectics

Abstract

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. • Characterize high-pressure eutectics for several aqueous binaries • Eutectic pressure dependences approximately follow pressure-melting curve of ice Ih • Develop methods to extract additional eutectic properties from measured P-T curves • Isochoric freezing method enables high-throughput measurement of multiphase equilibria The eutectic defines the threshold of stability for liquid phases, and high-pressure eutectic data are essential to the modeling of icy worlds. Chang et al. acquire measurements of the pressure dependences of five salty aqueous eutectics, providing both reference data and physical insight into the pressure evolution of the eutectic temperature.