The Role of Antifreeze in the Subsurface Oceans of Icy Moons

The icy moons Europa, Ganymede, Callisto, Enceladus and Titan contain plenty of liquid water, a key ingredient for life (Nimmo and Pappalardo, JGR-Planets, 2016). In addition to exploring the habitability, probing the internal structure of these icy moons, systems that are very different from terrestrial planets, is important for us to understand the evolution of the solar system. Subsurface oceans are widespread on these moons mainly due to the presence of antifreeze. Vance et al. (JGR-Planets, 2018) have built several elegant one-dimensional models of these icy ocean worlds based on properties such as density, temperature, sound velocity and electrical conductivity. According to the different adiabatic profile assumptions, assigning different surface ice thicknesses result in significant differences in the electrical conductivity of the subsurface oceans. We have begun an experimental program to explore electrical conductivity of liquid samples in a 3000-ton multi-anvil press. Deionized water is currently being tested at room temperature to refine experimental techniques. Subsequent conductivity measurements of water mixed with antifreeze, such as ammonia, at low temperature (Yong and Secco, Rev. Sci. Instrum., 2017) and at moderate pressures are planned. Based on these experimental data, we hope to optimize further the models proposed by Vance et al.