$190,422; NASA Solar System Workings (SSW)

Phase relations of salt-H2O solutions at high pressure: Implications for the icy worlds
Principal Investigator: Heather Watson, associate professor of physics and astronomy and director of undergraduate research; Co-Investigator: George Shaw, Professor Emeritus of Geosciences

The possibility that subsurface oceans on the icy satellites of the outer planets might harbor life has stimulated experimental efforts to better define the chemical and physical conditions within these water-rich bodies. These include studies of pure water under high pressure and high and low temperatures, extension of those studies to solutions of a variety of salts, and measurements of the effect of pressure on freezing point depression in various salt solutions. Currently there exist few experimental studies with direct relevance to melting on icy moons such as Europa, Enceladus, and Ganymede. Most of the high-pressure experiments have been performed in diamond anvil cells at room temperature or above and tend to explore higher pressures than will be investigated through the proposed research. The project team, led by PI Watson, will conduct a series of experiments aimed at measuring the melting/freezing phase relationships of H2O salt solutions at pressures up to ~0.2 GPa (2kbar), which are directly relevant to these bodies.

This project seeks to understand the general phase relationships of salt-water solutions that are directly relevant to the crusts and underlying oceans of several icy satellites in our Solar System. The generation of an experimental data set that covers a wide range of pressure – temperature - composition space will provide a useful framework for understanding the physical structure and composition of several known icy satellites with interior water oceans, and perhaps other planetary bodies in the future.