Elucidating the Dense Ice Phase Diagram at Low Temperatures

Water, along with being vital for life on Earth, is one of the most abundant species in the outer solar system where it is most commonly found in its solid state as ice. The pressure-temperature phase diagram of ice has been studied extensively, revealing the existence of many different polymorphs. Nevertheless the behaviour of ice is poorly understood above 80 GPa, and despite the existence of ice X being known for the past 30 years, the mechanism at which either ice VII or VIII transforms to X is unknown. We have conducted preliminary Raman spectroscopy measurements at low temperature which indicate that between ice VIII and X there is an intermediary phase. In this proposal we intend to explore the ice phase diagram between 80-300 K and up to pressures above 200 GPa. In particular we hope to establish whether the signatures observed in our spectroscopy experiments represents a metastable distortion of ice VIII, a disordered form of ice X, or a completely new phase.