Superionic ice at planetary interior

Water is abundant in natural environments, but its structure and physical properties at ultra extreme conditions remain uncertain. A family of superionic ices with highly mobile protons within the stable oxygen sublattice has been predicted at high pressures, in a pressure-temperature phase space that borders the familiar high-pressure solid ices and the fluid. However, the existence of superionic ices, their phase boundaries and the location of the melting line have been challenging to assess due to the extreme difficulties and uncertainties in both theory and experiments, which yielded contradictory results depending on the techniques applied and data interpretation. Here I will present results of recent measurements on superionic phase boundaries determined at different experimental conditions with extensive comparison to available static and dynamic data including theoretical simulations. Unique properties of superionic phases will be discussed in the light of understanding the pathway of phase transitions in the time-domain experiments.