Optical properties of superionic Water at 2 Mbar

Abstract:

Dynamic compression experiments now allow us to recreate planet deep interior conditions in the laboratory, providing valuable data on material properties at unprecedented conditions. These data are of paramount importance to build confidence in numerical simulation methods and establish new planetary structure and evolution models.

I will present new results on the optical properties and equation of state (pressure, density, temperature) of warm dense water at extreme conditions of pressure and temperature directly relevant to the deep interior of Uranus, Neptune and giant water-worldexoplanets.

Laser shock compression of water starting from ice VII (ρ₀=1.6 g/cc) obtained by coupling static and dynamic compression reached unprecedented conditions. We clearly identify the superionic phase near 1-2 Mbar, document its optical properties and obtain evidence for the transition to the dense metallic liquid. The EOS data in the conducting liquid state provide a stringent test on recent ab-initiosimulations.

As superionic ices could dominate the deep interior or giant icy planets and exoplanets, the new conductivity and equation of state experimental benchmark provide basis for improved modeling of the internal structure and magnetic field generation.

Prepared by LLNL under Contract DE-AC52-07NA27344