Forming metallic water: Implications for magnetic field generation in
Icy Giant Planets

Kanani K. M. Lee
Division of Geological & Planetary Sciences
California Institute of Technology

ABSTRACT

Although the giant gas planets are comprised of mostly hydrogen and
helium, the icy giants Neptune and Uranus are believed to be composed
of ~50% water (by mass), as well as significant amounts of methane
and ammonia (Hubbard, 1984).  Most of the water is in an
ultra-condensed, high-temperature state forming an "icy" interior
layer with pressures ranging between 10 and 500 GPa and temperatures
between 2000 and 5000 K (Hubbard, 1997).  It is theorized that it is
in this hot, dense layer that the planet's magnetic field is
produced.  To explore the physical properties of water at the extreme
conditions of this icy interior layer, we performed laser-driven
shock experiments on precompressed samples accessing thermodynamic
conditions unreachable by either static or single-shock compression
techniques alone.  Recent experiments using Rutherford Appleton
Laboratory's Vulcan Laser achieved final pressures up to ~200 GPa and
temperatures up to 10,000 K in water samples precompressed in a
diamond cell to ~1 GPa, thereby validating this new technique.