  Using ab initio simulations we investigate whether water ice is stable in the
cores of giant planets, or whether it dissolves into the layer of metallic
hydrogen above. By Gibbs free energy calculations we find that for pressures
between 10 and 40 Mbar the ice-hydrogen interface is unstable at temperatures
above approximately 3000 K, far below the temperature of the core-mantle
boundaries in Jupiter and Saturn that are of the order of 10000 K. This implies
that the cores of solar and extrasolar giant planets are at least partially
eroded.
