Equation of state of water in the megabar range

The mantle of Neptune and Uranus is mainly constituted by ice layers containing water, methane and ammonia. The magnetic field of both planets, as measured by the probe Voyager 2, is larger than what was expected and asymmetrical, hence originates from the conductivity of those layers. The range of temperature and pressure in the ice layers is of 0.2 to 6 Mbar and 2,000 K to 8,000 K. Estimations of the minimum conductivity capable of sustaining the magnetic field by dynamo effect give about 200 (Ω.cm)−1. Recent calculations predict a transition from electrolyte to metal in this regime for water and ammonia [1]. Yet no measure has so far confirmed its existence.