About: Above the core is the lower-density liquid mantle composed of ice materials under high pressure and temperature. This massive liquid layer would not be separated into layers of traditional ice compounds, but mixtures of radically different compounds originally consisting of water, carbon dioxide, methane, and ammonia […] Since the mass of the planet is dominated by the liquid mantle that itself consists of heated ices under pressure, both Uranus and Neptune are classified as giant ice planets.       Sponge   NotDistinct   Permalink