<P> Oceans, seas, lakes and other bodies of liquids can be composed of liquids other than water, for example the hydrocarbon lakes on Titan . The possibility of seas of nitrogen on Triton was also considered but ruled out . There is evidence that the icy surfaces of the moons Ganymede, Callisto, Europa, Titan and Enceladus are shells floating on oceans of very dense liquid water or water--ammonia . Earth is often called the ocean planet because it is 70% covered in water . Extrasolar terrestrial planets that are extremely close to their parent star will be tidally locked and so one half of the planet will be a magma ocean . It is also possible that terrestrial planets had magma oceans at some point during their formation as a result of giant impacts . Hot Neptunes close to their star could lose their atmospheres via hydrodynamic escape, leaving behind their cores with various liquids on the surface . Where there are suitable temperatures and pressures, volatile chemicals that might exist as liquids in abundant quantities on planets include ammonia, argon, carbon disulfide, ethane, hydrazine, hydrogen, hydrogen cyanide, hydrogen sulfide, methane, neon, nitrogen, nitric oxide, phosphine, silane, sulfuric acid, and water . </P> <P> Supercritical fluids, although not liquids, do share various properties with liquids . Underneath the thick atmospheres of the planets Uranus and Neptune, it is expected that these planets are composed of oceans of hot high - density fluid mixtures of water, ammonia and other volatiles . The gaseous outer layers of Jupiter and Saturn transition smoothly into oceans of supercritical hydrogen . The atmosphere of Venus is 96.5% carbon dioxide, which is a supercritical fluid at its surface . </P>

Which of the following zones is present only in oceans