Extraterrestrial liquid water Extraterrestrial liquid water Extraterrestrial liquid water (from the Latin words: "extra" ["outside of, beyond"] and "terrestris" ["of or belonging to Earth"]) is water in its liquid state that naturally occurs outside Earth. It is a subject of wide interest because it is recognized as one of the key prerequisites for life as we know it and thus surmised as essential for extraterrestrial life. With oceanic water covering 71% of its surface, Earth is the only planet known to have stable bodies of liquid water on its surface, and liquid water is essential to all known life forms on Earth. The
State of matter liquid, given that the pressure is higher than the triple point of the substance. Intermolecular (or interatomic or interionic) forces are still important, but the molecules have enough energy to move relative to each other and the structure is mobile. This means that the shape of a liquid is not definite but is determined by its container. The volume is usually greater than that of the corresponding solid, the best known exception being water, HO. The highest temperature at which a given liquid can exist is its critical temperature. A gas is a compressible fluid. Not only will a gas