Abstract
Water probably has played significant roles in the origin and evolution of the Earth. During the accretion period, an H2-H2O atmosphere would have been formed by impact degassing of planetesimals, which may have resulted in the formation of magma ocean (hence promoted metal-silicate separation) and condensed to form the proto-ocean. During the evolution of the Earth, water would have circulated between the surface and mantle reservoirs. This global water cycle may have controlled the ocean mass and water content in the mantle as it coupled with thermal evolution of the Earth through mantle rheology. It may also have oxidized the mantle and the atmosphere in the Earth's history.
