Magma ocean methane combustion as the origin of terrestrial water

The origin of Earth's hydrosphere remains unresolved. We show that the early magma ocean constituted a planetary-scale catalytic reactor in which lattice oxygen from silicate minerals (MgO, SiO2, FeO, CaO) was transferred to atmospheric methane, yielding water and CO2 as thermodynamically inevitable products. This process is independently documented at active volcanoes, in sedimentary basins, in lunar basalt experiments, and in industrial catalysis. The framework requires four cosmically guaranteed ingredients — hydrogen, carbon, metal oxide minerals, and gravitational energy — making ocean formation a stoichiometric inevitability rather than a stochastic delivery event. The model simultaneously resolves Venus's CO2 atmosphere, the Moon's volatile depletion and nearside-farside asymmetry, Titan's preserved methane, deep abiogenic hydrocarbons, and the inner solar system carbon deficit. Testable predictions are provided for JWST, lunar samples, exoplanet surveys, and the DAVINCI Venus mission.