excess volatile

…water vapour, have been called excess volatiles because their masses cannot be accounted for simply by rock weathering. These volatiles are thought to have formed the early atmosphere of Earth. At an initial crustal temperature of about 600 °C (about 1,100 °F), almost all of these compounds, including water (H₂O),…

…planetary interior have been called excess volatiles because their masses cannot be accounted for simply by rock weathering.