Hydrogen in the Core
When metallic iron reacts with water at pressure, hydrogen in water voluntarily dissolves into iron to form iron hydride (FeHx). In this study, hydrogen in molten iron hydride was first detected as numerous bubbles in recovered iron particles. The 98% of water accreted to the primordial Earth was taken away from the planetary surface by this reaction during the core formation of the Earth in 4.5 billion years ago. If this reaction did not occur, and if all accreted water remained in the Earth's surface to form oceans, its depth would have reached a few hundreds km depth that is far more deeper than the present value, and the surface environment of the Earth would be quite different from the present state.