Deep Hydrogen Reservoirs and Longevity

The oceans are voluminous H2O reservoirs that regulate climate and life on Earth. Yet much larger H2O reservoirs, potentially accounting for several oceans, may exist in the Earth’s mantle and core in the form of H atoms trapped into the structure of nominally anhydrous minerals (NAMs) and metallic alloys. Determining the size of these ‘hidden oceans’ is key to understanding planetary evolution and surface dynamics and can be done by combining data from rare natural samples with experimental and theoretical models. The longevity of these deep H reservoirs is controlled by H transport rates over geological times, which are dominated by percolation rates, once H partitions into melts, or by plate mobility, if H remains locked in NAMs.