Earth’s core may hold nine times more hydrogen than all oceans

New research suggests that Earth’s core could contain a staggering amount of hydrogen — possibly the planet’s largest hydrogen reservoir. Scientists estimate that the core may hold the equivalent of nine to 45 Earth oceans’ worth of hydrogen, accounting for roughly 0.36% to 0.7% of the core’s total weight, according to a study published on February 10 in Nature Communications.

The findings indicate that most of Earth’s hydrogen — and by extension, its water — was likely acquired during the planet’s formation, rather than arriving later via comet impacts, researchers say. Lead author Dongyang Huang, an assistant professor at Peking University, noted that the core formed early in Earth’s history, with the mantle and crust receiving progressively smaller shares of hydrogen, leaving the surface — where life exists — with the least.

Because hydrogen is extremely light and difficult to measure, previous estimates of the element in the core varied widely, from the equivalent of 0.1 oceans to more than 120 oceans. To refine these figures, Huang and colleagues replicated core conditions in the lab using iron as a proxy. They employed atom probe tomography, which observes individual atoms in three dimensions at the nanoscale, to study hydrogen’s interactions with silicon and oxygen.

The study also provides insights into Earth’s early magnetic field formation, as hydrogen’s behaviour in the core may have influenced heat flow into the mantle.

While promising, the researchers caution that uncertainties remain. Some hydrogen may have escaped during experiments, and other chemical interactions in the core are not fully accounted for. Experts not involved in the study suggest that the true hydrogen content could be even higher.

By Vugar Khalilov