Experimental quantification of hydrogen content in the Earth’s core

TL;DR

This study estimates Earth's core contains up to 45 oceans worth of hydrogen, suggesting water originated during planet formation, not from comets.

Contribution

First direct quantification of hydrogen in Earth's core using metal-silicate partitioning experiments and atom probe tomography.

Findings

Hydrogen sequesters with silicon and oxygen in Earth's core during formation.

Estimated hydrogen content is 0.07-0.36 wt.% in the core, equivalent to 9-45 oceans.

Earth's water likely originated during terrestrial accretion, not from comets.

Abstract

Earth’s core has long been speculated to be the largest reservoir of hydrogen (H) on the planet. However, current estimates of its H content involve substantial uncertainties, due to the challenge of quantifying H under extreme conditions. Here, we perform superliquidus metal-silicate partitioning experiments on H using laser-heated diamond anvil cells, and combine it with atom probe tomography. The direct observation of H at silicon- and oxygen-rich nanostructures in the iron alloy indicates coupled sequestration of silicon, oxygen and hydrogen into Earth’s core during its formation. With the observed molar Si/H ratio close to unity, Earth’s core is estimated to contain 0.07-0.36 wt.% H, equivalent to 9-45 oceans of water. Such an amount would require the Earth to obtain the majority of its water from the main stages of terrestrial accretion, instead of through comets during late addition.

Earth’s core is arguably the largest reservoir of hydrogen (H) on the planet. Experiments show that H sequestration is coupled with those of Si and O, enabling the core to store the equivalent of dozens of Earth’s oceans.

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