Experimental quantification of hydrogen content in the Earth's core

Area of Science:

• Geochemistry
• Planetary Science
• High-Pressure Mineral Physics

Background:

• Earth's core is hypothesized as a major hydrogen reservoir.
• Quantifying core hydrogen is challenging due to extreme conditions.

Purpose of the Study:

• To quantify hydrogen (H) content in Earth's core.
• To investigate hydrogen sequestration mechanisms during core formation.

Main Methods:

• Superliquidus metal-silicate partitioning experiments using laser-heated diamond anvil cells.
• Atom probe tomography for direct H observation.

Main Results:

• Direct observation of hydrogen associated with silicon- and oxygen-rich nanostructures in iron alloys.
• Evidence for coupled sequestration of Si, O, and H during core formation.
• Estimated core hydrogen content of 0.07-0.36 wt.%, equivalent to 9-45 oceans of water.

Conclusions:

• Earth's core likely contains a significant amount of hydrogen.
• The observed Si/H ratio suggests a specific sequestration mechanism.
• This finding implies Earth primarily gained its water during accretion, not via cometary impacts.