Earth May Be Hoarding a Secret Water Stash 1,800 Miles Beneath Our Feet

Researchers recreated lower mantle conditions at a depth of about 2900 km and discovered two previously unknown iron oxyhydroxides — Fe5O12Hx and Fe7O12Hx — capable of storing water. The compounds form even with minimal hydrogen content and can store primordial and 'recycled' water over geological timescales. The work is published in Nature Geoscience.

• Experiment recreated pressure of 2 million atmospheres and temperature of 2500 °C
• Conditions correspond to a depth of about 2900 km at the core-mantle boundary
• Compounds Fe5O12Hx and Fe7O12Hx form even from nearly anhydrous samples
• High density keeps water at the mantle-core boundary for billions of years