Scientists discovered a massive water storage mechanism nearly 2,900 kilometers beneath the Earth’s crust, according to research published on September 8 in Nature Geoscience. Rather than an underground ocean, researchers from China’s Centre for High Pressure Science and Technology Advanced Research found two new iron-rich compounds capable of trapping hydrogen and oxygen deep inside the Earth’s mantle.
Deep-Earth Water Storage via Iron Oxyhydroxides
The newly identified compounds, designated as Fe₅O₁₂Hₓ and Fe₇O₁₂Hₓ, are known as iron oxyhydroxides, according to the published study. These minerals do not contain liquid water directly. Instead, they hold the essential building blocks of water under extreme conditions.
To replicate the environment of the Earth’s inner layers, researchers placed samples of these compounds between diamond tips, squeezed them under intense pressure, and heated them with lasers up to 2,500°C. Geoscientist Alfred Wilson from the University of Leeds noted in an accompanying commentary that these stable, dense phases capture and retain water across a wide range of lower-mantle conditions.
Did you know? Water continuously seeps into the deep Earth when tectonic plates shift or sink. This newly identified mechanism suggests that water can remain trapped inside iron-rich minerals for extremely long periods.
Implications for Earth’s Habitability and Mantle Dynamics
Liquid water remains the key component of Earth’s habitability, making the identification of these dense phases critical for understanding internal geochemical cycles. According to Wilson, the specific minerals required to transport water into the deepest parts of the Earth’s mantle remained unclear prior to this research.
High-pressure and high-temperature experiments at lower-mantle conditions now point to iron oxyhydroxide phases as key agents in this transport process. However, scientists have yet to establish whether these newly identified compounds can occur naturally inside the Earth.
Frequently Asked Questions
Is there an actual ocean beneath the Earth’s crust?
No. Instead of a liquid ocean, scientists have found compounds like iron oxyhydroxides that trap hydrogen and oxygen—the building blocks of water—deep within the Earth’s mantle.
How do scientists study conditions 2,900 km underground?
Researchers recreate the extreme pressure and temperature of the Earth’s inner layers in laboratories by placing mineral samples between diamond tips and heating them with lasers up to 2,500°C.
How does water get deep into the Earth?
Water seeps into the Earth’s interior when tectonic plates shift or sink, where it can potentially become trapped in iron-rich minerals.
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