Deep Earth Minerals Reveal Hidden Reservoir of Water

Deep beneath the crust, scientists have identified a potential water reservoir trapped between the lower mantle and the planet's outer core. Researchers discovered two iron oxyhydroxide minerals capable of storing significant water volumes under extreme pressure, challenging long-held assumptions about the composition of the Earth's interior.

Editorial·September 15, 2026·reads: 1,547

For decades, geologists assumed the lower mantle—composed primarily of dry minerals like bridgmanite and ferropericlase—held little to no water. By using diamond anvil cells to simulate the intense heat and pressure found 660 to 2,900 kilometers below the surface, researchers recreated the environment of these ultralow velocity zones. The experiment revealed that iron oxyhydroxides remain stable in these conditions, even when water concentrations are as low as 0.1 percent.

This discovery suggests that water may have been sequestered since the cooling of the early magma ocean. As mantle material shifts, these minerals could potentially decompose, releasing moisture that eventually migrates toward the surface through volcanic activity. Alfred Wilson of the University of Leeds described the findings as a breakthrough in understanding how the planet retains its water, though he noted that the total capacity of these deep-seated minerals remains a subject of ongoing investigation. Mineral physicist Leonid Dubrovinsky, who contributed to the study published in Nature Geoscience, emphasized that even minute traces of hydrogen are sufficient to stabilize these dense, highly hydrated compounds.