Scientists confirm vast underground water reservoirs deep in Earth's mantle
A team led by Du Zhixue at the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, has published a breakthrough study in *Science* showing that Earth's lower mantle, located more than 660 kilometers beneath the surface, may contain massive primitive water reservoirs.Through high-temperature and high-pressure experiments simulating extreme underground conditions of 23-32 GPa and 1273-2100 K, researchers discovered that the mineral bridgmanite can store far more water than previously believed. Their findings suggest the mantle could hold between 0.08 and 1 times the total water of today's oceans, equivalent to 8% to 100% of all surface ocean water.
Bridgmanite, the earliest major mineral to crystallize during Earth's magma ocean stage, acts as a microscopic water container. Its ability to lock in water increases with temperature, meaning that during Earth's hottest early phase it could capture and store enormous amounts of water. Modeling based on experimental data shows that after the magma ocean solidified, the lower mantle became the largest aquifer in the solid Earth, with water storage capacity five to one hundred times higher than earlier scientific estimates.
About 4.6 billion years ago, Earth was not yet the "blue planet." Violent impacts churned its surface into a molten magma ocean where liquid water could not exist. As the planet cooled, minerals crystallized to form the mantle. Bridgmanite's ability to trap water during this process may explain how vast reservoirs became locked deep underground.
This discovery reshapes our understanding of Earth's water cycle and planetary evolution. It suggests that much of Earth's water may not only reside on the surface but also be stored deep within, influencing mantle dynamics, volcanic activity, and the long-term stability of oceans.
The Guangzhou Institute of Geochemistry, part of the Chinese Academy of Sciences, is a leading research institution specializing in Earth sciences, geochemistry, and planetary evolution. Its work on mantle water storage contributes to global efforts to understand Earth's deep structure and the origins of its oceans.
