A research team led by Professor Du Zhixue from the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (CAS), has proposed the possible presence of a massive underground water reservoir in the lower mantle of Earth. The findings were published in Science.

According to their estimates, at a depth of about 660 km, a “super-ocean” could exist, containing 8–100% of the total volume of all surface oceans. To obtain this data, the team created a technological platform capable of reproducing extreme conditions at such depths: pressures of 23–32 GPa and temperatures of 1273–2100 K.

Experiments revealed that the mineral bridgmanite, one of the earliest-forming minerals in the mantle, can retain significantly more water at higher temperatures. A crystallization model of the magmatic ocean suggests that after solidification, the lower mantle may become the largest subterranean water reservoir on Earth. Its potential capacity could be 5–100 times greater than previously estimated.