New Research Reveals Earth’s Hidden Water Reservoirs During Formation
A recent study led by Prof. Zhixue Du from the Guangzhou Institute of Geochemistry of the Chinese Academy of Sciences has unveiled that large quantities of water may have been stored deep within Earth’s mantle during its formation, rather than being lost to space. The findings, published in the journal Science on December 11, 2025, suggest that this hidden water reservoir played a crucial role in shaping the planet’s geology and environment.
About 4.6 billion years ago, Earth was a tumultuous, molten mass, bombarded by cosmic impacts that kept its surface in a fiery state. During this time, liquid water as we know it could not exist, as the planet resembled a furnace more than a haven for life. Today, however, oceans cover roughly 70% of Earth’s surface, and understanding how water persisted through such extreme conditions has puzzled scientists for decades.
The breakthrough in understanding came as the research team explored the mineral bridgmanite, the most abundant mineral in the Earth’s mantle. Previous studies indicated that bridgmanite could only hold minimal water, but the new findings reveal that it can function as a microscopic “water container,” potentially storing quantities of water comparable to today’s oceans.
In order to investigate this phenomenon, the researchers faced significant challenges. They needed to replicate the extreme pressures and temperatures found more than 660 kilometers below the Earth’s surface. To achieve this, the team developed a diamond anvil cell system combined with laser heating, which allowed them to reach temperatures as high as approximately 4,100 °C. This innovative setup enabled them to accurately measure how minerals absorb water under high heat.
Utilizing advanced analytical tools, including cryogenic three-dimensional electron diffraction and NanoSIMS, the researchers, in collaboration with Prof. LONG Tao from the Institute of Geology of the Chinese Academy of Geological Sciences, were able to map water distribution within tiny mineral samples. Their findings confirmed that water is structurally dissolved within bridgmanite, indicating that the lower mantle is likely far wetter than previously thought.
The study also revealed that bridgmanite’s water storage capacity increases significantly at higher temperatures. The research suggests that during Earth’s most intense magma ocean phase, bridgmanite could have stored much more water than scientists had believed, challenging the long-standing notion that the lower mantle is nearly dry. Their simulations indicate this water reservoir could be between five to one hundred times larger than earlier estimates, with total water amounts ranging from 0.08 to 1 times the volume of today’s oceans.
This water did not merely remain trapped underground. Instead, it acted as a “lubricant” for the Earth’s geological processes. By lowering the melting point and viscosity of mantle rocks, the water facilitated internal circulation and plate motion, providing the planet with long-term geological energy. Over eons, some of this water gradually resurfaced through volcanic activity, contributing to the formation of Earth’s early atmosphere and oceans.
The research team posits that this concealed reservoir of water was a decisive factor in transforming Earth from a fiery inferno into the hospitable planet we inhabit today. As scientists continue to unravel the mysteries of our planet’s formation, these findings provide a deeper understanding of how water has influenced Earth’s evolution and its capacity to support life.
