Chinese researchers have discovered a key mechanism explaining how Earth may have stored enormous amounts of water in its early history, offering fresh insights into the planet's transformation from a molten, fiery sphere to the life-supporting world we know today.
A team from the Guangzhou Institute of Geochemistry, part of the Chinese Academy of Sciences, conducted experiments suggesting that the planet's deep mantle could have served as a massive water reservoir more than four billion years ago.
The study, published on Friday, December 12, in the journal Science, addresses a longstanding question: "Where did the water go when Earth's early magma oceans crystallized?"
The answer, the researchers found, lies in bridgmanite, the dominant mineral in the lower mantle. Previously thought to have limited capacity for water, bridgmanite was shown to trap water molecules far more effectively than expected, with its ability strongly influenced by temperature.
Using a diamond anvil cell apparatus and laser heating to replicate the extreme pressures and temperatures of the lower mantle, reaching up to 4,100 ℃, the team discovered that the hotter the environment during formation, the more efficiently bridgmanite captured water from cooling magma.
According to the study, this process could have locked away an amount of water equivalent to between 0.08 and 1 times the volume of today's oceans within the solid mantle.
Over billions of years, this primordial water stockpile has gradually cycled back to Earth's surface through volcanic activity, helping shape the planet into a blue, habitable world.
The findings provide a vital piece in understanding Earth's early evolution and the processes that made it capable of supporting life.
