This surprising study reveals that the “secret water vault” inside the Earth is one of the most important geological discoveries of the last decade.
If we go back to 4.6 billion years ago, Earth was not like the calm, blue world we see today.
Meanwhile, powerful impacts from space kept the surface and interior of the planet in a constant state of turmoil.
A recent study led by Professor Zhixue Du of the Guangzhou Institute of Geochemistry of the Chinese Academy of Sciences (GIGCAS) offers a new explanation: large quantities of water may have been stored deep in the Earth’s mantle as it cooled from molten rock.
The results of the study were published in Science on December 11 and change scientists’ vision of water storage deep within the planet.
Researchers have demonstrated that bridgmanite, the most abundant mineral in the Earth’s mantle, can function as a microscopic “water container.”
Previous experiments showed that bridgmanite could only hold small amounts of water; however, these studies were conducted at lower temperatures.
To answer these lingering questions, researchers had to overcome significant challenges. They had to simulate the pressures and temperatures found more than 600 kilometers below the Earth’s surface and detect extremely tiny traces of water in mineral samples.
The team specifically built an anvil cell system combined with laser heating and high-temperature imaging to address these challenges.
The experiments revealed that bridgmanite’s ability to trap water is measured by a water partition coefficient, which describes how water is partitioned between different minerals.
During Earth’s hottest magma ocean, the newly formed bridgmanite could have stored much more water than scientists thought.
Recent discoveries challenge the traditional understanding that the lower mantle is completely dry.
These results helped the team model how Earth’s magma ocean cooled and crystallized.
Their simulations further suggest that bridgmanite retains water so effectively under extreme heat that the lower mantle has become the largest water reservoir on solid Earth.
The model showed that this reservoir could be five to 100 times larger than previous estimates, with a total water volume 0.08 to 1.0 times greater than the volume of today’s oceans.
This deeply stored water did not simply remain trapped, but rather acted as a lubricant for Earth’s internal engine.
By lowering the melting point and viscosity of mantle rocks, water helped stimulate internal circulation and plate movement, thereby maintaining the planet’s geological energy for a longer period of time.
The study further suggests that this buried “water spark” may have been the determining factor in Earth’s transformation from a molten inferno to the blue planet we know today.
