This surprising study reveals that the “secret water vault” within Earth is one of the most consequential geological discoveries of the last decade.
If we glimpse back to 4.6 billion years ago, Earth was not like the calm, blue world we see today.
Meanwhile, the powerful impacts from space kept the planet’s surface and interior in a constant state of agitation.
A recent study led by Prof. Zhixue Du of the Guangzhou Institute of Geochemistry of the Chinese Academy of Sciences (GIGCAS) offers a new explanation: large amounts of water could have been stored deep inside Earth’s mantle as it cooled from molten rock.
The study results were published in Science on December 11 and are changing scientists’ thinking about water storage deep inside the planet.
The researchers demonstrated that bridgmanite, the most plentiful mineral in Earth’s mantle, can function like a microscopic “water container.”
Earlier experiments showed that bridgmanite could only hold small amounts of water; however, those studies were conducted at lower temperatures.
To answer these lingering questions, the researchers had to overcome significant challenges. They needed to simulate the pressures and temperatures found more than 600 kilometers beneath Earth’s surface and detect extremely small traces of water in mineral samples.
The team has specifically built an anvil cell system combined with laser heating and high-temperature imaging to meet these challenges.
The experiments have revealed that bridgmanite’s ability to trap water is measured by a water partition coefficient, which describes how water is distributed between different minerals.
During Earth’s hottest magma ocean, newly formed bridgmanite could have stored far more water than scientists believed.
The recent findings challenge the traditional understanding of 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 holds water so efficiently under extreme heat that the lower mantle has become the largest water reservoir within the solid Earth.
The model showed that this reservoir could be five to 100 times larger than earlier estimates, with total water running from 0.08 to 1.0 times the volume of today’s oceans.
This deeply stored water did not simply remain trapped’ rather it acted as a lubricant for Earth’s internal engine.
By lowering the melting point and viscosity of mantle rocks, the water helped drive internal circulation and plate motion, sustaining the planet-geological energy for a longer period of time.
The research study further suggests that this buried “spark of water” may have been the determining factor in transforming Earth from a molten inferno into the blue planet we know today.
