The examination of a 90-million-year-old diamond from Juina, Brazil, leads researchers to believe there are many oceans worth of water in the Earth’s mantle, at a depth as far as 621 miles.
“If it wasn’t down there, we would all be submerged,” Steve Jacobsen at Northwestern University in Evanston, Illinois, whose team made the discovery, told New Scientist. “This implies a bigger reservoir of water on the planet than previously thought.”
The discovery of the water was made by examining a diamond that was spat out 90 million years ago by a volcano near the Sao Luiz river in Juina.
The diamond has a sealed-off inclusion containing minerals that were trapped during its formation. Upon inspecting the minerals with infrared microscopy, researchers found evidence of hydroxyl ions, which normally come from water.
Jacobsen said they were everywhere in the diamond’s inclusion.
The water source is the deepest ever discovered, located a third of the way to the edge of Earth’s core.
To find out the depth the diamond formed at and thus the depth of the water, researchers looked at the composition of the inclusion. They found it is made of ferropericlase mineral, a composition of iron and magnesium oxide that can absorb other metals like chromium, aluminum and titanium in ultra-high temperatures and pressures that are typical of the lower mantle.
Since the metals were present, the diamond is believed to have originated in the lower mantle, and because the inclusion was trapped in the diamond for tens of millions of years, the water signature had to come from its place of formation in the lower mantle.
“This is the deepest evidence for water recycling on the planet,” Jacobsen said. “The big take-home message is that the water cycle on Earth is bigger than we ever thought, extending into the deep mantle.”
Researchers at the University of Alberta have estimated about 1.5 percent of the weight of the planet exists in water locked in minerals in the Earth’s interior, according to International Business Times. That amount of water would be the same as all of the world’s oceans combined.
Before Jacobsen’s discovery, his team found evidence of water at more than 372 miles down, mixed with rock.
“Water clearly has a role in plate tectonics, and we didn’t know before how deep these effects could reach,” he said, according to New Scientist. “It has implications for the origin of water on the planet.”
Jacobsen believes this new water discovery may help explain why Earth is the only planet known to us that has plate tectonics.
“Water mixes with ocean crust and gets subducted at convergent plate boundaries,” he said. “Introducing water into the mantle promotes melting and weakens rock, likely helping out the motions of plates like grease.”
Mainak Mookherjee, who is working with a team of researchers from Florida State University and the University of Edinburgh, thinks Earth’s interior water is just as important as water on the surface.
“My goal is to understand how much water is stored in the deep Earth,” he told International Business Times. “If the planet becomes dry on the inside, the planet dies because geodynamic activity within the planet ceases."
Mookherjee does not foresee Earth’s interior water drying up anytime soon, but understanding that it may eventually can help us understand how planets die.
"If you look at our [neighboring] planets, like Mars, we always look for water on the surface,” he said. “That's a key thing. Water is crucial for life, but it is also responsible for sustaining the large scale mantle convection within the Earth, and that's crucial to plate tectonics. These plates are in constant motion -- and that is dictated by the large scale geodynamics that operate in Earth's interior."
If the interior water is removed, then the planet can no longer function because it becomes too dry.
"The geodynamics become affected, they become sluggish," Mookherjee said. "That will affect the plate tectonics and once the plate tectonics die, you have no more volcanoes. Volcanoes are important for generating the Earth's crust and eventually soil, so all kinds of things will come to a stop.”
It is this theory many scientists prescribe to planets that are already dead, but may have been similar to Earth.
“…Water in Earth's interior is crucial to sustain the geodynamic activity that drives everything,” Mookherjee said.