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Earth May Have Massive Subterranean Water Reservoir, Bigger Than All Our Oceans

There could be a large body of water buried deep beneath the Earth's surface containing as much water as in every ocean combined, according to scientists. You know, just your average secret trove of buried water, maybe. 

By Danielle Wiener-Bronner
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There could be a large body of water buried deep beneath the Earth's surface containing as much water as in every ocean combined, according to new scientific research. You know, just your average secret trove of buried water to sustain all life on Earth.

Ok, maybe we're jumping the gun. (A lot.) But according to research leader Graham Pearson, he and his team discovered a rare mineral that suggests a reservoir may exist 250-375 miles beneath the Earth's surface, below the crust. Pearson explains that his team analyzed a tiny diamond found in Brazil in 2008, and found a microscopic mineral crystal,  ringwoodite, that contains roughly one percent water by weight. The discovery indicates that more water can be found throughout the transition zone — the portion of the Earth's mantle where the diamond originated. One percent might not seem like a lot but, according to Pearson, "when you realize how much ringwoodite there is, the transition zone could hold as much water as all the Earth's oceans put together." 

Richard A. Lovett offers more detail in post on Nature's news site:

Most diamonds form at depths of about 150 to 200 kilometers, but 'ultradeep' diamonds come from a region of the mantle known as the transition zone, 410 to 660 kilometers below the surface, says Graham Pearson, a mantle geochemist at the University of Alberta in Edmonton and the lead author of the study. Impurities in ultradeep diamonds can be used as probes to study the regions in which the stones formed — and in particular to understand what minerals are present at those depths... if the minerals are trapped inside diamonds, they stay compressed in their original forms. “These high-pressure diamonds give you a window into the deep Earth,” says Pearson. 

This is not the first time scientists have considered the possibility of water in the transition zone, but they've had little evidence to back the claim until now. Pearson says that "this sample really provides extremely strong confirmation that there are local wet spots deep in the Earth in this area." Scientists speculate on where the water, if it's there, came from. Two theories prevail: The reservoir is filled with ocean water carried underground by shifting tectonic plates, or that the water has been present since the Earth formed, possibly carried from space via asteroid or comets. But Pearson isn't sure yet how to move forward with testing, saying "we have to think very carefully on what we do next on this sample because it's very small: 40 micrometers. That means you can only think of doing one or two additional analyses."

Still, it's possible that the discovery doesn't mean all that much. Geologist Hans Keppler told Agence France-Presse that scientists should be cautious in concluding so much from such a small sample, and adds that it is likely the water is trapped in molecular form in certain rocks.

But if a subterranean pool of water does exist, it would help explain the Earth's more volatile features, like volcanic eruptions, as resulting from water-fueled tectonic shifts. Otherwise, the water remains inaccessible. "You can't run a field trip to those areas," Pearson told CBC News. "No one's ever even going to drill to those areas." Ok, so don't leave the faucet running.

This article is from the archive of our partner The Wire.