Earth may hold far more water than previously thought

While climatologists continue the debate over projected sea level rises and climate fluctuations, an equally engaging debate is raging on the subject of subterranean oceans.

Scientists at the University of Tokyo have come up with a novel theory regarding Earth’s precious water resources. Motohiko Murakami and colleagues of the of Tokyo Institute of Technology in Japan believe that there may be about five times as much water as in all the world’s oceans deep beneath the Earth’s surface.

In an article published in the journal Nature, the researchers suggest that at a depth of 1,000 kilometres in the lower mantle, rocks heated to over 1,000 degrees Celsius could harbour immense quantities of water.

“The findings will boost the debate about how much water is locked away in the mantle,” says Bernard Wood, a geologist from the University of Bristol. There are already thought to be several oceans’ worth of water slightly higher in the mantle, at a depth of 400 – 600 km.

Murakami’s team mimicked the furious conditions of the lower mantle in the laboratory using a multi-anvil cell. This heats materials while squeezing them between hard teeth. They used three kinds of mineral thought to be found in the region: two perovskites – a type of oxide minerals, one rich in magnesium, the other in calcium, and magnesiowustite, a mixture of magnesium and iron oxides.

Having baked the minerals at 1,600 degrees Celsius and 250 thousand atmospheres, the team measured how much hydrogen the rocks contained. The researchers found more than previous studies had led them to believe.

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