Jules Verne imagined that there was an ocean inside the earth.
The writer was not entirely wrong, as has now been shown by an international research team, which includes geoscientists from the University of Frankfurt led by Frank Brenker.
However, the water that the researchers detected does not ripple on dark shores, but is enclosed in minerals.
The scientists analyzed a 1.5 centimeter diamond that came from Botswana.
It originated at a depth of 660 kilometers, in the transition zone between the upper and lower mantle.
There is enormous pressure of up to 23,000 bar.
It causes the mineral olivine, which makes up around 70 percent of the upper mantle of the earth, to change its crystal structure: the form found below 520 kilometers is called ringwoodite.
In the African diamond, the geologists found many ringwoodite inclusions that had a high water content.
By analyzing the chemical composition, they were able to show that the gem came from a normal piece of earth's mantle.
"With this study, we have demonstrated that the transition zone is not a dry sponge, but rather stores significant amounts of water," says Brenker.
In theory, it could hold six times the amount of water in all oceans.
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