Washington: Did our planet make its own water through geologic processes or did it come to us via icy comets from the far reaches of the solar system? The answer is likely to be both.
According to researchers from the Ohio State University, the same amount of water which currently fills the Pacific Ocean could be buried deep inside the planet right now.
The team reports the discovery of a previously unknown geochemical pathway by which the earth can sequester water in its interior for billions of years and still release small amounts to the surface via plate tectonics - feeding our oceans from within.
"When we look into the origins of water on the earth, what we are really asking is, why are we so different than all the other planets?" asked Wendy Panero, associate professor of earth sciences at Ohio State University.
"In this solar system, the earth is unique because we have liquid water on the surface. We are also the only planet with active plate tectonics. Maybe this water in the mantle is key to plate tectonics and that is a part of what makes the earth habitable," he hypothesised.
Central to the study is the idea that rocks that appear dry to the human eye can actually contain water - in the form of hydrogen atoms trapped inside natural voids and crystal defects.
Oxygen is plentiful in minerals, so when a mineral contains some hydrogen, certain chemical reactions can free the hydrogen to bond with the oxygen and make water.
Since there is no way to directly study deep mantle rocks, Panero and doctoral student Jeff Pigott are probing the question with high-pressure physics experiments and computer calculations.
The team shared the findings at the American Geophysical Union (AGU) meeting in San Francisco.