Water covers 70% of the Earth’s surface and is crucial to life. But how it got there is the subject of an old scientific debate.
A team of French researchers has contributed to the building by asserting that our planet would have been, from its origin, rich in water, probably contained in abundance in the rocks that made it up. The study was published in the journal Science.
Cosmochemist Laurette Piani, who led this study at the Center for Petrographic and Geochemical Research (CNRS / University of Lorraine), explained that this discovery undermined the dominant thesis according to which the water would have been brought later by asteroids and comets having bombarded a Land initially dry.
This hypothesis was favored by the fact that the too high temperatures of the solar system would have prevented water from condensing and agglomerating with other solids in the form of ice.
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A land rich in water from its formation?
French researchers looked at meteorites called enstatite chondrites, which have the particularity of having a chemical composition close to that of the Earth, which indicates that they are similar to the rocks that were part of it from its formation.
By measuring the hydrogen content of 13 of these relatively rare meteorites, the team found that these primitive rocks of the blue planet detected enough to provide it at least three times the mass of water of its oceans, if not more. “We found that the isotopic composition of hydrogen in enstatite chondrites was similar to that of water stored in the Earth’s mantle,” explains Laurette Piani.
The isotopic composition of the oceans is for its part compatible with a mixture containing 95% water of these chondrites, an additional element supporting the thesis according to which they are at the origin of terrestrial water. The authors also found that the nitrogen isotopes of these meteorites are similar to those of nitrogen from Earth.
This study does not rule out subsequent water supply from other sources, such as comets, but emphasizes that enstatite chondrites have significantly contributed to the presence of water on Earth from its origin.
This work “brings a crucial and elegant piece to this puzzle”, wrote Anne Peslier, researcher at NASA, in an editorial accompanying the study.
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