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The water covers 70% of the surface of the Earth and is crucial to life, but how she got there is the subject of an old scientific debate.
A team of French researchers made a contribution on Thursday by claiming that our planet would have been, from its origin, rich in water, probably contained in abundance in the rocks that made it up.
The cosmochemist Laurette Piani, who led this study by the Center for Petrographic and Geochemical Research (CNRS / University of Lorraine) published in the journal Science, explained to AFP that this discovery undermined the prevailing thesis that water was brought later by asteroids and comets that bombarded an initially dry Earth.
This hypothesis was favored by the excessively high temperatures of the Solar System which would have prevented water from condensing and agglomerating with other solids in the form of ice..
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 since its formation.
By measuring the hydrogen content of 13 of these relatively rare meteorites, the team found that the primitive rocks of the blue planet detected enough of it to provide it with at least three times the mass of water in its oceans, even more.
“Nous avons découvert que la composition isotopique de l’hydrogène des chondrites à enstatite était similaire à celle de l’eau stockée dans le manteau terrestre”, said Laurette Piani.
The isotopic composition of the oceans is for its part compatible with a mixture containing 95% of water from these chondrites, an additional element supporting the thesis that 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.
According to Laurette Piani, this study does not exclude subsequent water intake from other sources, like comets, but she insists that enstatite chondrites have contributed significantly since the formation of the planet.
Ce travail “apporte une pièce cruciale et élégante à ce puzzle”, wrote Anne Peslier, researcher at NASA, in an editorial accompanying the study.
World news – FR – Blue planet: study offers new theory on the origin of water on Earth – France 24