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Meteorites from the far reaches of the solar system delivered large amounts of water, carbon and volatile substances to the Earth. Only then could the Earth host life. Dr. María Isabel Varas-Reus, Dr. Stephan König, Aierken Yierpan and Professor Dr. Ronny Schönberg from Tübingen University's Isotope Geochemistry Group, and Dr. Jean-Pierre Lorand from the Université de Nantes, provide evidence for this scenario in a new study. Using a method recently developed at the University of Tübingen, the researchers measured selenium isotopes in rocks derived from the Earth's mantle. Identical isotope signatures in these rocks and in certain types of meteorites revealed the origin of the selenium as well as large amounts of water and other vital substances. The study has been published in the latest Nature Geoscience.
Strictly speaking, there shouldn't be any selenium in the Earth's mantle. "It is attracted to iron. That is why, in the early history of our planet, it went down into the iron-rich core," Dr. María Isabel Varas-Reus explains. There was no more selenium in the Earth's outer layer. "The previous selenium signatures were completely erased there. The selenium found in the Earth's mantle today must therefore have been added after the formation of the Earth's core. Geologically speaking, "at the last moment of the formation of the Earth, after our moon had also formed," Varas-Reus adds. It's hard to say exactly when—it could have been between 4.5 and 3.9 billion years ago.
Places - Research - Team - Samples - Mantle
In various places, the research team took samples of mantle rocks, which have been brought to the surface by plate tectonic processes and had remained unchanged with regard to its selenium isotope composition since the formation of the Earth. The researchers determined the isotope signature...
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