The formation of the moon brought water to Earth

The Earth is unique in our solar system: it is the only terrestrial planet with a large amount of water and a relatively large moon that stabilizes the axis of the Earth. Both were essential for the Earth to develop life. The planetologists of the University of Münster (Germany) have now been able to show, for the first time, that water has arrived on Earth with the formation of the Moon there are about 4.4 billion d & # 39; years. The Moon formed when the Earth was hit by a body the size of Mars, also called Theia. Until now, scientists had assumed that Theia came from the inner solar system located near the Earth. However, researchers from Münster can now show that Theia comes from the external solar system and has supplied large amounts of water to the Earth. The results are published in the last issue of Nature Astronomy.

From the outside in the internal solar system

The Earth has formed in the "dry" interior solar system, and so it is somewhat surprising that there is water on the Earth. To understand why this is so, we have to go back in time when the solar system was formed about 4.5 billion years ago. From previous studies, we know that the solar system is structured so as to separate "dry" materials from "wet" materials: so-called "carbonaceous" meteorites, relatively rich in water, come from the external solar system. , while the drier "non-carbon" meteorites come from the internal solar system. While previous studies had shown that carbonaceous materials were probably responsible for bringing water to the Earth, it was unknown to know when and how these carbonaceous materials – and therefore water – have arrived on Earth. "We have used molybdenum isotopes to answer this question.Molybdenum isotopes allow us to clearly distinguish carbonaceous materials from non-carbonaceous materials and represent as such a" genetic fingerprint "of the materials of the inner and outer solar system. says Dr. Gerrit. Budde of the Institute of Planetology in Münster and lead author of the study.

Measurements made by Münster researchers show that the isotopic composition of the Earth's molybdenum lies between those of carbonaceous and non-carbon meteorites, demonstrating that some of the Earth's molybdenum originates from the outer solar system. In this context, the chemical properties of molybdenum play an essential role because, as an element magnetizing iron, most of the molybdenum of the Earth is in its nucleus. "The molybdenum that is accessible today in the Earth's mantle is therefore coming from the last stages of its formation, whereas the molybdenum from the earlier phases is entirely at the heart," says Dr. Christoph Burkhardt, second author of the 39; study. The results of the scientists show for the first time that carbonaceous materials from the external solar system arrived on Earth late.

But scientists are going even further. They show that most of the Earth 's mantle molybdenum was supplied by the protoplanet Theia, whose collision with the Earth 4.4 billion years ago led to the formation of the Moon. However, since much of the molybdenum in the Earth's mantle comes from the outer solar system, this means that Theia itself also comes from the outer solar system. According to scientists, the collision provided enough carbonaceous material to represent all of the water on Earth. "Our approach is unique because, for the first time, it allows us to associate the origin of water on Earth with the formation of the moon." To put it simply, without the moon, it "There would probably be no life on Earth," says Thorsten. Kleine, professor of planetology at the University of Münster.