The source of water on Earth could not be comets, but a protoplanetary cloud

The eruption of one of the volcanoes of Iceland brings to the surface a substance from the deep layers of the Earth, the study of the composition of which allows you to get an idea of ​​the origin of water on our planet.

As you know, most of the earth's surface is covered with water. Yes, there is a lot of water on Earth, and its origin is the subject of debate by eminent scientists. The theory is quite popular, according to which our planet was formed without water, and the liquid that gives life appeared on Earth thanks to asteroids or comets. It is assumed that water-rich space objects fell to the Earth for tens and hundreds of millions of years, gradually saturating the planet with water.

Now another theory has appeared, according to which water was on Earth initially - when the planet was formed from a gas-dust cloud, which gave life to the solar system, the Earth took enough water already at the start. If this is true, then water-rich planets should not be rare in the universe.

In order to find out the source of water on Earth, scientists analyzed the composition of several potential sources of H2O, including asteroids and comets. In this case, the ratio of heavy hydrogen isotopes on cosmic bodies and in the oceans of the Earth was studied. True, this analysis may not be indicative at all, because, according to Linda Hallis, a planetologist at the University of Glasgow, the ratio of isotopes in the earth's water could change over time, and quite significantly.

Therefore, scientists decided to look for a place on Earth where the isotopic composition can be similar to what was at the very beginning of the history of the Earth. And such a place was found - this is Baffin Island , the Arctic. The island is of volcanic origin and consists mainly of basalts formed a very long time ago. Eruptions took place here, carrying matter from the deep layers of the mantle to the surface of the Earth. The substance at this depth is probably in an isolated state since the beginning of time. Now the previously erupted lava has turned into basalts. In theory, these basalts should preserve helium isotopes that were lost by bodies of water millions of years ago. Scientists decided to compare the “imprints” of light helium isotopes of space bodies and the island.

As it turned out, the concentration of helium isotopes in the basalts of the island and in the water bodies of the Earth is very different. This can serve as a confirmation of the theory of changes in the composition of the earth's water over time. In addition, the isotopic composition of the Earth’s ancient rocks differs from the isotopic composition of carbonaceous chondrites, a water-rich variety of asteroids that are believed to have served as a source of water for our planet. Studies conducted by the team of Linda Hallis, allow us to talk about the failure of the "asteroid theory."

Instead, Linda and her colleagues proposed a different theory: water came to Earth along with the substance of the gas-dust cloud, from which the solar system was formed. According to experts, the isotopic composition of Jupiter should be close to the isotopic composition of the gas-dust cloud - the ancestor of the solar system. And after carrying out the corresponding analyzes, it turned out that the “isotopic trace” of Jupiter is close to the “isotopic trace” of Baffin Earth.

Previously, it was also believed that the temperature of the proto-cloud was too high for water to be there. The team of Linda Hallis suggested that in the cloud, water was bound to dust particles, along with which H2O also fell on the nascent Earth. Modeling showed that such a scenario could indeed have taken place, and a similar isotopic composition of terrestrial rocks and space objects can serve as confirmation of a new theory.

Interestingly, the asteroid theory is not discarded by scientists. The fact is that experts consider asteroids to be the source of other elements for the young Earth, including carbon, nitrogen and noble gases. As for water, it could also have come to Earth with other types of asteroids that are no longer near our planet, cosmochemist Konel Alexander from Carnegie Institution for Science, USA said. Now, in his opinion, it is necessary to carefully study all the data that scientists have, compare theoretical calculations with a set of facts and draw the appropriate conclusions.

Nevertheless, if Linda Hallis and her colleagues are right, says Alexander, this means that the formation of water-rich planets is not at all uncommon for the Universe, but rather the rule.