(ORDO NEWS) — Chemists have discovered that a significant part of the water of the World Ocean did not come to Earth from space, but as a result of the decomposition of two forms of magnesium silicates, which were at its center in the early stages of the formation of the planet. The results of their research were published in the scientific journal Physical Review Letters, the press service of the Skolkovo Institute of Science and Technology writes briefly about this.
“It was hypothesized that comets could bring water to us, but, apparently, the significance of this source is very small. The fact is that the isotopic composition of water on Earth and in comets differs markedly. We proposed a theory that explains how water could survive the first epochs of the formation of the Earth in the deep layers of its bowels,” said one of the authors of the article, Professor of the Skolkovo Institute of Science and Technology Artem Oganov.
Scientists suggest that water came to Earth after its occurrence, as a result of a long asteroid or comet bombardment. Despite being generally accepted, both of these theories cannot explain either the isotopic composition of terrestrial water, or its total amount on the surface of the planet.
Oganov and his colleagues found an explanation for this anomaly by studying the properties of various minerals that could have been in the interior of the early Earth even before the so-called differentiation took place. So geologists call the process during which heavier elements and minerals sink towards the core of the planet, and lighter substances “float” towards its surface.
Chemists have suggested that exotic minerals that are not found in the bowels of the modern Earth could be involved in the process of differentiation. They could play an important role in the formation of its core, mantle, as well as in the accumulation of primary water reserves on the surface of the planet.
The mystery of the origin of water
Oganov and his colleagues tried to get answers to these questions. They calculated the properties of such minerals at ultra-high pressures that prevail in the core and lower layers of the Earth’s mantle. According to these calculations, only two minerals remained stable under such conditions, both of which were compounds of magnesium silicate molecules and water.
Both of these forms of magnesium silicate have been found by chemists to become unstable when the pressure is reduced, causing them to break apart and release large amounts of water. Something similar, as suggested by Oganov and his colleagues, began to happen on the early Earth about 30 million years after its formation, when magnesium silicates began to be forced out by a growing metal core into neighboring layers of the mantle.
Over the next 100 million years, these silicates began to rise to the Earth’s surface and gradually decompose. Such a theory, as scientists note, explains well why the isotopic composition of terrestrial water and moisture from comets and asteroids varies greatly. At the same time, chemists do not exclude that a significant part of the water could have been brought to Earth from space.
In turn, scientists suggest that the lack of large reserves of water on modern and ancient Mars is due to the fact that the pressure in its center was too low for the “water-bearing” magnesium silicates to remain stable there. As a result, most of the Martian water had to evaporate into space during the comet-meteorite “bombardment”.
Therefore, Oganov and his colleagues suggest that the remaining reserves of Martian water should be very close in isotopic composition and properties to moisture from asteroids and meteorites. Paleologists will be able to test this theory in the coming decades, when the first rock samples from Mars will be delivered to Earth, the chemists concluded.
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