Posted 26 января 2022,, 13:46
Published 26 января 2022,, 13:46
Modified 24 декабря 2022,, 22:37
Updated 24 декабря 2022,, 22:37
Water is of great importance for the origin of life, plate tectonics and climate. This element is central to all discussions about the habitability of Earth-like planets. However, despite such an important role of water, we do not know where the oceans came from on our planet. Skoltech professor of materials science Artyom Oganov, along with Chinese colleagues, presented their version of their origin in a recently published article in the journal Physical Review Letters.
“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, ”explains Oganov. This means that the water had to come from the bowels of the earth. But if so, it's not clear how the ocean could survive the first tens of millions of years in Earth's history when it was hot, bombarded by asteroids, and collided with a planet the size of Mars. These cataclysms were supposed to permanently evaporate water from the surface of the Earth.
A scientific group led by Nankai University professor Xiao Dong, in collaboration with Oganov, discovered a compound that could store water at greater depths for millions of years and release it in a calmer era - magnesium hydrosilicate Mg2SiO5H2. It contains 11% water by mass and is stable at extremely high temperatures and pressures of more than 2 million atmospheres - like in the Earth's core.
According to researchers, during the first 30 million years, part of the earth's water was safely hidden at the depth of the current core in the form of hydrosilicates. At this time, the planet was going through the most catastrophic phase of the asteroid bombardment. And when the process of core formation ended, the hydrosilicates were forced out of the central region of the planet into a zone of lower pressure, where they are unstable, and underwent decay. This is how magnesium oxide and silicate were formed - the mantle now consists of them - and water, the gradual rise of which to the surface took about another 100 million years.
“Meanwhile, the Earth was under fire from asteroids and even collided with a protoplanet, but the water had not yet had time to rise and therefore survived,” Oganov comments. “This is also a story about how material that existed for a moment on the scale of the history of the planet colossally influenced the evolution of the Earth”.
From the new hypothesis of the origin of terrestrial water, consequences are also drawn in relation to other celestial bodies. “Take, for example, Mars. It is too small to provide pressures at which magnesium hydrosilicate is stable, Oganov argues". That explains why there is so little water on Mars. Moreover, the water that is, most likely, was brought by comets.