The source of water on the moon is comets and asteroids, right? As scientists found out, not everything is so simple. The water on the moon is the result of a reaction with the solar wind.
When the astronauts returned the lunar rock and regolith samples, it was assumed that they would be completely dry. After all, the moon has no atmosphere.
But in a recent analysis of the regolith, scientists were surprised to find a small amount of water trapped in the lunar substance.
There is a small amount of ice all over the surface of the moon. In addition, there are large deposits of water in the polar craters, where sunlight does not penetrate. We now know that if the sun evaporates all the liquid from the surface, then there is a small amount of water that is frozen below the surface.
According to a new study by astrochemists Alice Stefant and Francois Robert from the National Museum d'Histoire Naturelle, Paris, the source of the vast majority of water trapped in regolith samples is not asteroids and comets — the two well-known sources of cosmic ice, but the Sun. More precisely, the water in the lunar regolith is formed by chemical reactions with the solar wind. Their findings were published in the works of the National Academy of Sciences.
Using an isotopic analysis of deuterium / hydrogen and lithium, the researchers were able to determine that the source of water is not the ancient effects, but the reaction in the silicate grains of the regolith. The high-energy protons of the solar wind act on these grains, releasing oxygen atoms, which allows them to bind with numerous hydrogen atoms, forming hydroxyl, which is a prerequisite for water. A simple hydroxyl molecule consists of one oxygen atom and a hydrogen atom, while water has two hydrogen atoms attached to an oxygen atom.
Although water is undoubtedly deposited on the surface of the moon as a result of exposure to comets and asteroids, a new study has helped to understand that the contribution of the solar wind is much greater. So it was estimated that about 85 percent of the water was formed due to this phenomenon.
Of course, this analysis applies only to the surface of the moon. Thus, water sources found below the surface may have a completely different origin.
