Until now, all information on the presence of water on the Earth's satellite has been obtained by less straightforward methods. Most importantly: data from China's Chang'e 5 shows that water on Selenium did not come from outside, but has an entirely different source.
China's Chang'e 5 landed on the Moon in 2020 and studied the lunar surface around it. Among other things, it attempted to determine the presence of water in local rocks. Even those originating from the moon's interior were found to contain water. To this day, the origin of this compound on the Moon is hotly debated among scientists.
The modern Moon appears water-free: this is in good agreement with the fact that it is 130 degrees above zero during the day. Such temperatures are conducive to water evaporation. However, back in the 1960s, American astronauts discovered rocks on Selene and a number of effects indicating the presence of water in its regolith. Traces of H2O were also found in samples of lunar rocks of volcanic origin, i.e. unrelated to the surface regolith. This contradicted the then available hypotheses about the origin and nature of the Moon, so NASA decided to attribute the results to water contamination from the Earth due to loosely sealed sample collection containers.
The Soviet lunar probe Luna 24 took samples and returned them to Earth - and also found traces of water. For similar reasons - the incompatibility of the presence of water on the Moon with the then hypotheses about its nature - this finding was ignored by the science of the time.
Already in the 21st century, a number of observations have shown that there is undoubtedly lunar ice - and at least 100 billion tonnes of it - near the poles of the satellite. Some scientists have attempted to explain it away by means of comets: their impact would have brought water to the originally dry Moon. However, Russian astronomers have shown convincingly that a cometary origin of this water is ruled out.
The new Chang'e 5 observations make a major contribution to understanding the situation. The instrumentation of the lander detected spectral traces of water not only in the lunar regolith, but also in a sample of basalt, material recovered from the Moon during lava eruptions. Whereas water in regolith and generally near the surface of the satellite may be of cometary or other external origin, lava from its deepest layers cannot have water of that origin.
Interestingly, the Chang'e 5 discovered only 120 parts per million of water in lunar regolith of surface origin and 180 parts per million in lunar basalt nearby. In other words, the water content inside Selene may be quite significant and higher than normal on its surface (though certainly lower than on Earth).
As Naked Science has written before, a number of scientific groups from Russia and Israel have shown that the most likely origin of lunar water is terrestrial. Under such hypotheses, the Moon was not formed after the collision of Earth and Teia, but during fundamentally different processes.
