A publication in the journal Nature Geoscience on March 27 presents results from the Chinese Chang’e-5 probe in December 2020, revealing the presence of water in glass marbles on the lunar surface.
According to the results of an international team coordinated by Pr Sen Hu, of the Chinese Academy of Sciences, with his assistant Huicin He, an estimate of 3 to 5% of the lunar ground would be covered with these balls, which would allow the less than 270 billion cubic meters of easily accessible water available for future human missions.
The question of water on the Moon is old. The Apollo missions of the 1970s concluded that there was almost no water. But from 1994, probes in orbit like Clementine, the first American lunar probe, revealed the presence of water ice in deep craters at the South Pole. Several hypotheses advanced as an explanation either a terrestrial origin of the Moon, or a supply of water by the regular bombardment of the lunar soil by comets, asteroids and meteorites.
At the end of 2020, NASA confirmed the presence of H20 molecules. But no in situ measurements had been made until this Chang’e 5 probe, placed north of the Ocean of Storms. His study revealed fragments of molten regolith containing water from the samples brought back, confirming the analyzes of the Lunar Mineralogical Spectrometer (LMS).
Small spheres acting like sponges
According to the Chinese researchers, two phenomena are intertwined in the mechanism: impacts of micrometeorites cause a melting of silica and minerals by producing very porous glass beads. The formation of water in situ would come from the hydrogen ions H+ of the solar wind hitting the oxygen atoms on their surface.
The water cycle on the Moon, through the formation of glass beads by the impact of micrometeorites and the action of H+ protons from the solar wind on oxygen atoms.
Like a sponge, these small spheres absorb water before degassing it. An active water cycle has been demonstrated, with tests showing water diffusion in and out of these beads. From the equatorial regions, a part migrates towards the polar regions while a part is lost in space. The reservoir of this cycle is therefore now located in the lunar regolith, through this profusion of water beads, in the form of H20 molecules or in the form of hydroxyl (OH).
The interest of this discovery lies in the useful applications for the human missions in preparation. The exploitation of this water will become a central issue. in the competition between the American Artemis missions and the Chinese taikonauts. And this, both for the seizure of the territories of the South Pole of the Moon and for the control of the processes to collect water, from the use of centrifuges to crush these balls to the proposal of the Chinese to carry out heating by evaporation .