"There is little doubt that most of the Moon's surface contains water in one form or another," said the study signed by Chinese researchers and published Monday in Nature Geoscience.

They examined in detail a hundred tiny glass beads, ranging in size from the thickness of a hair to a millimeter, brought back in 2020 by the Chang'e 5 mission.

These marbles, dated up to two billion years ago, were created by the impact of meteoroids -- meteorites or asteroids -- that melted the lunar material.

U.S. lunar missions had brought back samples, but this is the first time they have been studied in detail, according to the study.

They contain up to two millionths of a gram of water equivalent per gram of marble. Water from processes other than that resulting from lunar volcanism or the fall of comets (which contain ice).

The team led by researchers from the Chinese Academy of Sciences speculates that the glass beads formed during the impact of a meteoroid would have initially lost most of their water.

They would then have been bombarded by solar winds, delivering hydrogen which would then combine with the oxygen atoms contained in the balls. Thus giving rise to water molecules.

The lunar soil is composed of 3 to 5% glass beads, according to estimates based on the study of soil samples reported by the American Apollo missions.

The study concludes that these glass beads could be the "dominant reservoir" involved in the water cycle on the Moon. And that this reservoir could be "usable in situ in future lunar explorations". Especially since this water would be "quite easy to extract".

Meanwhile, on the American side, the focus is on water sources in the form of ice, whose existence has been confirmed on the south pole of the Moon and which could be transformed into fuel. NASA has planned a mission in 2024 with a robot, VIPER, to study the concentration of ice there.

© 2023 AFP