Two years ago, China sent the Chang'e 5 probe to the Moon with the intention of taking samples of Oceanus Procellarum, the dark spot on the Moon that can be seen from Earth.
Now those analyzes of those samples have been revealed.
Professor Hu Sen's team, from the Institute of Geology and Geophysics (IGG) of the Chinese Academy of Sciences,
found hitherto unknown water deposits among the crystallized fragments he collected.
It is the remnants of the cooled and scattered asteroid impacts that cover the floor of Luna.
They estimate that there are between 300,000 and almost 300 trillion kilograms of water in tiny glass beads scattered on the Moon.
Glass beads collected by the Chang'e-5 spacecraft contain water molecules.
According to their analysis, published today in Nature Geoscience, water forms from hydrogen released in the stream of charged particles streaming from the Sun, called the solar wind.
"These findings indicate that lunar soils contain a much larger amount of water derived from the solar wind than previously thought,"
they write.
This suggested that the grains played a central role in the Moon's water cycle and
could be an important reservoir that space bases could tap into.
Position of the Chang'e 5 landing site compared to the American Apollo and Russian Luna sample return sites.
"Impact glass beads have the ability to store significant amounts of solar wind-derived water at the surface...in addition to the possible presence of trapped water ice in permanent shadow zones in the polar regions."
Water in the ocean from storms
The Moon was previously thought to be dry, but in the past 20 years orbiting spacecraft have detected hydrogen and ice in deep craters at the lunar poles.
In 2020, a team of NASA scientists detected water molecules in sunlit areas of the Moon for the first time.
One of the lunar soil samples recovered by Chang'e-5
They proposed that the water might be trapped in glass beads, which would explain why it had not evaporated
.
Evidence of water had previously been found in the glass of samples collected by the Apollo missions 40 years ago.
In late 2020, China's Chang'e-5 spacecraft became the first spacecraft since the Apollo era to return to Earth with rocks from the Moon.
The Chang'e-5 probe successfully landed in 2020.
Change-5 landed in the Ocean of Storms, a geologically unique area that had not been previously sampled, explained Craig O'Neill, a planetary scientist at Queensland University of Technology, who was not involved in the study.
"It's an extraordinarily radioactive part of the Moon.
"It's also close enough to the equator to get a decent amount of sun... so [the water] is going to have to be bound to a mineral to be stable."
Glass beads are created when micrometeorites strike the surface melting the surrounding rock.
Previous analyzes dating the age of pearls collected by the Chang'e-5 spacecraft showed that the area had been bombarded over the past 2 billion years in a process known as impact gardening.