We know there's water on the Moon, but questions remain about how it got there, where it's stored, and how it moves around. In a new study, scientists from China have identified tiny glass beads in the lunar soil as potential places where water could hide.
And we're talking about a lot of water too, perhaps as much
as 270 trillion kilograms (297.6 billion tons) of the stuff.
The new findings are based on samples brought back from
China's Chang'e 5 rover mission. The spacecraft spent a couple of weeks
collecting material from the lunar surface in December 2020, and we've already
seen exciting new discoveries from subsequent analysis.
Microscopic glass beads typically form as bits of space rock
smack into another object's surface, vaporizing minerals which can cool into
vitreous particles barely a few tens or hundreds of micrometers across. Past studies
on beads found in Apollo lunar samples helped overturn prior assumptions on the
dryness of the Moon.
Current research suggests a good proportion of the Moon's
water is produced with a little help from the Sun's winds, as hydrogen ions
from these showers of solar particles bond with oxygen already stored in lunar
soil.
The reservoir of water potentially represented by these
beads could potentially play an important part in the lunar water cycle,
according to the researchers behind this latest study. As some water gets lost
to space, it can be replenished by the stores held in the amorphous impact
glass.
"The impact glass beads preserve hydration signatures
and display water abundance profiles consistent with the inward diffusion of
solar wind-derived water," the researchers write in their recently
published paper.
Each glass bead is capable of holding up to 2,000 micrograms
(0.002 grams) of water for every gram of the particle's mass. Based on a
hydration signatures analysis, the scientists think the beads can accumulate
water in the span of just a few years.
"This short diffusion time indicates that the solar
wind-derived water can be rapidly accumulated and stored in lunar impact glass beads,"
write the researchers.
This is all very useful to know when it comes to supporting
Moon missions and bases. Being able to tap into this vast reservoir of water
could make living on the lunar surface for extended periods of time much more
comfortable.
What's more, the scientists say that other "airless
bodies" like the Moon could be storing water in their surface layers in
the same way. Expect more discoveries along these lines as the samples from
Chang'e 5 continue to get analyzed.
"These findings indicate that the impact glasses on the
surface of the Moon and other airless bodies in the Solar System are capable of
storing solar wind-derived water and releasing it into space," says
geophysicist and study co-author Hu Sen from the Chinese Academy of Sciences.
The research has been published in Nature Geoscience.