Tiny glass beads on the moon formed by meteoroid impacts might collectively contain as much water as there is in ice near the moon’s poles, and could be harvested for water by future moon expeditions.
Mahesh Anand at the Open University in Milton Keynes, UK, and his colleagues analysed samples returned to Earth by China’s Chang’e-5 lunar probe and found glass beads, known as spherules, that are formed in the extremely hot aftermath of meteoroids hitting the lunar surface.
Using microscopes and spectroscopy to analyse the glass beads, the team found they contained water with the same hydrogen isotopes – atoms of the same element that differ by the number of neutrons they contain – as those found in charged particles ejected by the sun. Previous research has shown that spherules can contain oxygen, so the researchers suspect that hydrogen from the sun combined with this oxygen to make water.
The moon is constantly being pummelled by meteoroids because it has no atmosphere, meaning these beads should be scattered across its surface. The team estimates that there could be around 300 billion tonnes of water stored within them. That is comparable to the amount of water ice on the moon in permanently shadowed craters near the lunar poles, and is potentially much easier to access.
“This is not only scientifically interesting, but I think it is going to be of quite some interest for those who are planning to actually send missions to the moon, to extract resources such as water for enabling more sustainable and longer-term exploration,” says Anand.
These beads also showed evidence of having lost water near their edge, even in the relatively cold temperatures of the moon — which is good news for astronauts. “If, at the daytime temperature of the moon, you have evidence that, actually, some of the water is getting diffused out of these glass beads, then it shouldn’t be too difficult to actually heat this material and expect that some water would be released,” says Anand.
“The hydrogen, and therefore water, content of these glasses is remarkably high,” says Sara Russell at the Natural History Museum in London. “This is a very important study: since the abundance of impact-produced spherules is high on the moon, as well as on several other celestial bodies, spherules are likely a major method for water storage across our solar system.”