The Moon is ‘wet’.
That’s the latest conclusion of a trio of observations by various spacecraft over a decade (here, here, here, here.) The question is: just how wet? Not very, but a whole lot more than we once thought. A thin layer of water molecules coats the whole surface of the Moon, at least part of the day, and more may well be found towards the Lunar poles. The colder the surface, the longer it sticks, and it’s very, very cold in the permanently shadowed polar craters – down to just 35 K… colder than Pluto! There, it’s hoped, the water has ‘stuck around’ for billennia and slowly accumulated to substantial amounts.
So, the Moon has water. And there are signs of more within the Moon, evidenced by hydrated minerals around new craters. That really throws that cat in amongst the pigeons, as current Moon-formation models have the Moon condensing largely from vaporised rock after Theia smacked into the Earth. Robin Canup, Moon-maker extraordinaire, commented that the current modelling doesn’t have enough resolution to really tell if bits of the collision that became the Moon were cool enough or not for water to be retained.
Science-fiction, of course, has featured underground water on the Moon for over 100 years – H.G.Wells mentions seas within the Moon in his “First Men in the Moon” and Herge has Tintin discover ice in a cave, are two famous examples. “Moon Zero Two” – a daft movie from 1970 – also mentioned, in passing, that the Moon Colony got its water from hydrated minerals underground. A silly movie for a lot of reasons, but it had some redeeming features, including a portable computer (!) which was quite a leap for 1970.
Digressions aside, what does it mean for the development of the Moon? Water – especially its hydrogen component – features heavily in a lot of industrial chemistry as well as sustaining life-as-we-know-it. A slew of processes become easier when there’s available water. But it’ll need to be heavily recycled because of the difficulty of gathering together significant amounts of moon-water. Learning to do that might teach us some useful tricks down here on Earth too.