It's weird to think that there's water ice on the Moon. But it's there.
Scientists started to suspect it existed before the turn of the century, though it was difficult to prove. In the 1990s several missions found key but circumstantial evidence for it, in 2009 strong evidence was found, and then in 2018 it was confirmed.
Where is this ice? At the lunar poles, in craters so deep that the low-angle sunlight never touches their bottoms. These areas are called permanently shadowed regions, or PSRs. If you were standing in such a PSR, you'd never see the Sun; it doesn't get high enough above the horizon and, more importantly, above the crater's rim. Places like these remain a chilly -160°C (-260°F).
The location of ice found at the Moon’s south (left) and north (right) poles by NASA M3 instrument on India’s Chandrayaan-1 spacecraft. The shade of the background image of the Moon represents temperature, where darker is colder. Credit: NASA
How'd the water get there? Asteroids and comets have a lot of water in them. The idea is that when they impact the Moon, that water is spread out all over the lunar surface. In most places sunlight quickly ...