When I was first learning about the science of the Moon, there were a few basic facts that everyone got right. The Moon has practically no atmosphere, as when sunlight hits the Moon, it very quickly can give individual molecules and atoms enough energy to achieve escape velocity. We thought the same thing was true for any water on the Moon; sunlight would kick the water molecules so hard and so often that the molecules wouldn’t remain on the Moon for very long, and therefore it would be completely dry.
A watery Moon? Possible at all? Well, there was one hope. You see, the Earth rotates on an axis tilted at about 23 degrees around the Sun. But the Moon is barely tilted at all, with an axial tilt of less than 2 degrees. Well, that tilt is so tiny that it’s possible that the interior of deep craters at the North and South Poles of the Moon might never see sunlight. Check out this crater at a latitude of 89.54 degrees South, and see what I’m talking about:
Those places — it was thought — were the best bets for finding water on the Moon. But too much continuous sunlight was thought to kill the hope for water on the vast majority of the Moon. Even when the Apollo missions brought back Moonrocks that contained a little bit of water, it was assumed that the water was contamination from the humid Houston air.
Well, the Indian mission, Chandrayaan-1, completed its mineral analysis of the Moon, and guess what it found? Well, why bother telling you when I can show you. You see, water (and the hydroxyl ion, OH–) absorbs light at very particular wavelengths. If the Moon contained water, we would expect a drop in the reflectance of the Moon’s surface, like so:
Well, what did Chandrayaan-1 find? There are three papers being released today at 2:00 PM Eastern Time: one by Roger Clark, one by Paul Lucey, and one by Carle Pieters (and the rest of the Chandrayaan team). I owe my copies to the generosity of another scienceblogger, who was one of only a few hundred people to find out this news before the press leaked it. Not only do these teams find the dip in the spectrum characteristic of water:
They find it everywhere on the Moon, and just millimeters below the surface! Their estimates from the data show that for every cubic meter of the Moon’s soil, there is approximately one liter of water buried (and probably frozen) there.
Check out the signals; there’s water everywhere, even in areas constantly bathed in sunlight. This could be a huge boon to establishing a Moon base, as with water (or even hydroxyl ions) on the surface, we could possibly generate our own liquid water and breathable O2 gas!
And what an amazing breakthrough it is for the Indian space program to make this find!
This is a great day for lunar science! Perhaps you’ll look at our Moon a little differently now; I know that I will.