The moon is thought to have formed by a violent collision between a spacefaring rocky body and the proto-planet Earth. It was also assumed that the heat of this impact would have caused any water, or its constituent elements, to boil off into space, leaving the baby moon high and dry.
But recent studies have found that samples of volcanic glass, brought back from the moon on the Apollo missions, contain as much water as magma found here on Earth. Now, by examining the isotopic composition of that water, researchers have found that it matches that of meteorites, the likes of which also delivered Earth its first drink.
The simplest explanation is that our planet was all wet before the impact that gave rise to its satellite. Next mystery to unravel: how did the moon manage to maintain that moisture?
—Karen Hopkin
