Water has been found on the Moon. Before you get excited about the possibilities though, note that water has been found on the Moon inside pebbles. This doesn’t mean there are lakes, or even puddles, up there.

Using spectroscopy, Alberto Saal and colleagues peered inside glass rocks brought back in soil samples by the Apollo missions. In this week’s Nature they report finding both water and elements such as chlorine and fluorine.

“What is important for me is it’s telling me something about the origin of the Moon and the Earth and the presence of water at very early times,” says Saal, a geologist at Brown University (press release).

“The water that these guys have discovered is a scientific gold mine for us to figure out the history of the Moon,” says Jim Garvin, chief scientist at NASA’s Goddard Space Flight Center (LA Times).

In a News and Views piece accompanying the paper, Marc Chaussidon of Nancy Université in France writes:

These results raise many questions. Are the volatile contents of the melts that formed the green and orange glasses typical for the Moon? Can the general scarcity of most volatile elements on the Moon be reconciled with the apparent abundance of sulphur, chlorine, fluorine and especially water in the lunar glasses? What happened to all the water during the Moon’s formation? And if the Moon is not bone dry, where did the water come from?

Of course, what most people are interested in is whether there’s any water left on the Moon now, which could help us set up bases there. Most of the Moon’s water was probably boiled into space as the magmas that are now the Moon and those glass pebbles cooled. Saal holds out hope though, saying traces of water might have ended up in permanently shadowed craters at the Moon’s poles.

From a science point of view though, the results may be most useful in elucidating how the Earth and Moon came to be.

As John Zarnecki, a UK space scientist based at the Open University, says:

“It’s like a sort of detective story in which the crime happened 4.5bn years ago. On Earth all the evidence has gone, but on the moon there is evidence of what went on. Because the moon has been relatively inert and not much has happened we can actually use it as an indicator of what happened in the early history of the solar system, and of course that means what happened to us.” (Guardian.)

Image: the glass beads / NASA