If water on the surface is mobile, it could provide a different source of water for the permanently shadowed polar craters, whose main water source is thought to have been water-bearing comets that slammed into the moon.
"Even if it takes a couple of hops or a thousand hops or a million hops, ultimately [the water] could accumulate in a nice happy place like these permanently shadowed areas, and once it gets in there it's not going to come out," says Pieters.
But there is active debate on whether water lurks in the moon's dark craters. Radar signals reflected off polar craters have shown some ice-like signals. And neutrons detected by NASA's Lunar Prospector in 1998 suggested the presence of hydrogen, although it was not clear whether the atoms were locked up in water ice or in some other form.
NASA's Lunar Reconnaissance Orbiter, which launched in June, is now hunting for similar signatures.
NASA's LCROSS, which is set to collide with a crater on the moon's south pole on 9 October, could potentially help resolve the question. The spacecraft and the spent rocket stage it is currently shepherding will throw up plumes of debris that the spacecraft, LRO, and telescopes will scrutinise for signs of water ice.