The US Apollo missions in the late 1960s and early 1970s successfully collected lunar volcanic glasses, pebble-like beads. Since then scientists have been determining the nature of the chemical elements in the glasses.
Using secondary ion mass spectrometry (SIMS) technology, the team from Brown University, the Carnegie Institution for Science, and Case Western Reserve University, were able to detect extremely tiny amounts of water in glasses and minerals.
"We were really surprised to find a whole lot more in these tiny glass beads, up to 46 parts per million," said Erik Hauri, from the Carnegie Institution in Washington DC.They think that the water was contained in magma which erupted via "fire fountains" on the lunar surface more than 3 billion years ago. The eruptions themselves would have evaporated 95% of the water, but also leave some behind. Since the Moon's gravity is too weak to have an atmosphere, speculations indicate that some of the water vapour was likely forced into space. But some might have drifted towards the cold poles of the Moon, where ice may exists in constantly shadowed craters.