Green volcanic glasses, pebbles collected by the US Apollo missions in the late 1960's and early 1970's, are a good example of such rocks that contain crucial information about the Moon's formation.

One research team, from Brown University, the Carnegie Institution for Science, and Case Western Reserve University, used secondary ion mass spectrometry (SIMS) technology to detect extremely minute quantities of water in glasses and minerals. "We developed a way to detect as little as five parts per million of water," said Erik Hauri, from the Carnegie Institution in Washington DC. "We were really surprised to find a whole lot more in these tiny glass beads, up to 46 parts per million."