From the National Geographic (John Roach):
Tiny amounts of water have been found in some of the famous moon rocks brought back to Earth by the Apollo astronauts, scientists announced last Wednesday. The water levels detected in Apollo moon rocks and volcanic glasses are in the thousands of parts per million, at most—which explains why analyses of the samples in the late 1960s and early 1970s concluded that the moon was absolutely arid. “Only in the last decade have instruments become sensitive enough to even analyze water at those kinds of concentrations,” said Gary Lofgren, the lunar curator at NASA’s Johnson Space Center in Houston, Texas…
In part by bombarding the mineral with a particle beam from an electron microprobe, the researchers were able to calculate the amounts of the gases fluorine and chlorine within the sample. Given known formulas for apatite, the amounts of fluorine and chlorine present suggest there’s another compound needed to complete the mineral’s crystal structure. The missing molecule, the team concluded, must be hydroxide—a common component of apatite and a byproduct of the breakup of water. The finding is “one of the first to detect water in a lunar magmatic mineral” and adds to evidence that moon magma, in general, contains trace amounts of water, according to geoscientist Francis McCubbin, who participated in the research. But, though discoveries of moon water continue to mount, they’re really just drops in the bucket, said McCubbin, of the Carnegie Institution for Science in Washington, D.C. “While there is a lot more water in the moon than we previously thought,” he said, “it is still orders of magnitude drier than the Earth and Mars and therefore completely consistent with the last 40 years of lunar sample observation.”