Old rocks drown dry Moon theory

Samples collected during Apollo missions suggest a wet interior, raising questions about lunar origins.

Larry Taylor always said he'd eat his shorts if water was ever found on the Moon. He never expected his own research to bring that pledge back to haunt him.

The petrologist, based at the University of Tennessee in Knoxville, was just 32 years old at the first Lunar and Planetary Science Conference in 1970, where his colleagues described their analyses of Moon rocks collected the previous year during the Apollo 11 mission. Taylor saw only pure metallic iron in the samples — a sign that there wasn't any water around to rust the iron. This and other results that year led to the party line: the Moon is, and always was, bone dry.

Forty years on, at the same annual conference near Houston, Texas, Taylor and his colleagues announced that they have been wrong all along. At the meeting last week, three groups presented evidence that certain crystals in the volcanic rocks collected by Apollo astronauts contain as much as several thousand parts per million of water.

These findings go much deeper than the glimpses of frozen water on the Moon's surface — discoveries that were made recently by India's Chandrayaan-1 and NASA's Lunar Reconnaissance Orbiter spacecraft (see Nature doi:10.1038/news.2009.931; 2009). The new studies of the Apollo samples provide hints of what lurks within the Moon.

The results suggest that the lunar interior has always held some water — challenging theorists to change their thinking about how the Moon formed during a fiery impact, and how the once-molten body cooled. The work also hints that comets have played a more important part in delivering water to the Moon than researchers had previously thought.

"This is revolutionary," says Linda Elkins-Tanton, a lunar scientist at the Massachusetts Institute of Technology in Cambridge. As for Taylor, the one-time water sceptic has eaten his words — and more. In January, colleagues gave him a chocolate cake, iced white with pink polka dots to represent his boxer shorts.

via Old rocks drown dry Moon theory : Nature News.