Evidence of water in moon minerals found

It seems that the moon is not that dry as it was thought to be- California Institute of Technology (Caltech), working with colleagues at the University of Tennessee, have found structurally bound hydroxyl groups (i.e., water) in a mineral in a lunar rock returned to Earth by the Apollo program.

The team found the water in a calcium phosphate mineral, apatite, within a basalt collected from the Moon's surface by the Apollo 14 astronauts.

"The Moon, which has generally been thought to be devoid of hydrous materials, has water," Nature quoted John Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech, and a coauthor on the paper, as saying.

"The fact that we were able to quantitatively measure significant amounts of water in a lunar mineral is truly surprising," added lead author Jeremy Boyce, a visitor in geochemistry at Caltech, and a research scientist at the University of California, Los Angeles.

To be precise, they didn't find "water" -- the molecule H2O. Rather, they found hydrogen in the form of a hydroxyl anion, OH-, bound in the apatite mineral lattice.

"Hydroxide is a close chemical relative of water. If you heat up the apatite, the hydroxyl ions will 'decompose' and come out as water," explained coauthor George Rossman, Caltech's Eleanor and John R. McMillan Professor of Mineralogy.

The lunar basalt sample in which the hydrogen was found had been collected by the Apollo 14 Moon mission in 1971.

And the idea to focus the search for water on this particular sample was promoted by Larry Taylor, a professor at the University of Tennessee in Knoxville, who sent the samples to the Caltech scientists last year.

"The Moon has been considered to be bone dry ever since the return of the first Apollo rocks," noted Taylor.

However, there are lunar volcanic deposits interpreted as having been erupted by expanding vapour.

Although carbon dioxide and sulphur gases have generally been thought to dominate the expanding vapour, recent evidence from the study of the these deposits has suggested that water could also play a role in powering lunar volcanic eruptions.

The discovery of hydroxyl in apatite from lunar volcanic rocks is consistent with this suggestion.

"There's more water on the Moon than people suspected, but there's still likely orders of magnitude less than there is on the Earth," said Eiler.

Their findings are detailed in the latest issue of the journal Nature.