Scientists Find Traces Of Water on the Moon

The moon is not the dry, dull place it seems. Traces of water lurk in the dirt unseen.

Three space probes found the chemical signature of water all over the moon's surface, surprising the scientists, who doubted the unexpected measurement until it was confirmed independently and repeatedly.

It's not a lot of water. If you took a two-liter soda bottle full of lunar dirt, there would probably be a medicine dropper's worth of water in it, said University of Maryland astronomer Jessica Sunshine, one of the scientists who discovered the water. Another way to think of it is that if you wanted a drink of water, it would take a baseball diamond's worth of dirt, said team leader Carle Pieters of Brown University.

"It's sort of just sticking on the surface," Sunshine said. "We always think of the moon as dead, and this is sort of a dynamic process that's going on."

The discovery, with three studies being published in the journal Science on Thursday and a NASA briefing, could refocus interest in the moon. Over the past decade, astronomers have found some signs of underground ice on the moon's poles. But this latest discovery is quite different. It finds unexpected and pervasive water clinging to the surface of soil, not absorbed into it.

"It is drier than any desert we have here," Sunshine said.

The water was spotted by spacecraft that either circled the moon or flew by. All three ships used the same type of instrument, which looked at the absorption of a specific wavelength of light that is the chemical signature of only two molecules: water and hydroxyl. Hydroxyl is one atom of hydrogen with one atom of oxygen; in water consists of two hydrogen atoms and one atom of oxygen.

Because of the timing during the daylight when some of that wavelength disappears and some doesn't, it shows that both hydroxyl and water are present, Sunshine said.