LCROSS Confirms Lunar Prospector Findings: Water on the Moon

Feldman and his team didn't measure water directly, but their data showed evidence for inordinately large amounts of hydrogen in some craters.

Other phenomena, such as the solar wind and outgassing, could account for relatively high levels of hydrogen, "but there was a sufficient amount in some of these craters that it would be hard to understand if it came only from the solar wind or through other processes," Feldman said.

"So in our paper we didn't call it 'evidence for hydrogen,' but 'evidence for water'."

Not everyone agreed, and some controversy surrounded the paper. But, when NASA went looking for water on the Moon with the LCROSS mission, it headed for the Cabeus crater, about 62 miles from the Moon's south pole, that Feldman's Lunar Prospector team had identified as having the maximum hydrogen signature among all the high-latitude craters surveyed.

Not everyone agreed, and some controversy surrounded the paper. But, when NASA went looking for water on the Moon with the LCROSS mission, it headed for the Cabeus crater, about 62 miles from the Moon's south pole, that Feldman's Lunar Prospector team had identified as having the maximum hydrogen signature among all the high-latitude craters surveyed.

"This is a big, permanently shaded crater," Feldman said. "In fact, you can't even see it from the Earth because it has a rim that hides it. It takes a satellite to see it."

"When we converted the hydrogen signal to the amount of water ice in the regolith, we found that it was only about 1.5 percent by weight," Feldman added. "That's the reason the radar researchers really couldn't see it. There aren't large enough deposits of high-grade water ice to create the signal needed to identify ice with radar."

So it turns out that Feldman and the Lunar Prospector team showed the first experimental evidence for water on the Moon, which has now been conclusively confirmed by the LCROSS mission.

"There's a lot of interest in water on the Moon right now," Feldman said. "And there is more to be learned. The whole story is not in yet."