Two US spacecraft were crashed into a lunar crater yesterday but scientists said it was too early to say whether the mission to search for supplies of water on the Moon had been a success.
Nasa, which is hoping to find sufficient quantities of water to use as fuel for space exploration, said it could take two months to make a conclusive assessment of what was found.
A two-ton empty rocket stage slammed into the eternally dark Cabeus crater near the moon's south pole at 4.31 a.m. PDT (1131 GMT), intended to throw up a plume of spray from any ice that was there.
Instruments on a second craft, that flew through the plume and hit close to the same spot four minutes later, as well as a lunar orbiter and telescopes on Earth captured data that could show whether there was ice there.
Video transmitted back from the trailing craft did not show, as hoped, the eruption of debris, but infrared devices showed a hot flash that indicated a crater about 18 to 20 metres wide. "We didn't see a big splashy plume like we wanted to see," said Michael Bicay, director of science at the National Aeronautics and Space Administration's Ames Research Centre.
Scientists did not know whether there had been no plume or if it could not be seen in the Internet-quality video shown as the craft crashed. The $79 million programme, a bargain by space exploration standards, could help change views of the moon.
Recent signs of water have upended ideas of the lunar surface as barren and unchanging, and evidence of ice would also suggest new possibilities for space travel.
"Water is essentially energy," scientist Victoria Friedensen said on Nasa TV. "It can be used to make fuel."
Three studies released last month found clear evidence of water on the moon, but the skein of water bound with dust that was disclosed then was extremely thin.
"It's not enough to be of any economic importance," said Nasa Lunar Science Institute Director David Morrison.
Hidden in the Cabeus crater near the pole, out of sunlight, could be soil concentrations of two per cent to three per cent ice that would be usable. "You're going into a place where the sun hasn't shined for a billion years," Mr Morrison said.
Video from the trailing spacecraft gave the sense of the fast approaching crash as craters edged with light grew larger and larger.
"I was blown away by how long this little spacecraft lasted," Tony Colaprete, the mission's principal investigator, told a news conference. He said it got good spectroscopic data which would show what elements were in the crater and how they were changed by the heat of the first impact.