The space agency said Lunar Prospector landed on target, deep within a lunar crater near the Moon's south pole.
Nasa is hoping the impact, calculated at 6,000 km/h (3,800 mph), has sent up a plume of water vapour from what are believed to be ice formations near the pole.
So far there has been no direct sighting of debris and observatories around the world are watching to see if any ice was melted, generating water vapour.
"Initial reports indicate that no plume was visible at the expected impact time," said a Nasa spokesman.
![[ image: width=150]](/olmedia/405000/images/_406995_lpimp1150.jpg)
The discovery of water on the Moon could open the way to future lunar exploration and even the establishment of a lunar base.
A secondary mission for the spacecraft was to deposit the cremated remains of the renowned astronomer Eugene Shoemaker, making him the first person to be buried on another world.
Cautious optimism
Nasa scientists were wary of being too optimistic that they would hit the right part of the moon.
"This is a low probability of success," said Dr Lisa Chu-Thielbar, a Nasa spokeswoman. "In fact its been calculated at about 10% success."
"But it's still worth doing because the possible result is terrific."
Nasa insists that regardless of the outcome of this "final bold experiment", Lunar Prospector has yielded "a gold mine of science data".
"We now have invaluable global maps of the Moon's gravitational and magnetic fields, and the distribution of its key elements, giving us a much better understanding of the origin, evolution and composition of our rocky neighbour," said Dr Henry McDonald, director of Nasa's Ames Research Center.
'Outstanding mission'
After its launch in January 1998 and subsequent entry into orbit over the lunar poles, instruments on board the Lunar Prospector began surveying the Moon.
Among its discoveries:
Shoemaker honoured in death
![[ image: width=150]](/olmedia/405000/images/_408562_shoemaker150.jpg)
The "burial" of one ounce of Eugene Shoemaker's ashes is a rare honour accorded to a member of the space community.
Mr Shoemaker co-discovered the comet Shoemaker-Levy 9, which collided with the planet Jupiter in 1994.
The renowned astro-geologist, was killed in a car crash two years ago.
"He is the very first human inhabitant of Earth to be laid to rest on another celestial body," said Carolyn Porco, a University of Arizona professor and Shoemaker's college on Nasa's Voyager expeditions.
"That's very significant because it says we have arrived at our place in the solar system, the solar system is our own and it's beckoning us."
Moon burial for geologist
(28 Jul 99 | Sci/Tech)
Ice discovered on the Moon
(05 Mar 98 | Sci/Tech)
Spaceprobe to smash into Moon
(31 Jul 99 | Sci/Tech)
When will we go back?
(31 Jul 98 | Sci/Tech)
What we can make of Moon water
(05 Mar 98 | Sci/Tech)
Lunar Prospector impact page
NASA: LunarImpact.com
Lunar Prospector
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