LCROSS, meanwhile, is meant to take a more aggressive approach in the search for water ice.
Hints of moon water were first sent to Earth in the 1990s, when the Naval Research Laboratory's Clementine mission detected hydrogen at the lunar poles.
But that data did not reveal whether the element was contained in water (H2O) or other hydrogen-bearing compounds, such as hydrocarbons.
Since then three separate missions have sent probes barreling into the moon, but none of them returned proof of water.
The LCROSS mission will be the first to specifically look for water within a polar crater.
Once launched, LRO will take four days to reach lunar orbit. The probe will then spend several months searching for the best impact site and setting up a prime trajectory.
In early October, LCROSS is slated to fire up its car-size rocket and separate from the orbiter. The probe will then quickly shed the rocket and send it pummeling into the moon at 5,600 miles (9,000 kilometers) an hour.
The rocket's impact is expected to dislodge 220 tons of material, which should fly as far as 30 miles (50 kilometers) from the impact site.
Instruments aboard LCROSS will watch the rocket's impact and send back data on the plume's composition, including whether it contains water. Four minutes later, the probe will fly through the plume on its own collision course.
Telescopes around the world will be trained on the impact site to study the material kicked up by LCROSS's demise.
For those who simply want to watch the spectacle from a backyard telescope, the best viewing conditions will be in the Northern Hemisphere, from Hawaii to as far east as Texas or Mississippi. (See a U.S. map.)
NASA will also host live streaming video of the impact online.
The physical material will expand outward like an upside-down lampshade and then "will be all but settled in four minutes," said Tony Colaprete, a planetary atmospheric scientist at NASA Ames Research Center and the principle investigator on LCROSS.
Aside from the new crater, he added, LCROSS "will not damage the moon in any way."
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