The discovery of water on the moon opens up new possibilities for space exploration.
The moon has water locked into its polar craters, a finding that raises the prospects that future space travelers could use lunar resources for air and fuel, a key step for eventual human settlements beyond Earth.
NASA's Lunar Crater Observation and Sensing Satellite, or LCROSS, found what scientists called "a significant amount" of water and other materials on the floor of a lunar crater.
On Oct. 9, the LCROSS satellite released a 2.5-ton empty rocket motor, which crashed into a permanently shadowed lunar crater called Cabeus.
LCROSS observed the impact, then crashed itself into the crater as well. Both impacts were carefully monitored by an armada of space and ground based telescopes, which studied the ejected material for signs of water and other elements.
"If there's a lot of water, it's a possible resource for human exploration," said Greg Delory, a senior fellow with the Space Sciences Laboratory and Center for Integrative Planetary Sciences at the University of California, Berkeley.
The discovery, announced Friday, also raises a host of questions about the origin of the moon's water.
Scientists have speculated that water-bearing comets could have crashed into the moon, leaving deposits in the minus 364-degree Fahrenheit crater pits. Other possibilities for the source of the water include chemical breakdown of solar particles, internal processes on the moon and even Earth itself, Delory said.
Scientists estimate that about 25 gallons of water were seen within the plume of material rising from the crash site, far more than expected, said project scientist Anthony Colaprete, with NASA's Ames Research Center in Moffett Field, Calif.
A cocktail of still-to-be-determined chemicals -- including possibly organics -- was mixed in with the water, he added.
"We really need to sort out the 'flavor' of the water. We need to do the math," Colaprete said. "There's a lot of interesting stuff in there."
"If you could clean it," he added, "it'd be drinkable water."
Water also can be broken down into its constituent elements of hydrogen and oxygen to produce rocket fuel.
However, scientists still need to determine whether the LCROSS site is typical of the moon, or was simply a lucky strike. Previous lunar probes have found widespread hydrogen on the moon, but were not able to determine if the hydrogen was bound in water molecules.
"LCROSS is sort of pointing the way," Delory said. "It's really important to understand how the water is distributed."
NASA's next step may be to send a robotic probe to the Cabeus crater to learn how the water is distributed, he added.
"This has really turned our understanding of lunar water on its head," Delory said. "This is not your father's moon."