It'sofficial: There's water ice on the moon, and lots of it. When melted, the watercould potentially be used to drink or to extract hydrogen for rocket fuel.
NASA'sLCROSS probe discovered beds of water ice at the lunar south pole when itimpacted the moon last month, mission scientists announced today. The findingsconfirm suspicions announced previously, and in a big way.
"Indeed,yes, we found water. And we didn't find just a little bit, we found asignificant amount," Anthony Colaprete, LCROSS project scientist and principalinvestigator from NASA's Ames Research Center at Moffett Field, Calif.
The LCROSSprobe impacted the lunar south pole at a crater called Cabeus on Oct. 9.The $79 million spacecraft, preceded by its Centaur rocket stage, hit the lunarsurface in an effort to create a debris plume that could be analyzed byscientists for signs of water ice.
Those signswere visible in the data from spectrographic measurements (which measure lightabsorbed at different wavelengths, revealing different compounds) of theCentaur stage crater and the two-part debris plume the impact created. Thesignature of water was seen in both infrared and ultraviolet spectroscopicmeasurements.
"Wesee evidence for the water in two instruments," Colaprete said. "Andthat's what makes us really confident in our findings right now."
Based onthe measurements, the team estimated about 100 kilograms of water in the viewof their instruments ? the equivalent of about a dozen 2-gallon buckets ? inthe area of the impact crater (about 66 feet, or 20 meters across) and theejecta blanket (about 60 to 80 meters across), Colaprete said.
"I'mpretty impressed by the amount of water we saw in our little 20-meter crater,"Colaprete said.
"What'sreally exciting is we've only hit one spot. It's kind of like when you'redrilling for oil. Once you find it one place, there's a greater chance you'llfind more nearby," said Peter Schultz, professor of geological sciences at Brown University and a co-investigator on the LCROSS mission.
This waterfinding doesn't mean that the moon is wet by Earth's standards, but is likelywetter than some of the driest deserts on Earth, Colaprete said. And even thissmall amount is valuable to possible future missions, said Michael Wargo, chieflunar scientist for Exploration Systems at NASA Headquarters.
Scientistshave suspected that permanently shadowed craters at the south pole of the mooncould be cold enough to keep water frozen at the surface based on detections ofhydrogen by previous moon missions. Water has alreadybeen detected on the moon by a NASA-built instrument on board India's now defunct Chandrayaan-1 probe and other spacecraft, though it was in very smallamounts and bound to the dirt and dust of the lunar surface.
Waterwasn't the only compound seen in the debris plumes of the LCROSS impact.
"There'sa lot of stuff in there," Colaprete said. What exactly those othercompounds are hasn't yet been determined, but could include organic materialsthat would hint at comet impacts in the past.
Thefindings show that "the lunar poles are sort of record keepers" oflunar history and solar system history because these permanently-shadowedregions are very cold "and that means that they tend to trap and keepthings that encounter them," said Greg Delory, a senior fellow at theSpace Sciences Laboratory and Center for Integrative Planetary Sciences at theUniversity of California, Berkeley. "So they have a story to tell aboutthe history of the moon and the solar system climate."
"Thisis ice that's potentially been there for billions of years," said DougCooke, associate administrator at Exploration Systems Mission Directorate atNASA Headquarters in Washington, D.C.
Theconfirmation that water exists on the moon isn't the end of the story though.One key question to answer is where the water came from. Several theories havebeen put forward to explain the origin of the water, including debris fromcomet impacts, interaction of the lunar surface with the solar wind, and evengiant molecular clouds passing through the solar system, Delory said.
Scientistsalso want to examine the data further to figure out what state the water is in.Colaprete said that based on initial observations, it is likely water ice isinterspersed between dirt particles on the lunar surface.
Some otherquestions scientists want to answer are what kinds of processes move, destroyand create the water on the surface and how long the water has been there,Delory said.
Scientistsalso are looking to see if there is any link between the water observed byLCROSS and that discovered by Chandrayaan-1.
"Theirobservation is entirely unique and complementary to what we did,"Colaprete said. Scientists still need to work out whether the water observed byChandrayaan-1 might be slowly migrating to the poles, or if it is unrelated.
Bottomline, the discovery completely changes scientists' view of the moon, Wargosaid.
Thediscovery gives "a much bigger, potentially complicated picture for wateron the moon" than what was thought even just a few months ago, he said."This is not your father's moon; this is not a dead planetary body."
NASA plansto return astronauts to the moon by 2020 for extended missions on the lunarsurface. Finding usable amounts of ice on the moon would be a boon for thateffort since it could be a vital local resource to support a lunar base.
"Waterreally is one of the constituents of one of the most powerful rocket fuels,oxygen and hydrogen," Wargo said.
The waterLCROSS detected "would be water you could drink, water like any other water," Colapretesaid. "If you could clean it, it would be drinkable water."
The impactwas observed by LCROSS's sister spacecraft, the Lunar Reconnaissance Orbiter,as well as other space and ground-based telescopes.
The debrisplume from the impacts was not seen right away and was only revealeda week after the impact, when mission scientists had had time to combthrough the probe's data.
NASAlaunched LCROSS ? short for Lunar Crater Observation and Sensing Satellite ?and LRO in June.
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