The discovery of water on the moon announced this week could make our celestial neighbor a more attractive candidate for a future manned mission.
Plans to send American astronauts back to the moon are in limbo right now, while the Obama administration weighs whether or not to carry on with NASA's goal of reaching the moon by 2020. Now some scientists say the new finding of widespread water, in trace amounts, on the lunar surface could spur moon hopes.
"This makes the moon a more attractive destination to go to," said University of Colorado astrophysicist Jack Burns, chair of the science committee for the NASA Advisory Council. "It's a game-changer in the sense of future human exploration to the moon, in that now there is the potential of resources of water that future astronauts could tap so that we don?t have to bring this water from Earth."
Scientists announced the water discovery Wednesday and the details are outlined in the Sept. 25 issue of the journal Science. Three independent spacecraft identified the signature of water molecules spread across the lunar surface. Though many experts have believed the moon's poles to contain deposits of water ice, most scientists were surprised to hear of the more widespread finding.
New lunar lure
"The moon certainly becomes a more interesting place to go," said John Logsdon, director of the Space Policy Institute at George Washington University. "If you're going to any distant destination, it's much better the more you can live off of local resources and one of the most crucial resources is water. It's an important step towards the sustainability of a lunar outpost."
But Logsdon cautioned that the discovery of trace amounts of water in the top layer of lunar dirt doesn't necessarily mean it is abundant, or easy to obtain for drinking and other human purposes.
"People have to take a deep breath and say, 'All right, how is this water embedded on the moon, and how hard is it going to be to extract it for use?'" he said. "As far as I can tell, these findings don?t answer that question."
Experts seem to agree that more data on the moon's water resources is needed before NASA can pack off astronauts to the moon and plan to use the water that's there.
"It's a very good question about what it takes to actually do this on the moon," Burns told SPACE.com. "It would depend on how far below the surface it is, how concentrated it is. The little bit that?s there that is being seen in really trace amounts. Taking that and turning it into a substantial supply of drinking water would be pretty tough."
However, some scientists think the small quantities of water that have been confirmed so far might be just a hint of the moon's total water wealth.
"We see traces now, but imagine that there are polar regions that trap the water in," said geochemist Alberto Saal of Brown University in Rhode Island. "It could be a significant source."
Researchers think the moon might be hiding most of its water at the poles, which contain permanently shadowed craters that are cold enough that water would be less likely to evaporate away.
Other scientists echoed this hope: "The fact that there's that much water in the upper layers of the moon is exciting because it leads to the possibility of significantly larger amounts of water in the shadowed craters," Burns said.
A source of water on the moon would be useful to future missions in a variety of ways. Besides drinking and everyday use, water molecules could potentially be broken up into their constituent hydrogen and oxygen atoms, which are two major sources of rocket fuel. If a space ship needed only pack enough fuel for the way out, it would save precious weight for carrying other cargo. Then, once on the moon, astronauts could extract the resources directly from the moon to create enough fuel to fly home.
This is likely to be difficult, but not impossible. Same goes for extracting drinking water from trace amounts of water in moon dirt.
"That's an engineering challenge, and we're good at those," said John Olson, director of NASA's Exploration Systems Mission Directorate Integration Office. "We're all about engineering challenges. Small concentrations are something we can work."
Analogue for Mars
Besides making trips to the moon potentially easier, the water discovery makes the moon appealing as a training ground for future trips to Mars.
"The case has been made for a few years that the moon is a good analogue for Mars," Burns said. "If it really does have water, it becomes an excellent analogue for Mars, and a practical next destination to really learn how to live and work on an alien hostile destination."
Since Mars is thought to have stores of water, both in the atmosphere and in the form of ice on the surface, a water-bearing moon is a better simulation of what astronauts are likely to find on Mars. Sending astronauts to the moon could provide a good learning opportunity, and a testing ground to learn how to extract water for human use - an important skill to have when it's time to go to Mars.
And because it only takes three days to get to the moon, compared to about a year to get to Mars, a preliminary trip to our own satellite is a practical first step, some say.
"I think that it is important because now you can put a long-term base on the moon that will help probably to think about the next jump that is going to Mars," Saal said.
Pursuing a base on the moon is not just useful for future planetary missions, but also as a way to better learn how to live on Earth.
"It's really about developing our capability to live off the land and enhance our expertise in sustainability," Olson said.
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