NASAis on a flight path to replant astronauts on the Moon, looking to sustain ahuman presence on that cratered, airless orb on a "go-as-thenation-can-afford-to-pay" basis. That approach is seen asletting people step back onto the lunar surface no later than 2020.
Spaceengineers have honed in on one possible site for a lunar outpost: the Moon's southpole. It's a tactical setting on the rim of Shackleton Crater, a feature some12 miles (19 kilometers) in diameter. There's real estate here that basks innear-perpetual sunlight. Also, it's a region that is a doorway into the depthsof always dark, Sun-deprived, territory.
What'spossibly lurking there in that super-cold darkness is water ice--portrayed bysome researchers as the gold standard for future exploration on and from theMoon. Yet there is considerable debate about this resource. If there, such araw storehouse might be processed into usable oxygen and hydrogen.
Expertshave been chipping away at the water ice on the Moon issue for years.
Accordingto NASA Moon outpost thinkers, there are five key reasons for building up an encampment near a lunar pole:
- Polar sites have plenty of sunlight, which lessens concerns about energy storage. It would be possible to operate a polar outpost on solar power. While not highlighting it as such, NASA's go-solar tactic also doubles as a non-nuclear, perhaps more politically correct approach.
- The environment at the poles of the Moon is relatively benign, making it easier to design a habitat. Temperatures at the poles vary no more than about 50 degrees Celsius all year round, while temperatures at the equator can vary 250 degrees Celsius from day to night.
- At the Moon's south pole there is "ample evidence", NASA planners point out, of enhanced hydrogen - an important natural resource for future development for energy generation, propellant production and other potential uses.
- The poles can teach robotic and human explorers volumes about the Moon. This landscape is among the most complex of regions, yet very little is known about them.
- To land equipment and scientific payloads near the lunar south pole, specifically, as opposed to another location, will require less propellant and could be more cost effective.
Not in critical path
NASA'snotional positioning of a base at the Moon's south pole was not solely drivenby the thought of driving over and diving into a reservoir of potential waterice. On the other hand, if it's truly there, so much the better.
Therewere many reasons for choosing the polar regions of the Moon for the outpostlocation, said Jerry Sanders, In-Situ Resource Utilization (ISRU) ProjectManager at the NASA's Johnson Space Center in Houston, Texas.
Oneof them is the possibility of water/ice and other possible cometary volatiles,said Sanders. He noted with interest that the Stardust sample collectionmission to comet Wild 2 found methyl and ethylamines, which not only hashydrogen, but carbon and nitrogen as well.
"Thepresence of large quantities of readily assessable water would make long termsettlement of the Moon much more attainable," Sanders explained to SPACE.com."But for an initial outpost, oxygen alone from the regolith [the Moon's topsidelayer of dust and rocky debris] provides most of the benefits of earlyISRU...oxygen for extravehicular activity and life support backup."
Sandersunderscored a message that was made clear from an early December spaceexploration meeting in Houston, Texas during which NASA's lunar outpost proposal was rolledout in detail.
"BecauseISRU has never been demonstrated, it cannot be in the 'critical path' ofoutpost success...be it water or oxygen from regolith," Sanders said. "However,as ISRU capabilities and processes come online and are shown to be valid, ISRUproducts will help reduce the logistics required from Earth with the goal ofuse in propulsion and surface exploration activities."
Measurementstaken by NASA's robotic Lunar Prospector that orbited the Moon in 1998-1999reported hydrogen enhancement over large shadowed areas--exciting somescientists about the prospect of large quantities of water ice tucked away inalways dark nooks and crannies. The projection is that billions of gallons ofwater could be locked up in the form of water ice.
Thatfinding seemed to back an earlier data point from the U.S. Pentagon'sClementine Moon probe. Scientists on that project reported that Clementine datasuggested the presence of ice at the bottom of a permanently shadowed craternear the Moon's south pole.
Oflate, the Advanced Moon Imaging Experiment on the European Space Agency's (ESA)SMART-1 lunar orbiter searched for light, shadow and ice at the Moon's southpole before it was purposely plowed into the Moon in early September 2006. TheESA craft made long repeated camera exposures to see inside the shadowed areas,using imagery skills that could reveal patchy ice surface layers inside thecrater.
"Westill do not know if this hydrogen is due to enhanced trapping of solar wind,or to the water ice brought on the Moon by the bombardment of comets andasteroids," said Bernard Foing, ESA's SMART-1 project scientist. "We need toanalyze all remote sensing data sets consistently. Future lander and rovermissions to the Moon will help in the search and characterization of lunarpolar ice, both on the surface and below the subsurface," he explained.
However,astronomers recently utilized Earth-based radio-telescopes to scan the 1.3 mile(2 kilometer) wide inner edge of the Shackleton crater ridge. The report isthat they were not able to identify a distinctive signature of ice depositspigeon holed within that south pole region.
Covering all your bases
Shackletoncrater as the locale for a lunar outpost is not an X marks the spot, done deal,said Ben Bussey, senior staff scientist at The Johns Hopkins University AppliedPhysics Laboratory in Laurel, Maryland.
"Itmight be the place...but it might not," Bussey told SPACE.com. "Whatyou're doing is covering all your bases for planning a lunar outpost."
Busseysaid that there are places near the rim of Shackleton which have a lot ofillumination that is potentially constant. "And you know you are close to areasof permanent shadow that we know have enhanced hydrogen...and may or may not haveice...depending on who you believe."
India's Chandrayaan-1lunar orbiter, to be lofted in early 2008, has a good shot at furtheridentifying possible water ice-laden spots with a U.S.-provided low-powerimaging radar, Bussey advised--one of two U.S. experiments on the Indian Moon probe.
"Theidea is that we find regions of interest with Chandrayaan-1 radar. We wouldinvestigate those using all the capabilities of the radar on NASA's LunarReconnaissance Orbiter, Bussey added, a Moon probe to be launched late in 2008.
Still,going to and touching the ice via robotic landers is key, Bussey said. "Fromorbit, we're identifying what we hope is a resource. But to characterize theabsolute nature of the resource, you have to touch it physically and do thesort of measurements you can only do on the spot."
ForBussey, a verdict of ice would be a windfall if it's really there.
"Youdon't have to have ice at the poles to make that a good place for the initiallunar outpost. If you happen to have big resources of ice...well, that's justicing on the cake so to speak. Pardon the pun," Bussey concluded.