Ice may lurk in shadows beyond Moon's poles

Ice may lurk in shadows beyond Moon's poles


Catalogue of craters uncovers extra sites of interest for rovers.

• 
  Lucas Laursen
  

28 September 2012




Craters far from the moon's poles may harbour frozen water.
NASA/JPL/USGS

Water ice on the moon may be more widespread than
previously thought. Permanent shadows have been spotted far from the
lunar poles, expanding the number of sites that would be good candidates
for exploration by robotic rovers — or even for the locations of lunar
bases.

Researchers have known for decades that the Moon's poles
host craters with lofty rims that shield their floors from sunlight, so
searches for shadowed areas harbouring water ice have focused on the
poles^{1, 2}. But over the past few months, researchers have built a catalogue of permanently shadowed regions elsewhere on the Moon.

The team developed software called LunarShader to simulate
lighting conditions on the Moon throughout its solar cycles. They fed
in two topographical models — one from the Japanese spacecraft Kaguya,
and one from NASA's Lunar Reconnaissance Orbiter (LRO). The software
identified about 100 craters that should contain permanent shadows,
located as many as 58 degrees of latitude from the pole in both
hemispheres, reported team member Joshua Cahill, a space scientist at
Johns Hopkins University's Applied Physics Laboratory in Laurel,
Maryland, at the European Planetary Science Congress in Madrid this
week. The result is being prepared for publication in Icarus, he said.

The findings are significant because they open “a much
larger area where permanent manned stations could be established", says
Bruce Cutright, a hydrogeologist at the University of Texas at Austin.
Water ice on the Moon exists in such low concentrations that any mission
that seeks to study it, or to use it as a resource, will need a
detailed map of its distribution.

Ice under ground


Cahill and his colleagues also took the candidate craters'
temperature using the LRO's Diviner Lunar Radiometer instrument, to
determine which sites are most likely to contain ice. The craters are
only half the temperature of their better-lit surroundings, but they
still reach an average of 175 kelvin — hot enough to boil water in the
moon's thin atmosphere — so any water ice must be insulated beneath the
surface.

"While not as cold as the permanently shadowed regions
near the poles, these non-polar areas offer a unique environment that
may harbour volatiles," says Emerson Speyerer, an engineer at Arizona
State University in Tempe, who is part of another team that has
identified persistent shadows at the lunar poles. That team is now
characterizing other potential permanently shadowed regions using LRO
data. They made a preliminary report at the March Lunar and Planetary
Science Conference in The Woodlands, Texas.

Radar instruments on orbiting spacecraft allow some study
of the ice, but close-up observations are needed to confirm any
findings, says Speyerer. Some technological ingenuity will be required
to allow the solar-powered rovers to operate in the shadowy depths of
the craters. "A prospecting rover would be able to examine these
features with the lower half of the rover in shadow, while the upper
half and solar panel would remain illuminated," says Speyerer.

Cahill's group has also used LunarShader to identify which
parts of the permanently shadowed regions would be most accessible to a
rover. To explore the deepest craters, Cahill imagines rovers or
landers with solar panels on a mast up to ten metres high, acting like a
'solar snorkel'.




Source:-
http://www.nature.com/news/ice-may-lurk-in-shadows-beyond-moon-s-poles-1.11501