A permanently
shadowed crater at the moon's south pole has long been suspected of harboring water
ice deposits that might be used by future lunar colonists. No such luck, a new
study suggests.
Scientists have debated
whether or not these cold craters, constantly shielded from sunlight, could
contain water ice, which could be melted for drinking water and potentially
converted into rocket fuel.
NASA's Lunar Prospector
mission (1998–1999) recorded an enhanced signal of hydrogen in these features.
Some scientists contend that this hydrogen is in the form of water ice.
The
Pentagon's Clementine lunar orbiter (1994) gave positive indications of water
ice in one of the cold depressions called Shackleton crater, some scientists think.
Others have disputed this interpretation because Earth-based radar of that area
reflected a signal more indicative of rock than ice.
New images
of Shackleton taken by the Japanese lunar explorer satellite KAGUYA
(SELENE) support the view that there likely aren't any exposed water ice
deposits in the crater.
The images
were made during lunar mid-summer, when enough sunlight is scattered off the
upper inner wall of the crater to provide faint illumination of the inside of
the crater.
Junichi
Haruyama of the Japan Aerospace Exploration Agency and his team analyzed the
images and data. They suggest that temperatures in the crater are less than
-297 degrees Fahrenheit (-183 degrees Celsius), certainly cold enough to hold
ice. But the images reveal no conspicuous brightness that would indicate a
patch of pure water ice.
This new
analysis, detailed in the Oct. 24 issue of the journal Science, could
mean that there is no water ice present at all in Shackleton crater, or that
any ice that exists is mixed into the lunar dirt in low amounts, Haruyama and
his team concluded.
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