U.S. Water News Online
WASHINGTON -- The most exacting analysis yet of the moon's
mysterious polar craters found no sign of the vast expanses of ice
that scientists had hoped future lunar colonists could someday mine
for precious, life-sustaining water.
The findings do not mean there is no ice in the permanently shaded
craters. But if there is ice, it is probably mixed into the lunar
soil in widely scattered flecks or in thin layers.
``It certainly would have been nice to find some sort of lunar
skating rink, or thick layers of ice, but it looks like it's just not
there,'' said Bruce Campbell of the Smithsonian Institution's Center
for Earth and Planetary Studies.
He and colleagues at Cornell University used the mammoth radar
dish at Puerto Rico's Arecibo Observatory to bounce radio waves off
the craters. They probed more deeply than ever before into the
craters' floors -- as far as 20 feet down in the soil.
Like earlier Earth-based radar imaging that probed only a few feet
below the craters, the latest analysis showed no sign of thick ice
The findings appear in a recent issue of the journal Nature.
Campbell said the work supports the idea that any ice in the
moon's polar regions is in thin layers or widely scattered crystals
mixed in with the lunar soil.
That, in turn, means that moon colonists would need equipment to
either sort ice particles from the soil or heat up the crater floors
and collect the water vapor.
Five years ago, NASA's Lunar Prospector orbiter found tantalizing
evidence that deep, dark craters at the moon's poles could harbor ice
in their sunless depths.
Prospector found elevated levels of hydrogen around the poles,
with the highest readings in the shaded craters. But the evidence for
ice was indirect.
The moon's orientation means only about 20 percent of its shadowed
polar craters can be probed by Earth-based radar, but Campbell said
it is unlikely that large slabs of ice are hidden in the inaccessible
Astronomers have suspected since at least the early 1960s that the
moon's polar craters, miles-deep with raised rims that help keep out
the slanted polar sunlight, could have trapped ice from comets over
billions of years. The temperature in some craters is about minus-280
Alan Binder, director of the Lunar Research Institute in Tucson,
Ariz., said the only way to determine for sure how much ice is on the
moon is to send a human or a robot.
``You've got to go down and stick your finger in it, so to
speak,'' he said.
NASA has no such missions planned.
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