'97 probe could crack moon-ice question

Source: USA TODAY

USA TODAY from Dialog via Individual Inc. : Scientists are hotly debating whether the moon has ice at its shadowy south pole, as radar findings from a Department of Defense spacecraft suggest.

The question should be settled for good next year, once another probe named Lunar Prospector launches and circles the moon's poles.

``If there's water there, we'll see it,'' says Alan Binder, principal investigator for the Lunar Prospector spacecraft. ``We have extremely sensitive experiments aboard that are specifically designed to answer this question.''

The Pentagon spacecraft, called Clementine, was never designed to find ice on the moon.

The $75 million probe was built to test 23 new technologies developed by the Ballistic Missile Defense Organization, successor to the Strategic Defense Initiative or ``star wars.'' It is now in orbit around the sun, nearing Earth every 11 years.

But mission officials say ice -- and probably water-ice at that -- is just what it found when it took radar soundings in 1994 over parts of the south pole.

``I am reasonably certain this could be ice,'' says Paul Spudis of the Lunar and Planetary Institute at Rice University. ``It's not like an ice rink on the moon but more like ice mixed in with the dirt.''

The ice probably accumulated as long ago as 4 billion years as comets smashed into the moon, Spudis says. Comets are 90% water, and molecules of water could have bounced into the cold shadows of the moon, where temperatures drop to -380 F. and sunlight never reaches.

If it is water, scientists say, it mixed with soil and rock to become a sort of permafrost.

But other lunar scientists remain skeptical. Some say the same type of radar findings can be made by rocks buried under the lunar surface.

Others say the ice might well be frozen ammonia or methane as is found elsewhere in the solar system.

``I think they're stretching,'' says Wendell Mendell, a planetary scientist at NASA's Johnson Space Center in Houston.

``They've chosen not to explore all the possibilities. What they have found is one conceivable interpretation of the data, but they don't go into the others. I'm not convinced by it.''

The Clementine team is more cautious in explaining the radar signals in this week's Science magazine. ``There are several possible explanations for these observations, including the possibility that they are not due to (signals) from ice deposits,'' the article says.

But in a briefing Tuesday at the Pentagon, team members waxed enthusiastic about using such pockets of lunar water to help moon exploration. Astronauts, for example, could someday mine the water, splitting it into oxygen and hydrogen to use as rocket fuel.

``This may be the most valuable piece of real estate in the solar system,'' says Spudis. ``We could build a filling station on the moon.''

The discovery, says Dwight Duston, assistant technology chief at the Ballistic Missile Defense Organization, is ``beyond our wildest expectations.''

But any use of the ice, if it exists, could run afoul of the United Nations Treaty on Outer Space, signed by the USA and other nations in 1966. It effectively blocks nations from depleting a nonrenewable lunar resource like cometary ice.

``I'm always in favor of setting up a lunar base, but I don't see the magic bullet here that would cause us to rethink our strategies radically,'' says Mendell. ``Lunar Prospector has a better shot of finding water. That will be the real measure of whether or not it's there.''

The $63 million Lunar Prospector, built by Lockheed-Martin in Sunnyvale, Calif., is scheduled to launch Sept. 24 on a one-year mapping mission.

While Pentagon officials had to wait two years to analyze and interpret the data from Clementine, Prospector's scientists should know in a month's time.

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TEXT OF INFO BOX BEGINS HERE

Radio-beam bounce indicates ice.

Clementine, a $75 million Defense Department robot spacecraft launched in January 1994, found what scientists say may be ice crystals at the moon's south pole. The area measures about four football fields and is about 16 feet deep. The ice is thought to be inside what may be the largest crater in the solar system, twice the size of Puerto Rico with a depth 1 1/2 times the height of Mount Everest.

Clementine used its radio antenna as a sort of `flashlight' to illuminate the shadowy pole, looking for evidence of ice.

The radio beam penetrated the surface and bounced around inside, indicating the presence of ice. A surface of only rocks would have reflected the beam back cleanly.

Beams were sent back to NASA Deep Space Network antennas in Australia, South Africa, Spain and Goldstone, Calif., where scientists analyzed them.

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