MOONS WATER ICE = ROCKET FUEL
Sun, 8 Dec 1996 23:18:51 -0500 (EST)
Source: Ndunlks@aol.com
Scientists Report Water May Be Present on Moon
By JOHN NOBLE WILFORD
Scientists think they have detected water on the Moon, and suddenly
visions of people living in lunar colonies and stopping off there to refuel
on the way to Mars seem a little less farfetched.
After two years of careful analysis, scientists said Tuesday that radar
signals from an American spacecraft indicated the Moon was not as bone-dry as
is usually thought. The peculiar radar signatures suggested the presence of
water ice in the permanently cold shadows of a deep basin near the lunar
south pole.
The ice deposit is not at all like a frozen lake where astronauts might
try skating in one-sixth gravity. Instead, the scientists said, the survey
seemed to reveal a vast landscape of some 3,000 square miles in which ice
crystals are mixed with dirt, a kind of permafrost that is presumably the
residue of moisture from comets striking the Moon over the last three billion
years.
"We think we have found ice," said Dr. Paul D. Spudis, a geologist at the
Lunar and Planetary Institute in Houston. "We are not positive. But we see
signals consistent with ice, and we think it's there."
But Spudis and other scientists reporting the findings by Clementine, a
small Defense Department spacecraft, acknowledged that the discovery needed
to be confirmed by an independent investigation. That could come a year from
now when another spacecraft, Lunar Prospector, is to orbit the Moon with
instruments with even greater precision for determining the presence of lunar
water.
A detailed report on the findings has been published in the current issue
of the journal Science. The principal scientists, Spudis and Dr. Stewart
Nozette of the Air Force Phillips Laboratory in Alexandria, Va., described
the results at a news conference Tuesday at the Pentagon.
Other scientists reacted to the report with a mixture of caution and
enthusiasm. They wanted to believe, because of the important implications for
future exploration and colonization of the Moon. But they noted that the
radar results were particularly difficult to interpret.
"I'd be delighted if it's true," said Dr. Bruce C. Murray, a planetary
scientist at the California Institute of Technology in Pasadena, who in 1961
predicted that water ice would be found in polar shadows. "But we need to
look very carefully at the interpretation and wait for confirmation."
In the journal article, the discovery team also was extremely cautious.
"There are several possible explanations for these observations," the
scientists wrote, "including the possibility" that the signals do not result
from ice deposits.
But no one was ignoring the implications, if the ice proved to be real.
In a statement issued by the National Aeronautics and Space
Administration, Dr. Wesley T. Huntress Jr., the agency's associate
administrator for science, said the likely existence of water ice on the Moon
"could be a key ingredient in the support of future human lunar exploration,
due to its potential value as a source of the components of rocket fuel."
The discovery has "changed a desert to an oasis," said John E. Pike, a
space policy analyst at the Federation of American Scientists in Washington.
"The Moon used to be dry, now it's wet. Now it could become a gas station."
Ever since Murray's prediction in 1961, the possibility of ice on the Moon
has inspired speculation about using the resource for people living in
permanent outposts and as rocket fuel for interplanetary travel. Using solar
or nuclear power, the water ice could be converted into its components,
hydrogen and oxygen, which are valuable rocket fuels.
But Dr. John M. Logsdon, director of the Space Policy Institute at George
Washington University, said it was still not clear how practical a resource
the polar ice would be. He questioned the economic feasibility of using the
water for colonies or rocket fuel in the foreseeable future.
As the Clementine spacecraft discovered, the dominant topographic feature
in the south polar region of the Moon is a huge depression called the South
Pole-Aitken basin. Gouged out by a massive asteroid nearly four billion years
ago, the basin stretches 1,500 miles and in places is as deep as eight miles,
deeper than Mount Everest is high.
It is in the shadow of these deep walls that the cometary ice has
apparently accumulated as a mixture of dirt and rock. Temperatures in the
shadows are estimated to be as low as minus 387 degrees Fahrenheit. Any ice
in parts of the basin exposed to sunlight would have evaporated and escaped
into space. As it is, Spudis said, the ice in shadows is not a solid sheet
like a skating rink, but constitutes probably no more than 10 percent of the
material in the region, mostly dirt.
The ice's being near the south pole is another reason some scientists gave
for expressing reservations about its utility any time soon.
In a book "Mining the Sky," published last month by Addison Wesley, Dr.
John S. Lewis, a geologist at the Space Engineering Research Center of the
University of Arizona, wrote that in many respects "the lunar poles are not
an attractive site for the lunar base." They are harder to reach by
spacecraft from Earth and require more rocket energy. And it would be a
difficult engineering feat to transport the ice to a base closer to the
equator.
Spudis noted that there was a high point in the basin, near the actual
pole, that is almost permanently in sunlight. This would be an excellent
site, he said, for a lunar installation with solar power panels to run
equipment to melt the ice for water or convert it to breathing oxygen or
rocket fuel.
But he conceded: "We have a long way to go before we have people living on
the Moon. What this is, is an indication that living on the Moon might be
possible."
From an astronaut on the space shuttle Columbia came an even more
optimistic response. Told of the new findings by Mission Control, Dr. Story
Musgrave said, "Clearly if there is ice and there is water out there, that is
a natural resource which is extraordinarily important to establishing a
permanent thing such as an observatory on the Moon, or some kind of colony."
Nozette said the scientists were almost certain the radar was detecting
water ice, though there could be small amounts of other substances like
methane or carbon dioxide mixed in. Some 90 percent of a comet is composed of
ice and most of that is water ice.
About one-third of the south polar region appeared to be in permanent
shadow, the Clementine scientists said, but very little of the north pole is
in shadow.
The $80 million Clementine spacecraft was developed and launched by the
Defense Department's Ballistic Missile Defense Organization to test sensing
instruments for anti-missile defenses. Since the craft would be heading near
the Moon, where some of the tests could be made, scientists got permission to
put Clementine into a lunar orbit and re-map in greater detail much of the
surface.
Clementine was launched in January 1994 and operated in lunar orbit for
four months. It was the first American craft to explore the Moon since the
final Apollo landing in December 1972 and the last visit by any craft since
the unmanned Russian Luna 24 landed there in 1976, picked up rock samples and
returned them to Earth.
The next mission to the Moon is Lunar Prospector, a small unmanned craft
being developed for NASA by the Ames Research Center in Mountain View,
Calif., and built by Lockheed-Martin Corp. in Denver. Scheduled for launching
next September, the spacecraft is to go into an orbit of the Moon that
repeatedly crosses both poles. Its five remote-sensing instruments are
designed to map the composition of the lunar surface and observe its magnetic
and gravity fields.
Huntress of NASA said that Lunar Prospector's two neutron spectrometers
should be able to measure the amount of hydrogen on the lunar surface to an
accuracy of 50 parts per million. "This will permit scientists to infer the
presence or absence of ice with greater precision than possible via the
innovative but indirect method used by the Clementine team," he said.
Copyright 1996 The New York Times
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