101 USES FOR AN ASTEROID:

AN UNTAPPED MOTHER LODE FLOATS AIMLESSLY IN SPACE

Every couple of years someone gains a little publicity by warning that a nearby
asteroid could slam into the earth. In fact, at least 170 asteroids regularly
cross or graze the earth's orbit. Some scientists say those asteroids should be
put to uses other than periodically panicking the public.

The asteroids in question approach Earth's orbit more closely than those in the
asteroid belt and thus are relatively easy to reach. In late 1992, for
instance, an asteroid known as 1989ML will come within .43 astronomical units of
our planet-less than half the distance from Earth to the sun, and closer than
Mars ever gets. "It's a very accessible asteroid," says Robert Farquhar, senior
staff engineer for advanced programs at the Applied Physics Laboratory at Johns
Hopkins University in Baltimore.

Farquhar and his colleagues have been looking into a low-cost mission-less than
$150 million-to send a U.S. spacecraft to a near-Earth asteroid by 1997. Plans
call for a bare-bones, unmanned craft to be launched by a Delta 2 rocket,
Farquhar says. The ship's main cargo would be advanced instruments like a
spectral scanner and a gamma-ray spectrometer to scan the asteroid without
actually coming in physical contact with it, although Farquhar prefers to have
the craft pick up a sample of asteroid dirt.

Once the initial excursion mission tells scientists the composition of
near-Earth asteroids, manned missions-and mining missions-could follow. with the
round-trip taking only three years, including a year spent at the asteroid. "The
asteroid mission will also allow us to design and test procedures that we need
to get humans to Mars," says Lucy-Ann McFadden, a research physicist at the
University of California at San Diego's California Space Institute.

Even though scientists don't know precisely what asteroids are made of, they
have a pretty good idea o f the main components. For example, they consider
asteroids to be as much as one-fifth water, a desirable commodity because it can
be separated into liquid hydrogen and liquid oxygen to provide rocket fuel.
Having, in effect, an off-planet filling station allows future spacecraft to be
lighter and faster because they don't have to carry fuel for the entire trip.
NearEarth asteroids contain 200 times as much water and other volatile
materials-compounds of hydrogen, carbon, nitrogen, and oxygen-as the moon,
another suggested mining site, according to John Lewis, professor of planetary
science at the Lunar and Planetary Laboratory at the University of Arizona and
director of science programs at the University of Arizona/ NASA Space
Engineering Research Center.

Water also provides one of the most effective shields against radiation, so the
high water content of near- Earth asteroid dirt makes it an ideal radiation
shield for the space station. Lewis envisions sending a one-ton spacecraft,
specially designed to mine an asteroid, to bring back 50 or even 100 tons of
material.

A near-Earth asteroid's potential usefulness extends to becoming a vehicle for
transporting humans to Mars. Simply find an asteroid with an orbit that goes
past Mars, hollow it out, and hitch a ride. Hollowing but an asteroid would
require little more than shoveling, Lewis says, and you could use the asteroid
as a traveling hotel."