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Date: Fri Oct 18 2002 - 18:38:36 MDT
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Article Date 10/18/2002
United Press Int'l | Health News
NASA studies lasers to divert asteroids By DEE ANN DIVIS, Science and
Technology Editor
HOUSTON, Oct. 18 (UPI) -- Though there is only a remote chance that an
asteroid will strike Earth, the spectacular crash of the Shoemaker-Levy comet
into the planet Jupiter in 1993 and a razor-thin miss between an asteroid and
Earth only last year have sharpened attention on work NASA has been doing to
prevent impacts and their devastating results.
Even a small asteroid or comet of only about 100 meters can cause tremendous
damage. It was an asteroid of that size that flattened 2,000 square miles of
forest in Siberia in 1908. Though there is still only a one in 250,000 chance
of impact, an asteroid that is roughly 1.2 kilometer across -- big enough to
destroy a continent on impact -- is expected to pass near Earth on Feb. 1,
2019.
But it was a comet that did hit that really caught the world's attention.
When the comet Shoemaker-Levy struck about 10 years ago, scientists had a
ring-side seat as it tore planet-size holes in the golden surface of Jupiter
in a series of impacts -- impacts big enough to destroy Earth.
"I think it made an impression," Jonathan Campbell, a NASA researcher at
Marshall Space Flight Center, told United Press International.
There are roughly 1,000 to 2,000 Earth-orbiting asteroids in the one to
10-kilometer class, that is, if they were a smooth ball instead of large
lumpy rocks they would be about 1 km across. There are far more smaller
asteroids, about 200,000 in the 100-meter class.
Campbell, whose work at NASA is part of Marshall's new National Space Science
and Technology Center, is studying using a laser to shift the orbit of such
dangerous asteroids. Carlos Roithmayr, a scientist at NASA's Langley Research
Center in Hampton, Va., is also looking at using lasers. Both scientists
presented their projects Thursday to attendees at the World Space Congress in
Houston, Texas.
The lasers would be used to divert -- not destroy -- the threatening rocks.
Pulses from the laser would heat the asteroid's surface to such a point that
a small part of the surface explodes. The explosion does not remove enough of
the asteroid to render it harmless, but it does give it a tiny kick to one
side. A long series of such little kicks is enough to push the asteroid off
its collision course with Earth.
Campbell suggests using a laser based either on the Moon or at one of the
libration points -- a spot in space where the gravity of Earth and the Sun
cancel each other out and a laser-carrying spacecraft would sit relatively
motionless. Roithmayr envisions an option where a laser-bearing spacecraft
would travel to the asteroid and then use the laser to turn it aside.
Either system would require extensive advance notice however as the lasers
would need to continuously fire at the asteroid for a month or two -- at
least to divert it. Such notice involves scanning the skies constantly with
telescopes, to identify and map the orbits of asteroids and comets zooming
too near the planet.
One good place to place such telescopes would be the moon. Roithmayr
described the Comet/Asteroid Protection System, or CAPS, which would include
as part of the overall protection system a set of telescopes, each with
apertures larger than 3 meters, that would placed on the moon. The large
telescopes could be placed on tracks to allow them to be configured more
flexibly.
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Copyright 2002 by United Press International.
All rights reserved.
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