[meteorite-list] NASA Eyes Lasers To Divert Asteroids

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:07:02 2004
Message-ID: <200210181452.HAA04677_at_zagami.jpl.nasa.gov>

http://www.upi.com/view.cfm?StoryID=20021017-104159-2644r

NASA eyes lasers to divert asteroids
By Dee Ann Divis
UPI
October 18, 2002

HOUSTON -- Although there is only a remote chance an asteroid
will strike Earth in the near future, 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 only about 100 meters across could cause
tremendous damage. An asteroid of [half] that size flattened 2,000 square
miles of forest in Siberia in 1908. Though there is only a 1-in-250,000
chance of impact, an asteroid roughly 1.2 kilometer across -- big enough to
destroy a continent on impact -- is expected to pass near Earth on Feb. 1,
2019.

It was a comet that did hit -- actually a string of comet fragments -- that
really caught the world's attention. When 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
1-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 the use of lasers to shift the
orbit of such dangerous asteroids. Carlos Roithmayr, a scientist at NASA's
Langley Research Center in Hampton, Va., also is looking at lasers. Both
scientists have presented their projects to attendees at the World Space
Congress.

The lasers could divert -- not destroy -- the threatening rocks, the
scientists said. Pulses from the laser would heat an asteroid's surface to
the point where 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 would be enough to
push an asteroid off a collision course with Earth.

Campbell suggested basing a laser either on the Moon or at one of the
libration points -- spots in space where the gravity of Earth and the Sun
cancel each other out and laser-carrying spacecraft could sit relatively
motionless. Roithmayr said he envisions an option where a laser-bearing
spacecraft would travel to asteroids and use their lasers to turn them
aside.

Either system would require extensive advance notice, however, because the
lasers would need to fire continuously at an 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 our 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 an overall protection system, a set of telescopes, each
with apertures larger than 3 meters, placed on the moon. The large
telescopes could be placed on tracks to allow them to be configured more
flexibly.
Received on Fri 18 Oct 2002 10:52:17 AM PDT