[meteorite-list] Asteroid Annihilation a Reality?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:14 2004
Message-ID: <200404141958.MAA13074_at_zagami.jpl.nasa.gov>

http://www.ivpressonline.com/articles/2004/04/13/news/news08.txt

Asteroid annihilation a reality?

By J.D. HILLARD
Imperial Valley Press
April 13, 2004

WASHINGTON (MNS) - On March 18 an asteroid with the
potential to cause an explosion comparable to a nuclear
bomb passed within 26,500 miles of Earth, closer
than any recorded near-miss.

Eventually, asteroids this size or larger could hit
Earth unless early-warning systems are created to spot
and deflect them, scientist told a Senate committee
Wednesday.

Scientists from NASA's program to identify potentially
dangerous asteroids presented a $300 million plan they
said would eliminate most of the risk of an asteroid
collision within 20 years.

Dr. Lindley Johnson, program manager of NASA's Near Earth
Objects Observatory Program, told the Senate Subcommittee on
Science, Technology and Space that his program already has
identified 700 asteroids 1 kilometer in diameter or larger
near the Earth's orbit. Collisions with asteroids of this
size could wipe out Earth's population, he said. Scientists
theorize such an asteroid collided with the Earth 65 million
years ago, causing the extinction of the dinosaurs. Johnson
said none of the 700 found so far is on a collision
course with Earth.

But Donald Yeomans, manager for the NEO program office at NASA's
Jet Propulsion Laboratory in Pasadena, estimated that there are
1,100 of the most dangerous asteroids near enough to Earth's
orbit for a collision.

"Large ones can cause global damage," he said.

Congress first funded the NEO Observatory in the 1990s after
astronomers discovered several asteroids that passed near Earth,
Yeomans said.

Since 1998 his program has been searching for the larger
asteroids.

Yeomans projected the program would find 90 percent by 2008.

The next step, he said, is finding the smaller ones, which is
much harder. Congress is considering starting a program that
would identify asteroids between 100 meters and 1 kilometer in
diameter. The most common asteroids in this range can
cause damage similar to larger nuclear bombs, potentially
destroying large metropolitan areas.

Michael Griffin, head of the space department at the Johns
Hopkins University Applied Physics Lab in Maryland, told the
committee an asteroid this size exploded in the atmosphere
above Siberia, leveling forests in an area the size of New York
City.

"These are not terribly infrequent events in human terms,"
Griffin said.

However, Johnson estimated the likelihood of dying from in an
asteroid collision is about the same as dying in an airline
crash, somewhere between 1 in 500,000 and 1 in a million.

Yeomans said that there are more than 100,000 asteroids in
the 100-meter to 1-kilometer range near enough to Earth to
potentially hit Earth. He based the estimate on the relative
numbers of different crater sizes on the moon.

"The key is discover them early," he said. "If you can
discover an object 10 or 20 years before impact, the
technology exists to deflect it."

Methods to deflect an asteroid on a collision course include
firing nuclear weapons and lasers as well as landing
spacecrafts on the asteroids and using the spacecrafts'
engines to alter the asteroids' course.

Yeomans said there is no easy way to deflect an asteroid,
"but if you find one you would certainly have the motivation."
Received on Wed 14 Apr 2004 03:57:57 PM PDT