- KITT PEAK, AZ
- When Comet Shoemaker-Levy 9 broke apart and slammed into Jupiter in 1994,
earthlings had front-row seats to a spectacle their own planet hadn't seen
in 65 million years.
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- Now, a growing number of astronomers are asking that
people start giving serious thought to how to deal with the threat of an
impact on Earth.
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- Researchers have made substantial progress in identifying
larger near-Earth asteroids. They now are contemplating building a telescope
that would allow them to spot smaller near-Earth asteroids - space rocks
that could inflict substantial regional damage if they struck.
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- But to Daniel Durda, an astronomer with the Southwest
Research Institute, it's time to focus on dealing with the threat - from
identifying which official or agency gets the first phone call when a threatening
object is identified to establishing plans for coping with the aftermath
of an impact.
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- "Scientists have focused on physical and technical
issues" surrounding the threat from near-Earth asteroids (NEAs), says
Dr. Durda. "But there's been a hole in the discussion - the human
aspects of the threat."
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- As if to underscore the havoc that impact events can
wreak, researchers from the University of Washington and the University
of Rochester recently published a study concluding that a giant asteroid
or comet probably contributed to the largest mass extinction in Earth's
history.
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- The extinction marked the transition from the Permian
to the Triassic period 250 million years ago. More than 90 percent of all
marine species vanished. On land, widespread extinctions cleared the way
for the rise of dinosaurs - themselves done in by an impactor 65 million
years ago.
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- The team's "smoking guns" lie within tiny soccer-ball
shaped formations of carbon found in 250 million-year-old rock. The formations
trapped forms of helium and argon more similar to those found in meteorites
than in Earth's rocks.
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- Durda acknowledges the difficulty of trying to focus
public and political attention on a natural hazard that is rare, but devastating.
"People know an impact is going to happen, but not tomorrow,"
he says. "This gives them the weasel room to put off thinking about
it."
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- Even near misses can pose challenges.
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- In a recent report, Durda and Clark Chapman, also of
the SWRI, and Robert Gold of Johns Hopkins University, note that a close
brush with a comet's tail could destroy many of the communication satellites
orbiting Earth - satellites critical to economic activity worldwide.
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- Nor are US scientists alone in calling for national and
international efforts to develop approaches to dealing with the threat
or the aftermath of an impact.
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- Last year, Britain's Parliament established a scientific
commission to look at the near-Earth objects (NEOs) issue. And last month,
the government responded to the commission's report by promising to work
more closely with the European Space Agency on the issue. It apparently
declined, however, to pay for a new telescope to search for near-Earth
objects or to establish a center for them.
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- The lion's share of search work is done by the US, and
more "glass" is being applied to the effort. Last fall, the Spacewatch
program, headquartered at the University of Arizona, finished work on a
1.8 meter telescope on the summit of Kitt Peak, near Tucson. Astronomers
also have given a high priority to building an 8.4 meter telescope that,
among other projects, would attempt to catalog 90 percent of near-Earth
asteroids greater than 300 meters across within a decade.
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- Astronomers have been working to catalog NEAs that are
1 kilometer across or larger. So far, they have found approximately 50
percent of these asteroids, according to David Morrison, with the National
Aeronautics and Space Administration's Ames Research Center in Mountain
View, Calif.
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- Dr. Chapman, Durda, and Dr. Gold argue that it's time
to augment these surveys with efforts to plan for the day when astronomers
discover a speeding space rock with Earth's name on it. One critical step,
they say, is to be prepared to send unmanned probes to the asteroid to
study its composition and structure. The recently concluded Near Earth
Asteroid Rendezvous mission represents the kind of effort that would be
needed, they say.
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- Armed with such information, researchers would be in
a better position to recommend ways to deflect or even destroy the asteroid.
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- The trio holds that the key to coping lies in bringing
a broader range of expertise to bear on the issue and not just leaving
it to astronomers. Climate modelers, seismologists, meteorologists, emergency
response planners, and other groups have expertise that would bear on attempts
to prepare for an impact.
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- "The dinosaurs could not evaluate and mitigate the
natural forces that exterminated them," the authors write, "but
human beings have the intelligence to do so."
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