Scientists plot map of asteroids that could threaten Earth
Artist's concept of an asteroid impact on Earth
(CNN) -- An international team of scientists has estimated the locations of many as 900 large asteroids, some of which could eventually threaten the
Earth with disastrous collisions.
Plotting a map of known and suspected asteroid locations in
the inner solar system, the researchers said an object 1
kilometer (0.6 miles) or greater in size could conceivably
run into the Earth someday.
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"The odds of one hitting us tomorrow are very small, but
they're not zero. It behooves us to go out and find these
objects," said William Bottke, lead author of the report published last week in Science magazine.
Such space rocks could set off natural catastrophes that
freeze or fry the planet. Smaller ones could wipe out
millions of people and larger ones could wipe out most
species, according to Bottke.
"If a one-kilometer asteroid hit the Earth, it would launch
massive amount of dirt and debris in the atmosphere. The
smaller pieces take some time to rain out," he said.
"During that time, all that material is blocking the sun from
heating the planet. So it gets cooler on the planet and
agriculture worldwide is disrupted."
The Earth in 'bake mode'
More massive asteroids could do worse damage. Many scientists
think a space rock 10 km (six miles) across hit the Earth
65 million years ago, wiping out dinosaurs and most other
species. Such asteroids could cause the atmosphere to heat up
and turn much of the planet into a fireball.
"The entire Earth would be in bake mode," Bottke said.
Most asteroids remain in the main belt between Mars and
Jupiter. But sometimes collisions can launch large chunks
into unstable orbits that move them into what could become
collision courses with our planet.
Near Earth asteroids range in size from mere specks to more
than 64 kilometers (40 miles) in diameter.
Astronomers have identified about 40 percent of the candidate
killer space rocks. The computer map model should help them
locate many others, said Bottke, a Cornell University
Tracking nearby traffic
"We created something like a traffic map, like the Los
Angeles Freeway system," Bottke said. In some places,
asteroids experience traffic jams. In others they have plenty
of space, he said.
Scientists can calculate whether identified asteroids will
strike the Earth over the next hundred years or so. But they
cannot predict out several thousands of years in the future.
Scientists estimate that on average, a killer asteroid hits the Earth once every 500,000 to 1 million years. Pretty remote, but still cause for concern, Bottke said.
"It's possible some of these asteroids eventually will move
onto an Earth-collision trajectory. I think it's prudent to
find these big asteroids."
The team was able to predict the orbits of undetected nearby
asteroids by combining population estimates from the
University of Arizona and theoretical models produced at
Cornell University and an observatory in Nice, France.
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May 5, 2000
NASA unveils quartet of asteroid movies
April 28, 2000
University of Arizona, Lunar and Planetary Observatory, Spacewatch Project
Near-Earth Object Program, Jet Propulsion Laboratory
Asteroid and Comet Impact Hazards, NASA Ames Space Science Divisio
Observatoire de la Côte d'Azur
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