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Scientists plot map of asteroids that could threaten Earth

Artist's concept of an asteroid impact on Earth
Artist's concept of an asteroid impact on Earth  

June 28, 2000
Web posted at: 8:24 a.m. EDT (1224 GMT)

In this story:

The Earth in 'bake mode'

Tracking nearby traffic


(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.


"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 astronomer.

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.

Summer lets orbiter see asteroid Eros in new light
June 27, 2000
Spacecraft cozies up to distant asteroid
May 10, 2000
NASA unveils images of giant 'dog bone' asteroid
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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