Newspaper article The Christian Science Monitor

Threat of Asteroid Collision May Be Just a Movie, after All with Improved Detection, Scientists Now Believe Fewer Big Asteroids Will Hit the Earth Than Previously Thought

Newspaper article The Christian Science Monitor

Threat of Asteroid Collision May Be Just a Movie, after All with Improved Detection, Scientists Now Believe Fewer Big Asteroids Will Hit the Earth Than Previously Thought

Article excerpt

If the astronomical fireworks of "Deep Impact" or "Armageddon" kept you up at night, you can rest a bit easier. Our cosmic neighborhood appears to hold far fewer objects capable of snuffing out life on Earth than previously thought.

New research announced this week at an international meeting on asteroids and comets at Cornell University in Ithaca, N.Y., does not mean Earthlings can stop scanning the skies for objects that might hit home, however.

Earth's geological record alone suggests that during the 21st century the planet stands a 1-in-3 chance of colliding with an object that could cause heavy local damage, such as the event that flattened a Siberian forest in 1908. And the planet faces anywhere from a 1-in- 1,000 to a 1-in-10,000 chance of being hit by an object that could cause what Richard Binzel, a planetary scientist at the Massachusetts Institute of Technology in Cambridge, calls "instant global change."

These new, lower numbers do suggest that astronomers may be closer than they thought to reaching their goal of finding and tracking in the next 10 years at least 90 percent of potential Earth-crossing objects that measure over a half mile wide. This is the size range for asteroids that researchers say could cause a catastrophic change in global climate if one hits our planet.

Older approaches to spotting near-Earth objects (NEOs) led astronomers to estimate that from 1,000 to 2,000 asteroids with these diameters and higher had the potential to threaten Earth, according to David Rabinowitz, a member of CalTech's Jet Propulsion Laboratory in Pasadena, Calif.

"As of today, our best estimate is between 500 and 1,000," he says.

Improved search techniques that include new imaging detectors and telescopes specifically dedicated to finding asteroids have helped thicken the growing catalog of NEOs. These efforts scan over two- thirds of the sky and can spot objects 25,000 to 30,000 times fainter than objects humans can see with the naked eye. …

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