Watchers to look for potential "killer" asteroids

PRAGUE, Czech Republic — The International Astronomical Union said Thursday it has set up a special task force to monitor potential threats from asteroids or comets that might one day collide with Earth.

Experts say that there are about 1,100 comets and asteroids in the inner solar system that are at least a half-mile across, and that a collision with any one of them could kill millions of people.

"The goal is to discover these killer asteroids before they discover us," said Nick Kaiser of the University of Hawaii's Institute for Astronomy, which hopes to train four powerful digital cameras on the heavens to watch for such "near-Earth objects."

There are no asteroid busters to stop one right now, but scientists believe that one day a defense could be devised, such as using spacecraft to divert an incoming comet.

Congress has asked NASA for a plan to comb the cosmos for even smaller, more distant objects, including asteroids just 150 yards across. The space agency is to catalog their position, speed and course by 2020.

Already, there are 103 objects on an "impact risk" watch list.

Scientists warn there are as many as 100,000 of these smaller objects with the potential to destroy a city or set off a tsunami.

Scientists say expanding their database of the objects crowding Earth's neighborhood could help produce a permanent warning system like those that now monitor the Pacific for tsunamis or keep tabs on volcanoes and earthquake zones.