Thursday May 6 12:36 AM ET

Scientists Pinpoint Near-Earth Asteroid Belt

LONDON (Reuters) - British astronomers have calculated the position of a possible near-Earth asteroid belt that could increase the possibility of a disastrous collision.

N. Wyn Evans and Serge Tabachnik of Oxford University said the heavenly bodies could orbit anywhere under the right conditions, even quite near the Earth.

Although the research published in the science journal Nature Wednesday is theoretical, the scientists said objects had recently been discovered in the near-Earth asteroid belt.

``These near-Earth objects are a mixture of objects ejected from the main belt and possibly primordial objects too,'' Evans said in a telephone interview.

``There is a possibility that they may, at some point, come close to the Earth,'' he added.

The researchers used numerical simulations of stability zones in the inner Solar System to pinpoint areas, other than the two known belts, where asteroids might orbit without being perturbed by the gravity of the other planets.

One is a narrow band between the Sun and Mercury. The other is between Earth and Mars, but much closer to Earth.

``Just as the asteroid belt has certain locations where the belt is unstable, so these primordial belts will have locations where some of the objects will be unstable. Some of these objects may be kicked into Earth-crossing orbits,'' he said.

Asteroids are defined as pieces of space debris a kilometer or more in diameter, and scientists estimate the chances of such a body smashing into the Earth would be about one in 100,000 years. But if one did, it could kill a quarter of the world's population.

A collision 60 million years ago is thought to have wiped out the dinosaurs by changing the global climate.

Scientists have called for the establishment of a global monitoring system using six telescopes set up around the globe to track near-Earth asteroids and predict any possible collisions with our planet.

``What we'd like is a complete inventory of all the objects that lie between the Earth and Mars,'' said Evans.

``Once we have, for example, their position and their velocities we can simulate with the computer to see if those objects are likely to come close to the Earth within the next few thousand or million years.''