TODAY NEWS

New Asteroid Has Long Odds For Earth Crash

By KENNETH CHANG

A newly found asteroid, large enough to wreak worldwide destruction, will cross Earth's path in 2019, and although the chance of a collision is slim, astronomers cannot yet rule it out.

If the asteroid, named 2002 NT7, were to hit, it would be on Feb. 1, 2019. The odds of that happening are less than 1 in 200,000, NASA's Jet Propulsion Laboratory said yesterday. That is roughly the same chance that an unknown, as yet unseen meteor will hit Earth between now and then. Scientists expect the 1-in-200,000 odds to grow longer as they learn more about the asteroid's orbit.

On the 0-to-10 Torino scale describing asteroid hazards, 2002 NT7 ranks a 1, meriting careful monitoring but with the chance of impact judged extremely unlikely. A ranking of 0 means no danger; a 10 means certain impact with worldwide devastation.

In earlier asteroid scares, astronomers quickly ruled out any chance of impact, or the potential impact remains so far in the future that it is impossible to judge the risk.

Astronomers first spotted 2002 NT7 on July 9. With two weeks of observations, they have mapped out its orbit fairly precisely -- it circles around the Sun once every 837 days at a steep tilt of 42 degrees compared to the orbits of the planets.

But astronomers have not yet pinned down the asteroid's location, which means their predictions of where it will be on Feb. 1, 2019, may be off by tens of millions of miles.

''It's the old train on the track problem,'' Dr. Donald K. Yeomans of the Jet Propulsion Laboratory said. ''You don't know when the train is going to arrive at the crossing point.''

If NT7, which is one-and-one-quarter miles wide, does strike Earth at 60,000 miles an hour, the impact could gouge a crater many miles wide, destroying large swaths of the surrounding area.

On average, an asteroid of NT7's size hits Earth every few million years. The meteor that killed off the dinosaurs 65 million years ago was 6 to 9 miles wide.

After 2019, NT7 will have several more close passes by Earth, including 2044, 2053, 2060 and 2078. Dr. Yeomans said that with a few more weeks of observations, astronomers will probably be able to rule out any chance of impact for all of them.