Asteroid risk still real

2003-02-14 12:25

Judith Crosson

Denver - Do you want the good news or the bad news first? The good news is that of 650 massive asteroids hurtling close enough to Earth to cause concern, not one is actually headed here, scientists said on Thursday.

The bad news is that there are another 400 suspected asteroids of at least the size of a mountain out there whose orbits scientists have not yet figured out.

"It's a technical triumph," David Morrison, a scientist at the National Aeronautics and Space Administration, said of the Spaceguard Survey, which costs about $3.5 million a year.

A decade ago scientists started raising a "red flag" about the danger of Earth being slammed by a heavenly body.

The tricky part about studying asteroids and comets is that the likelihood of hitting Earth is very slight, but the damage if it did would be catastrophic. Scientists call this a "low probability-high consequence" event.

"We're finding almost one a day," Morrison said. "I can tell you of the 650 found so far not one poses a risk," Morrison told reporters at the American Association for the Advancement of Science annual meeting.

The monitoring programme was undertaken by a mandate from Congress to track 90 percent of the "near-Earth" objects larger than 0.6 miles in diameter, which constitute the greatest hazard, by 2008. The monitoring area extends outward from the Earth's orbit at a distance of 120 million miles

An asteroid the size of 0.6 miles hits Earth a few times every million years and causes regional calamity. One nearly 3 miles large hits once every 10 million years and would be catastrophic.

How much to tell?

A question arises whether the public should be told if an asteroid is detected and headed for Earth, Geoffrey Sommer, an economist at the Rand Corp, said, citing the panic that could be spread.

But Lee Clarke, a sociologist at Rutgers University, said people do not panic as much as might be thought, as evidenced by terminally ill patients who accept their fate calmly.

"If we were to discover a monster rock I'd want to know. It's not up to a bureaucrat or public policy maker to decide," Clarke said.

A nearly 2-mile asteroid would destroy civilisation, although that would not necessarily mean the end of the human race, Clark Chapman, an astronomer with Southwest Research Institute in Boulder, Colorado, said after the presentation.

"First it would destroy agriculture," he said, noting that dust arising from the impact would dim the sun for about six months. "Maybe one billion people would die."

Nasa's Morrison said no decisions have been made about which government agency would deal with asteroid issues.

- Reuters