Scientists Worry Over Asteroids

LOS ANGELES (AP)--A group of scientists is seeking a standardized protocol for dealing with the possibility of an asteroid or comet striking the Earth, saying humans can do more than the dinosaurs ever could before a colossal impact precipitated their extinction 65 millions years ago.

The call comes as interest grows in the swarm of asteroids and comets that orbit the sun in the Earth's immediate neighborhood. The concerns were sparked in part by several recent false alarms about impending impacts.

``In some sense, it's something we know we need to worry about, but we need to decide at what level we need to worry about it--and that's a question for everybody,'' said Daniel D. Durda, a research scientist in the department of space studies of the Southwest Research Institute in Boulder, Colo.

In recent weeks, a paper written by Durda and fellow scientists Clark R. Chapman and Robert E. Gold has been making the rounds among experts who study impact hazards. The goal, they write in the 19-page paper, is to encourage discussion of how to replace the ``haphazard and unbalanced'' way the world now addresses any potential impact.

``They are spot-on that this is a problem. They are also right on time in terms of this just now being recognized as serious enough a topic so as to go to the next step in terms of 'what if,''' said Richard Binzel, a professor of planetary science at the Massachusetts Institute of Technology who developed a scale to rank the potential danger of an impact. ``We have now overcome the giggle factor.''

How serious the potential threat could be is underscored by an effort sponsored by the National Aeronautics and Space Administration to catalog 90 percent of all near-Earth objects, or NEOs, that are 0.6 miles or larger in diameter.

The objects are a mix of comets, frozen balls of ice and dust that formed in the far reaches of the solar system, and asteroids, which were formed in the inner solar system between the orbits of Mars and Jupiter.

Occasionally, those objects are pushed closer to the sun, either through collisions or by the tug of gravity, and cross the orbit of the Earth.

So far, the search effort has turned up about half of an estimated population of 1,100 NEOs.

``It is really in the last few years the search effort has begun to bear fruit and bear it massively,'' said Thomas Morgan, discipline scientist for NASA's NEO observation program.

If an Earth-bound asteroid or comet were spotted, scientists have proposed either attaching a rocket engine to it to nudge it out of the way, or smashing it to pieces with an atomic bomb.

But even if a warning about a potential impact comes years or decades in advance, the feasibility and expense of such a deterrent is unknown.

If an attempt to destroy or deflect an NEO should fail, and an object just a half-mile in diameter struck the Earth, it would unleash an amount of energy equivalent to 10 million times the power of the atomic bomb dropped on Hiroshima. The event could do for many humans what a larger object is widely believed to have done for the dinosaurs.

``The public has all heard of the extinction of the dinosaurs, and they expect something to be done about (any potential impact), so therefore something should be done,'' said Bill Cooke, a NASA contractor and space environment expert who has penned his own paper on the subject.

The Federal Emergency Management Agency, for one, would respond in a way similar to how it does now with hurricanes--or the recent return to Earth of the Russian Mir space station.

``If we were dealing with a larger object, like an asteroid that could have a much more severe impact on the United States, as we have more advance knowledge of where it might hit, we would immediately start alerting states that something was coming,'' said Marc Wolfson, a FEMA spokesman.

For now, word of a potential threat comes by way of a casual bulletin posted on the Internet that is invariably redistributed by the media.

``There's nothing set in stone yet as far as procedures go. That's what we want to get people talking about: Who should be notified? Who shouldn't? There's no desire to be secretive, but you don't want to cry wolf too often,'' Durda said.

Such a cry has come once in each of the past three years, most recently in November when astronomers announced an object known as 2000 SG344 had a 1-in-500 chance of hitting the Earth in 2030.

According to a then-new International Astronomical Union policy, astronomers made that announcement within 72 hours of reaching a consensus that a risk to the planet existed.

With SG344, however, the alarm was retracted almost immediately as other astronomers better calculated the object's orbit.

``It was a very normal scientific process, but in the public's eye it looked like a mistake,'' Binzel said. ``It's a trade-off between being very open and honest about what we have and waiting and waiting until we have every last piece of data in hand.''

One expert said the flaps, while embarrassing, were an issue of public relations, and not science.

``These are problems in communication. They are not problems in the basics of what we're doing,'' said David Morrison, chairman of the International Astronomical Union's working group on NEOs. ``The issue is really one of how do we communicate with the media and the public.''