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Asteroid on course for near-collision with Earth


In this story:

March 12, 1998
Web posted at: 12:07 a.m. EST (0507 GMT)

CAMBRIDGE, Massachusetts (CNN) -- Astronomers say a mile-wide asteroid described as "the most dangerous one we've found so far" may be on course for a near-miss -- or even a collision -- with Earth in the year 2028.

Some astronomers say the asteroid will come within 30,000 miles of the Earth, and they agree with Dr. Brian Marsden of the International Astronomical Union (IAU) who says, "Chances are it will miss" Earth.

"The chance of an actual collision is small, but one is not entirely out of the question," says a notice filed by the IAU.

Message Board:
Asteroid collision

But there are those, including asteroid specialist Jack G. Hills, who find the asteroid designated as 1997 XF11 frightening.

"It is the first really big one to pass this close," says Hills, a Los Alamos National Laboratory scientist. "This is the most dangerous one we've found so far. It scares me, it really does. An object this big hitting the Earth has the potential of killing many, many people."

"It has enormous destructive potential," agreed Steven Maran of the American Astronomical Society, but he added it will take several more years of observations before experts are certain of its path.

Asteroid 1997 XF11 was discovered December 6 by Jim Scotti of the University of Arizona Spacewatch program, and has been added to a list of 108 asteroids considered to be "potentially hazardous objects."

Should pass 30,000 miles from Earth

The Central Bureau for Astronomical Telegrams -- which tracks asteroids -- conducted further observations that determined 1997 XF11 should pass just under 30,000 miles from Earth on October 26, 2028.

The estimate, Maran said, has a margin of error of more than 180,000 miles. This means a collision with Earth is theoretically possible, but uncertain at this time, he said.

Astronomers say the asteroid is projected to pass within 30,000 miles of the Earth on October 26, 2028  

Better estimates will be generated as astronomers plot the course of the asteroid during the next few years.

Astronomers say that even if it were on a path to hit Earth, technology might be available by then that would be capable of deflecting the asteroid.

"What would be scary is if it were three days from now or three weeks or even three years," Marsden says. "Thirty years is just right because it's far enough in the future. If it were going to hit us, and that's a big if, we would have time to plan to do something about it."

Marsden says, "It was quite startling to find that the nominal orbit that we were using brought it as close as we did. I have not seen anything like that."

An asteroid 6 to 10 miles across collided with the Earth about 65 million years ago and is thought to have caused the extinction of the dinosaurs, along with 75 percent of all other species.

Impact: 2 million atomic bombs

Hills said an asteroid the size of 1997 XF11 colliding with the Earth at more than 17,000 miles an hour would explode with an energy of about 320,000 megatons of dynamite. That equals almost 2 million Hiroshima-sized atomic bombs.

Such an asteroid hitting the ocean, Hills said, would create a tidal wave hundreds of feet high, causing extreme flooding along thousands of miles of coastline.

"If one like this hit in the Atlantic Ocean, all of the coastal cities would be scoured by the tsunami," said Hills. "Where cities stood, there would be only mudflats."

Animation from Sandia National Lab  

If it struck land, he said, it would blast a crater 20 miles across and so clog the sky with dust and vapor that the sun would be darkened "for weeks, if not months."

Marsden said the announcement about the asteroid was meant to alert astronomers, not to frighten the public. "It's not intended to be scary or alarmist," he said. "The Earth as a target is not very big."

Technology by the year 2028 could probably deal with any asteroid, Marsden said.

"Suppose we knew it were going to hit ... That is the time to start doing something about it and sending missions to it. A little deflection, that's what you need, and with time on your side you don't need much of a deflection."

He added that, "If it really is as close as 30,000 miles it will really be quite bright" and would be visible in Europe -- where it will be evening -- with the naked eye.

"It would actually be a rather nice thing to see."

Reuters contributed to this report.


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