|
Survey: 7 new asteroids could threaten Earth
July 31, 1997
Web posted at: 2:32 p.m. EDT (1832 GMT)BOSTON (CNN) -- Seven previously unknown asteroids that are close enough and large enough to threaten the Earth have been found by astronomers scanning the heavens for potentially dangerous space rocks.
None of the new discoveries pose an immediate threat, said Eleanor F. Helin of the Jet Propulsion Laboratory in Pasadena, California.
In a report this week to the American Astronomical Society meeting in Boston, Helin said the program, called Near-Earth Asteroid Tracking, has identified more than 5,000 asteroids in its first year of operation, but only seven of the space rocks are potentially dangerous to Earth.
But she emphasized only 10 percent of the sky has been searched by NEAT astronomers so far.
The new discoveries raise to 99 the known asteroids or comets that are considered potential threats to the Earth. Each rock is at least 3,000 feet (1,000 meters) across and located in orbits that will pass within 5 million miles of the Earth.
Helin said there may be another 800 smaller asteroids that could threaten the Earth.
If an asteroid were to strike land, the effect would be global, Helin said. A large object would fill the atmosphere with dust, blotting sunlight, causing extreme cold and killing plants. Smaller objects could cause continent-wide destruction.
"In terms of global destruction, it would take a kilometer-size object," she said. "But any of these smaller guys, say, 30 to 50 meters, can do a lot of local destruction."
A kilometer is about three-fifths of a mile, and 30 meters is about 100 feet.
Defending Earth with rockets
The biggest danger to Earth, Helin said, is from objects called Aten asteroids that orbit inside the Earth's orbit with the sun. The space rocks are bounced around by the gravitational influence of the Earth, Mercury and Venus, and could be set on an Earthward path at any time.
"You really can't predict what will happen with these beyond a hundred years," she said.
There are now 26 known Aten asteroids larger than 3,000 feet in size, including one discovered by the NEAT project.
While none of the Aten asteroids is projected to hit Earth, astronomers say that over time -- hundreds, thousands, or even millions of years -- the space rocks' orbits will change, which could put any of the asteroids on a collision course with Earth.
Helin, who has been searching for asteroids for 25 years, said the Earth's only protection from such asteroids is to find them well before they hit and then send up rocket-bombs to shatter them or divert the orbit.
The Associated Press contributed to this report.
Special section:
CNN Interactive's extended coverageRelated stories:
- Scientists release dramatic photos of asteroid - June 30, 1997
- Scientists thrilled by photos of 'stealth asteroid' - June 27, 1997
- Asteroid will pass near Earth Friday evening - November 29, 1997
- Was Earth walloped 360 million years ago? - Mar. 22, 1996
- Mega-telescope aims to bring universe into focus - Feb. 10, 1996
Related sites:
Note: Pages will open in a new browser window
- Asteroid Radar Research
- Asteroid shapes and spin states from radar and optical data
- European Asteroid Research Node
- Asteroid Radar Research
- Asteroid shapes and spin states from radar and optical data
External sites are not endorsed by CNN Interactive.
Watch these shows on CNN for more sci-tech stories:
CNN Computer Connection | Future Watch | Science & Technology Week
Sound off on our message boards
Tell us what you think!
You said it...
© 1997 Cable News Network, Inc.
All Rights Reserved.