|
 |
 advertisement
| |
|
|
|
|
|
DoD Satellite Tracked Siberian Fireball that Might have Hit Earth
By Robert Roy Britt
Senior Science Writer
posted: 12:45 pm ET
14 October 2002
|
Scientists are trying to piece together reports that a space rock recently lit of the skies over Siberia and might have crashed into Earth and left a crater The U.S. Department of Defense has confirmed an apparent space rock that lit a fire in the night sky above a remote region of Siberia last month. Meanwhile, scientists struggle to pin down whether or not the object slammed into the planet. Eyewitnesses in the Bodaibo district reported seeing a fireball race across the sky Sept. 24. Hunters later said they found a crater surrounded by burned forest. A seismic monitor in the region, according to the British NEO Information Center possibly recorded the event. NEOs are Near Earth Objects, mostly asteroids that roam the region of space through which Earth orbits the Sun. When one enters Earths atmosphere, it is termed a meteor. Smaller meteors burn up before reaching the surface and can be seen as "shooting stars." Objects as big as a car or bus generate so-called fireballs; a few small pieces, if anything, might reach the surface. While looking for nukes Now the U.S. Department of Defense has confirmed part of the Siberian meteors fiery path through the sky, according to Peter Brown in the Meteor Physics Group at the University of Western Ontario in Canada. The DoD monitored the rock by satellite from 39 miles (62 kilometers) down to 19 miles (30 kilometers) above the ground. The agency attempts to track meteors and impacts in order to differentiate them from missiles and possible nuclear explosions. Failing to properly identify a cosmic object as it slams into the planet could result in an unnecessary nuclear exchange, some military and asteroid analysts warn. Evidence for an actual impact near Bodaibo has not been verified by scientists. "Unfortunately, at present we do not know exactly what happen there," said Michael Nazarov of the Laboratory of Meteoritics Vernadsky Institute of Geochemistry and Analytical Chemistry. "The Bodaibo [seismic] station recorded a signal which cannot be easily interpreted." Other seismic recorders farther from the event recorded nothing, indicating that if the rock did survive its heated plunge through the atmosphere to hit the ground, the impact was relatively small. Echoes of 1908 Ironically, the Bodaibo event may go down in history as a small-scale cousin to another one in 1908, also in Siberia. Then, a meteor thought to be about the size of a football field exploded above the mostly unpopulated Tunguska region. Trees were leveled for hundreds of miles around. The explosion was recorded by less sophisticated seismic equipment farther away, as compared to the Bodaibo event, Nazarov pointed out in a communication to CCNet, an electronic newsletter devoted largely to NEO research and discussion.Nazarov said it would be difficult to find any possible Bodaibo crater in the remote region, since the event occurred at night and there are few witnesses to help scientists pin down the objects trajectory and possible impact location. Scientists are eager to study impacts and any chunks of meteor that might be found in order to learn more about the compositions of their parent bodies. Some asteroids are more solid than others and thus more likely to reach the ground intact. The threshold for an asteroid to be potentially devastating on a local scale is thought to be roughly the size of the 1908 Tunguska rock. Just last week, an asteroid theorist announced new calculations showing there are fewer of these small "Tunguska" asteroids in Earths vicinity and that theyre likely to hit Earth about once every 1,000 years. Astronomers had thought such minor catastrophes occurred about once per century.Larger rocks capable of widespread devastation hit the planet less frequently.More Asteroid News | Astronotes
|
|
|
|
|
