Killer asteroids more rare
Posted on 11/21/2002 3:27:14 AM PST by MeekOneGOP
Killer asteroids more rare
Satellite data show Earth threatened about once a millennium
11/21/2002
Medium-size asteroids that could flatten a city the size of New York strike Earth less frequently than previously believed, possibly only about once a millennium, according to a study aided by military satellites.
Rocky space debris created by collisions in the asteroid belt between Mars and Jupiter or chunks that break away from comets rain down on the Earth every day as meteroids, but most of the asteroid or comet pieces are tinier than grains of rice and quickly burn in the upper atmosphere as meteors.
A meteor in 1908 - estimated to be about 50 yards wide - nearly hit the ground before it burned up over Russia, causing an explosion that flattened hundreds of square miles of forest in Siberia.
In the new study, satellite data taken over the last eight years suggest that an intermediate-size asteroid like the one that struck Siberia occur an average of only once every 1,000 years - not every couple of centuries as previously believed, said Peter Brown, a University of Western Ontario astrophysicist.
His study, published Thursday in the journal Nature, was based on measurements of the flashes of light created when the debris burns after hitting the upper atmosphere.
Military satellites used to detect the flash of a nuclear explosion helped scientists look at the flashes caused by the asteroids to determine their potential size and explosive strength.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.