American scientists say that although they discovered that there are fewer "deadly" asteroids than previously thought, such an asteroid may hit the Earth in the next century.
American scientists say that although they discovered that there are fewer "deadly" asteroids than previously thought, such an asteroid may hit the Earth in the next century.
A lethal asteroid is defined as an asteroid with a diameter greater than XNUMX km. The impact of such an asteroid on the Earth will cause massive clouds of dust to be raised into the atmosphere and block the path of the sun's rays. In such a situation, the temperature on Earth will drop dramatically, and may not allow life of any kind to exist on its surface.
David Rabinowitz of the Jet Propulsion Laboratory at Cornell University says there may be between 500 and 1,000 near-Earth celestial objects in space that threaten humanity. This estimate is lower than the previous estimate according to which there are between one thousand and two thousand such bodies. However, only 15-20% of the deadly asteroids have been identified.
Deadly asteroids reach Earth's vicinity every 100 thousand years or so. Richard Binzel, of MIT University in Massachusetts, said that the chance of a fatal collision in the next century is between one in 1,000 and one in 10,000. Conversely, Binzel estimates that the chance of a collision of a slightly lower degree, which would cause widespread local damage, is one in three.
According to Paul Chodas of Cornell's Jet Propulsion Laboratory, it is entirely possible for a deadly asteroid to appear on very short notice. "Sometimes they are discovered only a week or a few days before the impact," he said.
© Published in "Haaretz" on 07/29/1999
