(Editor's Note: This report turned out to be a false alarm. Please see the ScienceNOW, 6 November, story: " Asteroid Threat Evaporates.")
An asteroid may be heading on a crash course for Earth, scientists at NASA and the Jet Propulsion Laboratory (JPL) in Pasadena, California, announced today. The massive space rock--the first object to score above zero on the Torino hazard scale, which ranks the danger of an extraterrestrial impact--has about 1 chance in 500 of colliding with Earth in 2030, astronomers estimate.
The asteroid, named 2000 SG344, appears to be about 30 to 70 meters in diameter. If it were to strike Earth, it would release about 100 times the energy of the Hiroshima bomb, or about one-tenth that of the Tunguska asteroid explosion that flattened forests in Siberia in 1908, according to a statement by David Morrison of NASA's Ames Research Center in Moffett Field, California.
Scientists are still tracking the asteroid, and additional data on its orbit could cause them to revise their predictions of its path--and reevaluate its danger. Because the asteroid's orbit closely resembles the path of the Earth around the sun, says Paul Chodas of JPL, the object may turn out to be a rocket booster discarded from an earlier space flight. In that case, the relatively hollow, lightweight booster would burn up as it entered Earth's atmosphere.
If it's any comfort, Chodas explains that the chance of asteroid SG344's colliding with Earth in 2030 is less than the chance that an undiscovered object of the same size will hit Earth in any given year.