Scientists: Asteroid unlikely to hit Mars

PASADENA, Calif. -- The possibility of a collision between Mars and an approaching asteroid has been effectively ruled out, according to scientists watching the space rock.

Tracking measurements of asteroid 2007 WD5 taken from four observatories have greatly reduced uncertainties about its Jan. 30 close approach to Mars so that the odds of impact have dropped to 1 in 10,000, the Near-Earth Object Program at NASA's Jet Propulsion Laboratory said in a posting on its Web site Thursday.

Scientists said the best estimate was for the asteroid to pass at a distance of more than 16,000 miles from the surface of Mars, or at worst, no closer than 2,480 miles.

The asteroid was discovered in November. Initial observations of its orbit raised the odds of an impact to as high as 1 in 25 before further refinements came in.

The asteroid is big enough to have blasted a half-mile-wide crater in the cold and dusty Martian surface, an event that astronomers would have liked to observe.

The NEO program normally looks for asteroids and comets that could pose a hazard to Earth.