Image: Path of uncertainty
This graphic, based on data collected through Wednesday, shows the region of uncertainty for asteroid 2007 WD5's path during a Jan. 30 encounter with Mars. The blue line traces the motion of the center of the uncertainty region, which marks the likeliest position of the asteroid. Such data have led scientists effectively to rule out a collision.
updated 1/10/2008 12:00:06 PM ET 2008-01-10T17:00:06

An asteroid nearing Mars will not crash into the planet later this month, scientists say.

New observations of the Mars-bound asteroid 2007 WD5 have allowed astronomers to refine their predictions for the space rock's position during its Red Planet rendezvous on Jan. 30, according an update by NASA's Near Earth Object Program.

"As a result, the impact probability has dropped dramatically, to approximately 0.01 percent or 1-in-10,000 odds, effectively ruling out the possible collision with Mars," researchers said in Wednesday's report.

The new odds were released one day after astronomers with NASA's NEO office at the Jet Propulsion Laboratory in Pasadena, Calif., lowered 2007 WD5's chances of striking Mars from 3.6 percent to 2.5 percent, or about a 1-in-40 chance. After analyzing results from a new round of observations between last Saturday and Tuesday, scientists now estimate the asteroid will make its closest pass by Mars at a maximum distance of about 16,155 miles (26,000 kilometers).

JPL researchers said that they are 99.7 percent confident that 2007 WD5 will pass no closer than 2,485 miles (4,000 kilometers) from the Martian surface.

Discovered late last year by astronomers at the University of Arizona as part of the Catalina Sky Survey, 2007 WD5 is a 164-foot-wide (50-meter-wide) space rock that circles the sun on a path ranging from just outside Earth's orbit to the outer fringe of the asteroid belt between Mars and Jupiter, NASA officials say. It is similar in size to the object that crashed into northern Arizona to form Meteor Crater 50,000 years ago, the agency has said.

The asteroid's Mars approach excited astronomers because an impact could have carved a crater a half-mile (0.8-km) in diameter into the Martian surface — a sight that could have been observed by a flotilla of spacecraft currently orbiting the Red Planet.

NASA's NEO program tracks asteroids and comets for any that may pose an impact risk to Earth. The program's goal, researchers said, is to identify 90 percent of such near-Earth objects that are larger than 0.6 miles (one kilometer) in size, and keep them under surveillance.

"For 2007 WD5, these analyses show there is no possibility of impact with either Mars or Earth in the next century," JPL researchers said.

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