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Asteroid's Chances of Smacking Mars Dip

Asteroid's Chances of Smacking Mars Dip
A computer-generated image showing the possible paths of asteroid 2007 WD5. On January 30, 2008, the asteroid may pass through any point seen in the dotted area.
(Image: © NASA/JPL)

This story was updated at 11:04 p.m. EST.

The chancesof an asteroid smacking into Mars this month are slipping away as astronomers continueto refine its course toward the red planet.

The spacerock, an asteroidcalled 2007 WD5, is now expected to miss Mars by about 18,641 miles (30,000km), according a Tuesday report by NASA's Near Earth-Object (NEO) program office.

Scientistsnow estimate the space rock's odds of walloping Mars on Jan. 30 at 2.5 percent,about a 1-in-40 chance, after a series of observations taken by astronomersusing Spain's 11.5-foot (3.5-meter) Calar Alto Observatory. The new analysislowered the asteroid's odds of a martian impact from a 3.6 percent chance releasedlast week.

"Ifthe estimated miss distance remains stable in future updates, the impactprobability will continue to fall as continuing observations further constrainthe uncertainties," said the report, which was compiled by researchers atNASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.

Astronomersat the University of Arizona firstglimpsed Asteroid 2007 WD5 last month while performing the Catalina SkySurvey. At the time, the space rock was hurtling through space at about 8 milesper second, which is about 28,800 miles per hour (46,349 kph) and15 times faster than a rifle bullet, researchers said.

With anestimated diameter of about 164 feet (50 meters), the asteroid is similar insize to the object that slammed into northern Arizona about 50,000 years ago tocreate MeteorCrater, NASA scientists have said. Earlier analysis of the space rock'strajectory suggested that, if it did impact Mars, it could slam into theplanet's surface at about 30,000 miles per hour (48,280 kph), release about 3megatons of energy and leave a crater about a half-mile (0.8-km) wide, theyadded.

Such animpact could be observed by the multiple spacecraft currently orbiting Mars,such as NASA's Mars Reconnaissance Orbiter, and provide a wealth of informationon the formation of craters and the red planet's interior, researchers havesaid.

"Weestimate such impacts occur on Mars every thousand years or so," said JPL researcherSteve Chesley, who released the refined asteroid course withcolleagues Paul Chodas and Don Yeomans, in a NASA announcement last week.

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