Scientists: 4 percent chance asteroid hits Mars

By Alicia Chang

updated 7:22 p.m. ET Dec. 28, 2007

LOS ANGELES - The chance of a football field-sized asteroid plowing into Mars next month has been increased to 4 percent, scientists said Friday after analyzing archival data.

Though still a long shot, some researchers are hoping for a cosmic smash.

"I think it'll be cool," said Don Yeomans, who heads the Near-Earth Object Program at NASA's Jet Propulsion Laboratory. "Usually when an asteroid is headed toward Earth, I'm not rooting for an impact."

The space rock, known as the nondescript 2007 WD5, was discovered in late November by the NASA-funded Catalina Sky Survey in Arizona. Based on the latest information available, scientists said last week there was a 1-in-75 chance the asteroid could hit Mars on Jan. 30.

The odds were increased to 1-in-25 this week after a Ph.D. student pored through the archives and plotted the asteroid's motions before its official discovery. The new information allowed scientists to improve their calculations of the asteroid's orbit and flight path.

Scientists will continue to monitor the asteroid to better predict the possibility of a Martian impact. Yeomans said he expects the odds to decrease with new observations gathered early next year.

The likelihood of an asteroid hit usually "peaks before plummeting to zero with additional data," he said.

The asteroid poses no threat to Earth and is closing in on the Red Planet at 27,900 mph.

Should a collision occur, it would likely blast a half-mile-wide crater north of where the rover Opportunity has been exploring since 2004.

The impact could release energy similar to the 1908 Tunguska object that exploded over remote central Siberia and wiped out 60 million trees.

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