Asteroid could hit Mars

A newly discovered hunk of space rock has a 1 in 75 chance of slamming into the Red Planet on January 30, scientists said Thursday.

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"These odds are extremely unusual," said Steve Chesley, an astronomer with the Near Earth Object Program at NASA's Jet Propulsion Laboratory. "We frequently work with really long odds when we track ... threatening asteroids."

The Odds

The asteroid, known as 2007 WD5, was discovered in late November and is similar in size to an object that hit remote central Siberia in 1908, unleashing energy equivalent to a 15-megaton nuclear bomb and wiping out 60 million trees.

Scientists tracking the asteroid, currently halfway between Earth and Mars, initially put the odds of impact at 1 in 350 but increased the chances this week. Scientists expect the odds to diminish again early next month after getting new observations of the asteroid's orbit, Chesley said.
"We know that it's going to fly by Mars and most likely going to miss, but there's a possibility of an impact," he said.

Excited, Not Afraid

If the asteroid does smash into Mars, it will probably hit near the planet's equator, close to where the rover Opportunity has been exploring the Martian plains since 2004. The robot is not in danger because it lies outside the impact zone. With the space rock moving at a speed of 8 miles (13 kilometers) a second, a collision would carve a hole into Mars the size of the famed Meteor Crater in Arizona. In 1994, fragments of the comet Shoemaker-Levy 9 smacked into Jupiter, creating a series of overlapping fireballs in space. Astronomers have yet to witness an asteroid impact with another planet.

"Unlike an Earth impact, we're not afraid, but we're excited," Chesley said.