Scientists hope for collision on Mars

0 Comments | Oakland Tribune, Dec 26, 2007 | by Julie Sevrens Lyons

If many scientists get their Christmas wish, an asteroid the size of a Boeing 737 jet will slam into Mars late next month, potentially leaving a crater more than a half-mile wide.

Astronomers recently discovered a 164-foot chunk of space rock hurtling toward the Red Planet, and they estimate it has a 1-in-75 chance of making contact -- at a cool 30,000 miles per hour -- sometime around Jan. 30.

Not exactly a sure thing, but it has researchers giddy at the prospect. Never before have they been able to watch such a large object hitting a solid planet.

"It would be like a free pass: It doesn't hit the Earth and hit anybody, but it hits a planet where we can observe the results," said Andrew Fraknoi, chairman of the astronomy program at Foothill College. "Mars fans would go crazy."

While astronomers hope the asteroid -- known as 2007 WD5 -- actually crashes into the planet, NASA analysts believe it could miss it by some 30,000 miles.

"We've seen plenty of craters on Earth and the Moon from past impacts, but the thing is, we haven't really watched one," said Ben Burress, staff astronomer at the Chabot Space & Science Center in Oakland. "It's happened on Earth mostly prehistorically."

The asteroid is about the size of the object that blasted out Meteor Crater in Arizona an estimated 50,000 years ago. Scientists are also comparing it to what is believed to have been a cometary fragment which exploded over Tunguska, Siberia in 1908, burning and felling trees within a 25-mile radius.

Scientists are studying the asteroid's trajectory and hope to have a better sense of its exact orbit in the coming weeks. When it was first discovered on Nov. 20, it was put on a "watch list" because its orbit passes near the Earth, but scientists have determined it isn't a threat to us.

NASA researchers believe that Mars is pounded by an asteroid every thousand years or so. If 2007 WD5 is the next culprit, it will hit at 15 times the speed of a rifle bullet, create a massive crater, and release about three megatons of energy.

And NASA would likely be able to get it on film. The Mars Reconnaissance Orbiter, which is mapping the planet, has a powerful camera on board, and images of the crater would be available within a few days.

But with just a 1-in-75 chance of impact, Fraknoi cautions star lovers against getting their hopes up.

"It's like buying a lottery ticket," he said. Chances are you're going to lose.

Contact Julie Sevrens Lyons at jlyons@mercurynews.com or 408-920- 5989.