[meteorite-list] Asteroid Boringly Whizzes Past Mars

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Wed, 30 Jan 2008 21:12:16 -0500
Message-ID: <fhb2q3pcc5j5hiem1s1t7lrocm9jtbvhnk_at_4ax.com>

http://www.foxnews.com/story/0,2933,326837,00.html

Asteroid Safely Whizzes Past Mars
Wednesday, January 30, 2008

By Jeremy Hsu

An asteroid once thought to be on a collision course with Mars passed the Red
Planet Wednesday without incident.

Astronomers first estimated that asteroid 2007 WD5 had as high as a 3.6 percent
chance of striking the Red Planet.

Newer observations kept lowering the odds for the 164-foot space rock until Jan.
9, when NASA's Near-Earth Object (NEO) program office effectively ruled out
chances of an impact.

? Click here to visit FOXNews.com's Space Center.

"Mars sees these kinds of near-miss encounters every ten or twenty years, but
the impact rate for asteroids this size is about once in a thousand years," said
Steve Chesley, an astronomer at the Jet Propulsion Lab in Pasadena, Calif.

Astronomers had hoped the fleet of spacecraft orbiting Mars would get a chance
to observe the asteroid plowing into the Martian surface.

The subsequent crater would have roughly equaled the size of the Meteor Crater
that formed in northern Arizona 50,000 years ago, with a 0.5-mile diameter.

Such an impact would have also allowed scientists to study the dust cloud from
the impact.

"We were hoping for a spectacular show to reveal a lot," Chesley said. "We've
actually never seen a significant impact on a terrestrial planet."

Mars is a smaller and harder target for space rocks to hit when compared with
Earth, but about five times as many asteroids cross the Martian orbit, according
to Chesley.

2007 WD5's path around the sun ranges from just outside Earth's orbit to the
outer edge of the asteroid belt between Mars and Jupiter, but will not impact
with either Mars or Earth in the next century, JPL researchers said.

The asteroid missed Mars by a distance of approximately 6.5 Mars radii.

Similar near misses occur with Earth. And similarly, astronomers sometimes give
odds on a possible impact and then, with further observations, reduce the odds
to zero.

In fact, the Mars flyby occurred a day after a 500-foot asteroid flew by Earth
at a distance somewhat greater than from the Earth to the Moon.

Chesley and other astronomers considered having one of the Martian rovers
eyeball the passing 2007 WD5, but judged the task too difficult for the robotic
explorers.

None of the orbiting spacecraft turned their cameras or other equipment on the
passing rock, either.

"After we knew it was going to miss, it's really a pretty ordinary asteroid
cruising around the solar system," Chesley said.

Copyright ? 2008 Imaginova Corp. All Rights Reserved. This material may not be
published, broadcast, rewritten or redistributed.
Received on Wed 30 Jan 2008 09:12:16 PM PST


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