[meteorite-list] Astrophysicist Raises Odds of Asteroid Strike on Mars (2007 WD5)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 8 Jan 2008 16:51:52 -0800 (PST)
Message-ID: <200801090051.QAA12361_at_zagami.jpl.nasa.gov>

http://www.adn.com/news/alaska/story/258025.html

UAA researcher gives Mars bad news

COLLISION: Astrophysicist raises odds of asteroid strike.

By GEORGE BRYSON
Anchorage Daily News
January 8, 2008

The odds are it will miss. Still, there's a huge asteroid -- a massive
rock about 160 feet long -- hurtling toward Mars.

Two weeks ago, NASA scientists said the chances it would collide with
the Red Planet were 1 in 75. Now they say it's 1 in 28, and astronomers
and physicists are beginning to take notice.

As they do, the scientists can credit Andrew Puckett, a 30-year-old
astrophysicist conducting post-doctoral research at the University of
Alaska Anchorage.

Working on his own during Christmas break, Puckett discovered archival
data that allowed NASA to refine its forecast on what's now being called
"Asteroid 2007 WD5."

"When I submitted the information, all I knew was that I was changing
the (projected) orbit," Puckett said in a telephone interview Monday.

"I was sure I would also change the impact odds, but I had no idea
whether it would go up or down. So the fact that it went up -- and
became a big story -- is just really exciting for me."

It might become exciting for a lot of other people as well, says UAA
physics and astronomy professor Travis Rector, who supervises Puckett's
research -- if the asteroid actually hits Mars.

Such an explosion -- a force equivalent to a 3-megaton nuclear bomb --
would leave a crater on Mars about a half mile wide. Exploring it with
satellites and terrestrial rovers could allow scientists to answer
questions about whether life forms have ever existed on other planets.

"If you consider the importance of that -- it would be an amazing event
if it occurs," Rector said.

Typically the odds that any of the asteroids that NASA regularly tracks
through its Near Earth Object Program will ever strike home -- or even a
neighboring planet -- are tiny, Rector said.

"They're like 'one in 10,000' and that sort of thing. So it's a very big
deal, and it's getting a lot of attention."

Scientists began to perk up in November, after 2007 WD5 whizzed past
Earth at about 30,000 miles an hour -- then resumed its orbit toward the
outer solar system on a trajectory that would take it even closer to Mars.

On Dec. 21, the NASA Near Earth Object Program reported the chances that
the flying rock might actually hit Mars were about 1.3 percent. But the
space agency's revised forecast on Dec. 28 -- using data provided by
Puckett -- increased that likelihood to 3.9 percent.

How'd he come by such information himself?

Last year, after earning a Ph.D. in astronomy and astrophysics while
studying comets and asteroids at the University of Chicago, Puckett was
hired by UAA to help develop a new physics and astronomy curriculum --
an initiative supported by a $500,000 grant from the National Science
Foundation.

Separate from that mission, however, he'd continued to pay attention to
obscure objects in our solar system -- and on Dec. 21 was startled to
hear news of the proximity to Earth of 2007 WD5. (Though it missed us by
5 million miles, Puckett says, that counts as close, in asteroid distance.)

Because of his familiarity with tracking asteroids through images
available online in the Sloan Digital Sky Survey -- a database
principally used to monitor distant galaxies -- Puckett was able to
provide earlier plot points for 2007 WD5.

After working out some calculations on Christmas Day, he sent his
findings to the Minor Planet Center at Harvard. The university, in turn,
provided the information to NASA's Jet Propulsion Laboratory in
California. Then just before New Year's Day, NASA readjusted the chances
the asteroid will strike Mars.

Now Puckett is rooting for a direct hit .

"I hope it happens," he told a UAA publicist last week, noting that such
a cataclysm would also draw attention to the general threat asteroids
pose toward Earth.

The impact here of a meteorite the size of Asteroid 2007 WD5 would
devastate a large metropolis, said Donald Yeomans, a planetary scientist
at NASA's Jet Propulsion Laboratory in Pasadena, interviewed recently by
the Discovery Channel.

(An asteroid is a sub-planet-sized object of rock or metal that orbits
the Sun; a meteor is an asteroid or meteoroid (if it's small) that
penetrates the Earth's atmosphere and catches fire; a meteorite is a
meteor that strikes Earth before burning up.)

The last time anything the size of the Mars-bound asteroid hit Earth was
in 1908, when a fragment of a comet slammed into a forested region of
Central Siberia with the force of a nuclear bomb, Puckett said.

But vastly larger meteorites that hit Earth eons ago are believed to
have caused mass extinctions, including one 65 million years ago that
may have killed off all the dinosaurs and launched the age of mammals.

If 2007 WD5 misses Mars on this orbit, Puckett said, then it's possible
that it could threaten Earth once more -- 81 years from now -- when our
orbits align once again.
Received on Tue 08 Jan 2008 07:51:52 PM PST