[meteorite-list] Yeomans Advises How to Deflect an Asteroid

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 1 Mar 2007 10:44:22 -0800 (PST)
Message-ID: <200703011844.KAA14066_at_zagami.jpl.nasa.gov>

http://www.lacanadaonline.com/articles/2007/03/01/news/lnws-deathfromabove0301.txt

Local Scientist Advises How to Deflect an Asteroid
By Mary O'Keefe
La Canada Valley Sun
March 1, 2007

The chance that an asteroid is somewhere out in space with our name on
it has fueled Hollywood plot lines and countless novels. The idea that a
brave soul would climb into a spacecraft, land on the asteroid and blow
it up with bravery, conviction and a plucky sidekick may not be exact
science however real scientists are looking at viable ways to stop an
Earthbound asteroid.

Donald Yeomans, manager of NASA's Near Earth Object office at the Jet
Propulsion Laboratory in La Canada Flintridge, looks out into space for
any and all dangers that may be heading our way.

"We are hit by at least 100 tons of [space] dust a day, [an asteroid]
the size of a basketball hits the Earth at least once a week and the
size of a Volkswagen hits every month or so," Yeomans said.

It is the larger kind of asteroids that scientists will be discussing in
Washington, D.C.

"The easiest way is to run into it with a large spacecraft," Yeomans
said. This would work if the scientists have enough time, like ten or 20
years before expected impact, he said.

Another possible way is to use gravity and send a spacecraft into the
asteroid's path, matching its orbit.

"[The spacecraft] would do a gravity tug to move it out of the way," he
said.

Then the Hollywood scenario really comes into play: "If all else fails
we could use a nuclear weapon," Yeonmans said.

This would be difficult, he admitted, because it would have to be
employed at precisely the right time. Many argue that if you destroy the
asteroid in this method, then instead of one large threat there will be
many small ones. Yeomans said that would be true if it was destroyed
within a year prior to impact.

"But [if it was destroyed] five years in advance, the vast majority
would not hit [Earth]."

For the past few years to present day the nemesis many scientists have
been focusing on is named Apophis. The meteor, appropriately named after
the an ancient Egyptian spirit of evil and destruction who lived in
eternal darkness, is approximately 250 meters wide.

"We haven't had anything this size coming this close [in modern times],"
Yeomans said.

The asteroid will makes its appearance on Friday, April 13, 2029. "It
will be a close approach, but it won't hit," Yeomans said.

Scientists estimate that it will pass 24,000 miles above Earth's
atmosphere. It will make another pass in 2035. This is the year that
scientists were looking at closely. Two years ago the chance of Apophis
hitting the Earth was a reported 1-in-5,500 chance.

"It is now a 1-in-45,000 chance to hit in 2035," Yeomans said. "Even
that [chance] will probably diminish once we look closer at it."

According to Yeomans, the Near Earth Object program uses earth based
telescopes and two planetary radar systems to track not only Apophis but
other near Earth objects.

NASA has five full time ground based telescopes looking for near Earth
objects. The telescopes are pointed toward a specific region in space,
then checked every 15 minutes and record any change. That data is then
analyzed at the JPL program facilities.

"Our Near Earth Object Program is responsible for taking that data and
tracing their motions. We can do this 100 years into the future," he said.

If they find that an asteroid will come close or even impact the Earth,
they then compute the impact probability.

"At any one time we have several asteroids on our risk page," Yeomans said.

He equates the observation to those of hurricane predications.

"When a hurricane is first detected, you don't know where it is going to
hit and then with more data you find if or when it is going to make land."

Yeomans will join other scientists in Washington who take this threat
seriously but are not yet panicking.

"Our principal goal [at NASA/JPL] is to find and track near Earth
objects," Yeoman said, adding that the point of NASA's search of
asteroids is to give scientists time to respond. If they do find that an
asteroids trajectory threatens Earth they will have some theories to put
into practice.

"We will have a few decades to do something about it," Yeomans said.
Received on Thu 01 Mar 2007 01:44:22 PM PST