[meteorite-list] NASA Team Finds Riches in Meteorite Treasure Hunt (Asteroid 2008 TC3)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 31 Mar 2009 10:36:15 -0700 (PDT)
Message-ID: <200903311736.KAA27593_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/features.cfm?feature=2094

NASA Team Finds Riches in Meteorite Treasure Hunt
Jet Propulsion Laboratory
March 30, 2009

Just before dawn on Oct. 7, 2008, an SUV-sized asteroid entered Earth's
atmosphere and exploded harmlessly over the Nubian Desert of northern
Sudan. Scientists expected the asteroid, called 2008 TC3, had blown to
dust in the resulting high-altitude fireball.

What happened next excited the scientific community.

Peter Jenniskens, a meteor astronomer with the SETI Institute in
Mountain View, Calif., who works at NASA's Ames Research Center in
Moffett Field, Calif., joined Muawia Shaddad of the University of
Khartoum in Sudan to search for possible extraterrestrial remnants from
the asteroid. A paper on their findings is featured in the March 26
issue of the journal Nature.

Now, for the first time, scientists are studying recovered celestial
meteorites that have a definitive link with an asteroid from space. This
presents the science community an unprecedented opportunity to interpret
asteroid data and learn more about the origins and differentiations
between asteroids and may provide better answers about the formation of
our solar system.

The asteroid was discovered by a telescope of the NASA-sponsored
Catalina Sky Survey. Astronomers and scientists around the world tracked
and scanned TC3 for 20 hours prior to its demise. This marked the first
time a celestial object was located prior to entering Earth's
atmosphere. The asteroid had a velocity of 27,700 miles per hour when it
entered the atmosphere. It created a fiery trail 51 miles long before
exploding 121,000 feet from the ground.

"When Dr. Shaddad and I first arrived and started interviewing
eyewitnesses, things looked very bleak," said Jenniskens. "They all
described an immense explosion in the sky, but none had seen any
material flying out of the fireball."

The location and subsequent recovery was like searching for a needle in
a haystack. Scientists used what they referred to as a treasure map to
locate the meteorites. NASA's Jet Propulsion Laboratory, or JPL, in
Pasadena, Calif., produced a chart that gave the recovery team its
search grid and specific target area.

"My work usually begins and ends with trajectories of objects in space,"
said Steve Chesley, a scientist at NASA's Near-Earth Object Program
Office at JPL. "We had accurately predicted when and where TC3 would
enter over the Sudan. Jenniskens was asking for a map of where any
surviving fireball fragments could have landed. That was a first for the
Near-Earth Object Program Office."

Armed with the treasure map, Jenniskens, Shaddad and students and staff
from the University of Khartoum began their trek in the afternoon of
Dec. 6, 2008. After a three-day search, the team had scoured 18 miles
along Chesley's asteroid path and recovered 15 samples with a total mass
1.24 pounds. Scientists observed the meteorites to be porous, rocky
material, rounded like a pebble, with a broken face, and very black in
color.

Jenniskens and the Khartoum team visited the site on two more occasions
and collected 280 meteorites with a total mass of approximately 11
pounds. Samples were sent for analysis to Ames, NASA's Johnson Space
Center in Houston, the Carnegie Institution of Washington, and Fordham
University in New York.

"We certainly found a treasure," said Michael Zolensky, a cosmic
mineralogist at Johnson. "We have never seen a meteorite on Earth
exactly like this one because they are so fragile that they explode high
in the atmosphere. The samples appear to have originated from the
surface of the original asteroid, making them especially valuable to
planetologists explaining the geological history of primitive bodies and
planning spacecraft missions to asteroids." By measuring how asteroid
2008TC3 reflected sunlight in space and comparing it to how the
meteorites found on the ground reflected sunlight, the team concluded
that the meteorites came from the surface of an F-class asteroid in our
solar system's asteroid belt. Furthermore, the team determined that the
meteorite was what astronomers refer to as a polymic ureilite, in other
words, a very rare and unusually fragile, dark rock.

NASA's JPL manages the Near-Earth Object Office. Johnson manages the
Astromaterials Research and Exploration Science Directorate. NASA
detects and tracks asteroids and comets passing close to Earth through a
program commonly called Spaceguard.

Asteroid 2008TC3 was relatively small to most objects detected and
tracked by Spaceguard. Scientists estimate asteroids of its size enter
Earth's atmosphere approximately once a year, but meteorites rarely
survive once they land because of weather and water damage as well as
human disturbance. Scientists are astounded at the good luck that not
only did the meteorites land in a part of the world with ideal
conditions to preserve such cosmic artifacts, but the observatories on
the ground were able to detect and track the asteroid's entry.

For more information about NASA's Near-Earth Object office, visit:

http://neo.jpl.nasa.gov

For more images from 2008TC4 detection and recovery effort, visit:

http://www.nasa.gov/topics/solarsystem/tc3/

Media contact: DC Agle/JPL
818-393-9011


Images


Image taken by a cellphone of the contrail left by 2008 TC3 during its
decent. Image courtesy: Shaddad
<http://jpl.nasa.gov/images/asteroid/20090325/apod-browse.jpg>

Meteorite from asteroid TC3.
<http://www.jpl.nasa.gov/images/asteroid/20090325/tc3.jpg>
Received on Tue 31 Mar 2009 01:36:15 PM PDT