[meteorite-list] Meteorite Just One Piece of an Unknown Celestial Body (Asteroid 2008 TC3)

[Ron Baalke]

http://carnegiescience.edu/news/meteorite_just_one_piece_unknown_celestial_body  

Meteorite just one piece of an unknown celestial body
Carnegie Institution For Science
December 15, 2010

Washington, D.C. - Scientists from all over the world are taking a
second, more expansive, look at the car-sized asteroid that exploded
over Sudan's Nubian Desert in 2008. Initial research was focused on
classifying the meteorite fragments that were collected two to five
months after they were strewn across the desert and tracked by NASA's
Near Earth Object astronomical network. Now in a series of 20 papers for
a special double issue of the journal Meteoritics and Planetary
Science, published on December 15, researchers have expanded their work
to demonstrate the diversity of these fragments, with major implications
for the meteorite's origin.

In the first round of research, Carnegie Geophysical scientist Doug
Rumble, in collaboration with Muawia Shaddad of the University of
Khartoum, examined one fragment of the asteroid, called 2008 TC3, and
determined that it fell into a very rare category of meteorite called
ureilites. Ureilites have a very different composition from most other
meteorites. It has been suggested that all members of this meteoric
family might have originated from the same source, called the ureilite
parent body, which could have been a proto-planet.

Now Rumble has expanded his work to examine 11 meteorite fragments,
focusing on the presence of oxygen isotopes. Isotopes are atoms of the
same element that have extra neutrons in their nuclei.

Rumble explains: "Oxygen isotopes can be used to identify the
meteorite's parent body and determine whether all the fragments indeed
came from the same source. Each parent body of meteorites in the Solar
System, including the Moon, Mars, and the large asteroid Vesta, has a
distinctive signature of oxygen isotopes that can be recognized even
when other factors, such as chemical composition and type of rock, are
different."

Rumble and his team prepped tiny crumbs of these 11 meteorite fragments
and loaded them into a reaction chamber where they were heated with a
laser and underwent chemical reactions to release oxygen and then used
another device, called a mass spectrometer, to measure the
concentrations of these oxygen isotopes. Results showed that the full
range of oxygen isotopes known to be present in ureilites were also
present in the studied fragments.

"It was already known that the fragments in the Nubian Desert came from
the same asteroid. Taking that into account, these new results
demonstrate that the asteroid's source, the ureilite parent body, also
had a diversity of oxygen isotopes," says Rumble.

The diversity of oxygen isotopes found in ureilites probably arises from
the circumstances of the parent this body's formation. Rumble theorizes
that the rock components of this parent body were heated to the point of
melting and then cooled into crystals so quickly that the oxygen
isotopes present could not come to an equilibrium distribution throughout.

Together the collection of 20 papers published in Meteoritics and
Planetary Science offer enormous insight about the formation and
composition of ureilites and their hypothesized parent body.

This study was supported through a grant from NASA's Cosmochemistry
program, a grant from NASA under the Planetary Geology and Geophysics
program and a grant from NASA's Planetary Astronomy program. The samples
were made available by the University of Khartoum.

The Carnegie Institution for Science (carnegiescience.edu ) is a
private, nonprofit organization headquartered in Washington, D.C., with
six research departments throughout the U.S. Since its founding in 1902,
the Carnegie Institution has been a pioneering force in basic scientific
research. Carnegie scientists are leaders in plant biology,
developmental biology, astronomy, materials science, global ecology, and
Earth and planetary science.