[meteorite-list] NASA Discovers Asteroid 2008 TC3 Delivered Assortment of Meteorites

[Ron Baalke]

Dec. 15, 2010

Dwayne Brown 
Headquarters, Washington                                    
202-358-1726 
dwayne.c.brown at nasa.gov 

Rachel Hoover                                               
Ames Research Center, Moffett Field, Calif.                          
650-604-0643 
rachel.hoover at nasa.gov 
RELEASE: 10-340

NASA DISCOVERS ASTEROID DELIVERED ASSORTMENT OF METEORITES

WASHINGTON -- An international team of scientists studying remnants of 
an asteroid that crashed into the Nubian Desert in October 2008 
discovered it contained at least 10 different types of meteorites. 
Some of them contained chemicals that form the building blocks of 
life on Earth, and those chemicals were spread through all parts of 
the asteroid by collisions. 

Chemists at Stanford University found that different meteorite types 
share the same distinct fingerprint of polycyclic aromatic 
hydrocarbons (PAHs). These complex organic molecules are distributed 
throughout the galaxy and form on Earth from incomplete combustion. 

A research team from NASA's Goddard Space Flight Center in Greenbelt, 
Md., found amino acids in strongly heated fragments of the asteroid, 
where all such molecules should have been destroyed. Both PAHs and 
amino acids are considered building blocks of life. 

Before landing on Earth, the 13-foot asteroid was detected by a 
telescope from the NASA-sponsored Catalina Sky Survey based at the 
University of Arizona in Tucson. Hours prior to its demise, 
astronomers and scientists around the world tracked and scanned the 
asteroid. It was the first time a celestial object was observed prior 
to entering Earth's atmosphere. 

NASA's Jet Propulsion Laboratory in Pasadena, Calif., created a search 
grid and impact target area. The data helped Peter Jenniskens, an 
astronomer at NASA's Ames Research Center in Moffett Field, Calif., 
and the SETI Institute of Mountain View, Calif., guide a recovery 
team from the University of Khartoum in Sudan to search the desert 
landscape. During four expeditions, approximately 150 students 
recovered nearly 600 meteorite fragments weighing a total of more 
than 23 pounds. 

"Right from the start, the students were surprised to find so much 
diversity in meteorite texture and hue," said Muawia Shaddad, an 
astronomer at the University of Khartoum, who led the search effort. 
"We estimate the asteroid initially weighed about 59 tons, of which 
about 86 pounds survived the explosion high in the atmosphere." 

Subsequently, scientists determined most of the fragments are a rare 
type of meteorite called ureilites. Less than 10 of the nearly 1,000 
known meteorites are ureilites. The recovery team made history when 
they found the first-ever freshly fallen mixed-composition, or 
polymict ureilite. The majority of the remaining fragments are 
similar to the more common types of meteorites called chondrites. 

Other Ames researchers showed the ureilite fragments contained widely 
varying amounts of the minerals called olivine and pyroxene. Carnegie 
Institute of Washington researchers found these minerals have the 
full range of oxygen atom signatures detected in previous ureilites. 
Scientists believe this is evidence all ureilites originated from the 
same source, called the ureilite parent body. Astronomers theorize 
the parent body experienced a giant collision approximately 4.5 
billion years ago and caused iron-rich minerals to smelt into 
metallic iron. However, the olivine and pyroxene didn't melt, which 
allowed the oxygen atoms in them to stay in the same arrangement as 
when they first formed. 

Researchers at NASA's Johnson Space Center in Houston were able to 
deduce that much of the ureilite parent body was reduced to fragments 
measuring 30 to 300 feet during this giant collision. After the 
catastrophic collision, scientists believe the material that ended up 
making 2008 TC3 had a long history of violent collisions and impacts. 
These later collisions ground the fragments down into the smaller 
sand grain-sized pieces that gathered loosely together with many 
voids. 

Researchers believe the amino acids were delivered to 2008 TC3 during 
the later impacts, or formed directly from trapped gases as the 
asteroid cooled following the giant collision. Other non-ureilite 
types of meteorites also became part of the asteroid. To date, ten 
different meteorite types have been identified, accounting for 20-30 
percent of the asteroid's recovered remains. 

"Asteroids have just become a lot more interesting," Jenniskens said. 
"We were surprised to find that not all of the meteorites we 
recovered were the same, even though we are certain they came from 
the same asteroid." 

Astronomers have known asteroids orbiting the sun frequently are 
broken and reassembled during collisions, but until now they thought 
little mixing occurred because asteroids, or impactors that broke 
them apart, are usually very small. The research is featured in 20 
papers published this week in an issue of the Meteoritical Society's 
journal Meteoritics and Planetary Science. For information about NASA 
and agency programs, visit: 

http://www.nasa.gov 
	
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