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The Impact and Recovery of Asteroid 2008 TC3

[2008 October 7, 2:46 UT]

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The recovery of asteroid 2008 TC3

The Almahata Sitta meteorite number 15 in-situ on the desert floor during its find on 2008 December 8, much as it fell on October 7 earlier that year. Photo: P. Jenniskens, SETI Institute.

[Pictures from NASA Media Telecon March 25, 2008]
[Audio from NASA Media Telecon (11 MByte)]

2009 March 26 - In the March 26 issue of Nature magazine, it is reported that fragments of asteroid 2008 TC3 have been recovered in a search expedition led by Dr. Muawia Shaddad of the Physics Department of the Faculty of Sciences of the University of Khartoum. Under the guidance of outside expert meteor astronomer Dr. Peter Jenniskens of the SETI Institute and NASA Ames Research Center in California, the team searched along the projected ground path of the asteroid on December 6-8, 2008. Eye witness interviews suggested no large pieces survived the explosion, so we started looking in the area where small fragments would have fallen. Students were lined up along a kilometer to comb the desert. The first meteorite was found by student Mohammed Alameen just down track from the explosion that turned most of the 80,000 kg sized asteroid into dust. In total, only about 5 kg survived and came out of the explosion with cosmic speed of 12.4 km/s. Because it took long for the larger pieces to be slowed down, they ended up falling 29 km downrange from where the first meteorite was found. Two more expeditions were organized by the University of Khartoum, netting a total of some 280 meteorites. Never before have meteorites been recovered from something exploding this high in the atmosphere. Sure enough, this turns out to be a very unusual meteorite not yet in our collections. It is an anomalous polymic ureilite. By comparing the reflection properties of the meteorite with those of the asteroid in space, we were able to conclude that this was an F-class asteroid. We now know that (some) F-class asteroids have a dark surface because they are made up of a black and porous anomalous kind of ureilite.


- Eye witness Abdel Moniem Magzoub, the station attendant, describes the altitude of the fireball explosion as seen at Station 6 to interviewer Dr. Muawia Shaddad of the University of Khartoum on December 5, 2008. Magzoub was woken by the bright light from the first explosion, sat up, and then saw the fireball briefly continue until the second weaker explosion. A short while later, he heard a sound "doe-doe-doe-doe-doe".

- Some 45 students and staff of the University of Khartoum, and all necessary logistics for transport, eating, and sleeping, were brought to Station 6 in the middle of the Nubian Desert to help find the meteorites. Here they are at Station 6, with their mode of transportation in the background.

- Schematic map of the region, in northern Sudan, with Station 6 and the path of the fireball marked. Image based on Meteosat 8 detection (note: position of the explosion is slightly off due to glancing perspective).

- In order to comb the desert for meteorites, the University of Khartoum students and staff were distributed along a 1 km line, here on the third day of the first search expedition on December 8, 2008. In the green shirt is team leader Dr. Muawia Shaddad, an astronomer with the University of Khartoum.

- The Nubian Desert has rocky plains, interspersed with hills, rocky outcrops and sandy river valleys. The rocky terrain demanded a foot search at relatively close distance between the searchers.

- The first meteorite, now called "Almahata Sitta", was found after only 2 hours of searching by student Mohammed Alameen on December 6, 2008. The search was concentrated in the area where (more common) small fragments were expected to have fallen. The meteorite is handled with aluminum foil to prevent contamination from touching.

- Five more black scruffy looking meteorites like this lager one were found the next day, spread along the asteroid path, which proved that we were picking up meteorites from 2008 TC3.

- The third day, December 8, the students walked 18 kilometers and gradually saw the size of the meteorites increase from small pebbles to chicken egg size, as expected for debris from asteroid 2008 TC3. Here, Muawia Shaddad and Peter Jenniskens are pointing at the meteorite, in the company of several of the University of Khartoum students.

- Each meteorite's location was carefully marked to help study how the asteroid broke during entry. When a meteorite was found, students would wait for Jenniskens or Shaddad to log the location of the find and collect the meteorites. Here, the bus got stuck in the search area, and a meteorite was found when the students departed from the bus. While others helped push the bus free from the sand, a student waited until the meteorite had been officially logged.

- Finding a meteorite was an incredible experience, according to Jenniskens. Here, he finds his first meteorite: one that broke in two druing landing. "For a moment you realise that you are the first person to lay eyes on these rocks from space, laying there in the sand much the same as the day they fell on the ground," he says. Every find brought back that euphoric sense of discovery. This picture was taken during the third search on February 28, 2009.

- Peter's second find happend just minutes later when he and his driver were catching up on the line of students and his driver decided to go over a black rock on the desert floor. An adrenaline rush, a call to "stop", and sure enough: another great piece of asteroid 2008 TC3.

Sudan impact

Meteosat 8 detected the impact of asteroid 2008 TC3 over northern Sudan, during a 5-second image scan of Earth.
Sudan impact

Just before dawn, this luminous train was visible over the area. Photo from a video by Mohamed Elhassan Abdelatif Mahir (Noub NGO), image courtesy Dr. Muawia H. Shaddad (Univ. Karthoum).
Sudan impact

Luminous train from a video by Mohamed Elhassan Abdelatif Mahir (Noub NGO), image courtesy Dr. Muawia H. Shaddad (Univ. Karthoum).

2008 November 08 - 2008 TC3 impact train is Astronomy Picture of the Day, in an effort to collect more of such observations. If you observed the fireball or train in the early morning of October 7 over Northern Sudan, please contact:

Dr. Muawia Hamid Shaddad, 
PO Box 114, 
Khartoum Centre, Sudan 
Tel: +249 912 359317; 

Dr. Peter Jenniskens
SETI Institute
515 N. Whisman Road
Mountain View, CA 94043
Tel.: +1-650-8100216

2008 October 06 - For the first time, a small (2-3 meter sized) asteroid was discovered in space on approach to Earth, just before hitting the Earth. While initially very faint, the close approach made it bright enough (about +14 magnitude) for spectroscopic studies and studies of asteroid lightcurve. This data might be compared to collected samples if a meteorite is recovered. In most cases, this will not be the case because most impacts are over the ocean or difficult terrain on land. The impact point was calculated with 8 hours warning over northern Sudan in a desert area. The impact was seen by observers on the ground, from an airplane over Tsad, as a flash in video cameras pointed elsewhere, detected by low frequency sound waves (infrasound), and detected as a flash in rapid scanning Meteosat 8 images. No spectroscopic information of the object was obtained.

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