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Donnerstag, 12. März 2009 um 01:00 Uhr |
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The fact that meteorites had been recovered in Sudan after the first predicted bolide (see Update #320) has been known for a while, but now more details have been revealed. In the first search campaign in the Nubian Desert on 5th - 8th December, 15 meteorites were recovered over an area 29 km long along the calculated approach path of the 4-meter sized asteroid. In later searches, a total of 4 kg of meteorites was found, which still accounts for only a small fraction of the 80 tonnes that crashed into the Earth's atmosphere.
The asteroid was made of a particularly fragile material that caused it to explode at a high 37 km altitude, before it was significantly slowed down, so that the few surviving fragments scattered over a large area: The recovered meteorites were unlike anything in the meteorite collections up to that point.
After measuring how the meteorites reflected light, it was discovered that the spectra of the asteroid and meteorites agree well, which implies that the asteroid was not covered in dust and did not have much weathering from radiation in space. More importantly, it was determined that 2008 TC3 was a rare type of asteroid, called F-class, corresponding to dark ureilite achondrite meteorites with a texture and composition unlike any other ureilite meteorites found on Earth before. 2008 TC3, an 80 tonne, 4 meter asteroid with a rare composition, was first sighted by US telescopes on 6th October 2008. Subsequent observations by an international army of professional and amateur astronomers had led to the discovery that it was racing towards our planet and was due to enter the atmosphere the following morning - a first in space history.
You can find Daniel Fischers Cosmic Mirror here. |
