2008 TC3

( Name of meteorites found: " Almahata Sitta " )

2008 TC3 ( provisional name of the discoverer: 8TA9D69 ) was the first asteroid, for a collision with Earth was predicted correctly ( entry into the atmosphere). The crash took place on 7 October 2008 on the Nubian Desert. Months later fragments of asteroids ( meteorites ) could be recovered in the crash area.

Discovery, observation and prediction

The very small asteroid was discovered on October 6, 2008, only about 20 hours before his collision with Earth by Richard A. Kowalski (Catalina Sky Survey ) when he was still outside the moon's orbit. After the first message astronomers observed in many countries, the approach of the celestial body. Astronomical observations were until entry into the Earth's shadow, on 7 October at 03:49 CEST possible. The observations also periodic brightness variations were noted and concluded that 2008 TC3 exceptionally quickly rotated. The tumbling rotations around two axes showed periods of 99.173 and 96.988 seconds from over 500 astrometric measurements have to calculate the exact collision course. The path data of about 4 m wide and 80 -ton asteroid showed that he was on 7 October 2008 east of the Nile, crash at 04:46 CEST on the north of Sudan, in the Nubian Desert. Due to the path geometry of the asteroid, the calculated entry into the Earth's atmosphere at a low relative velocity of 12.8 km / s The entrance angle with respect to the horizontal, has been calculated to be about 19 ​​°. Because of the small size of the celestial body were to be expected on earth no significant damage.

Crash

An infrasound measurement of Kenya confirmed the point of entry and detonation of the asteroid with an estimated energy from 1.1 to 2.1 kT TNT. The explosion took place in 37 km altitude at 20.8 ° north latitude and 32.2 degrees eastern longitude. Even satellite observations confirmed entry into the Earth's atmosphere at the calculated point. The observations of pilots of a passenger aircraft of KLM from 1400 km distance and the recording of a webcam in Egypt from 725 km distance also occupied the entrance of the asteroids in the atmosphere. The case established flicker of light indicated a fragmentation of the asteroids in several phases. At least three eyewitnesses near the railway station Almahata Sitta saw a meteor and minutes later heard the explosion and case noise. Those left behind in the sky smoke trail of the asteroid were filmed and photographed on the morning of eyewitnesses from Wadi Halfa.

Search and finds

Initially it was assumed that the asteroid was completely burns up in the atmosphere. Peter Jenniskens, a scientist at the SETI Institute, and Muawia Shaddad of the University of Khartoum launched in December 2008, a search expedition to the potential meteorite fall area. On December 6, 2008 could, after a systematic search, several fragments of asteroids are found. The analysis showed that the asteroid was a rare, very black, carbon-rich Ureilit, who probably belonged to the fragile F- class asteroids. The fragments found now carry the official name Almahata Sitta by a lying near the railway station sites. In the first search over 280 fragments were recovered with a total weight of nearly 4 kg and were scattered on an approximately 30 km long and up to 7 km wide area. Recent findings of which are also for sale. A small piece of the asteroid was Richard A. Kowalski, the discoverer of 2008 TC3. In December 2009, a workshop and a new expedition was carried out into the crash area of the University of Khartoum, to which interested parties were able to register from around the world. During the expedition 250 more, small fragments of asteroids were found. By January 2010, over 600 meteorites were with a total weight of 10.7 kg has been found. The majority of the meteorite had a mass between 1 and 100 grams, with the largest weighed 379 g. Particularly noteworthy is the very different composition and density of the meteorite. So are 20% to 30 % of the found masses to the classes of enstatites or carbonaceous chondrites. It is therefore believed that the initial asteroid consisted of various fragments.

Scientific research

Because of the unprecedented discovery, observation and find circumstances in 2008 TC3 of Special Scientific Interest. It was thus determined subsequently that the asteroid was shaped like a loaf of bread and came forward with the flat side up into the air surrounding the Earth. Scientists estimate that 2008 TC3 was once blasted off from a larger object. By analyzing and comparing the spectra, it should now be easier to classify other asteroids in space. In the fragments of asteroids, the scientists identified 18 different amino acids, which supports the assumption that the ingredients for the origin of life could have come from asteroids. Also polycyclic aromatic hydrocarbons have been discovered, which is not yet clear how these complex organic compounds could survive the high temperatures of 1300 ° C, which was exposed to billions of years ago the asteroid. In 2011, the results of scientific studies have been published which show that 2008 TC3 probably originated from the collision of three different asteroids, the relatively slow collisions must be expired ( less than 0.5 km / s). Due to the composition of meteorites compared to spectral analysis and trajectory data of known asteroids, the scientists suspect the origin in the Nysa - Polana asteroid family, which collided with asteroids of Flora and Massalia families.

Importance

The discovery of 2008 TC3 shows that it is possible asteroid colliding with the earth, to find in space, and then predict the crash site and time accurately. The correct prediction of asteroid impacts is important to time may take defensive or evacuation measures if the impact of a large asteroid threatens. For a defense, however, far longer -term predictions are needed (in the range of years ). There are several observation programs such as Lincoln Near Earth Asteroid Research (LINEAR ) to catalog and explore near-Earth asteroids for this purpose.

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