2008 TC3

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Showing the estimated path and altitude of the meteor in red, with the possible location for the METEOSAT IR fireball as orange crosshairs and the infrasound detection of the explosion in green.

2008 TC3 (Catalina Sky Survey temporary designation 8TA9D69) was an 80 tonnes 4.1 meters (13 ft) diameter asteroid[1] that entered Earth's atmosphere on October 7, 2008[2] and exploded at an estimated 37 kilometers (23 mi) above the Nubian Desert in Sudan. Some 600 meteorites, weighing a total of 10.5 kilograms (23 lb), were recovered; many of these belonged to a rare type known as ureilites, which contain, among other minerals, nanodiamonds.[1][3][4]

It was the first time that an asteroid impact had been predicted prior to its entry into the atmosphere as a meteor.[5]

Discovery[edit]

An animation of 2008 TC3's excited rotation prior to entering the atmosphere.

The asteroid was discovered by Richard A. Kowalski at the Catalina Sky Survey (CSS) 1.5-meter telescope at Mount Lemmon, north of Tucson, Arizona, USA, on October 6, 06:39 UTC, 19 hours before the impact.[6][7][8]

It was notable as the first such body to be observed and tracked prior to reaching Earth.[5] The process of detecting and tracking a near-Earth object, an effort sometimes referred to as Spaceguard, was put to the test. In total, 586 astrometric and almost as many photometric observations were performed by 27 amateur and professional observers in less than 19 hours and reported to the Minor Planet Center, which issued 25 Minor Planet Electronic Circulars with new orbit solutions in eleven hours as observations poured in. On October 7, 01:49 UTC,[8] the asteroid entered the shadow of the Earth, which made further observations impossible.

Impact predictions were performed by University of Pisa's CLOMON 2 semi-automatic monitoring system[9][10] as well as Jet Propulsion Laboratory's Sentry system. Spectral observations that were performed by astronomers at the 4.2-meter William Herschel Telescope at La Palma, Canary Islands are consistent with either a C-type or M-type asteroid.

Entry[edit]

Meteosat 8/EUMETSAT infrared image of the explosion

The meteor entered Earth's atmosphere above northern Sudan at 02:46 UTC (05:46 local time) on October 7, 2008 with a velocity of 12.8 kilometres per second (29,000 mph) at an azimuth of 281 degrees and an altitude angle of 19 degrees to the local horizon. It exploded tens of kilometers above the ground with the energy of 0.9 to 2.1 kilotons of TNT over a remote area of the Nubian Desert causing a large fireball or bolide.[11]

The Times reported that the meteor's "light was so intense that it lit up the sky like a full moon and an airliner 1,400 km (870 mi) away reported seeing the bright flash."[12] A webcam captured the flash lighting up El-Gouna beach 725 kilometres north (see this webcam frame).[13] A low-resolution image of the explosion was captured by the weather satellite Meteosat 8.[14] The Meteosat images place the fireball at 21°00′N 32°09′E / 21.00°N 32.15°E / 21.00; 32.15 (2008 TC3 fireball).[15] Infrasound detector arrays in Kenya also detected a sound wave from the direction of the expected impact corresponding to energy of 1.1 to 2.1 kilotons of TNT.[16] Asteroids of this size hit Earth about two or three times a year.[17]

The trajectory showed intersection with Earth's surface at roughly 20°18′N 33°30′E / 20.3°N 33.5°E / 20.3; 33.5 (2008 TC3 projected impact)[18] though the object was expected to break up perhaps 100–200 kilometers (62–124 mi) west as it descended, somewhat east of the Nile River, and about 100 kilometers (62 mi) south of the Egypt–Sudan border.

According to U.S. government sources[19][20] U.S. satellites detected the impact at 02:45:40 UT, with the initial detection at 20°54′N 31°24′E / 20.9°N 31.4°E / 20.9; 31.4 (2008 TC3 initial detection) at 65.4 kilometers (40.6 mi; 35.3 nmi) altitude and final explosion at 20°48′N 32°12′E / 20.8°N 32.2°E / 20.8; 32.2 (2008 TC3 final explosion) at 37 kilometers (23 mi; 20 nmi) altitude. These images have not been publicly released.

Recovered fragments (Almahata Sitta meteorite)[edit]

2008 TC3 fragment found on Feb. 28, 2009 by Peter Jenniskens, with help from students and staff of the University of Khartoum. Nubian Desert, Sudan.

Search[edit]

A search of the impact zone that began on December 6, 2008, turned up 10.5 kilograms (23 lb) of rock in some 600 fragments. These meteorites are collectively named Almahata Sitta,[21] which means "Station Six"[22] in Arabic and is a train station between Wadi Halfa and Khartoum, Sudan. This search was led by Peter Jenniskens from the SETI Institute, California and Muawia Shaddad of the University of Khartoum in Sudan and carried out with the collaboration of students and staff of the University of Khartoum. The initial 15 meteorites were found in the first three days of the search. Numerous witnesses were interviewed, and the hunt was guided with a search grid and specific target area produced by NASA's Jet Propulsion Laboratory in Pasadena, California.[23][24][25][26][27]

Analysis[edit]

Samples of the Almahata Sitta meteorite were sent for analysis to a consortium of researchers led by Jenniskens, the Almahata Sitta consortium, including NASA Ames in California, the Johnson Space Center in Houston, the Carnegie Institution of Washington, and Fordham University in New York City. The first sample measured was an anomalous ultra-fine-grained porous polymict ureilite achondrite, with large carbonaceous grains. Reflectance spectra of the meteorite, combined with the astronomical observations, identified asteroid 2008 TC3 as an F-type asteroid class. These fragile anomalous dark carbon-rich ureilites are now firmly linked to the group of F-class asteroids.[1] Amino acids have been found on the meteorite.[28]

Full circle[edit]

Richard Kowalski, who discovered the object, received a tiny fragment of Almahatta Sitta, a gift from friends and well-wishers on the Minor Planet Mailing List, which Kowalski founded in order to help connect professional and amateur astronomers.[29]

See also[edit]

References[edit]

  1. ^ a b c Jenniskens, P.; et al. (2009). "The impact and recovery of asteroid 2008 TC3". Nature 458 (7237): 485–488. Bibcode:2009Natur.458..485J. doi:10.1038/nature07920. PMID 19325630. 
  2. ^ Plait, P. (2008-10-06). "Incoming!!!". Bad Astronomy. Archived from the original on 7 October 2008. Retrieved 2008-10-08. 
  3. ^ Chang, K. (2009-03-25). "Recovered Pieces of Asteroid Hold Clues to Early History". New York Times. Archived from the original on 31 March 2009. Retrieved 2009-03-26. 
  4. ^ Borenstein, S. (2009-03-26). "Astronomers catch a shooting star for 1st time". ABC news. The Associated Press. Retrieved 2009-09-15. [dead link]
  5. ^ a b Roylance, F. (2008-10-07). "Predicted meteor may have been sighted". Maryland Weather. Archived from the original on 10 October 2008. Retrieved 2008-10-08. 
  6. ^ Williams, G. V. (2008-10-06). "MPEC 2008-T50". Minor Planet Center. Archived from the original on 9 October 2008. Retrieved 2008-10-08. 
  7. ^ Huntington, J. (2008-10-07). "Small Asteroid Enters Earth's Atmosphere". eFluxMedia. Archived from the original on 10 October 2008. Retrieved 2008-10-08. 
  8. ^ a b Chesley, S.; Chodas, P.; Yeomans, D. (2008-11-04). "Asteroid 2008 TC3 Strikes Earth: Predictions and Observations Agree". Near Earth Object Program. NASA. Archived from the original on 18 June 2009. Retrieved 2009-06-18. 
  9. ^ "NEODys Main Risk Page". Retrieved 2008-10-08. 
  10. ^ "NEODys 2008 TC3 page". Retrieved 2008-10-08. 
  11. ^ "Astronomers predict shooting star over Sudan from space boulder". Agence France-Presse. 2008-10-06. Archived from the original on 11 October 2008. Retrieved 2008-10-08. 
  12. ^ Simon, P. (2008-10-08). "Weather Eye: NASA spots asteroid before annihilation". The Times. Retrieved 2008-10-08. 
  13. ^ Javaux, G. "2008 TC3... Première détection d'un astéroïde avant son impact sur Terre... quelques heures plus tard" (in French). Retrieved 2009-09-15. "Une webcam de surveillance, située sur la plage de la Mer Rouge à El Gouna en Egypte, a enregistré indirectement le flash de l'explosion qui s'est produit à environ 725 km plus au sud." 
  14. ^ "Asteroid Impact". SpaceWeather.com. 2008-10-08. Archived from the original on 10 October 2008. Retrieved 2008-10-08. 
  15. ^ "m8 HRV 200810070245". 2008-10-08. Archived from the original on 17 October 2008. Retrieved 2008-10-08. 
  16. ^ "Impact of Asteroid 2008 TC3 Confirmed". Near Earth Object Program. 2008-10-07. Archived from the original on 10 October 2008. Retrieved 2008-10-08. 
  17. ^ Borenstein, S. (2008-10-06). "Small Asteroid Headed for Light Show Over Africa". ABC News. The Associated Press. Retrieved 2009-09-15. [dead link]
  18. ^ Mike (2008-10-06). "Very near NEO Meteoroid impact!". MKVH.de. [dead link]
  19. ^ "Asteroid Update". SpaceWeather.com. 2008-10-15. Retrieved 2008-10-18. 
  20. ^ "Fireball detection". University of Western Ontario. 2008-10-15. Retrieved 2008-10-18. 
  21. ^ "Almahata Sitta". Meteoritical Bulletin Database. 2013-08-12. Retrieved 2013-08-13. 
  22. ^ Gebauer, S. (2008-04-16). "Station Nr. 6. – Nubian Desert". Panoramio. Archived from the original on 2009-06-17. Retrieved 2009-06-15. 
  23. ^ "NASA Team Finds Riches in Meteorite Treasure Hunt". NASA. 2009-03-27. Archived from the original on 31 March 2009. Retrieved 2009-04-05. 
  24. ^ "Found: Pieces of meteorite spotted before impact". New Scientist (2697): 15. 2009-02-25. 
  25. ^ Shiga, D. (2009-02-19). "First tracked space rock recovered after impact". New Scientist. 
  26. ^ Courtland, R. (2009-03-25). "Meteorite hunters 'strike gold' in Sudan". New Scientist. Archived from the original on 2009-06-01. Retrieved 2009-04-04. 
  27. ^ Kwok, R. (2009-03-26). "Astronomy: The Rock That Fell to Earth". Nature 458 (7237): 401–403. doi:10.1038/458401a. 
  28. ^ "Life's Building Blocks Found on Surprising Meteorite". Space.com. 2010-12-16. Retrieved 2013-08-13. 
  29. ^ Lakdawalla, E. (2009-09-20). "A piece of an asteroid returns to the telescope that discovered it". The Planetary Society. Retrieved 2009-10-07. 

Further reading[edit]

External links[edit]

External images
An image of 2008 TC3
Animation of 2008 TC3
Smoky trail (spaceweather.com November 8, 2008)