Morokweng crater

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Morokweng crater (or Morokweng impact structure) is a large meteorite crater buried beneath the Kalahari Desert near the town of Morokweng in the Northwest Province of South Africa, close to the border with Botswana.

The crater, formed by an asteroid 5-10 kilometers (3-6 mi) in diameter, is at least 70 kilometers (43 mi) in diameter and the age is estimated to be 145.0 ± 0.8 million years, placing it on the Jurassic-Cretaceous boundary. Discovered in 1994, it is not exposed at the surface but has been mapped by magnetic and gravimetric surveys. Core samples have shown it to have been formed by the impact of an L chondrite asteroid.[1]

In May, 2006, a group of scientists drilling into the site announced the discovery of a 25-centimetre (9.8 in) diameter fragment of the original asteroid at a depth of 770 metres (2,500 ft) below the surface, along with several much smaller pieces a few millimetres across at other depths. This discovery was unexpected since previous drillings on large impact craters had not produced such fragments, and it was thought that the asteroid had been almost entirely vaporised.[2] Some of the fragments can be seen in the Antenna Wing of London's Science Museum.

[edit] References

  1. ^ Christian Koeberl, Bernhard Peucker-Ehrenbrink, Wolf Uwe Reimold. "Meteoric component in impact melt rocks from the Morokweng, South Africa, impact structure: An OS isotopic study". Lunar and Planetary Science 31. 
  2. ^ Maier, WD; Andreoli MA, McDonald I, Higgins MD, Boyce AJ, Shukolyukov A, Lugmair GW, Ashwal LD, Graser P, Ripley EM, Hart RJ (May 11 2006). "Discovery of a 25-cm asteroid clast in the giant Morokweng impact crater, South Africa". Nature 441 (7090): 203-6. PMID 16688173. 

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