Morokweng crater

Summary

Morokweng crater
Morokweng impact structure
Morokweng crater is located in South Africa
Morokweng crater
Location of the crater in South Africa
Impact crater/structure
ConfidenceConfirmed
Diameter70 km (43 mi)
Age146.06 ± 0.16 Ma
ExposedNo
DrilledYes
Bolide typeLL chondrite
Location
Coordinates26°28′00″S 23°32′00″E / 26.466667°S 23.533333°E / -26.466667; 23.533333Coordinates: 26°28′00″S 23°32′00″E / 26.466667°S 23.533333°E / -26.466667; 23.533333
CountrySouth Africa
ProvinceNorth West

The Morokweng crater (or Morokweng impact structure) is an impact structure buried beneath the Kalahari Desert near the town of Morokweng in South Africa's North West province, close to the border with Botswana.[1]

Description

The crater is at least about 75–80 km (47–50 mi) in diameter and the age is estimated to be 146.06 ± 0.16 million years, making it significantly older than the JurassicCretaceous boundary.[2][3] 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 estimated to have been 5 to 10 km (3.1 to 6.2 mi) in diameter.[4]

In May, 2006, a group of scientists drilling into the site announced the discovery of a 25 cm (9.8 in)-diameter fragment of the original asteroid at a depth of 770 m (2,530 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.[5] Some of the fragments can be seen in the Antenna Wing of London's Science Museum.

References

  1. ^ "Morokweng". Earth Impact Database. Planetary and Space Science Centre University of New Brunswick Fredericton. Retrieved 2017-10-09.
  2. ^ Kenny, G.G., Harrigan, C.O., Schmitz, M.D., Crowley, J.L., Wall, C.J., Andreoli, M.A., Gibson, R.L. and Maier, W.D., 2021. Timescales of impact melt sheet crystallization and the precise age of the Morokweng impact structure, South Africa. Earth and Planetary Science Letters, 567, no. 117013, 13 p.
  3. ^ Schmieder, M. and Kring, D.A., 2020. Earth's impact events through geologic time: a list of recommended ages for terrestrial impact structures and deposits. Astrobiology, 20(1), pp.91-141.
  4. ^ Mcdonald, I., Andreoli, M.A.G., Hart, R.J. and Tredoux, M., 2001. Platinum-group elements in the Morokweng impact structure, South Africa: Evidence for the impact of a large ordinary chondrite projectile at the Jurassic-Cretaceous boundary. Geochimica et Cosmochimica Acta, 65(2), pp.299-309.
  5. ^ 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. Bibcode:2006Natur.441..203M. doi:10.1038/nature04751. PMID 16688173. S2CID 4373614.

Further reading

  • Morelle, Rebecca (10 May 2006). "Relic of ancient asteroid found". BBC News. Retrieved 2006-05-31.
  • Peplow, Mark (10 May 2006). "Meteorite survivor unearthed". Nature. doi:10.1038/news060508-7. S2CID 129248764.

External links

  • Fossil Meteorite Unearthed From Crater