Hoba meteorite

Hoba
Size relative to a human being
Type Iron
Class 12
Coordinates 19°35′32″S 17°56′01″E / 19.59222°S 17.93361°E / -19.59222; 17.93361Coordinates: 19°35′32″S 17°56′01″E / 19.59222°S 17.93361°E / -19.59222; 17.93361
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The Hoba[1] (/ˈhoʊbə/ HOH-bə) or Hoba West meteorite lies on the farm "Hoba West", not far from Grootfontein, in the Otjozondjupa Region of Namibia. It has been uncovered but, because of its large mass, has never been moved from where it fell. The main mass is estimated at more than 60 tonnes,[1] making it the largest known meteorite (as a single piece)[2] and larger than the 37-tonne fragment of the Campo del Cielo. It is also the most massive naturally occurring piece of iron (actually ferronickel) known on Earth's surface. The name "Hoba" comes from Khoekhoegowab word meaning "gift".[3]

Impact

The Hoba meteorite impact is thought to have occurred more recently than 80,000 years ago. It is inferred[4] that the Earth's atmosphere slowed the object to the point that it impacted the surface at terminal velocity, thereby remaining intact and causing little excavation. Assuming a drag coefficient of about 1.3, the meteor would have been slowed to about 720 miles per hour (0.32 km/s) from its speed on entering the Earth's atmosphere, typically in excess of 10 km/s for similar objects. The meteorite is unusual in that it is flat on both major surfaces.

Discovery

The Hoba meteorite left no preserved crater and its discovery was a chance event. The owner of the land, Jacobus Hermanus Brits, encountered the object while ploughing one of his fields with an ox. During this task, he heard a loud metallic scratching sound and the plough came to an abrupt halt. The obstruction was excavated, identified as a meteorite and described by Mr. Brits, whose report was published in 1920 and can be viewed at the Grootfontein Museum in Namibia.

Friedrich Wilhelm Kegel took the first published photograph of the Hoba meteorite.[5]

Description and composition

Hoba is a tabloid body of metal, measuring 2.7×2.7×0.9 metres (8.9×8.9×3.0 ft). In 1920 its mass was estimated at 66 tonnes. Erosion, scientific sampling and vandalism reduced its bulk over the years. The remaining mass is estimated at just over 60 tonnes. The meteorite is composed of about 84% iron and 16% nickel, with traces of cobalt. It is classified as an ataxite iron meteorite belonging to the nickel-rich chemical class IVB. A crust of iron hydroxides is locally present on the surface, owing to weathering.

Modern history

In an attempt to control vandalism and with permission from Mrs. O. Scheel, owner of the farm at the time, the government of South West Africa (now Namibia) on March 15, 1955, declared the Hoba meteorite to be a national monument.[6] In 1979 the proclamation was changed to include not only the meteorite but also 25 m x 25 m land on which it is situated.[7] In 1985 Rössing Uranium Ltd. made resources and funds available to the Namibian government to provide additional protection against vandalism. In 1987 Mr. J. Engelbrecht, the owner of Hoba West farm, donated the meteorite and the site where it lies to the state for educational purposes. Later that year, the government opened a tourist centre at the site.[7] As a result of these developments, vandalism of the Hoba meteorite has ceased and it is now visited by thousands of tourists every year.

See also

Notes and references

  1. 1 2 Meteoritical Bulletin Database: Hoba
  2. ↑ McSween, Harry (1999). Meteorites and their parent planets (2nd ed.). Cambridge: Cambridge University Press. ISBN 0521583039. OCLC 39210190.
  3. ↑ Cassidy, Joseph (2009). Place Names of Namibia A Historical Dictionary. Windhoek: Macmillan Education Namibia Publishers (Pty) Ltd. p. 37. ISBN 978-99916-0-654-5.
  4. ↑ Field Guide to Meteors and Meteorites - O. Richard Norton and Lawrence Chitwood. Springer Science + Business Media 2008, ISBN 978-1-84800-156-5
  5. ↑ Spencer, L. J.; Hey, M. H. (March 1932). "Hoba (South-West Africa), the largest known meteorite" (PDF). The Mineralogical Magazine and Journal of the Mineralogic Society. XXIII (136): 4. Archived (PDF) from the original on 2016-12-15.
  6. ↑ Comerford, M.F. (September 1967). "Comparative erosion rates of stone and iron meteorites under small-particle bombardment". Geochimica et Cosmochimica Acta. Elsevier Science, New York. 31 (9): 1470. Bibcode:1967GeCoA..31.1457C. doi:10.1016/0016-7037(67)90021-X. ISSN 0016-7037.
  7. 1 2 Voigt, Andreas (2004). National Monuments in Namibia: An Inventory of Proclaimed National Monuments in the Republic of Namibia. Gamsberg Macmillan. pp. 4–5. ISBN 9991605932.

Further reading

  • Universe: The Definitive Visual Dictionary, Robert Dinwiddie, DK Adult Publishing, (2005), pg. 223.
  • Spargo, P. E. (2008). "The History of the Hoba Meteorite Part I: Nature and Discovery" (PDF). Monthly Notes of the Astronomical Society of Southern Africa. 67 (5/6): 85–94. Bibcode:2008MNSSA..67...85S. Retrieved 2018-07-24.
  • Spargo, P. E. (2008). "The History of the Hoba Meteorite Part II: The News Spreads" (PDF). Monthly Notes of the Astronomical Society of Southern Africa. 67 (9/10): 166–177. Bibcode:2008MNSSA..67..166S. Retrieved 2018-07-24.
  • Spargo, P. E. (2008). "The History of the Hoba Meteorite Part III: Known and Loved by All" (PDF). Monthly Notes of the Astronomical Society of Southern Africa. 67 (11/12): 202–211. Bibcode:2008MNSSA..67..202S. Retrieved 2018-07-24.
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