Campo del Cielo

Campo del Cielo refers to a group of iron meteorites and to the area in Argentina where they were found.[1] The site straddles the provinces of Chaco and Santiago del Estero, 1,000 kilometers (620 mi) north-northwest of Buenos Aires, Argentina. It is half that distance, north-east, to Paraguay's capital, Asunción. The crater field covers 3 by 18.5 kilometres (1.9 by 11.5 mi) and contains at least 26 craters, the largest being 115 by 91 metres (377 by 299 ft).[2]

Campo del Cielo
Impact crater/structure
Diameter115 m × 91 m (377 ft × 299 ft) (largest)
Age4200 to 4700 years ago
Holocene
ExposedYes
DrilledYes
Bolide typeCoarse octahedrite to granular hexahedrite
Location
Coordinates27°38′S 61°42′W
CountryArgentina
ProvinceChaco, Santiago del Estero
Location of the craters in Chaco Province, Argentina

The craters' age is estimated as four to five thousand years. Containing iron masses, they were reported in 1576, but were already well known to local aboriginal inhabitants. The craters and their surrounds contain many fragments of an iron meteorite. The total weight of the pieces recovered is about 100 tonnes, making the meteorite possibly the greatest recovery.[3]

The largest two fragments, the 30.8-ton Gancedo and 28.8-ton El Chaco, are among the heaviest single-piece meteorite masses recovered on Earth, along with the 60-ton Hoba and a 31-ton fragment of the Cape York meteorite.

History
"Las Víboras" fragment, exhibited at the Universidad Nacional del Nordeste (Chaco, Argentina)

In 1576, the governor of a province in Northern Argentina commissioned the military to search for a huge mass of iron, which he had heard that natives used for their weapons who claimed that the mass had fallen from the sky in a place they called Piguem Nonralta which the Spanish translated as Campo del Cielo ("Field of heaven (or the sky)"). The expedition found a large mass of metal protruding out of the soil. They assumed it was an iron mine and brought back a few samples, which were described as being of unusual purity. The governor documented the expedition and deposited the report in the Archivo General de Indias in Seville, but it was quickly forgotten and later local reports merely repeated the Native legends.

Following the legends, in 1774 Don Bartolomé Francisco de Maguna rediscovered the iron mass which he called el Mesón de Fierro ("the Table of Iron"). Maguna thought the mass was the tip of an iron vein. The next expedition, led by Rubin de Celis in 1783, used explosives to clear the ground around the mass and found that it was probably a single stone. Celis estimated its mass as 15 tonnes and abandoned it as worthless. He himself did not believe that the stone had fallen from the sky and assumed that it had formed by a volcanic eruption. However, he sent the samples to the Royal Society of London and published his report in the Philosophical Transactions of the Royal Society.[4] Those samples were later analyzed and found to contain 90% iron and 10% nickel and assigned to a meteoritic origin.[5]

Later, many iron pieces were found in the area weighing from a few milligrams to 34 tonnes. A mass of about 1 tonne known as Otumpa was found in 1803. A 634-kilogram (1,398 lb) portion of this mass was taken to Buenos Aires in 1813, then donated to the British Museum. Other large fragments are summarized in the table below. The mass called el Taco was originally 3,090 kilograms (6,810 lb), but the largest remaining fragment weighs 1,998 kilograms (4,405 lb).[6]

The second-largest mass of 28,840 kg named El Chaco was found in 1969 5 metres (16 ft) down using a metal detector.[5] It was extracted in 1980 and estimated to weigh around 37 tonnes. This stone was at the time the second heaviest meteorite after the Hoba in Namibia of about 60 tonnes. The total mass of the Campo del Cielo fragments found so far exceeds 60 tonnes, making it the heaviest set of such finds on Earth.[7]

In 1990 a local Argentine highway police officer foiled a plot by Robert Haag to steal El Chaco; having gone abroad it was returned to Campo del Cielo and is now protected by provincial law.[8]

In 2015, police arrested four alleged smugglers trying to steal more than a ton of protected meteorites.[9]

In 2016, the largest-known meteorite of the record-tonnage strewn field was unearthed. Named the Gancedo meteorite after the nearby town of Gancedo which lent equipment to aid in the extraction, this nickel-iron meteorite has a mass of 30,800 kg. Originally, it was thought to weigh less than "El Chaco". Due to a suspected lack of precision when "El Chaco" was weighed in 1980, the latter was then reweighed with the same instruments and it was discovered that it only had a mass of 28,840 kg, thus less than Gancedo.[10][11]

The meteorite impact, age and composition
Campo del Cielo
Campo del Cielo iron meteorite with natural hole, 576 grams
TypeIron
Structural classificationOctahedrite
GroupIAB
Composition92.9% Fe, 6.7% Ni, 0.4% Co
CountryArgentina
RegionChaco Province and Santiago del Estero Province
Coordinates27°38′S 61°42′W
Observed fallNo
Fall date4,000–5,000 years ago
Found date<1576
TKW>100 tonnes
Strewn fieldYes
Related media on Wikimedia Commons
"La Perdida" fragment, 1530 kg

A crater field of at least 26 craters was found in the area, with the largest being 115 by 91 metres (377 by 299 ft). The field covered an area of 3 by 18.5 kilometres (1.9 by 11.5 mi) with an associated strewn area of smaller meteorites extending farther by about 60 kilometres (37 mi). At least two of the craters contained thousands of small iron pieces. Such an unusual distribution suggests that a large body entered the Earth's atmosphere and broke into pieces which fell to the ground. The size of the main body is estimated as larger than 4 meters in diameter. The fragments contain an unusually high density of inclusions for an iron meteorite, which might have facilitated the disintegration of the original meteorite. Samples of charred wood were taken from beneath the meteorite fragments and analyzed for carbon-14 composition. The results indicate the date of the fall to be around 4,200–4,700 years ago, or 2,200–2,700 years BC.[2][5] The age is estimated to be 4.5 billion years old, formed as part of the development of our solar system.

The average composition of the Campo del Cielo meteorites is 6.67% Ni, 0.43% Co, 0.25% P, 87 ppm Ga, 407 ppm Ge, and 3.6 ppm Ir, with the remaining 92.6% being iron.[5][12]

Major fragments of the Campo del Cielo meteorite[12][13][14][15][16]
Mass (tonnes) Name Year of discovery
>15 el Meson de Fierro or Otumpa (missing) 1576
>0.8 Runa Pocito or Otumpa 1803
4.21 el Toba 1923
0.02 el Hacha 1924
0.73 el Mocovi 1925
0.85 el Tonocote 1931
0.46 el Abipon 1936
1 el Mataco 1937
2 el Taco 1962
1.53 la Perdida 1967
3.12 las Viboras 1967
28.8 el Chaco 1969 (extracted in 1980)
>10 Tañigó II (missing) 1997
15 la Sorpresa 2005
7.85 el Wichí or Meteorito Santiagueño 2006
30.8 Gancedo 2016

See also

References
  1. "Campo del Cielo". Earth Impact Database. Planetary and Space Science Centre University of New Brunswick Fredericton. Retrieved 2017-10-10.
  2. Bobrowsky, Peter T.; Rickman, Hans (2007). Comet/asteroid impacts and human society: an interdisciplinary approach. Springer. pp. 30–31. ISBN 978-3-540-32709-7.
  3. Viano, Lucas (19 June 2015). "Meteorite Thefts Pose a Problem in Ancient Impact Field". Scientific American. Retrieved 31 March 2017. Of the 300 tons that impacted, one third has been recovered.
  4. de Celis, Michael Rubin (1788). Joseph Banks. "An account of a mass of native iron found in South America". Philosophical Transactions of the Royal Society. London. 78: 183–189. doi:10.1098/rstl.1788.0004.
  5. McCall, G. J. H.; Bowden, A. J.; Howarth, R. J., eds. (2006). The History of Meteoritics and Key Meteorite Collections: Fireballs, Falls and Finds. Geological Society. pp. 28–30. ISBN 978-1-86239-194-9.
  6. Giménez Benítez, S. R.; López, A. M.; Mammana, L. A. "Meteoritos de Campo del Cielo: Impactos en la cultura aborigen" (in Spanish). El Taco: Hexahedrita de 3090kg. Hoy, luego de sucesivas fragmentaciones, su parte más grande tiene un peso de 1998kg.
  7. "Campo del Cielo". Planetarium de Montreal. Archived from the original on 2009-06-25. Retrieved 2009-07-07.
  8. Aeberhard, Danny; Benson, Andrew; Phillips, Lucy (2000). The Rough Guide to Argentina. Rough Guides. p. 370. ISBN 1-85828-569-0.
  9. "Four arrested in Argentina smuggling more than ton of meteorites". AFP. May 30, 2015.
  10. Ferrara, Michele (Oct 25, 2016). "The second biggest meteorite discovered" (PDF). Free Astronomy Magazine. No. November–December 2016. Astro Publishing. p. 10. Retrieved Sep 19, 2018.
  11. "2nd-largest meteorite in world, weighing nearly 68K pounds, found in Argentina". Fox News Latino. Sep 13, 2016.
  12. Buchwald, Vagn F. (1975). The Handbook of Iron Meteorites, Their History, Distribution, Composition and Structure. 2. Berkeley: University of California Press. ISBN 0-520-02934-8. Archived from the original on 2012-11-24.
  13. Grady, Monica M.; Natural History Museum, London (2000). Catalogue of meteorites (5th ed.). Cambridge University Press. p. 126. ISBN 0-521-66303-2.
  14. Wright, S. P.; Vesconi, M. A.; Gustin, A.; Williams, K. K.; Ocampo, A. C.; Cassidy, W. A. (2006). "Revisiting the Campo del Cielo, Argentina crater field: A new data point from a natural laboratory of multiple low velocity, oblique impacts" (PDF). Lunar and Planetary Science. XXXVII: 1102. Bibcode:2006LPI....37.1102W.
  15. Rocca, M. C. L.; et al. (2006). "A catalogue of large meteorite specimens from Campo del Cielo meteorite shower, Chaco province, Argentina" (PDF). 69th Annual Meteoritical Society Meeting: 5501.
  16. Compacto Nea (2016-09-12). "Video del momento histórico en que extraen el meteorito 'Gancedo'". Retrieved 2016-09-13.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.