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Meteor Crater

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Template:Short description Template:Hatnote group Template:Use mdy dates Template:Infobox terrestrial impact site

Meteor Crater, or Barringer Crater, is an impact crater about Template:Convert east of Flagstaff and Template:Convert west of Winslow in the desert of northern Arizona, United States. The site had several earlier names, and fragments of the meteorite are officially called the Canyon Diablo Meteorite, after the adjacent Canyon Diablo.<ref>La Pas, L. (1943). "Remarks on four notes recently published by C. C. Wylie", Popular Astronomy, vol. 51, p. 341</ref>

Meteor Crater lies at an elevation of Template:Convert above sea level.<ref>Images of America: Meteor Crater (p. 107), Neal F. Davis, Arcadia Publishing, 2016. Template:ISBN.</ref> It is about Template:Convert in diameter, some Template:Convert deep, and is surrounded by a rim that rises Template:Convert above the surrounding plains. The center of the crater is filled with Template:Convert of rubble lying above crater bedrock.<ref name="EID"/> One of the features of the crater is its squared-off outline, believed to be caused by existing regional jointing (cracks) in the strata at the impact site.<ref>Template:Cite book</ref>

Despite an attempt to make the crater a public landmark,<ref name=Plotkin>Template:Cite journal</ref> the crater remains privately owned by the Barringer family to the present day through their Barringer Crater Company. The Lunar and Planetary Institute, the American Museum of Natural History, and other science institutes proclaim it to be the "best-preserved meteorite crater on Earth".<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It was designated a National Natural Landmark in November 1967.<ref name=nps_nnl>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

FormationEdit

File:Meteoroid size comparison.svg
Comparison of approximate sizes of notable impactors with the Hoba meteorite, a Boeing 747 and a New Routemaster bus

The crater was created about 50,000 years ago during the Pleistocene epoch, when the local climate on the Colorado Plateau was much cooler and damper.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> The area was an open grassland dotted with woodlands inhabited by mammoths and giant ground sloths.<ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The object that excavated the crater was a nickel-iron meteorite about Template:Convert across. The speed of the impact has been a subject of some debate. Modeling initially suggested that the meteorite struck at up to Template:Cvt, but more recent research suggests the impact was substantially slower, at Template:Cvt. About half of the impactor's bulk is believed to have been vaporized during its descent through the atmosphere.<ref name="r1">Template:Cite journal</ref> Impact energy has been estimated at 10 megatons TNTe. The meteorite was mostly vaporized upon impact, leaving few remains in the crater.<ref>Schaber, Gerald G. "The U.S. Geological Survey, Branch of Astrogeology – A Chronology of Activities from Conception through the End of Project Apollo (1960–1973)", 2005, U.S. Geological Survey Open-File Report 2005-1190. (PDF)</ref>

Since the crater's formation, the rim is thought to have lost Template:Convert of height at the rim crest as a result of natural erosion. Similarly, the basin of the crater is thought to have roughly Template:Convert of additional postimpact sedimentation from lake sediments and alluvium.<ref>Template:Cite journal</ref> Very few remaining craters are visible on Earth, since many have been erased by erosive geological processes. The relatively young age of Meteor Crater, paired with the dry Arizona climate, has allowed this crater to remain comparatively unchanged since its formation. The lack of erosion that preserved the crater's shape greatly accelerated its groundbreaking recognition as an impact crater from a natural celestial body.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Discovery and investigationEdit

File:Meteor Crater 08 2010 151.JPG
The Holsinger fragment, at roughly 0.8 m (2½ ft) across, is the largest discovered piece of the meteorite that created Meteor Crater, and it is exhibited in the crater visitor center.

Meteor Crater came to the attention of scientists after American settlers encountered it in the 19th century. The crater was given several early names, including "Coon Mountain", "Coon Butte", "Crater Mountain", "Meteor Mountain," and "Meteor Crater."<ref name="Farrington 1906">Template:Cite journal</ref><ref>Template:Cite book</ref><ref name="Fairchild 1907">Template:Cite journal</ref> Daniel M. Barringer was one of the first people to suggest that the crater was produced by a meteorite impact, with the Barringer family filing mining claims and purchasing it and its surroundings in the early 20th century.<ref>Grieve, R.A.F. (1990) "Impact Cratering on the Earth", Scientific American, 262 (4), 66–73.</ref><ref name="bbarr1964">Template:Cite journal</ref> This led to the crater also being known as "Barringer Crater."<ref name="tbcceop">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=lpibsp>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Meteorites from the area are called Canyon Diablo meteorites, after Canyon Diablo, Arizona, which was the closest community to the crater in the late 19th century. The canyon also crosses the strewn field, where meteorites from the crater-forming event are found. The crater was initially assumed to have been formed by a volcanic steam explosion; evidence of geologically recent volcanic activity occurs across this part of Arizona – the southeastern edge of the San Francisco volcanic field is only about Template:Convert northwest of Meteor Crater.<ref>Template:Cite book</ref>

Albert E. FooteEdit

In 1891, mineralogist Albert E. Foote presented the first scientific paper about the meteorites of Northern Arizona.<ref>Template:Cite journal</ref><ref name="Foote 1891">Template:Cite journal</ref> Several years earlier, Foote had received an iron rock for analysis from a railroad executive. Foote immediately recognized the rock as a meteorite and led an expedition to search and retrieve additional meteorite samples. The team collected samples ranging from small fragments to over Template:Cvt. Foote identified several minerals in the meteorites, including microscopic diamonds. His paper to the Association for the Advancement of Science provided the first geological description of Meteor Crater to a scientific community.<ref name="Kring 2007">Template:Cite book</ref>

Grove Karl GilbertEdit

In November 1891, Grove Karl Gilbert, chief geologist for the U.S. Geological Survey, investigated the crater and concluded that it was the result of a volcanic steam explosion.<ref name="Kring 2007"/> Gilbert assumed that, if it were an impact crater, then the volume of the crater, as well as meteoritic material, should still be present in the crater's rim. Gilbert also assumed a large portion of the meteorite should be buried in the crater and that this should generate a large magnetic anomaly. Gilbert's calculations showed that the volume of the crater and the debris on the rim were roughly equivalent, which meant that the mass of the hypothetical impactor was missing. There were also no detectable magnetic anomalies; he argued that the meteorite fragments found on the rim were coincidental or placed there. Gilbert publicized his conclusions in a series of lectures.<ref name=barringercrater.com>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In 1892, Gilbert would be among the first scientists to propose that the Moon's craters were caused by impact rather than volcanism.<ref name=Cosmic_Debris>Template:Cite book</ref>

Daniel M. BarringerEdit

File:Barringer-1001.jpg
Looking into the crater from the north rim: The rust-colored area on the far (south) rim is where the last drilling for the meteorite occurred, in 1929. This is where Daniel M. Barringer believed the bulk of the meteorite was buried. Rock around the south rim is visibly uplifted.

Mining engineer and businessman Daniel M. Barringer suspected that the crater had been produced by the impact of a large iron meteorite.<ref>Template:Cite journal From p. 885: "That this great hole in the upper strata of the Aubrey formation was made at the instant of time when the meteor fell upon this exact spot. Having proved these facts, the conclusion is unavoidable that this hole, which as we have seen cannot have been produced by a volcano or by a steam explosion, was produced by the impact of the meteor, […] "</ref> The theory that the crater was of meteoric origin had been met with skepticism. At the time, the craters visible on the Moon were thought to be volcanic, and no one had conclusively proved that impact craters existed.

Barringer had amassed a small fortune as an investor in the successful Commonwealth Mine in Pearce, Cochise County, Arizona. Barringer believed that the bulk of the Meteor Crater impactor could still be found under the crater floor. Impact physics was poorly understood at the time, and Barringer was unaware that most of the meteorite had vaporized on impact. Barringer incorporated a company, the Standard Iron Company, and staked a mining claim on the land, hoping to mine the asteroid that had produced the crater.<ref name="ReferenceA">Southgate, Nancy; Barringer, Felicity (2002). A Grand Obsession: Daniel Moreau and His Crater. Barringer Crater Co.</ref> He estimated from the size of the crater that the meteorite had a mass of 10 million tons.<ref name="barringercrater.com"/>

The metal content of the iron meteorites found around the crater was valued at the time at US$125/ton, so Barringer was searching for a lode he believed to be worth more than a billion 1903 dollars.<ref name="ReferenceA"/> "By 1928, Barringer had sunk the majority of his fortune into the crater – $500,000, or roughly $7 million in 2017 dollars."<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Barringer spent 27 years trying to locate the nonexistent deposit of meteoric iron, and drilled to a depth of Template:Convert, but no significant deposit was ever found.<ref>Template:Cite book</ref>Template:Self-published inline

Barringer was politically well-connected. He received a land patent signed by Theodore Roosevelt for 640 acres (1 sq mi, 260 ha) around the center of the crater in 1903.<ref name=DRO-GS2002>Template:Cite book</ref><ref name=RJHowarth-GS2006>Template:Cite book</ref><ref name="bbarr1964" /> In 1906, at his request, President Roosevelt also authorized the establishment of a post office unconventionally named "Meteor", located at Sunshine, a stop on the Atchison, Topeka and Santa Fe Railway, Template:Convert north of the crater.<ref>Template:Cite book</ref> The Meteor post office closed on April 15, 1912, due to disuse.

File:Meteorite fragment from the Cañon Diablo Meteorite.jpg
Fragment of the Canyon Diablo meteorite

In 1929, astronomer F.R. Moulton was employed by the Barringer Crater Company to investigate the physics of the impact event. Moulton concluded that the impactor likely weighed as little as 300,000 tonnes, and that the impact of such a body would have generated enough heat to vaporize the impactor instantly.<ref name=Meteor_Crater_Report_I>Template:Cite book</ref><ref name=Meteor_Crater_Report_II>Template:Cite book</ref><ref>Template:Cite journal</ref> Barringer died just ten days after the publication of Moulton's second report.

By this time, "the great weight of scientific opinion had swung around to the accuracy of the impact hypothesis ... Apparently an idea, too radical and new for acceptance in 1905, no matter how logical, had gradually grown respectable during the intervening 20 years."<ref>Template:Cite journal</ref>

Harvey H. NiningerEdit

Harvey Harlow Nininger was an American meteoriticist and educator, and he initiated a widespread interest in the scientific study of meteorites in the 1930s, and assembled the largest personal collection of meteorites up to that time. While based in Denver, Colorado, Nininger published the first edition of a pamphlet titled "A Comet Strikes the Earth", which described how Meteor Crater formed when an asteroid impacted the Earth.<ref>Template:Cite book</ref> In 1942, Nininger moved his home and business from Denver to the Meteor Crater Observatory, located near the turn-off for Meteor Crater on Route 66.<ref>Template:Cite book</ref> He christened the building the "American Meteorite Museum" and published a number of meteorite and Meteor Crater-related books from the location. He also conducted a wide range of research at the crater, discovering impactite, iron-nickel spherules related to the impact and vaporization of the asteroid, and the presence of many other features, such as half-melted slugs of meteoric iron mixed with melted target rock. Nininger's discoveries were compiled and published in a seminal work, Arizona's Meteorite Crater (1956).<ref>Template:Cite book</ref> Nininger's extensive sampling and fieldwork in the 1930s and 40s contributed significantly to the scientific community's acceptance of the idea that Meteor Crater formed by the impact of an asteroid.<ref>Template:Cite journal</ref> Many of his discoveries were later observed at other relatively fresh impact craters, including Henbury and Monturaqui.

Nininger believed that the crater should be a national monument and, in 1948, he successfully petitioned the American Astronomical Society to pass a motion in support of nationalizing the crater by making "the unauthorized - and false - claim that the [Barringers] would be receptive to a fair purchase for the crater."<ref name="Plotkin" /> By this time, mining activity at the crater had ceased, and the Barringers were in the process of planning a tourist attraction on the rim of the crater. Nininger was operating the American Meteorite Museum nearby, on Route 66, at the time. Nininger hoped that a public museum could be built on the crater's rim, and that the project might lead to the founding of a federal institute of meteorite research.<ref name=Plotkin/> Offended by Nininger's attempt to nationalize the crater, the Barringer family promptly terminated his exploration rights and ability to conduct further fieldwork at the crater.<ref name=Plotkin/> A few years later, in 1953, the Standard Iron Company was renamed the "Barringer Crater Company," and a private museum was constructed on the crater rim.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Eugene M. ShoemakerEdit

File:Barringer Crater aerial photo by USGS.jpg
Meteor Crater from the southeast; the uplift around the rim can be seen

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Eugene Merle Shoemaker continued investigations at the crater. A key discovery was the presence in the crater of the minerals coesite and stishovite, rare forms of silica found only where quartz-bearing rocks have been severely shocked by an instantaneous overpressure. Shocked quartz cannot be created by volcanic action; the only known mechanisms of creating it are naturally through lightning or an impact event, or artificially, through a nuclear explosion.<ref name=DRO-GS2002 /><ref>Shoemaker, Eugene M. (1987). "Meteor Crater, Arizona", Geological Society of America Centennial Field Guide – Rocky Mountain Section.</ref> In 1960, Edward C. T. Chao and Shoemaker identified coesite at Meteor Crater, adding to the growing body of evidence that the crater was formed from an impact generating extremely high temperatures and pressures. He confirmed what F.R. Moulton and H.H. Nininger already proposed: the impact vaporized the vast majority of the impactor. The pieces of Canyon Diablo meteorite found scattered around the site broke away from the main body before and during the impact.<ref name="Levy">Template:Cite book</ref> Shoemaker published his conclusions in his 1974 book, the Guidebook to the geology of Meteor Crater, Arizona.<ref name="Shoemaker1974">Template:Cite book</ref>

Geologists used the nuclear detonation that created the Sedan crater, and other such craters from the era of atmospheric nuclear testing, to establish upper and lower limits on the kinetic energy of the meteor impactor.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

GeologyEdit

The impact created an inverted stratigraphy, so that the layers immediately exterior to the rim are stacked in the reverse order to which they normally occur; the impact overturned and inverted the layers to a distance of 1–2 km outward from the crater's edge.<ref>Template:Cite book</ref><ref name=stratigraphy>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Specifically, climbing the rim of the crater from outside, one finds:

Soils around the crater are brown, slightly to moderately alkaline, gravelly or stony loam of the Winona series; on the crater rim and in the crater itself, the Winona is mapped in a complex association with rock outcrop.<ref name="USDASoil">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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ClimateEdit

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Template:AnchorTemplate:AnchorRecent historyEdit

During the 1960s and 1970s, NASA astronauts trained in the crater to prepare for the Apollo missions to the Moon,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite book</ref> and ongoing field training for astronauts continues to this day.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

File:Barringer crater as viewed from airplane (cropped).jpg
Barringer crater as viewed from airplane

On August 8, 1964, two commercial pilots in a Cessna 150 flew low over the crater. After crossing the rim, they could not maintain level flight. The pilot attempted to circle in the crater to climb over the rim. During the attempted climb out, the aircraft stalled, crashed, and caught fire. The plane is commonly reported to have run out of fuel, but this is incorrect. Both occupants were severely injured, but survived.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> A small portion of the wreckage not removed from the crash site remains visible.<ref>Plane Crash At Meteor Crater Revisited, September 1, 2008 Meteorite-times.com</ref>

In 2006, a project called METCRAX (for METeor CRAter eXperiment) investigated "the diurnal buildup and breakdown of basin temperature inversions or cold-air pools and the associated physical and dynamical processes accounting for their evolving structure and morphology."<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Tourist attractionEdit

Meteor Crater is a popular tourist destination with roughly 270,000 visitors per year.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The crater is owned by a family company, the Barringer Crater Company.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Meteor Crater is an important educational and research site.<ref>D. A. Kring, 2017, Guidebook to the Geology of Barringer Meteorite Crater, Arizona (aka Meteor Crater), Second edition, Lunar and Planetary Institute (Contribution No. 2040), Houston, 272p. </ref> It was used to train Apollo astronauts and continues to be an active training site for astronauts.<ref>D. A. Kring, C. A. Looper, Z. A. Ney, and B. A. Janoiko, with foreword by G. Griffin, 2020, Training for Lunar Surface Operations (p. 12), Lunar and Planetary Institute (Contribution No. 2576), Houston, 40p. https://www.lpi.usra.edu/science/kring/lunar_exploration/Artemis-Major-Skills-Training_DV1_2_w-appendix.pdf</ref><ref>N. F. Davis, 2016, Images of America: Meteor Crater, Arcadia Publishing, Charleston, 127p.</ref> The Meteor Crater Visitor Center sits on the north rim of the crater. It features interactive exhibits and displays about meteorites and asteroids, space, the Solar System, and comets including the American Astronaut Wall of Fame and such artifacts on display as an Apollo boilerplate command module (BP-29), a Template:Convert meteorite found in the area, and meteorite specimens from Meteor Crater that can be touched. Formerly known as the Museum of Astrogeology, the Visitor Center includes a Discovery Center & Space Museum,<ref>"Meteor Crater". Meteor Crater. Retrieved 2022-6-24. </ref> a movie theater, a gift shop, and observation areas with views inside the rim of the crater. Guided tours of the rim are offered daily, weather permitting.<ref>Template:Cite news</ref>

See alsoEdit

ReferencesEdit

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External linksEdit

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