Meteor Crater Museum

Meteor Crater, or Barringer Crater, is a meteorite impact crater about east of Flagstaff and 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 Cañon Diablo. Because the United States Board on Geographic Names recognizes names of natural features derived from the nearest post office, the feature acquired the name of "Meteor Crater" from the nearby post office named Meteor.

Meteor Crater lies at an elevation of above sea level. It is about in diameter, some deep, and is surrounded by a rim that rises above the surrounding plains. The center of the crater is filled with of rubble lying above crater bedrock. One of the interesting 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.

Despite historic attempts to make the crater a public landmark, the crater remains privately owned by the Barringer family to the present day through their Barringer Crater Company, which proclaims it to be the "best-preserved meteorite crater on Earth". Since the crater is privately owned, it is not protected as a national monument, a status that would require federal ownership. It was designated a National Natural Landmark in November 1967.

Formation

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. The area was an open grassland dotted with woodlands inhabited by mammoths and giant ground sloths.

The object that excavated the crater was a nickel- iron meteorite about across. The speed of the impact has been a subject of some debate. Modeling initially suggested that the meteorite struck at up to , but more recent research suggests the impact was substantially slower, at . About half of the impactor's bulk is believed to have been vaporized during its descent through the atmosphere. Impact energy has been estimated at about 10 megatons TNT_e. The meteorite was mostly vaporized upon impact, leaving few remains in the crater.

Since the crater's formation, the rim is thought to have lost of height at the rim crest as a result of natural erosion. Similarly, the basin of the crater is thought to have roughly of additional postimpact sedimentation from lake sediments and alluvium. 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.

Discovery and investigation

The 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". The Meteoritical Society refers to the crater as Barringer Meteorite Crater because Daniel M. Barringer was one of the first people to suggest that it was produced by meteorite impact, and because the Barringer family filed mining claims on the crater and purchased the crater and its surroundings in the early 20th century. Meteorites from the area were 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 were found. The crater had initially been ascribed to the actions of a volcanic steam explosion, because the San Francisco volcanic field lies only about to the west.

Albert E. Foote

In 1891, mineralogist Albert E. Foote presented the first scientific paper about the meteorites of Northern Arizona. 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 . Foote identified several minerals in the meteorites, including diamond, albeit of little commercial value. His paper to the Association for the Advancement of Science provided the first geological description of the crater to a scientific community.

Grove Karl Gilbert

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. Gilbert had assumed that if it were an impact crater, then the volume of the crater, as well as meteoritic material, should exist in the rim. Gilbert also assumed a large portion of the meteorite should be buried in the crater and that this would generate a large magnetic anomaly. Gilbert's calculations showed that the volume of the crater and the debris on the rim were roughly equivalent, so that the mass of the hypothetical impactor was missing, nor were there any magnetic anomalies; he argued that the meteorite fragments found on the rim were coincidental. Gilbert publicized his conclusions in a series of lectures. In 1892, however, Gilbert would be among the first to propose that the Moon's craters were caused by impact rather than volcanism.

Daniel M. Barringer

In 1903, mining engineer and businessman Daniel M. Barringer suggested that the crater had been produced by the impact of a large iron-metallic meteorite. Barringer's company, the Standard Iron Company, staked a mining claim to the land and received a land patent signed by Theodore Roosevelt for 640 acres (1 sq mi, 260 ha) around the center of the crater in 1903. The claim was divided into four quadrants coming from the center clockwise from north-west named Venus, Mars, Jupiter, and Saturn. In 1906, Roosevelt authorized the establishment of a newly named Meteor, Arizona, post office (the closest post office before was away in Winslow, Arizona). This new post office was located at Sunshine, a stop on the Atchison, Topeka and Santa Fe Railway, 6 mi north of the crater.

Standard Iron Company conducted research on the crater's origins between 1903 and 1905. It concluded that the crater had indeed been caused by an impact. Barringer and his partner, mathematician and physicist Benjamin Chew Tilghman, documented evidence for the impact theory in papers presented to the U.S. Geological Survey in 1906 and published in the ''Proceedings of the Academy of Natural Sciences'' in Philadelphia.

Barringer's arguments were met with skepticism, as a reluctance existed at the time to consider the role of meteorites in terrestrial geology. He persisted and sought to bolster his theory by locating the remains of the meteorite. At the time of discovery, the surrounding plains were covered with about 30 tons of large, oxidized iron meteorite fragments. This led Barringer to believe that the bulk of the 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 vaporized on impact. He spent 27 years trying to locate a large deposit of meteoric iron, and drilled to a depth of , but no significant deposit was ever found.

Barringer, who in 1894 was one of the investors who made US$15 million in the Commonwealth silver mine in Pearce, Cochise County, Arizona, had ambitious plans for the iron ore.Southgate, Nancy; Barringer, Felicity (2002). ''A Grand Obsession: Daniel Moreau and His Crater''. Barringer Crater Co. He estimated from the size of the crater that the meteorite had a mass of 100 million tons. Iron ore of the type found at 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. "By 1928, Barringer had sunk the majority of his fortune into the crater – $500,000, or roughly $7 million in 017dollars."

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. Daniel M. 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."

Harvey H. Nininger

Harvey Harlow Nininger was an American meteoriticist and educator, and although he was self-taught, he revived interest in 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. In 1942, Harvey Nininger moved his home and business from Denver to the Meteor Crater Observatory, located near the turn-off for Meteor Crater on Route 66. He renamed 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 features still unique to the crater, 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). 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.

Harvey Nininger believed that the crater should be nationalized as a public park, and in 1948, successfully petitioned the American Astronomical Society to pass a motion in support by giving the false claim that the Barringers were willing to sell it, when in fact they intended to continue mining there. Nininger was operating a private meteorite museum on the premises at the time, and perhaps he saw public ownership of the crater as an opportunity to move his museum to the rim, obtain a government salary, and possibly found a Federal institute of meteorite science. The Barringer family promptly terminated his exploration rights and ability to conduct further fieldwork at the crater.

Eugene M. Shoemaker

Later research by Eugene Merle Shoemaker confirmed that the crater had formed due to a significant asteroid impact. 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. It cannot be created by volcanic action; the only known mechanisms of creating it are naturally through an impact event, or artificially through a nuclear explosion. 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. The impact would have vaporized much of the main body of iron mass. The pieces of Canyon Diablo meteorite found scattered around the site would have broken away from the main body before impact.

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.

Geology

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. Specifically, climbing the rim of the crater from outside, one finds:
* Coconino Sandstone ( sandstone formed 265 million years ago) nearest the top of the rim
* Toroweap Formation ( limestone formed 255 million years ago)
* Kaibab Formation ( dolostone formed 250 million years ago)
* Moenkopi Formation (mudstone formed 245 million years ago) nearest the outer foot of the rim

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.

Recent history

During the 1960s and 1970s, NASA astronauts trained in the crater to prepare for the Apollo missions to the Moon.

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. A small portion of the wreckage not removed from the crash site remains visible.

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."

Tourist attraction

Meteor Crater is a popular tourist destination with roughly 270,000 visitors per year. The crater is owned by a family company, the Barringer Crater Company. Meteor Crater is an important educational and research site. It was used to train Apollo astronauts and continues to be an active training site for astronauts. 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 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, 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.

See also

* Barringer Medal
* List of impact craters on Earth
* Elugelab – a smaller-volume nuclear blast crater, despite being created by an object with an almost identical estimated energy release as the Barringer event, 10.4 megatons.

References

External links

Barringer Crater official site

Meteor Crater Visitor Center
nbsp;– official site

USGS Meteor Crater Sample Collection
nbsp;– historical documents, interactive map and sample requests
*

Impact Meteor Crater Viewer
Google Maps Page with Locations of Meteor Craters around the world


shows that the meteor may have been traveling more slowly than previously thought

Computer generated movie
based on satellite imagery and topography data

Aerial Exploration of the Barringer Structure

Geologic Map of the Eastern Quarter of the Flagstaff 30ʹ x 60ʹ Quadrangle, Coconino County, Northern Arizona
United States Geological Survey
*

Herman Leroy Fairchild: An Early Promoter and Defender of Meteorite Impact Cratering
nbsp;– includes details of early investigations into Meteor Crater

3 Dimensional stereoscopic image pair of the Barringer Crater by Volkan Yuksel (arranged for crossed-eye viewing technique)

Guidebook to the Geology of Barringer Meteorite Crater, Arizona (a.k.a. Meteor Crater)

"Mine Shaft is Sunk to Solve Meteor Mystery"
''Popular Mechanics'', January 1930

''Milwaukee Sentinel'' – Dec 14, 1941 "Metal in Arizona Meteorite may solve defense problem"
US Govt. considered mining nickel from the crater for the war effort.

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Impact craters of the United States
National Natural Landmarks in Arizona
Pleistocene impact craters
Tourist attractions along U.S. Route 66
Museums in Coconino County, Arizona
Science museums in Arizona
Geology museums in Arizona
Landforms of Coconino County, Arizona
Tourist attractions in Coconino County, Arizona