Morokweng crater
Encyclopedia
The Morokweng crater is an impact crater
buried beneath the Kalahari Desert
near the town of Morokweng in the Northwest Province of South Africa, close to the border with Botswana
.
The crater, formed by an asteroid 5 to 10 km (3.1 to 6.2 mi) in diameter, is at least about 160 km (99.4 mi) in diameter and the age is estimated to be 145.0 ± 0.8 million years, placing it on the Jurassic
–Cretaceous
boundary. 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.
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 (2,526.2 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. Some of the fragments can be seen in the Antenna Wing of London's Science Museum
.
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
buried beneath the Kalahari Desert
Kalahari Desert
The Kalahari Desert is a large semi-arid sandy savannah in Southern Africa extending , covering much of Botswana and parts of Namibia and South Africa, as semi-desert, with huge tracts of excellent grazing after good rains. The Kalahari supports more animals and plants than a true desert...
near the town of Morokweng in the Northwest Province of South Africa, close to the border with Botswana
Botswana
Botswana, officially the Republic of Botswana , is a landlocked country located in Southern Africa. The citizens are referred to as "Batswana" . Formerly the British protectorate of Bechuanaland, Botswana adopted its new name after becoming independent within the Commonwealth on 30 September 1966...
.
The crater, formed by an asteroid 5 to 10 km (3.1 to 6.2 mi) in diameter, is at least about 160 km (99.4 mi) in diameter and the age is estimated to be 145.0 ± 0.8 million years, placing it on the Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
–Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
boundary. Discovered in 1994, it is not exposed at the surface but has been mapped by magnetic and gravimetric
Gravimetry
Gravimetry is the measurement of the strength of a gravitational field. Gravimetry may be used when either the magnitude of gravitational field or the properties of matter responsible for its creation are of interest...
surveys. Core samples have shown it to have been formed by the impact of an L chondrite
L chondrite
The L type ordinary chondrites are the second most common type of meteorite, accounting for approximately 35% of all those catalogued, and 40% of the ordinary chondrites....
asteroid.
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
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
at a depth of 770 m (2,526.2 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. Some of the fragments can be seen in the Antenna Wing of London's Science Museum
Science Museum (London)
The Science Museum is one of the three major museums on Exhibition Road, South Kensington, London in the Royal Borough of Kensington and Chelsea. It is part of the National Museum of Science and Industry. The museum is a major London tourist attraction....
.