Bolide
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The term bolide (from the Greek βολις, bolis, missile) can refer to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface.
The object itself is a meteoroid; the streak of light is a meteor (or shooting star). If the meteor is brilliant enough to cast shadows, it is a fireball. Finally, if the object appears to explode, it is called a detonating fireball or bolide; an alternate definition holds that it is a bolide if sound can be heard coming from its passage. (Example: 3 December 2005 near Albany in south-west Western Australia [link].)
When used in the first sense, the bolide may explode either on impact with the Earth's surface or at a low altitude above it, creating a large impact crater. It is a generic term that does not imply the nature of the impacting body, i.e., whether it is a rocky or metallic meteorite, asteroid, icy comet, etc. Some scientists suggest that a glancing collision with a planet about the mass of Mars, called Theia, ca. 4.5 billion years ago, may have formed the Moon.
Since the Chicxulub bolide has been suggested as the cause of the extinction event that exterminated the dinosaurs 65 million years ago, bolides are frequently suggested as causes of major climate changes and mass extinctions. However, no further bolide-induced extinction events have yet been securely identified. Compare Tollmann's hypothetical bolide for an example of bolide speculations in currently popular alternative geology.
Noteworthy bolide impacts include:
- Vredefort Crater in South Africa, the largest known impact crater on Earth (300 km diameter from an estimated 10 km wide bolide).
- Sudbury Basin in Ontario, Canada (250 km diameter).
- Chicxulub Crater off the coast of Yucatan (170 km diameter)
- Manicouagan Reservoir in Québec, Canada (100 km diameter)
- Popigai crater in Russia (100 km diameter)
- Acraman crater in South Australia (90 km diameter)
- Chesapeake Bay impact crater (90 km diameter)
- Mjølnir impact crater in the Barents Sea (40 km diameter)
- Silverpit crater in the North Sea (2.4 km diameter)
- Barringer crater in Arizona, also known as 'Meteor Crater' (1.2 km diameter)
- Manson crater in Iowa (38 km crater is buried)
- Tunguska event in Siberia 1908 (no crater)
- Vitim event in Siberia 2002 (no crater)
See also
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