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.
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 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, 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. No further bolide-induced extinction events have been securely identified as yet, however. Compare Tollmann's hypothetical bolide for an example of bolide speculations in currently popular alternative geology.
Noteworthy bolide impacts include:
See also