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A meteorite is a portion of a meteoroid or asteroid that survives its passage through the atmosphere and hits the ground without being destroyed. [22] Meteorites are sometimes, but not always, found in association with hypervelocity impact craters; during energetic collisions, the entire impactor may be vaporized, leaving no meteorites.
Meteoroids enter the Earth's atmosphere from outer space traveling at speeds of at least 11 km/s (7 mi/s) and often much faster. Despite moving through the rarified upper reaches of Earth's atmosphere the immense speed at which a meteor travels rapidly compresses the air in its path.
The mesosphere (/ ˈ m ɛ s ə s f ɪər, ˈ m ɛ z-, ˈ m iː s ə-,-z ə-/; [1] from Ancient Greek μέσος (mésos) 'middle' and -sphere) is the third layer of the atmosphere, directly above the stratosphere and directly below the thermosphere. In the mesosphere, temperature decreases as altitude increases.
Afterglow of the troposphere (orange), the stratosphere (blue) and the mesosphere (dark) at which atmospheric entry begins, leaving smoke trails, such as in this case of a spacecraft reentry. The mesosphere is the third highest layer of Earth's atmosphere, occupying the region above the stratosphere and below the thermosphere.
Some fragments may impact Earth as meteorites, if the meteor starts to break up or explodes in mid-air. These phenomena are then called Earth-grazing meteor processions and bolides . [ 1 ] Famous examples of Earth-grazers are the 1972 Great Daylight Fireball and the Meteor Procession of July 20, 1860 .
Meteorites might look like boring bits of rock – but each one has a fascinating story. Curious Kids: what are meteorites made of and where do they come from? Skip to main content
The stony objects, like chondritic meteorites, tend to burn, break up, or explode before leaving the upper atmosphere. Those that do make it to the surface need a minimum energy of about 10 Mt (4 × 10 16 J ) or about 50 m (160 ft) diameter to breach the lower atmosphere (this is for a stony object hitting at 20 kilometres per second (40,000 mph)).
Meteoritics [note 1] is the science that deals with meteors, meteorites, and meteoroids. [note 2] [2] [3] It is closely connected to cosmochemistry, mineralogy and geochemistry. A specialist who studies meteoritics is known as a meteoriticist. [4]