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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. [77] 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.
Chondrules typically constitute between 20% and 80% of a chondrite by volume. [4] Chondrites can be distinguished from iron meteorites by their low iron and nickel content. Non-metallic meteorites that lack chondrules are achondrites, which are believed to have formed more recently than chondrites. [5]
Once it settles on the larger body's surface, the meteor becomes a meteorite. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create an impact crater. [2] Meteorites that are recovered after being observed as they transit the atmosphere and impact Earth are called meteorite falls.
Metallic core formation and cooling can be dated by applying the 187 Re/ 187 Os method to iron meteorites. [12] [13] Large scale impact events or even the destruction of the parent body can be dated using the 39 Ar/ 40 Ar method and the 244 Pu fission track method. [14] After breakup of the parent body meteoroids are exposed to cosmic radiation.
Because ordinary chondrites represent 80% of the meteorites that fall to earth, and because ordinary chondrites contain 60–80% chondrules, it follows that (excluding dust) most of the meteoritic material that falls on earth is made up of chondrules.
The Geminid meteor shower this year is set to peak at almost the same time as December's full moon, ... according to Bill Cooke, lead of NASA's Meteoroid Environment Office. More than half of the ...
Meteorite classification may indicate that a "genetic" relationship exists between similar meteorite specimens. Similarly classified meteorites may share a common origin, and therefore may come from the same astronomical object (such as a planet, asteroid, or moon) known as a parent body. However, with current scientific knowledge, these types ...
The dominance of carbonaceous chondrite-like MMs and their low abundance in meteorite collections suggests that most MMs derive from sources different from those of most meteorites. Since most meteorites derive from asteroids, an alternative source for MMs might be comets. The idea that MMs might originate from comets originated in 1950. [4]