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chondrite

An abundant class of stony meteorites with chemical compositions similar to that of the Sun and characterized by the presence of chondrules. Chondrites come from asteroids that did not melt when formed and are designated as H, L, LL, E, or C depending on chemical compositions. The H, L, and LL types are called ordinary chondrites. The L chondrites are composed of silicate minerals (mostly olivine and pyroxene, but feldspar as well), metallic nickel-iron, and iron sulfide (called troilite). Most L chondrites are severely shocked-damaged, probably by a large impact on the asteroid in which they formed. The E type are called enstatite chondrites, a rare type that formed under very reducing conditions and are composed primarily of a magnesium silicate called enstatite. They are subdivided into the low-iron (EL) chemical group and the high-iron (HL) group. The C (or carbonaceous) chondrites contain water-bearing minerals and carbon compounds including a variety of organic molecules such as amino acids. Carbonaceous chondrites are the most primitive meteorites--primitive in a chemical way. For example, the CI group of carbonaceous chondrites are closest in composition to the photosphere (visible surface) of the Sun.

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