Meteorites

Some meteorites record and can reveal the conditions in the protoplanetary disk. Many meteorites date from 4.5 billion years ago.

There are several basic types of meteorites:

  • stony meteorites -- make up 95% of all meteorites. Represent outer parts of disrupted asteroids. Two subclasses:
    chondrites: contain chondrules, which are glassy spherules -- melted material from the formation of the Solar System.
    achondrites: contain no chondrules.
  • stony-irons -- 1% of all meteorites. Some stony material, some iron material. Come from core-mantle boundary of disrupted asteroid.
  • irons -- 4% of all meteorites. Come from core of disrupted asteroids.

    Interesting sub-subclass: carbonaceous chondrites, which have water and carbon compounds -- and often amino acids -- in them.

    There are also known meteorites from the Moon and from Mars.

    A convenient reference guide (which also answers the question, "How do I know if this cool rock I just picked up is a meteorite?") can be found here.

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