[Page no. 3.3.1]
[Title: Meteorites]
[Image: Caption: TBD suggest e.g. the famous Orgueil meteorite for historic connection]
[Text:
Meteorites are pieces of rock and metal that fall to the Earth. They are fragments broken from asteroids, with a compositional variation that spans a whole range of planetary materials, from completely unmelted and unfractionated stony chondrites to highly fractionated and differentiated iron meteorites.
These materials, and the components within them carry records of all stages of Solar System history. Study of meteorites allows a more complete understanding of the processes undergone by the material that resulted in today's Earth.
The most significant meteorites, for early Solar System chronology, are the chondrites, the most primitive of all meteorites, which have undergone only mild thermal or hydrothermal metamorphism since accretion into parent-bodies.
Chondrites are composed of high-temperature components (CAIs, chondrules) set in a matrix of fragmented chondrules mixed with minerals formed at lower temperatures. The CAIs (for Calcium, Aluminium-rich Inclusions) are refractory inclusions (up to ~ 1 cm in size) of spinel, hibonite, melilite, etc. Chondrules are spherical to sub-spherical silicate assemblages, up to 1 mm in diameter, that have been partially or totally melted prior to parent-body accretion.
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