Achondrite
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An achondrite is a stony meteorite that is made of material similar to terrestrial basalts or plutonic rocks. Compared to the chondrites, they have all been differentiated and reprocessed to a lesser or greater degree due to melting and recrystallization on or within meteorite parent bodies. As a result, achondrites have distinct textures and mineralogies indicative of igneous processes.
Achondrites account for about 8% of meteorites overall, and the majority (about two thirds) of them are HED meteorites, originating from the crust of asteroid 4 Vesta. Other types include Martian, Lunar, and several types thought to originate from other as-yet unidentified asteroids. These groups have been determined on the basis of e.g. the Fe/Mn chemical ratio and the 17O/18O oxygen isotope ratios, thought to be characteristic "fingerprints" for each parent body.
Achondrites are classified into the following groups:
* Primitive achondrites (PAC group)
o Acapulcoites
o Lodranites
o Brachinites
o Winonaites
o Ureilites
* HED (Vesta) meteorites
o Howardites
o Eucrites
o Diogenites
o Dunite diogenite
o Olivine diogenites
* Lunar meteorites
* Martian (SNC) meteorites
* Other evolved achondrites
o Angrites
o Aubrites
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