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)
  • Acapulcoites
  • Lodranites
  • Brachinites
  • Winonaites
  • Ureilites
• HED (Vesta) meteorites
  • Howardites
  • Eucrites
  • Diogenites
  • Dunite diogenite
  • Olivine diogenites
• Lunar meteorites
• Martian (SNC) meteorites
• Other evolved achondrites
  • Angrites
  • Aubrites

[edit] External links

• http://www.meteorite.fr/en/classification/stonymain.htm
• Achondrite Images from Meteorites Australia - Meteorites.com.au