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How to Classify Meteorites

Meteorites are otherworldly rocks that fall from the skies and strike the earth. They can vary in size, from a tiny pebble to huge rocks more than 3,000 feet in diameter. They can have minimal effects on their landing site, such as those found in deserts, or they can alter the course of history, as the giant meteor that struck the Yucatan peninsula did 65 million years ago. Scientists have devised multiple classification systems based on a meteor's material makeup, with the ultimate goal of identifying from which interplanetary body the meteorite originated.

Instructions

- 1
  Determine if the meteorite is differentiated or differentiated. Undifferentiated meteorites contain material that has not undergone a melting process, while differentiated meteorites have been in a molten state.
- 2
  Determine if the meteorite is a chondrite, achondrite or an iron. Chondrites are always undifferentiated, achondrites can sometimes be differentiated if they are primitive achondrites, and irons and stony-irons are always differentiated. Between 80 and 85 percent of all meteorites are chondrites.
- 3
  Classify the chondrite group into carbonaceous, ordinary, rumuruti or enstatite chondrites. These four types are further classified based on their mineral composition. Carbonaceous chondrites contain large amounts of organic compounds, ordinary chondrites are just common stony meteorites, rumuruti chondrites are nearly entirely made of oxidized iron and enstatite chondrites have a high percentage of enstatite and iron that has been reduced to its metallic form.
- 4
  Classify the achondrite group based on their origin, which can be martian, aubrites, ureilites, angrites, lunar or HED, which are howardites, eucrites, diogenites. Aubrites contain enstatite but no chondrules, ureilites are composed of magnesian olivine, pyroxenes, nickel-iron and graphite, and angrites are made primarily of pyroxene fassaite. The HED group originated from the Vesta asteroid, and are classified based on the depth of the asteroid's surface from which they came: Howardites from the crust, followed by eucrites in a middle layer and diogenites near the core.
- 5
  Categorize Martian achondrites, originating from the planet as shergottites, nakhlites or chassigny. Shergottite meteorites are mostly olivine and pigeonite, along with plagioclase feldspar. Nakhlites are extremely rare; their composition is mainly augite, formed in Martian magma flows. Chassigny achondrites, named after the French town where in 1815 the first meteorite of this subgroup fell, is mostly olivine and some noble gases.
- 6
  Classify the stony-iron group into pallasites or mesosiderites, and the iron group into IA, IIA, IIB, IIIA, IVA or others. Pallasites are believed to come from the core of a differentiated asteroid, while mesosiderites come from the crust. The iron group is determined by plotting the amount of germanium, gallium or iridium against the amount of nickel present.

Astronomy