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CI chondrites, also called C1 chondrites or Ivuna-type carbonaceous chondrites, are a group of rare carbonaceous chondrite, a type of stony meteorite. They are named after the Ivuna meteorite , the type specimen .
Ehrenfreund et al. (2001) [9] found that amino acids in CI chondrites Ivuna and Orgueil were present at much lower concentrations than in CM chondrites (~30%), and that they had a distinct composition high in β-alanine, glycine, γ-ABA, and β-ABA but low in α-aminoisobutyric acid (AIB) and isovaline. This implies that they had formed by a ...
CM chondrites are composed of about 70% fine-grained material (matrix), and most have experienced extensive aqueous alteration. The much studied Murchison meteorite, which fell in Australia in 1969, is the best-known member of this group. CO chondrites have only about 30% matrix and have experienced very little aqueous alteration.
The CM group most resembles the CI and CO chondrites; a CM–CO is sometimes described. [7] [8] [9] All three groups contain clearly anomalous 50 Ti and 54 Cr isotopes. [10] [11] Though the C-chondrites are far rarer than ordinary chondrites, the CM group is "the most abundant type of" them.
Because ordinary chondrites represent 80% of the meteorites that fall to earth, and because ordinary chondrites contain 60–80% chondrules, it follows that (excluding dust) most of the meteoritic material that falls on earth is made up of chondrules. Chondrules can range in diameter from just a few micrometers to over 1 centimetre (0.39 in).
In chondritic mixing models, the compositions of chondrites are used to estimate planetary compositions. For example, one model mixes two components, one with the composition of C1 chondrites and one with just the refractory components of C1 chondrites.
The element is present in all meteorites; carbonaceous chondrites and enstatite chondrites in particular have higher sulfur contents than the ordinary chondrites. In C1 and C2 chondrites, sulfur is found predominantly as free sulfur, sulfate minerals, and in organic compounds at a net 2–5 percent. [41]
Robert H. McNaught (born in Scotland [citation needed] in 1956 [citation needed]) is a Scottish-Australian astronomer at the Research School of Astronomy and Astrophysics of the Australian National University (ANU).