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CI chondrites and the closely related CM chondrites are very rich in volatile substances, especially in water. It is assumed that they originally formed in the outer asteroid belt, at a distance surpassing 4 AU – the reason for this being the so-called snow line situated at this distance and representing a temperature of 160 K. At these ...
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).
Nagy B, Claus G, Hennessy DJ (1962) Organic Particles Embedded in Minerals in Orgueil and Ivuna Carbonaceous Chondrites. Nature 193 (4821) p. 1129 Fitch FW, Anders E (1963) Organized Element - Possible Identification in Orgueil Meteorite.
They are classified on the same rank (historically called "Class") and lying between chondrites and achondrites. They are called primitive because they are achondrites that have retained much of their original chondritic properties. Very characteristic are relic chondrules and chemical compositions close to the composition of chondrites. These ...
Carbonaceous chondrites compose about 4 percent of all meteorites observed to fall from space. Prior to 1969, the carbonaceous chondrite class was known from a small number of uncommon meteorites such as Orgueil, which fell in France in 1864. Meteorites similar to Allende were known, but many were small and poorly studied. [3]