Some carbonaceous chondrites. From left to right: Allende, Yukon and Murchison.

A carbonaceous chondrite or a C-type chondrite is a type of chondritic meteorite which contains high levels of water and organic compounds, representing only a small proportion (~5%) of known meteorites. Their bulk composition is mainly silicates, oxides and sulfides, whilst the minerals olivine and serpentine are characteristic. The presence of volatile organic chemicals and water indicates that they have not undergone significant heating (>200°C) since they formed, so their composition is considered to be representative of the solar nebula from which the solar system condensed. Image File history File links Carbonaceous_chondrites. ... Image File history File links Carbonaceous_chondrites. ... Chondrules in the chondrite Grassland. ... A meteorite is a small extraterrestrial body that reaches the Earths surface. ... Water (from the Old English word wæter; c. ... An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with the exception of carbides, carbonates, carbon oxides and gases containing carbon. ... In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. ... An oxide is a chemical compound of oxygen with other chemical elements. ... In chemistry, a sulfide (sulphide in British) is a chemical compound or combination of sulfur with an oxidation number of -2, with another chemical element or a radical thereof. ... Olivine The mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)2SiO4 in which the ratio of magnesium and iron varies between the two endmembers of the series: forsterite (Mg-rich) and fayalite (Fe-rich). ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg,Fe)3Si2O5(OH)4) minerals; it is also often rich in other metal ores, including chromium, manganese, cobalt and nickel. ... In cosmogony, the solar nebula is the gaseous cloud (or accretion disc) from which our solar system is believed to have formed. ... Presentation of the solar system (not to scale) The solar system comprises our Sun and the retinue of celestial objects gravitationally bound to it. ...

Carbonaceous chondrites are grouped according to dinstinctive compositions thought to reflect the type of parent body from which they originated. These are named after a prominent meteorite - often the first to be discovered - in the group.

Some famous carbonaceous chondrites are: Orgueil, Ivuna, Murray, Murchison, Tagish Lake. On May 14, 1864 the carbonaceous chondrite Orgueil meteorite landed near Orgueil in southern France. ... Fragment of the Murchison meteorite (at right) and isolated individual particles (shown in the test tube). ...

CI group

This group, named after the Ivuna meteorite, are considered the least altered of all carbonaceous chondrites. They typically contain a high proportion of water (up to 20%), and organic matter in the form of amino acids and PAHs. Aqueous alteration promotes a composition of hydrous phyllosilicates, magnetite, and olivine crystals occurring in a black matrix, and a possible lack of chondrules. It is thought they have not been heated above 50°C, indicating that they condensed in the cooler outer portion of the solar nebula. In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... Pah: God of the Moon. ... The silicate minerals make up the the largest and most important class of rock-forming minerals. ... Magnetite is a ferromagnetic mineral form of iron(II,III) oxide, with chemical formula , one of several iron oxides and a member of the spinel group. ... Olivine The mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)2SiO4 in which the ratio of magnesium and iron varies between the two endmembers of the series: forsterite (Mg-rich) and fayalite (Fe-rich). ... Chondrules in the chondrite Grassland. ...

There are only 5 known CI chondrites: Ivuna, Orgueil, Alais, Tonk and Revelstoke. On May 14, 1864 the carbonaceous chondrite Orgueil meteorite landed near Orgueil in southern France. ...

Ehrenfreund et al. (2001) found that amino acids in 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 AIB and isovaline. This implies that they had formed by a different synthetic pathway, and on a different parent body from the CM chondrites. Alanine is one of the 20 most common natural amino acids. ... Glycine (Gly, G) is a nonpolar amino acid. ...

External links

• CI chondrites at The Meteorite Catalogue Database

References

• Carbonaceous chondrites at The Encyclopedia of Astrobiology, Astronomy, and Spaceflight
• Ehrenfreund, P., Glavin, D., Botta, O., Cooper, G. and Bada, J. Extraterrestrial amino acids in Orgueil and Ivuna: Tracing the parent body of Cl type carbonaceous chondrites. Proceedings of the national academy of sciences of the united states of america, 98(5):2138 -- 2141, 2001.
• Gilmour I, Wright I, Wright J 'Origins of Earth and Life', The Open University, 1997, ISBN 0749281820