Carbonaceous Chondrites - Main Page

The carbonaceous chondrites or C chondrites represent some of the most pristine matter known, thus far, and their chemical compositions match the chemistry of the Sun more closely than do any other class of chondrites. All carbonaceous chondrites are more or less primitive and undifferentiated meteorites that formed in oxygen- rich regions of the primordial solar nebula so that most of the metal is not found in its free form but in the form of silicates, oxides, or sulfides. Several of them do also contain water or minerals that have been altered in the presence of water, and some of them do even contain certain amounts of carbon as well as different organic compounds, such as amino acids. This is especially true for the carbonaceous chondrites that have been more or less unaltered by heating during their history. E.g., the most primitive carbonaceous chondrites of the CI group have never been heated above 50°C, and they do contain up to 20% of water!

Representing less than 4.5% of all witnessed meteorite falls, carbonaceous chondrites are extremely rare. They are also of highest scientific interest as they also often contain curious calcium-aluminium inclusions (so-called "CAIs"). These CAIs consist of minerals uncommon on Earth, with high concentrations of refractory elements such as titanium, as well as grains of interstellar or pre- solar materials and minerals, including nano-diamonds with strange isotopic patterns that point to an origin outside of our own solar system. Other carbonaceous chondrites do contain amino acids, the building blocks of life and several other organic compounds, as well as substantial amounts of water, raising the question of the origin of life itself!

However, the carbonaceous chondrites do represent a rather heterogenous class and there are different clans and groups of carbonaceous chondrites that formed on their respective parent bodies in different regions of the early solar nebula under different conditions. The main groups of carbonaceous chondrites are designated as the CI chondrites, CM chondrites, CV chondrites, CK chondrites, CO chondrites, CR chondrites, and last but not least, the relatively metal-rich CH chondrites. Each of these groups will be discussed on its own page, as well as two new groups, the CB chondrites, also known as the bencubbinites, and the brand-new MCC group. Besides that, there are some ungrouped carbonaceous chondrites that don’t fit into the existing classification schemes, and several of these "CC UNGs" will also be introduced on a separate page.

Learn more about the different types of carbonaceous chondrites – just follow the respective links.