Carbon Isotope Abundance in Meteoritic Carbonates.

The C(13)/C(12) ratio in the carbonate minerals of Orgueil, a carbonaceous chondrite, is 6 percent greater than the ratio in any known terrestrial carbon. The effect may be produced by a chemical isotope fractionation involving processes not common on earth, or it may be the result of incomplete homogenization of substances with different histories of nucleosynthesis.