Nitrogen isotope fractionations in the Fischer-Tropsch synthesis and in the Miller-Urey reaction

Abstract Nitrogen isotope fractionations have been measured in Fischer-Tropsch and Miller-Urey reactions in order to determine whether these processes can account for the large 15 N/ 14 N ratios found in organic matter in carbonaceous chondrites. Polymeric material formed in the Fischer-Tropsch reaction was enriched in 15 N by only 3‰ relative to the starting material (NH 3 ). The 15 N enrichment in polymers from the Miller-Urey reaction was 10–12‰. Both of these fractionations are small compared to the 80–90‰ differences observed between enstatite chondrites and carbonaceous chondrites. These large differences are apparently due to temporal or spatial variations in the isotopic composition of nitrogen in the solar nebula, rather than to fractionation during the production of organic compounds.