Meteorites carbon isotopes

Romanek CS, Grossman EL, Morse JW (1992) Carbon isotopic fractionation in synthetic aragonite and calcite Effects of temperature and precipitation rate. Geochim Cosmochim Acta 56 419-430 Rowe MW, Clayton RN, Mayeda TK (1994) Oxygen isotopes in separated components of Cl and CM meteorites. Geochim Cosmochim Acta 58 5341-5347... 

As is the case for hydrogen, carbon isotope signatures in Martian meteorites present evidence for different carbon reservoirs. Wright et al. (1990) and Ro-manek et al. (1994) distingnished three carbon compounds one component released... 

EmUiani C (1966) Paleotemperature analysis of Caribbean core P6304-8 and P6304-9 and a generalized temperature curve for the past 425000 years. J Geol 74 109-126 Emiich K, Ehhalt DH, Vogel JC (1970) Carbon isotope fractionation during the precipitation of calcium carbonate. Earth Planet Sci Lett 8 363-371 Engel MH, Macko SA, SUfer JA (1990) Carbon isotope composition of individual amino acids in the Murchison meteorite. Nature 348 47-49... 

Carbon isotopic compositions of silicon carbide grains from the Murchison meteorite compared with the carbon isotopic compositions of carbon stars (low- to intermediate-mass AGB stars). The composition of carbon in the solar system is indicated by the vertical line. Note the similarity in the distributions of compositions in the two plots. These data indicate that the silicon carbide in the Orgueil meteorite came from a population of carbon stars very similar to that in the galaxy today. 

Swart, P. K., Grady, M. M. Pillinger, C. T. 19836 A method for the identification and elimination of contamination during carbon isotopic analysis of extraterrestrial material. Meteorites 18, 137-154. 

It appears that FTT reactions can account reasonably well for most features of organic matter in meteorites. The only alternative process, the Miller-Urey synthesis, fails to account for the aliphatic and aromatic hydrocarbons, nitrogen heterocyclics, many oxygen compounds, the polymer, and carbon isotope fractionations, though it remains an alternative and perhaps superior source of amino acids and may, in an extended sense, be responsible for the deuterium enrichments. 

Figure 3 Nitrogen and carbon isotopic ratios of individual presolar SiC grains. Because rare grain types were located by automatic ion imaging, the number of grains of different types do not correspond to their abundances in the meteorites these abundances are given in the legend (sources Alexander, 1993 Hoppe et al, 1994, 1996a Nittler et al, 1995 Huss et al, 1997 Amari et al, 2001a,b,c).

Figure 6 The distributions of carbon isotopic ratios measured in presolar SiC (Hoppe et al, 1994 Nittler et al., 1995) and graphite grains (Hoppe et al., 1995) from the Murchison meteorite are compared to astronomical measurements of the atmospheres of carbon stars (Lambert et al., 1986).

Clayton R. N. (1963) Carbon isotopes in meteoritic carbonates. Science 140, 192-193. 

Grady M. M., Wright 1. P., Swart P. K., and PiUinger C. T. (1988) The carbon and oxygen isotopic composition of meteoritic carbonates. Geochim. Cosmochim. Acta 52, 2855-2866. 

Table 5 Carbon isotope compositions of CO, CO2, carboxybc acids, dicarboxylic acids, and volatile hydrocarbons in the Murchison (CM2), Tagish Lake (Cl), and Orgueil (CIl) meteorites together with hydrogen isotope...

Engel M. H., Macko S. A., and Silfer J. A. (1990) Carbon isotope composition of individual amino acids in the Murchison meteorite. Nature 348, 47-49. 

Yuen G., Blair N., Des Marais D. J., and Chang S. (1984) Carbon isotope composition of low molecular weight hydrocarbons and mono carboxylic acids from Murchison meteorite. Nature 307, 252-254. 

Figure 13 Isotopic composition of C (lull etai, 1997) and O (Valley etal., 1997 Leshin etal., 1998) in carbonates of the ALH84001 martian meteorite. Heavy isotopes correlate with the Mg content of the carbonate.

Stadermann F. J., Walker R. M., and Zinner E. (1989) Ion microprobe measurements of nitrogen and carbon isotopic variations in individual IDPs. Meteoritics 24, 327. 

There now exist numerous observations of mass-independent isotopic compositions in nature. Most of these have recently been reviewed and will not be repeated here. When the first laboratory measurements of the mass-independent isotope effect were reported by Thiemens and Heidenreich (1983), their occurrence in nature was not expected, except possibly for the early solar system to produce the observed meteoritic CAI data. It is significant to note that, at present, all oxygen-bearing molecules in the atmosphere (except water) possess mass-independent isotopic compositions. These molecules include O2, O3, CO2, CO, N2O, H2O2, and aerosol nitrate and sulfate. Mass-independent sulfur isotopic compositions are also observed in aerosol (solid) sulfates and nitrates and sulfide and sulfate minerals from the Precambrian, Miocene volcanic sulfates, Antarctica dry valley sulfates, Namibian Gypretes, and Chilean nitrates. In addition, martian (SNC meteorites) carbonates and sulfates possess both mass-independent sulfur and oxygen isotopic compositions. These studies have been reviewed recently (Thiemens et al., 2001 Thiemens, 1999). 

Distributions in the solar system. More data on volatiles throughout the solar system are clearly required to confidently describe the volatile acquisition history of the terrestrial planets in the proper context. There are several unknown values for the solar composition, including the nitrogen-and carbon-isotope compositions. The compositions of comets from different orbital distances are needed to assess the extent of radial transport of volatiles late in accretion history. In addition, the causes of carbon- and nitrogen-isotope variations in chondrites must be better understood. While it is clear that the Earth cannot be constructed simply by mixing of different meteorite classes, it is not yet possible to unambiguously extrapolate to the volatile compositions of protoplanetary materials. 

LancetM.S., Anders E. (1970) Carbon isotope fractionation in Fischer-Tropsch synthesis and in meteorites. Science 170, 980-2. 

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