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  • Other Sources  (6)
  • 1990-1994  (6)
  • 1985-1989
  • 1925-1929
  • 1991  (6)
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  • 1990-1994  (6)
  • 1985-1989
  • 1925-1929
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  • 1
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    Stable hydrogen and carbon isotope ratios of extractable hydrocarbons in the Murchison meteorite (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A fairly fool-proof method to ensure that the compounds isolated from meteorites are truly part of the meteorites and not an artifact introduced by exposure to the terrestrial environment, storage, or handling is presented. The stable carbon and hydrogen isotope ratios in several of the chemical compounds extracted from the Murchison meteorite were measured. The results obtained by studying the amino acids in this meteorite gave very unusual hydrogen and carbon isotope ratios. The technique was extended to the different classes of hydrocarbons and the hydrocarbons were isolated using a variety of separation techniques. The results and methods used in this investigation are described in this two page paper.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., 22nd Lunar and Planetary Science Conference; p 39-40
    Format: application/pdf
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  • 2
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    Implanted 3He, 4He, and Xe in further studies of diamonds from Western Australia (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: In measurements of the noble gases in additional samples of diamonds from the Argyle and Ellendale lamproites in Western Australia we have failed to encounter any neon-rich stones such as showed solar-like isotopic compositions in earlier work. No neon was detected above the relatively high blank levels in our glass apparatus. White and brown diamonds showed no differences in noble gas content, nor did samples segregated by the color of long-wave UF fluorescence. The rare gas patterns in the 1.2 Ga Argyle pipe are largely consistent with implanted 3He, 4He, and fissiogenic Xe from U/Th in the matrix rock in which the diamonds have been stored for so long. These implanted species are absent in diamonds from the much younger (approximately 20 Ma) Ellendale pipe. We give implantation formulae for several models of inhomogeneously distributed U/Th. Differences in 3He content between pipe and alluvial Argyle samples are consistent with expected cosmogenic production in the latter. An expanded data base for helium and carbon isotopic data on the same samples supports a negative [4He]-delta 13C correlation seen earlier in work from our group, but if the Argyle samples, which contain light carbon, are corrected for implanted 4He, the correlation is considerably weakened. We no longer see an earlier 3He/4He-delta 13C correlation.
    Keywords: Exobiology
    Type: Geochimica et cosmochimica acta (ISSN 0016-7037); 55; 1977-89
    Format: text
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  • 3
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    Isotopic composition of hydrogen in insoluble organic matter from cherts (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Robert (1989) reported the presence of unusually enriched hydrogen in the insoluble HF-HCl residue extracted from two chert samples of Eocene and Pliocene ages. Since the presence of heavy hydrogen might be due to the incorporation of extraterrestrial materials, we desired to reexamine the same samples to isolate the D-rich components. Our experiments did not reveal any D-rich components, but the hydrogen isotope composition of the insoluble residue of the two chert samples was well within the range expected for terrestrial organic matter. We also describe a protocol that needs to be followed in the hydrogen isotope analysis of any insoluble organic matter.
    Keywords: Exobiology
    Type: Geochimica et cosmochimica acta (ISSN 0016-7037); 55; 2985-8
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  • 4
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    Correlated Si isotope anomalies and large C-13 enrichments in a family of exotic SiC grains (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A hypothesis is presented to the effect that the distinctive morphological characteristics and comparatively simple Si isotope systematics identify the platy SiC crystals as a genetically related family, formed around a single isotopically heterogeneous presolar star on an association of related stars. The enrichments in C-13 and the Si isotope systematics of the platy SiC are broadly consistent with theoretical models of nucleosynthesis in low-mass, carbon stars on the ASG. The Si isotope array most plausibly reflects mixing between (Si-28)-rich material, inherited from a previous generation of stars, and material enriched in Si-29 and Si-30, produced in intershell regions by neutron capture during He-burning. The absence of a correlation between the Si and C isotopic compositions of the SiC suggests either episodic condensation of SiC, extending over several thermal pulses, in the atmosphere of a single star, or the derivation of the SiC from several stars characterized by different rates of C-13 production.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters (ISSN 0012-821X); 107; 4-Mar
    Format: text
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  • 5
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    Implanted He-3, He-4, and Xe in further studies of diamonds from Western Australia (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: In measurements of the noble gases in additional samples of diamonds from the Argyle and Ellendale lamproites in Western Australia, no neon-rich stones were encountered. No neon was detected above the relatively high blank levels in the glass apparatus. White and brown diamonds showed no differences in noble gas content, nor did samples segregated by the color of long-wave UF fluorescence. The rare gas patterns in the 1.2 Ga Argyle pipe are largely consistent with implanted He-3, He-4, and fissiogenic Xe from U/Th in the matrix rock in which the diamonds have been stored for so long. These implanted species are absent in diamonds from the much younger (about 20 Ma) Ellendale pipe. Implantation formulas for several models of inhomogeneously distributed U/Th are given. Differences in He-3 content between pipe and alluvial Argyle samples are consistent with expected cosmogenic production in the latter. An expanded data base for helium and carbon isotopic data on the same samples supports a negative (He-4)-delta(C-13) correlation seen in earlier work.
    Keywords: GEOPHYSICS
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 55; 1977-198
    Format: text
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  • 6
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    Isotopic analyses of amino acids from the Murchison meteorite (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: An account is given of the results of H-2, C-13 isotopic analyses of the Murchison meteorite incorporating an ultrafiltration step to exclude the possibility of fine particulate contaminants. The meteorite's amino acids were chromatographically separated in order to preclude isotopic enrichment by basic compounds other than the amino acids. The results indicate that the Murchison amino acids are isotopically highly unusual; delta-C-13 is elevated by about 40 percent, and delta-D by fully 2500 percent. This high D content of the meteorite's alpha-amino acids may be due to the synthesis of their molecular precursors by low-temperature ion-molecule reactions in an interstellar cloud.
    Keywords: SPACE BIOLOGY
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 55; 905-910
    Format: text
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