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  • Journal article
    Ehrenfreund P, Sephton MA, 2006,

    Carbon molecules in space: from astrochemistry to astrobiology

    , FARADAY DISCUSSIONS, Vol: 133, Pages: 277-288, ISSN: 1359-6640
  • Journal article
    Court RW, Sephton MA, Parnell J, Gilmour Iet al., 2006,

    The alteration of organic matter in response to ionising irradiation: Chemical trends and implications for extraterrestrial sample analysis

    , Geochimica et Cosmochimica Acta, Vol: 70, Pages: 1020-1039

    Ionising radiation is an energy source capable of generating and altering complex organic matter. A full understanding of the radiolytic formation and devolution of organic matter is essential to appreciate the budget of organic chemicals that exist in cometary and interstellar ices, carbonaceous meteorites, and to understand the results of analyses of irradiated extraterrestrial organic matter, such as that in cometary nuclei. The effects of ionising radiation on a set of 10 naturally occurring, terrestrial organic assemblages have been revealed by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), carbon isotopic analysis, and stepped combustion-isotope ratio mass spectrometry (SC-IRMS). Progressive radiolytic alteration of biogenic complex-hydrocarbon mixtures induces a decrease in the average size and extent of alkylation of polyaromatic hydrocarbons (PAH) and an increase in the abundance of oxygen-containing compounds, as indicated by Py-GC-MS, and an enrichment in C-13. These changes are attributed to reactions with free radicals, produced by ionising radiation. In contrast, the progressive radiolytic alteration of bitumens proposed to have derived from the radiolytic polymerisation of methane into an organic solid produces, upon pyrolysis, PAH of increasing average size and degree of alkylation. This, the opposite of the trend observed in the irradiated complex-hydrocarbons mixtures, cannot be explained in terms of the radiolytic alteration of a pre-existing array of complex organic molecules. Instead, it suggests the gradual construction of PAH from smaller molecules, supporting the hypothesis of a methane origin. Radiolytic alteration is also associated with a previously unrecognised increase in the mean combustion temperature of organic matter. This leads to predictions regarding the combustion characteristics of the irradiated organic matter present on cometary nuclei. A full understanding of the relationship between the combustion characteristics

  • Book chapter
    Bland PA, Zolensky ME, Benedix GK, Sephton MAet al., 2006,

    Weathering of chondritic meteorites

    , Meteorites and the Early Solar System II, Editors: Lauretta, McSween, Lauretta, McSween, Arizona, Publisher: University of Arizona Press, Pages: 853-867, ISBN: 9780816525621
  • Conference paper
    Sephton MA, Perry RS, Hoover RB, 2006,

    Thiophenes as indicators of aqueous alteration in carbonaceous meteorites

    , Conference on Instruments, Methods, and Missions for Astrobiology IX, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
  • Journal article
    Perry RS, Lynne BY, Sephton MA, Kolb VM, Perry CC, Staley JTet al., 2006,

    Baking black opal in the desert sun: the importance of silica in desert varnish, 2006, Geology, 34, 537-540

    , Geology, Vol: 34, Pages: 537-540, ISSN: 0091-7613
  • Journal article
    Sephton MA, 2005,

    Organic matter in carbonaceous meteorites: past, present and future research

    , PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 363, Pages: 2729-2742, ISSN: 1364-503X
  • Journal article
    Sephton MA, Looy CV, Brinkhuis H, Wignall PB, de Leeuw JW, Visscher Het al., 2005,

    Catastrophic soil erosion during the end-Permian biotic crisis

    , GEOLOGY, Vol: 33, Pages: 941-944, ISSN: 0091-7613
  • Journal article
    Bada JL, Sephton MA, Ehrenfreund P, Mathies RA, Skelley AM, Grunthaner FJ, Zent AP, Quinn RC, Josset JL, Robert F, Botta O, Glavin DPet al., 2005,

    New strategies to detect life on Mars

    , ASTRONOMY & GEOPHYSICS, Vol: 46, Pages: 26-27, ISSN: 1366-8781
  • Journal article
    Montgomery W, Zaug JM, Howard WM, Goncharov AF, Crowhurst JC, Jeanloz Ret al., 2005,

    Melting curve and high-pressure chemistry of formic acid to 8 GPa and 600 K

    , JOURNAL OF PHYSICAL CHEMISTRY B, Vol: 109, Pages: 19443-19447, ISSN: 1520-6106
  • Journal article
    Sephton MA, Love GD, Meredith W, Snape CE, Sun CG, Watson JSet al., 2005,

    Hydropyrolysis: A new technique for the analysis of macromolecular material in meteorites

    , PLANETARY AND SPACE SCIENCE, Vol: 53, Pages: 1280-1286, ISSN: 0032-0633
  • Journal article
    Verchovsky AB, Sephton MA, 2005,

    A noble record

    , ASTRONOMY & GEOPHYSICS, Vol: 46, Pages: 12-14, ISSN: 1366-8781
  • Journal article
    Goncharov AF, Manaa MR, Zaug JM, Gee RH, Fried LE, Montgomery WBet al., 2005,

    Polymerization of formic acid under high pressure

    , PHYSICAL REVIEW LETTERS, Vol: 94, ISSN: 0031-9007
  • Conference paper
    Perry RS, Kolb VM, Lynne BY, Sephton MA, Mcloughlin N, Engel MH, Olendzenski L, Brasier M, Staley JTet al., 2005,

    How desert varnish forms? (art. no. 59060V)

    , Conference on Astrobiology and Planetary Missions, Publisher: The International Society for Optical Engineering, Pages: 1-12
  • Conference paper
    Sephton MA, Looy CV, Visscher H, Brinkhuis H, de Leeuw JWet al., 2005,

    The combined petrographic and chemical analysis of end-Permian kerogens

    , 8th International Meeting on Response of the Earth System to Impact Processes (IMPACT), Pages: 467-478

    The end of the Permian was marked by one of the greatest mass extinctions of all time. A valuable record of life and death during this event is contained within sedimentary organic matter. The stable isotopic, molecular and morphological information contained within remains of end-Permian organisms represent an important resource for scientists attempting to produce paleoenvironment reconstructions. Most meaningful data derive from multidisciplinary analyses of the same samples. In these circumstances it is desirable that sample preparation for one approach does not hinder subsequent analysis by another. To ensure compatibility of sample processing procedures the petrographic and chemical consequences of two common kerogen preparation steps, demineralization and screening (sieving), were simultaneously monitored using transmitted light microscopy and flash pyrolysis. Two end-Permian sediments, whose organic content was predominated by land-plant debris, were chosen for this purpose. A limestone was used to assess the problem of fluoride production when dematerializing carbonates and a marl was used to investigate the possibility of introducing a sampling bias following kerogen screening. Flash pyrolysis results of demineralization residues indicate that neoformed fluorides can be effectively removed by repeated treatments with excess concentrated HCl. Flash pyrolysis of screened size fractions (< 10 mu m, 10-18 mu m, 18-30 mu m, 30-125 mu m, 125-250 mu m, > 250 mu m) suggest that, for the end-Permian kerogen used, the various fractions are qualitatively representative of the unscreened kerogen. In a paleoenvironmental context, the homogeneity of the land plant derived kerogen reflects a period of organic accumulation on land followed by rapid deposition and burial in a marine setting. These findings constitute a step forward in the quest for parity between petrographic and chemical analyses of the same kerogen samples.

  • Journal article
    Sephton MA, Meredith W, Sun CG, Snape CEet al., 2005,

    Hydropyrolysis of steroids: a preparative step for compound-specific carbon isotope ratio analysis

    , RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Vol: 19, Pages: 3339-3342, ISSN: 0951-4198
  • Journal article
    Sephton MA, Botta O, 2005,

    Recognizing life in the solar system: guidance from meteoritic organic matter

    , INT J ASTROBIOL, Vol: 4, Pages: 269-276, ISSN: 1473-5504
  • Conference paper
    Perry RS, Kolb VM, Philip A I, Lynne BY, Mcloughlin N, Sephton MA, Wacey D, Green ORet al., 2005,

    Making silica rock coatings in the lab: synthetic desert varnish (art. no. 59060U)

    , Conference on Astrobiology and Planetary Missions, Publisher: The International Society for Optical Engineering, Pages: 1-11
  • Journal article
    Watson JS, Sephton MA, Looy CV, Gilmour Let al., 2005,

    Oxygen-containing aromatic compounds in a Late Permian sediment

    , ORGANIC GEOCHEMISTRY, Vol: 36, Pages: 371-384, ISSN: 0146-6380
  • Journal article
    Sephton MA, Meredith W, Sun CG, Snape CEet al., 2005,

    Hydropyrolysis as a preparative method for the compound-specific carbon isotope analysis of fatty acids

    , RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Vol: 19, Pages: 323-325, ISSN: 0951-4198
  • Journal article
    Koeberl C, Farley KA, Peucker-Ehrenbrink B, Sephton MAet al., 2004,

    Geochemistry of the end-Permian extinction event in Austria and Italy: No evidence for an extraterrestrial component

    , GEOLOGY, Vol: 32, Pages: 1053-1056, ISSN: 0091-7613

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