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• 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

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• 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
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• Conference paper
  Heslop D, Muxworthy AR, 2006,

  Selecting suitable smoothing factors for First-Order Reversal Curve distributions (poster)

  , EGU
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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
  • Author Web Link
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  • Citations: 97
• Conference paper
  Sephton MA, Self S, Verchovsky AB, Grady MM, Perry RS, Engel MH, Wright Iet al., 2006,

  Carbon isotopic gradients in the Martian crust: implications for past or present life on Mars

  , Conference on Instruments, Methods, and Missions for Astrobiology IX, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
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• 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
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• Journal article
  Muxworthy AR, King JG, Odling N, 2006,

  Magnetic hysteresis properties of interacting and non-interacting micron-sized magnetite produced by electron-beam lithography (poster)

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• Conference paper
  Krasa D, Williams W, Wilkinson CD, Gadegaard N, Zhou H, Roberts AP, Muxworthy ARet al., 2006,

  Nanosized Magnetite Particle Assemblages Produced by Electron Beam Lithography (poster)

  , AGU Fall
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• 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
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  • Citations: 3
• Journal article
  Martins Z, Watson JS, Sephton MA, Botta O, Ehenfreund P, Gilmour Iet al., 2006,

  Free dicarboxylic and aromatic acids in the carbonaceous chondrites Murchison and Orgueil

  , Meteoritics & Planetary Science, Vol: 41, Pages: 1073-1080, ISSN: 1086-9379
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• 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
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  • Citations: 37
• Journal article
  Blackhurst RL, Genge MJ, Kearsley AT, Grady MMet al., 2005,

  Cryptoendolithic alteration of Antarctic sandstones: Pioneers or opportunists?

  , JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS, Vol: 110, ISSN: 2169-9097
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  • Citations: 22
• Journal article
  Collins GS, Wünnemann K, 2005,

  How big was the Chesapeake Bay impact?: Insight from numerical modeling

  , GEOLOGY, Vol: 33, Pages: 925-928, ISSN: 0091-7613
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  • Citations: 99
• 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
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  • Citations: 227
• 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
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  • Citations: 25
• Journal article
  Schönbächler M, Rehkämper M, Fehr MA, Halliday AN, Hattendorf B, Günther Det al., 2005,

  Nucleosynthetic zirconium isotope anomalies in acid leachates of carbonaceous chondrites

  , GEOCHIMICA ET COSMOCHIMICA ACTA, Vol: 69, Pages: 5113-5122, ISSN: 0016-7037
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  • Citations: 54
• Journal article
  Fehr MA, Rehkämper M, Halliday AN, Wiechert U, Hattendorf B, Günther D, Ono S, Eigenbrode JL, Rumble Det al., 2005,

  Tellurium isotopic composition of the early solar system -: A search for effects resulting from stellar nucleosynthesis, <SUP>126</SUP>Sn decay, and mass-independent fractionation

  , GEOCHIMICA ET COSMOCHIMICA ACTA, Vol: 69, Pages: 5099-5112, ISSN: 0016-7037
  • Author Web Link
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  • Citations: 36
• 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
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  • Citations: 26
• Conference paper
  Genge MJ, Preston L, 2005,

  Dust-sized meteorite ablation debris among micrometeorites

  , 68th Annual Meeting of the Meteoritical-Society, Publisher: METEORITICAL SOC, Pages: A55-A55, ISSN: 1086-9379
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• Journal article
  Collins GS, Melosh HJ, Marcus RA, 2005,

  Earth Impact Effects Program: A Web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth

  , Meteoritics & Planetary Science, Vol: 40, Pages: 817-840, ISSN: 1086-9379
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