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Journal articleWatson JS, Sephton MA, Sephton SV, et al., 2007,
Rapid determination of spore chemistry using thermochemolysis gas chromatography-mass spectrometry and micro-Fourier transform infrared spectroscopy
, PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES, Vol: 6, Pages: 689-694, ISSN: 1474-905X- Author Web Link
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- Citations: 45
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Journal articleSiegert MJ, Behar A, Bentley M, et al., 2007,
Exploration of Ellsworth Subglacial Lake: a concept paper on the development, organisation and execution of an experiment to explore, measure and sample the environment of a West Antarctic subglacial lake
, Reviews in Environmental Science and Biotechnology, Vol: 6, Pages: 161-179, ISSN: 1569-1705 -
Journal articlePerry RS, Sephton MA, 2007,
Baking black opal in the desert sun: The importance of silica in desert varnish: comment and reply
, GEOLOGY, Vol: 35, Pages: e123-e123, ISSN: 0091-7613 -
Journal articleParbhakar A, Cuadros J, Sephton MA, et al., 2007,
Adsorption of L-lysine on montmorillonite
, COLLOID SURFACE A, Vol: 307, Pages: 142-149, ISSN: 0927-7757Amino acid adsorption on smectite is relevant to prebiotic processes involving possible catalytic reactions in the early Solar System, as implied by the clay-organic correlation found in meteorites, and the generation and modification of organic components essential for the origin of life. Here we report the results of a study investigating the adsorption of l-lysine (0.025–0.4 M) onto montmorillonite. The reaction products were studied using X-ray diffraction, chemical analysis and infrared spectroscopy.We find that lysine adsorption is first dominated by cation exchange and then by adsorption of electrically neutral lysine (as a zwitterion), as indicated by chemical and FTIR evidence. At the maximum concentration, lysine displaces only ∼1/3 of the original interlayer cations. The d-spacing of the smectite–lysine complex increases from 1.2 to 2.1 nm as more lysine enters the interlayer space, and water is expelled. We propose a structural model of lysine sorption in the interlayer in which lysine is oriented at >45–90◦ to the plane of siloxane O atoms.
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Journal articleWignall PB, Zonneveld J-P, Newton RJ, et al., 2007,
The end Triassic mass extinction record of Williston Lake, British Columbia
, PALAEOGEOGR PALAEOCL, Vol: 253, Pages: 385-406, ISSN: 0031-0182 -
Journal articlePearson VK, Kearsley AT, Sephton MA, et al., 2007,
The labelling of meteoritic organic material using osmium tetroxide vapour impregnation
, PLANET SPACE SCI, Vol: 55, Pages: 1310-1318, ISSN: 0032-0633 -
Journal articleCourt RW, Sephton MA, Parnell J, et al., 2007,
Raman spectroscopy of irradiated organic matter
, GEOCHIM COSMOCHIM AC, Vol: 71, Pages: 2547-2568, ISSN: 0016-7037Raman spectroscopy of a range of irradiated and nonirradiated natural terrestrial bitumens has revealed that radiolytic alteration is generally associated with an increase in structural disorganisation. An interpretational methodology designed to overcome the considerable difficulties in obtaining reproducible, meaningful parameters of structural disorganisation is also presented, and should prove useful for future Raman applications. Raman investigation of a set of bitumens reported to have formed by the radiolytic polymerisation of light hydrocarbons, such as methane, has revealed excessive structural disorganisation, relative to biogenic complex-hydrocarbon-derived bitumens of similar radioelement concentrations, which may indicate the importance of precursor materials on the organic products of irradiation. Variations in the R1 ratio (D1/G band intensity) are found to be the best guide to variations in structural organisation. Comparisons of Raman spectra of the same sample, but produced by different exciting wavelengths, reveal the importance of the selection of a suitable laser wavelength. The results are discussed in terms of analyses of irradiated organic matter in the solar system, especially cometary nuclei and carbonaceous chondrites.
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Journal articleParnell J, Cullen D, Sims MR, et al., 2007,
Searching for Life on Mars: Selection of Molecular Targets for ESA’s Aurora ExoMars Mission
, Astrobiology, Vol: 7, Pages: 578-604, ISSN: 1531-1074The European Space Agency’s ExoMars mission will seek evidence of organic compounds of biological and non-biological origin at the martian surface. One of the instruments in the Pasteur payload may be a Life Marker Chip that utilizes an immunoassay approach to detect specific organic molecules or classes of molecules. Therefore, it is necessary to define and prioritize specific molecular targets for antibody development. Target compounds have been selected to represent meteoritic input, fossil organic matter, extant (living, recently dead) organic matter, and contamination. Once organic molecules are detected on Mars, further information is likely to derive from the detailed distribution of compounds rather than from single molecular identification. This will include concentration gradients beneath the surface and gradients from generic to specific compounds. The choice of biomarkers is informed by terrestrial biology but is wide ranging, and nonterrestrial biology may be evident from unexpected molecular distributions. One of the most important requirements is to sample where irradiation and oxidation are minimized, either by drilling or by using naturally excavated exposures. Analyzing regolith samples will allow for the search of both extant and fossil biomarkers, but sequential extraction would be required to optimize the analysis of each of these in turn.
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Journal articleCockell CS, Kennerley N, Lindstrom M, et al., 2007,
Geomicrobiology of a weathering crust from an impact crater and a hypothesis for its formation
, Geomicrobiology Journal: an international journal of geomicrobiology and microbial biogeochemistry, Vol: 24, Pages: 425-440Understanding the role of microbe-mineral interactions in rock weathering is vital to an understanding of nutrient availability to the biosphere and, in so far as weathering influences carbon dioxide drawdown, climate control. We studied a weathering crust on a resurge tsunami deposit (Loftarstone) from the 455 Ma old Lockne impact crater, central Sweden with an integrated approach using XRD, electron microprobe analysis, SEM-EDS and GCMS analysis of organics. The lichens and fungal hyphae network preferentially weather the chlorite in the Loftarstone compared to feldspars and quartz. We demonstrate, using a fungal isolate (identified by ITS sequencing), that biologically induced dissolution of the calcite component produces cavities which increase the surface area of interaction between the biota and the rock substrate. The weathering crust exfoliates from the rock surface in sheets, which we attribute to the dissolution of the calcite matrix. We present a hypothesis for the crust development. As well as providing insights into weathering on substrates derived from a diversity of high-energy geological disturbances, such as impact events and tsunamis, the weathering crust provides a model system to understand weathering processes in other common lithologies with mixed mineralogies at small spatial scales, including many sedimentary rocks. This work reveals how each different clast plays a unique part in the weathering process, leading to a well-defined weathering sequence.
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Journal articlePerry RS, Mcloughlin N, Lynne BY, et al., 2007,
Defining biominerals and organominerals: Direct and indirect indicators of life
, SED GEOL, Vol: 201, Pages: 157-179, ISSN: 0037-0738 -
Journal articlePearson VK, Sephton MA, Gilmour I, 2006,
Molecular and isotopic indicators of alteration in CR chondrites
, METEORITICS & PLANETARY SCIENCE, Vol: 41, Pages: 1291-1303, ISSN: 1086-9379- Author Web Link
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- Citations: 17
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Journal articlePerry RS, Sephton MA, 2006,
Desert varnish: an environmental recorder for Mars
, ASTRONOMY & GEOPHYSICS, Vol: 47, Pages: 34-35, ISSN: 1366-8781- Author Web Link
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- Citations: 10
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Journal articleSephton MA, James RH, Zolensky ME, 2006,
The origin of dark inclusions in Allende: New evidence from lithium isotopes
, METEORITICS & PLANETARY SCIENCE, Vol: 41, Pages: 1039-1043, ISSN: 1086-9379- Author Web Link
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- Citations: 15
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Journal articlePearson VK, Sephton MA, Franchi IA, et al., 2006,
Carbon and nitrogen in carbonaceous chondrites:Elemental abundances and stable isotopic compositions
, METEORIT PLANET SCI, Vol: 41, Pages: 1899-1918, ISSN: 1086-9379 -
Journal articleSephton MA, Howard LE, Bland PA, et al., 2006,
Delving into Allende's dark secrets
, ASTRON GEOPHYS, Vol: 47, Pages: 37-38, ISSN: 1366-8781 -
Journal articleMeredith W, Sun C-G, Snape CE, et al., 2006,
The use of model compounds to investigate the release of covalently bound biomarkers via hydropyrolysis
, ORG GEOCHEM, Vol: 37, Pages: 1705-1714 -
Journal articleMartins Z, Watson JS, Sephton MA, et 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 -
Conference paperSephton MA, Self S, Verchovsky AB, et 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 -
Book chapterWestall F, de Vries ST, Nijman W, et al., 2006,
The 3.466 Ga Kitty’s Gap Chert, an Early Archean microbial ecosystem
, Processes on the early Earth, Editors: Reimold, Gibson, Publisher: Geological Society of Amer, ISBN: 9780813724058 -
Conference paperMartins Z, Botta O, Fogel ML, et al., 2006,
Isotopic analysis of nucleobases in the Murchison meteorite
, METEORIT PLANET SCI
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