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  • Journal article
    Ehrenfreund P, Roling WFM, Thiel CS, Quinn R, Sephton MA, Stoker C, Kotler JM, Direito S, Martins Z, Orzechowska G, Kidd RD, van Sluis CA, Foing BHet al., 2011,

    Astrobiology and habitability studies in preparation for future Mars missions: trends from investigating minerals, organics and biota

    , International Journal of Astrobiology, Vol: 10, Pages: 239-253
  • Journal article
    Gowen RA, Smith A, Fortes AD, Barber S, Brown P, Church P, Collinson G, Coates AJ, Collins G, Crawford IA, Dehant V, Chela-Flores J, Griffiths AD, Grindrod PM, Gurvitis LI, Hagermann A, Hussmann H, Jaumann R, Jones AP, Joy KH, Karatekin O, Miljkovic K, Palomba E, Pike WT, Prieto-Ballesteros O, Raulin F, Sephton MA, Sheridan S, Sims M, Storrie-Lombardi MC, Ambrosi R, Fielding J, Fraser G, Gao Y, Jones GH, Kargl G, Karl WJ, Macagnano A, Mukherjee A, Muller JP, Phipps A, Pullan D, Richter L, Sohl F, Snape J, Sykes J, Wells Net al., 2011,

    Penetrators for in situ subsurface investigations of Europa

    , ADV SPACE RES, Vol: 48, Pages: 725-742, ISSN: 0273-1177

    We present the scientific case for inclusion of penetrators into the Europan surface, and the candidate instruments which could significantly enhance the scientific return of the joint ESA/NASA Europa-Jupiter System Mission (EJSM). Moreover, a surface element would provide an exciting and inspirational mission highlight which would encourage public and political support for the mission.Whilst many of the EJSM science goals can be achieved from the proposed orbital platform, only surface elements can provide key exploration capabilities including direct chemical sampling and associated astrobiological material detection, and sensitive habitability determination. A targeted landing site of upwelled material could provide access to potential biological material originating from deep beneath the ice.Penetrators can also enable more capable geophysical investigations of Europa (and Ganymede) interior body structures, mineralogy, mechanical, magnetic, electrical and thermal properties. They would provide ground truth, not just for the orbital observations of Europa, but could also improve confidence of interpretation of observations of the other Jovian moons. Additionally, penetrators on both Europa and Ganymede, would allow valuable comparison of these worlds, and gather significant information relevant to future landed missions. The advocated low mass penetrators also offer a comparatively low cost method of achieving these important science goals.A payload of two penetrators is proposed to provide redundancy, and improve scientific return, including enhanced networked seismometer performance and diversity of sampled regions.We also describe the associated candidate instruments, penetrator system architecture, and technical challenges for such penetrators, and include their current status and future development plans.

  • Journal article
    Visscher H, Sephton MA, Looy CV, 2011,

    Fungal virulence at the time of the end-Permian biosphere crisis?

    , GEOLOGY, Vol: 39, Pages: 883-886, ISSN: 0091-7613

    Throughout the world, latest Permian records of organic-walled microfossils are characterized by the common presence of remains of fi lamentous organisms, usually referred to the palynomorph genus Reduviasporonites. Although generally regarded as indicators of global ecological crisis, fundamental controversy still exists over the biological and ecological identity of the remains. Both fungal and algal affinities have been proposed. We seek to resolve this enigma by demonstrating close morphological similarity of the microfossils to resting structures (monilioid hyphae, sclerotia) of Rhizoctonia, a modern complex of soil-borne filamentous fungi that includes ubiquitous plant pathogens. By analogy with present-day forest decline, these findings suggest that fungal virulence may have been a significant contributing factor to widespread devastation of arboreal vegetation at the close of the Permian Period.

  • Journal article
    Fraser WT, Sephton MA, Watson JS, Self S, Lomax BH, James DI, Wellman CH, Callaghan TV, Beerling DJet al., 2011,

    UV-B absorbing pigments in spores: biochemical responses to shade in a high-latitude birch forest and implications for sporopollenin-based proxies of past environmental change

    , Polar Research, Vol: 30, Pages: 8312-8318, ISSN: 1751-8369

    Current attempts to develop a proxy for Earth’s surface ultraviolet-B (UV-B) flux focus on the organic chemistry of pollen and spores because their constituent biopolymer, sporopollenin, contains UV-B absorbing pigments whose relative abundance may respond to the ambient UV-B flux. Fourier transform infrared (FTIR microspectroscopy provides a useful tool for rapidly determining the pigment content of spores. In this paper, we use FTIR to detect a chemical response of spore wall UV-B absorbing pigments that correspond with levels of shade beneath the canopy of a high-latitude Swedish birch forest. A 27% reduction in UV-B flux beneath the canopy leads to a significant (p<0.05) 7.3% reduction in concentration of UV-B absorbing compounds in sporopollenin. The field data from this natural flux gradient in UV-B further support our earlier work on sporopollenin-based proxies derived from sedimentary records and herbaria collections.

  • Journal article
    Boardman CP, Gauci V, Watson JS, Blake S, Beerling DJet al., 2011,

    Contrasting wetland CH4 emission responses to simulated glacial atmospheric CO2 in temperate bogs and fens

    , New Phytologist, Vol: 192, Pages: 898-911

    Wetlands were the largest source of atmospheric methane (CH(4) ) during the Last Glacial Maximum (LGM), but the sensitivity of this source to exceptionally low atmospheric CO(2) concentration ([CO(2) ]) at the time has not been examined experimentally. We tested the hypothesis that LGM atmospheric [CO(2) ] reduced CH(4) emissions as a consequence of decreased photosynthate allocation to the rhizosphere. We exposed minerotrophic fen and ombrotrophic bog peatland mesocosms to simulated LGM (c. 200ppm) or ambient (c. 400ppm) [CO(2) ] over 21months (n=8 per treatment) and measured gaseous CH(4) flux, pore water dissolved CH(4) and volatile fatty acid (VFA; an indicator of plant carbon supply to the rhizosphere) concentrations. Cumulative CH(4) flux from fen mesocosms was suppressed by 29% (P<0.05) and rhizosphere pore water [CH(4) ] by c. 50% (P<0.01) in the LGM [CO(2) ], variables that remained unaffected in bog mesocosms. VFA analysis indicated that changes in plant root exudates were not the driving mechanism behind these results. Our data suggest that the LGM [CO(2) ] suppression of wetland CH(4) emissions is contingent on trophic status. The heterogeneous response may be attributable to differences in species assemblage that influence the dominant CH(4) production pathway, rhizosphere supplemented photosynthesis and CH(4) oxidation.

  • Journal article
    Westall F, Foucher F, Cavalazzi B, de Vries ST, Nijman W, Pearson V, Watson J, Verchovsky A, Wright I, Rouzaud JN, Marchesini Det al., 2011,

    Volcaniclastic habitats for early life on Earth and Mars: A case study from ~3.5 Ga-old rocks from the Pilbara, Australia

    , Planetary and Space Science, Vol: 59, Pages: 1093-1106

    Within the context of present and future in situ missions to Mars to investigate its habitability and to search for traces of life, we studied the habitability and traces of past life in similar to 3.5 Ga-old volcanic sands deposited in littoral environments an analogue to Noachian environments on Mars. The environmental conditions on Noachian Mars (4.1-3.7 Ga) and the Early Archaean (4.0-3.3 Ga) Earth were, in many respects, similar: presence of liquid water, dense CO(2) atmosphere, availability of carbon and bioessential elements, and availability of energy. For this reason, information contained in Early Archaean terrestrial rocks concerning habitable conditions (on a microbial scale) and traces of past life are of relevance in defining strategies to be used to identify past habitats and past life on Mars. One such example is the 3.446 Ga-old Kitty's Gap Chert in the Pilbara Craton, NW. Australia. This formation consists of volcanic sediments deposited in a coastal mudflat environment and is thus a relevant analogue for sediments deposited in shallow water environments on Noachian Mars. Two main types of habitat are represented, a volcanic (lithic) habitat and planar stabilized sediment surfaces in sunlit shallow waters. The sediments hosted small (<1 mu m in size) microorganisms that formed colonies on volcanic particle surfaces and in pore waters within the volcanic sediments, as well as biofilms on stabilised sediment surfaces. The microorganisms included coccoids, filaments and rare rod-shaped organisms associated with microbial polymer (EPS). The preserved microbial community was apparently dominated by chemotrophic organisms but some locally transported filaments and filamentous mat fragments indicate that possibly photosynthetic mats formed nearby. Both microorganisms and sediments were silicified during very early diagenesis. There are no macroscopic traces of fossilised life in these volcanic sediments and sophisticated instrumentation and specialized

  • Book
    Rothery DA, Gilmour I, Sephton MA, 2011,

    An Introduction to Astrobiology

    , Cambridge, Publisher: Cambridge University Press, ISBN: 9781107600935
  • Journal article
    Wainipee W, Weiss DJ, Sephton MA, Coles BJ, Unsworth C, Court Ret al., 2010,

    The effect of crude oil on arsenate adsorption on goethite

    , WATER RESEARCH, Vol: 44, Pages: 5673-5683, ISSN: 0043-1354
  • Patent
    Baki AO, Sephton MA, Sims MR, Cullen DCet al., 2010,

    Aqueous solvents for hydrocarbons and other hydrophobic compounds

    , WO2010122295

    The present invention provides a method of solubilising in an aqueous medium a hydrocarbon or a hydrophobic compound having a hydrocarbon skeleton that carries one or more heteroatom containing functional groups, e.g. hydroxyl, carboxylic acid or aldehyde (CHO) groups. The method comprises contacting the hydrocarbon or the hydrophobic compound with the aqueous medium that includes at least one non-ionic surfactant containing a hydrophilic part and a hydrophobic part, the hydrophilic part comprising a polyhydroxylated moiety and the hydrophobic part comprising a hydrocarbon chain containing at least 12 carbon atoms, e.g. ethoxylated sorbitol. The amount of surfactant used is sufficient to form micelles including a core formed of the hydrocarbon or the hydrophobic compound.

  • Journal article
    Sephton MA, Court RW, 2010,

    Meteorite gases and planetary atmospheres

    , ASTRONOMY & GEOPHYSICS, Vol: 51, Pages: 21-22, ISSN: 1366-8781
  • Journal article
    Blyth AJ, Watson JS, Woodhead J, Hellstrom Jet al., 2010,

    Organic compounds preserved in a 2.9 million year old stalagmite from the Nullarbor Plain, Australia

    , Chemical Geology, Vol: 279, Pages: 101-105
  • Journal article
    Jolley D, Gilmour I, Gurov E, Kelley S, Watson Jet al., 2010,

    Two large meteorite impacts at the Cretaceous-Paleogene boundary

    , Geology, Vol: 38, Pages: 835-838

    The end-Cretaceous mass extinction has been attributed by most to a single asteroid impact at Chicxulub on the Yucatán Peninsula, Mexico. The discovery of a second smaller crater with a similar age at Boltysh in the Ukraine has raised the possibility that a shower of asteroids or comets impacted Earth close to the Cretaceous-Paleogene (K-Pg) boundary. Here we present palynological and δ13C evidence from crater-fi ll sediments in the Boltysh impact crater. Our analyses demonstrate that a post-impact fl ora, formed on the ejecta layer, was in turn devastated by the K-Pg event. The sequence of fl oral recovery from the K-Pg event is directly comparable with that in middle North America. We conclude that the Boltysh crater predated Chicxulub by ~2–5 k.y., a time scale that constrains the likely origin of the bodies that formed the two known K-Pg craters.

  • Journal article
    Watson JS, Sephton MA, Gilmour I, 2010,

    Thermochemolysis of the Murchison meteorite: identification of oxygen bound and occluded units in the organic macromolecule

    , INT J ASTROBIOL, Vol: 9, Pages: 201-208, ISSN: 1473-5504

    An organic macromolecular residue, prepared from the Murchison meteorite by treatment with hydrofluoric and hydrochloric acids, was subjected to online thermochemolysis with tetramethylammonium hydroxide (TMAH). The most abundant compound released by thermochemolysis was benzoic acid. Other abundant compounds include methyl and dimethyl benzoic acids as well as methoxy benzoic acids. Short chain dicarboxylic acids (C4–8) were also released from the organic macromolecule. Within the C1 and C2 benzoic acids all possible structural isomers are present reflecting the abiotic origin of these units. The most abundant isomers include 3,4-dimethylbenzoic acid (DMBA), 3,5-DMBA, 2,6-DMBA and phenylacetic acid. Thermochemolysis also liberates hydrocarbons that are not observed during thermal desorption; these compounds include naphthalene, methylnaphthalenes, biphenyl, methylbiphenyls, acenaphthylene, acenaphthene, phenanthrene, anthracene, fluoranthene and pyrene. The lack of oxygen containing functional groups in these hydrocarbons indicates that they represent non-covalently bound, occluded molecules within the organic framework. This data provides a valuable insight into oxygen bound and physically occluded moieties in the Murchison organic macromolecule and implies a relative order of synthesis or agglomeration for the detected organic constituents.

  • Book chapter
    Verchovsky AB, Sephton MA, 2010,

    Noble Gases - Space

    , The Encyclopedia of Mass Spectrometry, Editors: Gross, Houk, Publisher: Elsevier Science Ltd, ISBN: 9780080438047

    In addition to accelerator mass spectrometry and isotope ratio mass spectrometry (formeasurement of isotope abundances in nature), the work reviews ionization ...

  • Journal article
    Sephton MA, 2010,

    Drilling in Extreme Environments: Penetration and Sampling on Earth and other Planets, Yoseph Bar-Cohen, Kris Zacny (Eds.), Wiley-VCH, 2010. (Book Review)

    , International Journal of Rock Mechanics and Mining Science, Vol: 47, Pages: 1405-1405, ISSN: 1365-1609
  • Journal article
    Grant J, Westall F, Beaty D, Cady S, Carr M, Ciarletti V, Coradini A, Elfving A, Glavin D, Goesmann F, Hurowitz J, Ori JG, Phillips R, Salvo C, Sephton MA, Syvertson M, Vargo Jet al., 2010,

    Two Rovers to the Same Site on Mars, 2010: Possibilities for Cooperative Science

    , Astrobiology, Vol: 10, Pages: 663-685, ISSN: 1531-1074
  • Journal article
    Cockell CS, Osinski GR, Banerjee NR, Howard T, Gilmour I, Watson JSet al., 2010,

    Microbe–mineral environment and gypsum neogenesis in a weathered polar evaporite

    , Geobiology, Vol: 8, Pages: 293-308

    Evaporitic deposits are a globally widespread habitat for micro-organisms. The microbe–mineral environment in weathered and remobilized gypsum from exposed mid-Ordovician marine evaporite beds in the polar desert of Devon Island, Nunavut, Canadian High Arctic was examined. The gypsum is characterized by internal green zones of cyanobacterial colonization (dominated by Gloeocapsa/Aphanothece and Chroococcidiopsis spp. morphotypes) and abundant black zones, visible from the surface, that contain pigmented cyanobacteria and fungi. Bioessential elements in the gypsum are primarily provided by allochthonous material from the present-day polar desert. The disruption, uplift and rotation of the evaporite beds by the Haughton meteorite impact 39 Ma have facilitated gypsum weathering and its accessibility as a habitat. No cultured cyanobacteria, bacteria and fungi were halophilic consistent with the expectation that halophily is not required to persist in gypsum habitats. Heterotrophic bacteria from the evaporite were slightly or moderately halotolerant, as were heterotrophs isolated from soil near the gypsum outcrop showing that halotolerance is common in arctic bacteria in this location. Psychrotolerant Arthrobacter species were isolated. No psychrophilic organisms were isolated. Two Arthrobacter isolates from the evaporite were used to mediate gypsum neogenesis in the laboratory, demonstrating a potential role for microbial biomineralization processes in polar environments.

  • Journal article
    Meredith W, Gomes RL, Cooper M, Snape CE, Sephton MAet al., 2010,

    Hydropyrolysis over a platinum catalyst as a preparative technique for the compound-specific carbon isotope ratio measurement of C27 steroids

    , RAPID COMMUN MASS SP, Vol: 24, Pages: 501-505, ISSN: 1097-0231

    Compound-specific stable carbon isotope analysis by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) is an important method for the determination of the 13C/12C ratios of biomolecules such as steroids, for a wide range of applications. However, steroids in their natural form exhibit poor chromatographic resolution, while derivatisation adds carbon thereby corrupting the stable isotopic composition. Hydropyrolysis with a sulphided molybdenum catalyst has been shown to defunctionalise the steroids, while leaving their carbon skeleton intact, allowing for the accurate measurement of carbon isotope ratios. The presence of double bonds in unsaturated steroids such as cholesterol resulted in significant rearrangement of the products, but replacing the original catalyst system with one of platinum results in higher conversions and far greater selectivity. The improved chromatographic performance of the products should allow GC/C/IRMS to be applied to more structurally complex steroid hormones and their metabolites.

  • Journal article
    Sephton MA, 2010,

    Organic Geochemistry and the Exploration of Mars

    , J COSMOLOGY, Vol: 5, Pages: 1141-1149

    The Red Planet provides a relatively accessible world on which theories of life’s diversity and origin can be tested. Such examinations are imminent with a number of missions to Mars forthcoming. These missions contain several life detection instruments that will sample the surface and subsurface. Organic geochemical knowledge from terrestrial studies can inform our search for organic matter in Mars rocks. Recent data on Mars minerals and atmospheric gases suggest which methods may be most useful to access any organic records present. A mineralogically-diverse Mars provides varying opportunities for the preservation of past and present life. Extinct or extant life will occupy specific size fractions that must be targeted. Studies suggest that methane is most likely derived from the subsurface. Even if abiotic in origin, the combination of reduced gases and oxidised minerals provides opportunities for life. In the near subsurface methane may be polymerised by cosmic radiation to form abiotic organic matter. This paper considers terrestrial approaches that may be useful in a Martian context.

  • Journal article
    Court RW, Baki AO, Sims MA, Cullen D, Sephton MAet al., 2010,

    Novel solvent systems for in situ extraterrestrial sample analysis

    , PLANET SPACE SCI, Vol: 58, Pages: 1470-1474, ISSN: 0032-0633

    The life marker chip (LMC) is being designed to test for the chemical signature of life in the soil and rocks of Mars. It will use an antibody array as part of its detection and characterisation system and aims to detect both polar and non-polar molecules at the sub-ppm to tens of ppb level. It is necessary to use a solvent to transfer organic compounds from the Martian samples to the LMC itself, but organic solvents such as dichloromethane or hexane, commonly used to dissolve non-polar molecules, are incompatible with the LMC antibodies. Hence, an aqueous-based solvent capable of dissolving the biomarkers that might exist in the soil or rocks of Mars is required. Solvent extractions of a Martian soil analogue, JSC Mars-1, spiked with a range of standards show that a 20:80 (vol:vol) mixture of methanol and water is incapable of extracting compounds insoluble in water. However, addition of 1.5 mg ml−1 of the surfactant polysorbate 80 produces extraction efficiencies of the aliphatic standards, hexadecane and phytane, equal to 25–30% of those produced by the common organic solvent mixture 93:7 (vol:vol) dichloromethane:methanol. Extraction of squalene and stigmasterol using the polysorbate solution is less efficient but still successful, at 5–10% of the efficiency of 93:7 dichloromethane:methanol. Such aliphatic compounds with occasional functional groups represent the compound classes to which most fossil organic biomarkers belong. The polysorbate solution did not extract the aromatic compounds pyrene and anthracene with great efficiency. A solvent of 20:80 methanol:water with 1.5 mg ml−1 polysorbate 80 is therefore capable of selectively extracting aliphatic biomarkers from Martian samples and transferring them to the antibody sites on the life marker chip.

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