Search or filter publications

Filter by type:

Filter by publication type

Filter by year:

to

Results

  • Showing results for:
  • Reset all filters

Search results

  • Conference paper
    Court RW, Sephton MA, 2011,

    VOLATILE PRODUCTION FROM ABLATING MICROMETEORITES-EVIDENCE FROM STEPPED PYROLYSIS-FTIR

    , 74th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A51-A51, ISSN: 1086-9379
  • Journal article
    Montgomery W, Tuff J, Kohn SC, Jones RLet al., 2011,

    Reactions between organic acids and montmorillonite clay under Earth-forming conditions

    , CHEMICAL GEOLOGY, Vol: 283, Pages: 171-176, ISSN: 0009-2541
  • Book
    Rothery DA, Gilmour I, Sephton MA, 2011,

    An Introduction to Astrobiology

    , Cambridge, Publisher: Cambridge University Press, ISBN: 9781107600935
  • Book chapter
    Sephton MA, 2011,

    Meteoritics

    , Encyclopedia of Geobiology, Editors: Reitner, Thiel, Publisher: Springer Verlag, Pages: 568-574, ISBN: 9781402092114

    The Encyclopedia of Geobiology is designed as a key reference for students, researchers,teachers, and the informed public to provide basic, but comprehensible ...

  • Journal article
    Marlow JJ, Martins Z, Sephton MA, 2011,

    Organic host analogues and the search for life on Mars

    , INT J ASTROBIOL, Vol: 10, Pages: 31-44, ISSN: 1473-5504

    Mars analogue sites represent vital tools in our continued study of the Red Planet; the similar physico-chemical processes that shape a given analogue environment on Earth allow researchers to both prepare for known Martian conditions and uncover presently unknown relationships. This review of organic host analogues – sites on Earth that mimic the putatively low organic content of Mars – examines specific locations that present particular Mars-like obstacles to biological processes. Low temperatures, aridity, high radiation and oxidizing soils characterise modern-day Mars, while acid–saline waters would have presented their own challenges during the planet's warmer and wetter past. By studying each of these hurdles to life on Earth, scientists can prepare instruments headed for Mars and identify the best locations and approaches with which to look for biological signatures. As our use of organic host analogues becomes increasingly sophisticated, researchers will work to identify terrestrial sites exhibiting multiple Mars-like conditions that are tailored to the distinct mineralogical and physical characteristics of Martian locations. Making use of organic host analogues in these ways will enhance the search for signs of past or present life on Mars.

  • Journal article
    Martins Z, Sephton MA, Foing BH, Ehrenfreund Pet al., 2011,

    Extraction of amino acids from soils close to the Mars Desert Research Station (MDRS), Utah

    , International Journal of Astrobiology, Vol: 10, Pages: 231-238
  • Journal article
    Court RW, Sephton MA, 2011,

    The contribution of sulphur dioxide from ablating micrometeorites to the atmospheres of Earth and Mars

    , GEOCHIM COSMOCHIM AC, Vol: 75, Pages: 1704-1717, ISSN: 0016-7037

    Atmospheric composition is a key control on climate and the habitability of planetary surfaces. Ablation of infalling micrometeorites has been recognised as one way in which atmospheric chemistry can be changed, especially at times in solar system history when the infall rates of exogenous material were high. Despite its potential to influence climate and habitability, extraterrestrial sulphur dioxide is currently an unquantified contribution to the atmospheres of the terrestrial planets. We have used flash pyrolysis to simulate the atmospheric entry of micrometeorites and Fourier-transform infrared spectroscopy to identify and quantify the sulphur dioxide produced from the carbonaceous meteorites Orgueil (CI1), ALH 88045 (CM1), Cold Bokkeveld (CM2), Murchison (CM2) and Mokoia (CV3). We have used this approach to understand the introduction of sulphur dioxide to the atmospheres of Earth and Mars from infalling micrometeorites. Sulphates, present in carbonaceous chondrites at a few wt.%, are resistant to thermal decomposition, limiting the yields of sulphur dioxide from unmelted micrometeorites. Infalling micrometeorites are a minor source of present-day sulphur dioxide on Earth and Mars, calculated to be up to around 2400 tonnes and about 350 tonnes, respectively. During the Late Heavy Bombardment (LHB), the much greater infall rates of micrometeoritic dust are calculated to be associated with average production rates of sulphur dioxide of around 20 Mt yr 1 for the early Earth and 0.5 Mt yr 1 for early Mars, for a LHB of 100 Myr. These rates of delivery of sulphur dioxide at high altitudes would have reduced the solar energy reaching the surfaces of these planets, via scattering of sunlight by stratospheric sulphate aerosols, and may have had detrimental effects on developing biospheres by promoting cooler climates and reducing the probability of liquid water on planetary surfaces.

  • 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

  • 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
    Sephton MA, Court RW, Baki AO, Sims MR, Cullen DCet al., 2011,

    New Solvents for Space Missions: Utility for Life Detection Instruments and Notable Terrestrial Applications

    , Recent Patents on Space Technology, Vol: 1, Pages: 7-11, ISSN: 2210-6871

    Instruments designed to test for signs of life on Mars must have operational simplicity and efficiency. One example is the Life Marker Chip being developed to fly on the forthcoming European Space Agency ExoMars mission. Target organic compounds include both polar and non polar molecules and, prior to our patented discovery, no solvent had been tested which effectively extracted both types of molecule in a fashion which was compatible with antibodybased detectors. We have compared the extraction efficiency of water-based solvents alongside conventional organic solvents to determine their suitability for extracting organic mixtures on space missions. Using a range of hydrocarbon standards and a Mars regolith simulant (JSC Mars-1) we have concluded that a water-methanol mix with 1.5 to 2.5 g/L of polysorbate 80 represents the most suitable solvent with extraction efficiencies that can achieve up to approximately 30% of that using conventional organic solvents (assuming 100%efficiency with 93:7 (vol:vol) dichloromethane:methanol mixtures). The surfactant solution will also provide solutions to terrestrial problems, one of which is explored in the patented work.

  • Journal article
    Jennings E, Montgomery W, Lerch P, 2010,

    Stability of Coronene at High Temperature and Pressure

    , JOURNAL OF PHYSICAL CHEMISTRY B, Vol: 114, Pages: 15753-15758, ISSN: 1520-6106
  • 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
  • Conference paper
    Matthewman R, Court RW, Martins Z, Sephton MAet al., 2010,

    VOLATILE RELEASE FROM CHONDRITES: CONSEQUENCES FOR EARLY PLANETARY ATMOSPHERES

    , 73rd Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL PUBLISHING, INC, Pages: A129-A129, ISSN: 1086-9379
  • 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 ...

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://www.imperial.ac.uk:80/respub/WEB-INF/jsp/search-t4-html.jsp Request URI: /respub/WEB-INF/jsp/search-t4-html.jsp Query String: id=419&limit=20&page=6&respub-action=search.html Current Millis: 1721256409194 Current Time: Wed Jul 17 23:46:49 BST 2024