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  • Journal article
    Sephton MA, 2012,

    Pyrolysis and mass spectrometry studies of meteoritic organic matter.

    , Mass Spectrom Rev, Vol: 31, Pages: 560-569

    Meteorites are fragments of extraterrestrial materials that fall to the Earth's surface. The carbon-rich meteorites are derived from ancient asteroids that have remained relatively unprocessed since the formation of the Solar System 4.56 billion years ago. They contain a variety of extraterrestrial organic molecules that are a record of chemical evolution in the early Solar System and subsequent aqueous and thermal processes on their parent bodies. The major organic component (>70%) is a macromolecular material that resists straightforward solvent extraction. In response to its intractable nature, the most common means of investigating this exotic material involves a combination of thermal decomposition (pyrolysis) and mass spectrometry. Recently the approach has also been used to explore controversial claims of organic matter in meteorites from Mars. This review summarizes the pyrolysis data obtained from meteorites and outlines key interpretations. © 2012 Wiley Periodicals, Inc. Mass Spec Rev 31:560-569, 2012.

  • Journal article
    McLennan SM, Sephton MA, Allen C, Allwood AC, Barbieri R, Beaty DW, Boston P, Carr M, Grady M, Grant J, Heber VS, Herd CDK, Hoffman B, King P, Mangold N, Ori GG, Rossi AP, Raulin F, Ruff SW, Sherwood-Lollar B, Symes S, Wilson MGet al., 2012,

    Planning for Mars Returned Sample Science:Final Report of the MSR End-to-End InternationalScience Analysis Group (E2E-iSAG)

    , Astrobiology, Vol: 12, Pages: 175-230, ISSN: 1531-1074
  • Journal article
    Sims MR, Cullen DC, Rix CS, Buckley A, Derveni M, Evans D, Garcia-Con LM, Miguel García-Con L, Rhodes A, Rato CC, Stefinovic M, Sephton MA, Court RW, Bulloch C, Kitchingman I, Ali Z, Pullan D, Holt J, Blake O, Sykes J, Samara-Ratna P, Canali M, Borst G, Leeuwis H, Prak A, Norfini A, Geraci E, Tavanti M, Brucato N, Holm Net al., 2012,

    Development Status of the Life Marker Chip Instrument for ExoMars

    , Planetary and Space Science, ISSN: 0032-0633

    The Life Marker Chip (LMC) is one of the instruments being developed for possible flight on the 2018 ExoMars mission. The instrument uses solvents to extract organic compounds from samples of martian regolith and to transfer the extracts to dedicated detectors based around the use of antibodies. The scientific aims of the instrument are to detect organics in the form of biomarkers that might be associated with extinct life, extant life or abiotic sources of organics. The instrument relies on a novel surfactant-based solvent system and bespoke, commercial and research-developed antibodies against a number of distinct biomarkers or molecular types. The LMC comprises a number of subsystems designed to accept up to four discrete samples of martian regolith or crushed rock, implement the solvent extraction, perform microfluidic-based multiplexed antibody-assays for biomarkers and other targets, optically detect the fluorescent output of the assays, control the internal instrument pressure and temperature, in addition to the associated instrument control electronics and software. The principle of operation, the design and the instrument development status as of December 2011 are reported here. The instrument principle can be extended to other configurations and missions as needed.

  • Journal article
    Watson JS, Fraser WT, Sephton MA, 2012,

    Formation of a polyalkyl macromolecule from the hydrolysable component within sporopollenin during heating/pyrolysis experiments with Lycopodium spores

    , Journal of Analytical and Applied Pyrolysis, Vol: 95, Pages: 138-144

    The most resistant component of Lycopodium spores is the macromolecule sporopollenin. The recent and fossil representatives of this material are structurally distinct and the transformations that bring about this chemical discord are poorly understood. To investigate the diagenesis of spores and their biopolymer, solvent extracted and saponified examples of Lycopodium clavatum underwent simulated diagenesis by heating (100–400 ◦C) under vacuum for 48 h. Following simulated maturation, spores were analysed by pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS) and thermochemolysis-GC–MS. Py-GC–MS data clearly demonstrate that there is an increase in the polyalkyl hydrocarbon material in the pyrolysable component with increasing anhydrous maturation temperature. Hydrous pyrolysis of spores leads to similar changes but with an increased response from aliphatic relative to aromatic material. If the spores are hydrolysed prior to heating the generation of the polyalkyl portion of the macromolecule is markedly reduced. It appears, therefore, that the polyalkyl portion of fossil sporopollenin may be formed by maturation-induced polymerisation of the ‘labile’ hydrolysable component to form a recalcitrant polyalkyl network.

  • Journal article
    Chan HS, Martins Z, Sephton MA, 2012,

    Spectrofluorometric analysis of amino acid mixtures: Implications for future space missions

    , Planetary and Space Science, Vol: 60, Pages: 336-341
  • Journal article
    Matthewman R, Cotton LJ, Martins Z, Sephton MAet al., 2012,

    Organic geochemistry of Late Jurassic paleosols (Dirt Beds) of Dorset, UK

    , Marine and Petroleum Geology, Vol: 37, Pages: 41-52, ISSN: 0264-8172

    Paleosols from the lower part of the Purbeck Limestone Group, which crops out extensively in Dorset, southern England, are shown to contain type IV kerogens. Comparisons with Mesozoic organic materials suggest that some of the paleosol kerogen is composed of fossil charcoal. The charcoal would have been produced by wildfires in the undergrowth of Purbeck gymnosperm forests. Contrasting the paleosol charcoal with laboratory produced counterparts suggest that, originally, significant amounts of functionalised organic matter should have persisted. Secondary oxidation and decay processes, therefore, must have removed all but the most resistant aromatic units in the charcoal. The importance of post-fire processes implies a strong influence on preservation from oxygen supply, water washing and host sediment type. These factors may have been related to pedogenesis, relative sea level and local fault movement in the late Jurassic.

  • Conference paper
    Montgomery WB, Court RW, Watson JS, Sephton MA, Rees ACet al., 2012,

    Quantitative laboratory assessment of aquathermolysis chemistry during steam-assisted recovery of heavy oils and bitumen

    , World Heavy Oil Congress Paper WHOC12-402

    In order to quantitatively study aquathermolysis chemistry during the thermal (steam-assisted) recovery of heavy oils & bitumen we have subjected a well-characterized heavy oil sample to 325°C and 2000 psi (13.8 MPa) in the continued presence of liquid water for 24 hours. The reaction products include gases, oil flotate, water-soluble products, and water-insoluble residues. All have been studied with a variety of analytical techniques, including FTIR spectroscopy, chromatographic fractionation (SARA analysis), and GC-MS. Results suggests that some in-situ upgrading of the oil occurs under these conditions. The methods discussed will be useful for the measurement of data to support model development for use in the engineering design of facilities for the thermal recovery of heavy oils and bitumen.

  • Journal article
    Court RW, Sims MR, Cullen DC, Sephton MAet al., 2012,

    Potential failure of life detection experiments on Mars resulting from adsorption of organic compounds on to common instrument materials

    , Planetary and Space Science, Vol: 73, Pages: 262-270, ISSN: 0032-0633

    Some life detection instruments under development for operation on Mars use solvents to extract organic compounds from samples of martian regolith and rock and to transfer the extracts to dedicated detectors. However, it is possible that organic compounds extracted from martian samples and dissolved in the solvent could adsorb to instrument surfaces, potentially resulting in a failure to detect organic matter that could have been avoided by using more appropriate instrument materials. If successful detection and characterisation is to take place it is therefore essential to understand the interactions between dissolved organic targets and the surfaces of space instrument components. One such life detection instrument is the Life Marker Chip (LMC) being developed for the ExoMars mission, which relies on a novel surfactant-based solvent system and antibody-based detectors. We have tested the ability of a range of materials, including titanium, stainless steel, aluminium, the fluoropolymer Viton™, polytetrafluoroethylene (PTFE), nylon, polypropylene, polyethersulfone and cellulose acetate to adsorb a range of organic standards from the surfactant solution intended to be used by the LMC. Results indicate that aromatic hydrocarbons, specifically anthracene, are more prone to adsorption than straight chain, branched and cyclic aliphatic species. Titanium, aluminium and stainless steel show little adsorption ability and are suitable for larger-area applications. PTFE and Viton™ are suitable for use in small-area applications such as seals and filters. Nylon, polypropylene, polyethersulfone and cellulose acetate show stronger adsorption characteristics and should be avoided in the forms employed here. The ability of some materials to selectively adsorb organic compounds from solvent extracts can lower the sensitivity of life detection instruments. In future, it would be prudent to test all space instrument materials for their ability to adsorb target organic com

  • Journal article
    Lomax BH, Fraser WT, Harrington G, Blackmore S, Sephton MA, Harris NBWet al., 2012,

    A novel palaeoaltimetry proxy based on spore and pollen wall chemistry

    , Earth and Planetary Science Letters, Vol: 353-354, Pages: 22-28, ISSN: 0012-821X

    Understanding the uplift history and the evolution of high altitude plateaux is of major interest to a wide range of geoscientists and has implications for many disparate fields. Currently the majority of palaeoaltimetry proxies are based on detecting a physical change in climate in response to uplift, making the relationship between uplift and climate difficult to decipher. Furthermore, current palaeoaltimetry proxies have a low degree of precision with errors typically greater than 1 km. This makes the calculation of uplift histories and the identification of the mechanisms responsible for uplift difficult to determine. Here we report on advances in both instrumentation and our understanding of the biogeochemical structure of sporopollenin that are leading to the establishment of a new proxy to track changes in the flux of UV-B radiation over geological time. The UV-B proxy is based on quantifying changes in the concentration of UV-B absorbing compounds (UACs) found in the spores and pollen grains of land plants, with the relative abundances of UACs increasing on exposure to elevated UV-B radiation. Given the physical relationship between altitude and UV-B radiation, we suggest that the analysis of sporopollenin chemistry, specifically changes in the concentration of UACs, may offer the basis for the first climate independent palaeoaltimetry proxy. Owing to the ubiquity of spores and pollen in the fossil record, our proposed proxy has the potential to enable the reconstruction of the uplift history of high altitude plateaux at unprecedented levels of fidelity, both spatially and temporally.

  • Journal article
    Court RW, Sephton MA, 2012,

    Extrasolar Planets And False Atmospheric Biosignatures: The Role Of Micrometeoroids

    , Planetary and Space Science, Vol: 73, Pages: 233-242, ISSN: 0032-0633

    The coexistence of oxygen and a reduced gas such as methane in the atmosphere of an extrasolar planet is considered to be strong evidence for the presence of a biosphere. Proposed spacecraft such as Darwin or Terrestrial Planet Finder are designed to be capable of spectroscopically characterising the atmospheres of exoplanets, detecting chemical disequilibrium indicative of life. However, methane can be produced by various abiological mechanisms, including the ablation of carbonaceous micrometeoroids upon atmospheric entry, and it is possible that extrasolar planets in dust-rich systems might receive enough micrometeoroidal infall to produce a false atmospheric biosignature. Here, we review the production of methane from carbonaceous meteoroids upon atmospheric ablation in our solar system and discuss its application to extrasolar planets. The current paucity of data regarding dust densities in systems possessing terrestrial planets in the habitable zones of their stars makes firm conclusions difficult. However, the data suggest that only very young systems possessing very dense debris disks, or systems undergoing reorganisation similar to the Late Heavy Bombardment in our early solar system, would be capable of producing sufficient methane to be mistaken for an atmospheric biosignature.

  • Journal article
    Chan HS, Martins Z, Sephton MA, 2012,

    Amino acid analysis of type 3 chondrites Colony, Ornans, Chainpur and Bishunpur

    , Meteoritics & Planetary Science, Vol: 47, Pages: 1502-1516, ISSN: 1086-9379

    The CO3s Colony and Ornans and LL3s Chainpur and Bishunpur were analyzed for the first time for amino acids using gas chromatography–mass spectrometry (GC-MS). Type 3 chondrites have relatively unaltered metamorphic and petrological histories. Chainpur was the most amino acid rich of the four type 3 chondrites with a total amino acid abundance of 3330 parts per billion (ppb). The other type 3 chondrites had total amino acid abundances that ranged from 660 to 1110 ppb. A d/l ratio of <0.7 for all proteic amino acids suggests at least some amino acid terrestrial contamination. However, a small fraction of indigenous extraterrestrial amino acids cannot be excluded because of the presence of the nonprotein amino acid α-aminoisobutyric acid (α-AIB), and unusually high relative abundances (to glycine) of β-alanine and γ-ABA. The comparisons between the free and total amino acid contents of the samples also indicate a low free/total amino acid ratio (ranging from about 1:4 in CO chondrites to about 1:50 in Chainpur), which indicate that amino acids are present mainly in the bound form and were made detectable after acid hydrolysis.

  • Report
    Beaty DW, Kminek G, Allwood AC, Arvidson R, Borg LE, Farmer JD, Goesmann F, Grant JA, Hauber E, Murchie SL, Ori GG, Ruff SW, Rull F, Sephton MA, Sherwood Lollar B, Smith CL, Westall F, Pacros AE, Wilson MG, Meyer MA, Vago JL, Bass DS, Joudrier L, Laubach S, Feldman S, Trautner R, Milkovich SMet al., 2012,

    Report of the 2018 Joint Mars Rover Mission Joint Science Working Group (JSWG)

    , Publisher: Mars Exploration Analysis Group (MEPAG)
  • Journal article
    Chan HS, Martins Z, Sephton MA, 2012,

    Fluorescence spectroscopy for the detection of life in the Salten Skov Mars regolith analogue

    , Planetary and Space Science, Vol: 68, Pages: 42-47
  • Journal article
    Court RW, Rix CS, Sims MR, Cullen DC, Sephton MAet al., 2012,

    Extraction of polar and nonpolar biomarkers from the martian soil using aqueous surfactant solutions

    , Planetary and Space Science, Vol: 67, Pages: 109-118, ISSN: 0032-0633

    The Life Marker Chip is being designed to detect the chemical evidence of life in the martian soil. It will use an aqueous surfactant solution to extract polar and nonpolar biomarkers from the martian soil and to transport them into an antibody-based detector for characterisation. Currently, a solution of 1.5 g l−1 polysorbate 80 in 20:80 (vol:vol) methanol:water is being considered and appears to be suitable. Here, we have investigated the ability of a range of other surfactant solutions to extract a suite of eight standards spiked on the surfaces of the martian soil simulant JSC Mars-1 and tested the compatibility of the best two surfactants with a representative antibody assay for the detection of pyrene. The results show that using 20:80 (vol:vol) methanol:water as the solvent leads to increased recoveries of standards than using water alone. The poloxamer surfactants Pluronic® F-68 and Pluronic® F-108 are not effective at extracting the standards from JSC Mars-1 at any of the concentrations tested here. The fluorosurfactant Zonyl® FS-300 is able to extract the standards, but not as efficiently as polysorbate 80 solutions. Most successful of the alternative surfactants was the polysiloxane poly[dimethylsiloxane-co-[3-(2-(2-hydroxyethoxy)ethoxy)propyl]methylsiloxane] (PDMSHEPMS) which is able to extract the standards from JSC Mars-1 with an efficiency approximately equal to that of polysorbate 80 solutions of the same concentration. Enhanced recovery of the standards using polysorbate 80 and PDMSHEPMS solutions can be achieved by increasing the concentration of surfactant, from 1.5 g l−1 to 10 g l−1, leading to an increase in the recovery of standards of about 50%. Polysorbate 80 at concentrations of 1.5 g l−1 and 10 g l−1 and Zonyl® FS-300 and PDMSHEPMS (both at a concentration of 10 g l−1) are also compatible with the representative pyrene antibody assay.

  • Conference paper
    Sephton MA, Meredith W, Verchovsky A, Watson JS, Snape CEet al., 2011,

    CATALYTIC HYDROGENATION OF THE MACROMOLECULAR MATERIAL IN METEORITES

    , 74th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A211-A211, ISSN: 1086-9379
  • 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
    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.

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