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  • Journal article
    Sephton MA, Jiao D, Engel MH, Looy CV, Visscher Het al., 2015,

    Terrestrial acidification during the end-Permian biosphere crisis?

    , Geology, Vol: 43, Pages: 159-162, ISSN: 1943-2682

    Excessive acid rainfall associated with emplacement of the Siberian Traps magmatic province is increasingly accepted as a major contributing factor to the end-Permian biosphere crisis. However, direct proxy evidence of terrestrial acidification is so far not available. In this paper, we seek to determine the probability that relative proportions of extractable monophenolic components from soil-derived organic matter in marine sediments provide a molecular proxy for estimating soil acidity. Intermittently low and high ratios of vanillic acid to vanillin detected in latest Permian and earliest Triassic deposits of the southern Alps, Italy, support concepts of pulses of severe acidification (pH <4) during the main phase of the biosphere crisis.

  • Journal article
    Montgomery WB, Sephton MA, Watson JS, Zeng H, Rees Aet al., 2015,

    Minimising hydrogen sulphide generation during steam assisted production of heavy oil

    , Scientific Reports, Vol: 5, ISSN: 2045-2322

    The majority of global petroleum is in the form of highly viscous heavy oil. Traditionally heavy oil in sands at shallow depths is accessed by large scale mining activities. Recently steam has been used to allow heavy oil extraction with greatly reduced surface disturbance. However, in situ thermal recovery processes can generate hydrogen sulphide, high levels of which are toxic to humans and corrosive to equipment. Avoiding hydrogen sulphide production is the best possible mitigation strategy. Here we use laboratory aquathermolysis to reproduce conditions that may be experienced during thermal extraction. The results indicate that hydrogen sulphide generation occurs within a specific temperature and pressure window and corresponds to chemical and physical changes in the oil. Asphaltenes are identified as the major source of sulphur. Our findings reveal that for high sulphur heavy oils, the generation of hydrogen sulphide during steam assisted thermal recovery is minimal if temperature and pressure are maintained within specific criteria. This strict pressure and temperature dependence of hydrogen sulphide release can allow access to the world’s most voluminous oil deposits without generating excessive amounts of this unwanted gas product.

  • Journal article
    Sephton MA, Watson JS, Meredith W, Love GD, Gilmour I, Snape CEet al., 2015,

    Multiple cosmic sources for meteorite macromolecular materials?

    , Astrobiology, Vol: 15, ISSN: 1557-8070
  • Journal article
    Lewis JMT, Watson JS, Najorka J, Luong D, Sephton MAet al., 2015,

    Sulfate Minerals: A Problem for the Detection of Organic Compounds on Mars?

    , Astrobiology, Vol: 15, ISSN: 1557-8070

    The search for in situ organic matter on Mars involves encounters with minerals and requires an understanding of their influence on lander and rover experiments. Inorganic host materials can be helpful by aiding the preservation of organic compounds or unhelpful by causing the destruction of organic matter during thermal extraction steps. Perchlorates are recognized as confounding minerals for thermal degradation studies. On heating, perchlorates can decompose to produce oxygen, which then oxidizes organic matter. Other common minerals on Mars, such as sulfates, may also produce oxygen upon thermal decay, presenting an additional complication. Different sulfate species decompose within a large range of temperatures. We performed a series of experiments on a sample containing the ferric sulfate jarosite. The sulfate ions within jarosite break down from 500 °C. Carbon dioxide detected during heating of the sample was attributed to oxidation of organic matter. A laboratory standard of ferric sulfate hydrate released sulfur dioxide from 550 °C, and an oxygen peak was detected in the products. Calcium sulfate did not decompose below 1000 ° C. Oxygen released from sulfate minerals may have already affected organic compound detection during in situ thermal experiments on Mars missions. A combination of preliminary mineralogical analyses and suitably selected pyrolysis temperatures may increase future success in the search for past or present life on Mars.

  • Journal article
    Sephton MA, Lewis JMT, Watson JS, Montgomery W, Garnier Cet al., 2014,

    Perchlorate-induced combustion of organic matter with variable molecular weights: implications for Mars missions

    , Geophysical Research Letters, Vol: 41, Pages: 7453-7460, ISSN: 1944-8007

    Instruments on the Viking landers and Curiosity rover analysed samples of Mars and detected carbon dioxide and organic compounds of uncertain origin. Mineral assisted reactions are leading to uncertainty, particularly those involving perchlorate minerals which thermally decompose to produce chlorine and oxygen which can then react with organic matter. Mineral assisted reactions produce organochlorine compounds and carbon dioxide. Although generally considered a problem for interpretation, the release profiles of generated gases can indicate the type of organic matter present. We have performed a set of experiments with perchlorate and organic matter of variable molecular weights. Results indicate that organic susceptibility to thermal degradation and mineral-assisted reactions is related to molecular weight. The natural occurrence and association of organic matter with differing molecular weights helps to discriminate between contamination (usually low molecular weight organic matter only) and indigenous carbon (commonly low and high molecular weight organic matter together). Our results can be used to provide insights into data returning from Mars.

  • Journal article
    Court RW, Sephton MA, 2014,

    New estimates of the production of volatile gases from ablating carbonaceous micrometeoroids at Earth and Mars during an E-belt-type Late Heavy Bombardment

    , Geochimica et Cosmochimica Acta, Vol: 145, Pages: 175-205, ISSN: 0016-7037
  • Conference paper
    Verchovsky AB, Hunt SA, Montgomery W, Sephton MAet al., 2014,


    , 77th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A421-A421, ISSN: 1086-9379
  • Journal article
    Montgomery W, Lerch P, Sephton MA, 2014,

    In-situ vibrational optical rotatory dispersion of molecular organic crystals at high pressures

    , Analytica Chimica Acta, Vol: 842, Pages: 51-56, ISSN: 0003-2670
  • Journal article
    Court RW, Sims MR, Cullen DC, Sephton MAet al., 2014,

    Searching for Life on Mars: Degradation of Surfactant Solutions Used in Organic Extraction Experiments

    , Astrobiology, Vol: 14, Pages: 733-752, ISSN: 1531-1074
  • Journal article
    Luong D, Court RW, Sims MR, Cullen DC, Sephton MAet al., 2014,

    Extracting organic matter on Mars: A comparison of methods involving subcritical water, surfactant solutions and organic solvents

    , Planetary and Space Science, Vol: 99, Pages: 19-27, ISSN: 0032-0633
  • Journal article
    Sephton MA, 2014,

    Astrobiology can help space science, education and the economy

    , Space Policy, Vol: 30, Pages: 146-148, ISSN: 0265-9646
  • Journal article
    Sephton MA, Carter JN, 2014,

    Statistics Provide Guidance for Indigenous Organic Carbon Detection on Mars Missions

    , Astrobiology, Vol: 14, Pages: 706-713, ISSN: 1531-1074
  • Journal article
    Montgomery W, Watson JS, Sephton MA, 2014,

    An organic cosmo-barometer: Distinct pressure and temperature effects for methyl substituted polycyclic aromatic hydrocarbons

    , Astrophysical Journal, Vol: 784, ISSN: 0004-637X

    There are a number of key structures that can be used to reveal the formation and modification history of organic matter in the cosmos. For instance, the susceptibility of organic matter to heat is well documented and the relative thermal stabilities of different isomers can be used as cosmothermometers. Yet despite being an important variable, no previously recognized organic marker of pressure exists. The absence of a pressure marker is unfortunate considering our ability to effectively recognize extraterrestrial organic structures both remotely and in the laboratory. There are a wide variety of pressures in cosmic settings that could potentially be reflected by organic structures. Therefore, to develop an organic cosmic pressure marker, we have used state-of-the-art diamond anvil cell (DAC) and synchrotron-source Fourier transform infrared (FTIR) spectroscopy to reveal the effects of pressure on the substitution patterns for representatives of the commonly encountered methyl substituted naphthalenes, specifically the dimethylnaphthalenes. Interestingly, although temperature and pressure effects are concordant for many isomers, pressure appears to have the opposite effect to heat on the final molecular architecture of the 1,5-dimethylnaphthalene isomer. Our data suggest the possibility of the first pressure parameter or "cosmo-barometer" (1,5-dimethylnaphthalene/total dimethylnaphthalenes) that can distinguish pressure from thermal effects. Information can be obtained from the new pressure marker either remotely by instrumentation on landers or rovers or directly by laboratory measurement, and its use has relevance for all cases where organic matter, temperature, and pressure interplay in the cosmos. © 2014. The American Astronomical Society. All rights reserved.

  • Journal article
    Fraser WT, Watson JS, Sephton MA, Lomax BH, Harrington G, Gosling WD, Self Set al., 2014,

    Changes in spore chemistry and appearance with increasing maturity

    , Review of Palaeobotany and Palynology, Vol: 201, Pages: 41-46, ISSN: 0034-6667
  • Book chapter
    Sephton MA, 2014,

    Organic Geochemistry of Meteorites

    , Treatise on Geochemistry, Editors: Turekian, Publisher: Elsevier Science, Pages: 1-31
  • Conference paper
    Montgomery W, Sephton MA, Watson J, Zeng Het al., 2014,

    The Effects Of Minerals On Heavy Oil And Bitumen Chemistry When Recovered Using Steam-assisted Methods

    , SPE Heavy Oil Conference-Canada

    The production of gaseous sulfur-containing species during the steam-assisted recovery of heavy oil and bitumen have important consequences for both economics and safety. Factors such as the effects of mineral matrices require laboratory data to produce accurate models. To study mineral effects on gas production we studied a well-characterized oil-containing core and the isolated crude oil from that core. The samples were run at 250-300°C in the continued presence of liquid water for 24 hours. The reaction products of all experiments include gases, oil flotate, oil sinkate, water-soluble products, and water- insoluble residues. All reaction products were studied with a variety of analytical techniques, including FTIR spectroscopy, chromatographic fractionation (SARA analysis), GC-MS, pyrolysis GCMS and GC-FPD/TCD. These techniques were applied to whole oil, maltenes and asphaltene fractions. Physical properties including viscosity and density were also measured. Our data provide insights into the physical and chemical consequences of steam assisted recovery of heavy oils and bituments from sedimentary rock reservoirs and reveal that geological and geochemical context is an essential consideration.

  • Journal article
    Fraser WT, Lomax BH, Jardine PE, Gosling WD, Sephton MAet al., 2014,

    Pollen and spores as a passive monitor of ultraviolet radiation

    , Frontiers in Ecology and Evolution, Vol: 2

    Sporopollenin is the primary component of the outer walls of pollen and spores. The chemical composition of sporopollenin is responsive to levels of ultraviolet (UV) radiation exposure, via a concomitant change in the concentration of phenolic compounds. This relationship offers the possibility of using fossil pollen and spore chemistry as a novel proxy for past UV flux. Phenolic compounds in sporopollenin can be quantified using Fourier Transform infrared spectroscopy. The high potential for preservation of pollen and spores in the geologic record, and the conservative nature of sporopollenin chemistry across the land plant phylogeny, means that this new proxy has the potential to reconstruct UV flux over much longer timescales than has previously been possible. This new tool has important implications for understanding the relationship between UV flux, solar insolation and climate in the past, as well as providing a possible means of assessing paleoaltitude, and ozone thickness.

  • Journal article
    Martins Z, Price MC, Goldman N, Sephton MA, Burchell MJet al., 2013,

    Shock synthesis of amino acids from impacting cometary and icy planet surface analogues

    , Nature Geoscience, Vol: 6, Pages: 1045-1049, ISSN: 1752-0894
  • Journal article
    Howard K, Bailey MJ, Berhanu D, Bland PA, Cressey G, Howard LE, Jeynes C, Matthewman R, Martins Z, Sephton MA, Stolojan V, Verchovsky Set al., 2013,

    Biomass preservation in impact melt ejecta

    , Nature Geoscience
  • Journal article
    Olsson-Francis K, Watson JS, Cockell CS, 2013,

    Cyanobacteria isolated from the high-intertidal zone: a model for studying the physiological prerequisites for survival in low Earth orbit

    , International Journal of Astrobiology, Vol: 12, Pages: 292-303, ISSN: 1473-5504

    <jats:title>Abstract</jats:title><jats:p>Cyanobacteria are capable of surviving the adverse conditions of low Earth orbit (LEO). We have previously demonstrated that<jats:italic>Gloeocapsa</jats:italic>strain OU_20,<jats:italic>Chroococcidiopsis</jats:italic>and akinetes of<jats:italic>Anabaena cylindrica</jats:italic>were able to survive 548 days of exposure to LEO. Motivated by an interest to understand how cyanobacteria can survive in LEO, we studied the strategies that<jats:italic>Gloeocapsa</jats:italic>strain OU_20 employs to survive in its natural environment, the upper region of the intertidal zone. Here, cyanobacteria are exposed to fluctuations in temperature, UV radiation, desiccation and salinity. We demonstrated that an increase in salinity from 6.5‰ (BG-11 medium) to 35.7‰ (similar to that of seawater), resulted in increased resistance to UV radiation (254 nm), vacuum (0.7×10<jats:sup>−3</jats:sup>±0.01 kPa) and cold temperatures (–20 °C). Concomitantly, biochemical analyses demonstrated that the amount of fatty acids and mycosporine-like amino acids (a UV absorbing pigment) were higher in the stressed cells. Morphological analysis demonstrated that the electron density and thickness of the mucilaginous sheath were also greater than in the control cells. Yet, the control and stressed cells both formed aggregates. As a result of studying the physiological adaptation of<jats:italic>Gloeocapsa</jats:italic>strain OU_20 in response to salinity, we postulate that survival in the high-intertidal zone and LEO involves a dense extracellular mucilaginous sheath and the formation of aggregates. We conclude that studying the physiological adaptation of cyanobacteria in the intertidal zone provides insight into understanding survival in LEO.</jats:p>

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