Publications
283 results found
Sephton MA, Jiao D, Engel MH, et 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.
Montgomery W, Sephton MA, Watson JS, et al., 2015, The effects of minerals on heavy-oil and bitumen chemistry when recovered by steam-assisted methods, Journal of Canadian Petroleum Technology, Vol: 54, Pages: 15-17, ISSN: 0021-9487
Research from this paper provides insight into the physical and chemical consequences of steam-assisted recovery of heavy oils and bitumens from sedimentary-rock reservoirs and reveals that geological and geochemical context is an essential consideration. To study mineral effects on gas production, the authors of the complete paper studied a well-characterized oil-containing core and the isolated crude oil from that core. The samples were run at 250 to 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 Fourier-transform infrared spectroscopy, chromatographic fractionation [saturate, resin, and asphaltene (SARA) analysis], gas chromatography mass spectrometry (GCMS), pyrolysis GCMS, and gas chromatography (GC) flame photometric detectors (FPDs)/thermal-conductivity detectors. These techniques were applied to whole oil, maltenes, and asphaltene fractions. Physical properties, including viscosity and density, were also measured.
Sephton MA, Watson JS, Meredith W, et al., 2015, Multiple cosmic sources for meteorite macromolecular materials?, Astrobiology, Vol: 15, ISSN: 1557-8070
Montgomery WB, Sephton MA, Watson JS, et 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.
Lewis JMT, Watson JS, Najorka J, et 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.
Sephton MA, Lewis JMT, Watson JS, et 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: 0094-8276
<jats:title>Abstract</jats:title><jats:p>Instruments on the Viking landers and Curiosity rover analyzed 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 to generate 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. Low molecular weight organic matter reacts at lower temperatures than its high molecular weight counterparts. 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.</jats:p>
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
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
Verchovsky AB, Hunt SA, Montgomery W, et al., 2014, REACTION OF Q TO THERMAL METAMORPHISM IN THE PARENT BODIES: HIGH-PRESSURE EXPERIMENTS, 77th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A421-A421, ISSN: 1086-9379
Court RW, Sims MR, Cullen DC, et 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
Luong D, Court RW, Sims MR, et 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
Sephton MA, 2014, Astrobiology can help space science, education and the economy, Space Policy, Vol: 30, Pages: 146-148, ISSN: 0265-9646
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
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.
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Fraser WT, Watson JS, Sephton MA, et al., 2014, Changes in spore chemistry and appearance with increasing maturity, Review of Palaeobotany and Palynology, Vol: 201, Pages: 41-46, ISSN: 0034-6667
Sephton MA, 2014, Unlocking the biochemical secrets of the red planet: Life on Mars, Biochemist, Vol: 36, Pages: 20-23, ISSN: 0954-982X
The planet Mars is a focus for numerous life search missions. As a near neighbour to Earth and with evidence of similar conditions in its early history, contemporaneous with the origin of life on Earth, there is a reasonable possibility of finding evidence for alien life on the red planet. With a whole planet to choose from and only a limited number of in situ analyses possible, the selection of samples to analyse is crucial. Fortunately, clues from analogues on Earth can provide effective guidance for sample choice. The harsh environment of Mars suggests that fine-grained sediments with features suggestive of past liquid water are the most likely to host organic records of past life. Also, with high doses of radiation experienced at the surface, digging deep will increase the probabilities of success for detecting carbon-based records. Past and current in situ missions to Mars are experiencing problems with unexpected amounts of aggressive salts on the planet surface, but the future holds the potential for returning samples of Mars to Earth where multiple sophisticated techniques can be employed to reveal the biochemical secrets of the red planet. 2014
Sephton MA, 2014, Organic Geochemistry of Meteorites, Treatise on Geochemistry, Editors: Turekian, Publisher: Elsevier Science, Pages: 1-31
Montgomery W, Sephton MA, Watson J, et 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.
Fraser WT, Lomax BH, Jardine PE, et 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.
Martins Z, Price MC, Goldman N, et 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
Howard K, Bailey MJ, Berhanu D, et al., 2013, Biomass preservation in impact melt ejecta, Nature Geoscience
Emmerton S, Muxworthy AR, Sephton MA, 2013, A magnetic solution to the Mupe Bay mystery, Marine and Petroleum Geology, Vol: 46, Pages: 165-172, ISSN: 0264-8172
Martins Z, Modica P, Sephton MA, et al., 2013, THE SOLUBLE ORGANIC CONTENT OF THE PARIS METEORITE THE MOST PRIMITIVE CM CHONDRITE, 76th Annual Meeting of the Meteoritical-Society, Publisher: WILEY, Pages: A236-A236, ISSN: 1086-9379
Emmerton S, Muxworthy AR, Sephton MA, et al., 2013, Correlating biodegradation to magnetization in oil bearing sedimentary rocks, Geochimica et Cosmochimica Acta, Vol: 112, Pages: 146-165, ISSN: 0016-7037
Carter JN, Sephton MA, 2013, A Bayesian statistical assessment of representative samples for asteroidal or meteoritical material, Meteoritics & Planetary Science, Vol: 48, Pages: 976-996, ISSN: 1086-9379
<jats:title>Abstract</jats:title><jats:p>Primitive substances in asteroid and meteorite materials represent a record of early solar system evolution. To allow the study of these materials, they must be collected and transferred to the laboratory. Collection during sample return missions requires an assessment of the size of samples needed. Meteorite falls or finds must be subdivided into appropriate subsamples for analysis by successive generations of scientists. It is essential, therefore, to determine a representative mass or volume at which the collected or allocated sample is representative of the whole. For the first time, we have used a Bayesian statistical approach and a selected meteorite sample, Murchison, to identify a recommended smallest sample mass that can be used without interferences from sampling bias. Enhancing background knowledge to inform sample selection and analysis is an effective means of increasing the probability of obtaining a positive scientific outcome. The influence of the subdivision mechanism when preparing samples for distribution has also been examined. Assuming a similar size distribution of fragments to that of the Murchison meteorite, cubes can be similarly representative as fragments, but at orders of magnitude smaller sizes. We find that: (1) at all defined probabilities (90%, 95%, and 99%), nanometer‐sized particles (where the axes of a three‐dimensional sample are less that a nanometer in length) are never representative of the whole; (2) at the intermediate and highest defined probabilities (95% and 99%), micrometer‐sized particles are never representative of the whole; and (3) for micrometer‐sized samples, the only sample that is representative of the whole is a cube and then only at a 90% probability. The difference between cubes and fragments becomes less important as sample size increases and any >0.5 mm‐sized sample will be representative of the whole with a probability of 99.9%. The resul
Sephton MA, 2013, Aromatic units from the macromolecular material in meteorites: Molecular probes of cosmic environments, Geochimica et Cosmochimica Acta, Vol: 107, Pages: 231-241, ISSN: 0016-7037
Berthoud L, Schroeven-Deceuninck H, Vrublevskis J, et al., 2013, Concept for a lunar and asteroid sample return facility, Pages: 8937-8946, ISSN: 0074-1795
The objective of this European Space Agency study was to examine an initial concept and requirements for a Lunar and Asteroid Receiving Facility (LaARF). Then to investigate the evolution from a facility dealing with only Moon and asteroid returned sample material to a facility dealing with Mars returned sample material with potential biohazard. The LaARF concept and requirements were broadly derived from requirements including Infrastructure, Equipment, People & Knowledge. The facility concept was required to deal with samples from a number of possible missions returning from asteroids or the lunar surface. A number of past and planned missions were outlined to draw both general features that can be used to develop the concept, and more importantly to derive the range of likely hardware and samples to be handled by the facility. Requirements for the general sample quantity and make-up were that the facility should accommodate 500g of samples comprising dust, grains and rocks of varying composition and sizes. The initial concept was evolved using review of literature and inputs from a dedicated Concept Definition Workshop involving scientific and industry experts. A functional architecture was established and technologies & techniques were assessed. It was recognised that tele-operations are especially needed. Information flow through the facility was analysed. Commonality with a Mars Sample Receiving Facility (MSRF) was assessed and possible evolutions to a MSRF were considered. Then Scenario Definition Workshops were held with leading scientists and industry experts to determine the optimal scenario to evolve the LaARF to an MSRF. The result of this analysis was that independent facilities without 'future-proofing' prior to expansion were the optimal solution. This approach maximised the potential future capability in a cost-efficient manner. Finally, analysis of potential users for the facility showed that Planetary Protection (PP) hardware samples, meteo
Montgomery W, Sephton MA, Court RW, et al., 2013, Quantitative Laboratory Assessment Of Aquathermolysis Chemistry During Steam-assisted Recovery Of Heavy Oils And Bitumen, With A Focus On Sulfur, SPE Heavy Oil Conference, Publisher: Society of Petroleum Engineers
The production of gaseous sulfur-containing species during the steam-assisted recovery of heavy oil and bitumen presents problems owing to their toxicity, corrosion properties and odor. In order to quantitatively study aquathermolysis sulfur chemistry during the thermal (steam-assisted) recovery of heavy oils we have subjected a well-characterized and sulfur-rich bitumen core sample to 150 - 325°C and 70 - 1740 psia (0.48 - 12 MPa) conditions in the continued presence of liquid water for 24 hours. The reaction products include gases, oil flotate, oil sinkate, water-soluble products, and water- insoluble residues. All have been studied with a variety of analytical techniques, including FTIR spectroscopy, chromatographic fractionation (SARA analysis), GC-FPD and GC-MS. Moreover, these techniques have been extended to analysis of the asphaltene fractions. Results suggest that some in-situ upgrading of the oil occurs under these conditions; additionally, gaseous hydrogen sulfide is released at temperatures at and above 250 °C. Variations in the relative abundances of solubility classes and chemical fractions imply that the source of sulfur is via the thermal degradation of resins and/or asphaltenes. The experimental methods, results and quantification approach discussed herein will be useful to support the development of models for engineering design of facilities for the steam-assisted recovery of heavy oils and bitumen.
Sephton MA, Sims MR, Court RW, et al., 2013, Searching for biomolecules on Mars: Considerations for Operation of a Life Marker Chip instrument, Planetary and Space Science, Vol: 86, Pages: 66-74, ISSN: 0032-0633
The search for life on Mars requires instruments that detect organic matter and discriminate between potential sources. One such instrument is the Life Marker Chip that recognizes small molecules which are characteristic of particular organic provenances. The use of an antibody-based detection system requires the delivery of small organic compounds in a suitable solvent. Dedicated extraction protocols have been developed partly through the use of a Life Marker Chip breadboard system. Techniques which provide the strong diagnostic potential of the Life Marker Chip necessitate specific extraction protocols and appropriate sample types. Clay mineral-rich rocks are attractive targets owing to their i) association with liquid water, ii) propensity for organic matter and clay mineral co-deposition following transport from a wide hinterland, and iii) relatively large surface area and therefore potential for trapping/adsorption of organic materials. The most appropriate target organic compounds are the hydrocarbon-dominated lipids that can be highly diagnostic and have relatively high preservation potentials. The sample sites on Mars and sample preparation steps that are needed for successful detection require careful consideration. In this paper we explore the scientific results that may be obtained through the operation of a Life Marker Chip instrument on Mars.
Montgomery W, Court RW, Rees AC, et al., 2013, High temperature reactions of water with heavy oil and bitumen: insights into aquathermolysis chemistry during steam-assisted recovery, Fuel, Vol: 113, Pages: 426-426, ISSN: 0016-2361
To better understand the hot water-mediated organic transformation process (aquathermolysis) that occurs during the steam-assisted recovery of heavy oils and bitumen we have performed a series of experiments that subject a heavy oil to progressively higher temperatures and pressures in the presence of liquid water. As temperature and pressure increases, from ambient conditions to 300 °C and 1250 psig (8.6 MPa), a floating oil (flotate) is generated and is composed of mostly aliphatic hydrocarbons that appear to be generated at the expense of polars and asphaltenes. Analyses of hopane maturity parameters for the flotate indicate lower temperatures than the starting material suggesting the liberation of hopanes and, therefore, other hydrocarbons, from asphaltenes. Infrared spectra confirm changes in overall organic constitution as the relative abundance of hydrocarbons to oxygen-containing functional groups increases in the flotate. At the highest temperatures and pressures (325 °C, 1750 psig (13.8 MPa)) the flotate is at a maximum relative amount, the untransformed heavy oil is at a minimum and significant amounts of methane are generated indicating the onset of cracking. Steam-assisted recovery of heavy oil, therefore, leads to changes in the chemical constitution of a number of chemical fractions generating a lighter oil and gases that must be taken into account when planning field operations for production.
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