Publications
283 results found
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
Court RW, Baki OA, Sims MR, et al., 2011, THE LIFE MARKER CHIP-EXTRACTING POLAR AND NONPOLAR BIOMARKERS FROM THE MARTIAN SOIL USING A SURFACTANT-BASED SOLVENT, 74th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A50-A50, ISSN: 1086-9379
Sephton MA, Meredith W, Sun CG, et al., 2011, Biomedical and forensic applications of combined catalytic hydrogenation-stable isotope ratio analysis, Analytical Chemistry: Methods and Applications, Pages: 266-277, ISBN: 9781926692586
Studies of biological molecules such as fatty acids and the steroid hormones have the potential to benefit enormously from stable carbon isotope ratio measurements of individual molecules. In their natural form, however, the body’s molecules interact too readily with laboratory equipment designed to separate them for accurate measurements to be made. Some methods overcome this problem by adding carbon to the target molecule, but this can irreversibly overprint the carbon source ‘signal’. Hydropyrolysis is a newly-applied catalytic technique that delicately strips molecules of their functional groups but retains their carbon skeletons and stereochemistries intact, allowing precise determination of the carbon source. By solving analytical problems, the new technique is increasing the ability of scientists to pinpoint molecular indicators of disease, elucidate metabolic pathways and recognise administered substances in forensic investigations.
Fraser WT, Sephton MA, Watson JS, et 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.
Rothery DA, Gilmour I, Sephton MA, 2011, An Introduction to Astrobiology, Cambridge, Publisher: Cambridge University Press, ISBN: 9781107600935
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.
Gowen RA, Smith A, Fortes AD, et 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.
Ehrenfreund P, Roling WFM, Thiel CS, et 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
Sephton MA, Court RW, Baki AO, et 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.
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.
Martins Z, Sephton MA, Foing BH, et 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
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.
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 ...
Wainipee W, Weiss DJ, Sephton MA, et al., 2010, The effect of crude oil on arsenate adsorption on goethite, WATER RESEARCH, Vol: 44, Pages: 5673-5683, ISSN: 0043-1354
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- Citations: 41
Baki AO, Sephton MA, Sims MR, et 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.
Sephton MA, Court RW, 2010, Meteorite gases and planetary atmospheres, ASTRONOMY & GEOPHYSICS, Vol: 51, Pages: 21-22, ISSN: 1366-8781
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- Citations: 1
Matthewman R, Court RW, Martins Z, et 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
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
Grant J, Westall F, Beaty D, et al., 2010, Two Rovers to the Same Site on Mars, 2010: Possibilities for Cooperative Science, Astrobiology, Vol: 10, Pages: 663-685, ISSN: 1531-1074
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 ...
Court RW, Baki AO, Sims MA, et 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.
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.
Meredith W, Gomes RL, Cooper M, et 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.
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.
Ehrenfreund P, Foing BH, Quinn R, et al., 2009, Mars desert research station MDRS-crew 77: Terrestrial field research, Pages: 273-274
The goal of the EuroGeoMars campaign in Utah at the Mars Desert Research Station (MDRS) in February 2009 was to perform field research and to demonstrate instrument capabilities in support of current and future Mars missions, such as MarsExpress, Mars Science Laboratory and Exomars. The MDRS Crew 77 collected soil samples from different locations in the vicinity of the MDRS station in Utah from the Morrison formation and investigated those soils in the laboratory with Terra XRD/XRF (X-ray diffraction/X-ray fluorescence) from InXitu Inc. and a Raman InPhotonics (LAS-750-300 Class3b embedded Diode Laser, 785 nm wavelength) instrument. We also measured selected soil properties including pH value and elemental composition of Ca, K, P, Mg, and nitrate directly in the field using colorimetric chemical reactions (LaMotte Soil Testing System). Salt concentrations were estimated with a conductivity probe. According to this combined measurements we selected soils that most likely trigger oxidative processes when incubated with chemo-metric sensor arrays similar to the Mars Oxidation Instrument (MOI). We present the analysis flow of sampling, in-situ investigation and data interpretation at MDRS and report on post-analysis activities. The reported field investigations are crucial to support future endeavors to search for organic compounds on Mars.
Martins ZCTP, 2009, Extraterrestrial amino acids, Amino Acids, Peptides and Proteins in Organic Chemistry, Origins and Synthesis of Amino Acids, Publisher: John Wiley & Sons, ISBN: 9783527320967
Closing a gap in the literature, this practical book series draws on the expertise of the international "who's who" in amino acid research to provide a comprehensive discussion of the occurrence, uses and applications of amino acids, their ...
Needham AW, Smith CL, Howard KT, et al., 2009, GAMMA IRRADIATION EFFECTS IN MARS ANALOGUES, 72nd Annual Meeting of the Meteoritical-Society, Publisher: METEORITICAL SOC, Pages: A155-A155, ISSN: 1086-9379
Fehr MA, James RH, Sephton MA, et al., 2009, Primitive lithium isotope signatures in CR carbonaceous chondrites?, 19th Annual VM Goldschmidt Conference, Publisher: PERGAMON-ELSEVIER SCIENCE LTD, Pages: A359-A359, ISSN: 0016-7037
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- Citations: 3
Athwal V, Scerri D, Prasad N, et al., 2009, IS COLONOSCOPY QUALITY AND OPERATOR EXPERTISE IMPORTANT FOR PATIENT SATISFACTION? A COMPARISON OF ACCREDITED AND NON-ACCREDITED BOWEL CANCER SCREENING CONSULTANTS AND TRAINEE COLONOSCOPISTS, Annual Meeting of the British-Society-of-Gastroenterology, Publisher: B M J PUBLISHING GROUP, Pages: A137-A137, ISSN: 0017-5749
Peeters Z, Quinn R, Martins Z, et al., 2009, Habitability on planetary surfaces: interdisciplinary preparation phase for future Mars missions, INT J ASTROBIOL, Vol: 8, Pages: 301-315, ISSN: 1473-5504
Life on Earth is one of the outcomes of the formation and evolution of our solar system and has adapted to every explored environment on planet Earth. Recent discoveries have shown that life can exist in extreme environments, such as hydrothermal vents, in deserts and in ice lakes in Antarctica. These findings challenge the definition of the ‘planetary habitable zone’. The objective of future international planetary exploration programmes is to implement a long-term plan for the robotic and human exploration of solar system bodies. Mars has been a central object of interest in the context of extraterrestrial life. The search for extinct or extant life on Mars is one of the main goals of space missions to the Red Planet during the next decade. In this paper we describe the investigation of the physical and chemical properties of Mars soil analogues collected in arid deserts. We measure the pH, redox potential and ion concentrations, as well as carbon and amino acid abundances of soils collected from the Atacama desert (Chile and Peru) and the Salten Skov sediment from Denmark. The samples show large differences in their measured properties, even when taken only several meters apart. A desert sample and the Salten Skov sediment were exposed to a simulated Mars environment to test the stability of amino acids in the soils. The presented laboratory and field studies provide limits to exobiological models, evidence on the effects of subsurface mineral matrices, support current and planned space missions and address planetary protection issues.
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