Imperial College London

ProfessorMarkSephton

Faculty of EngineeringDepartment of Earth Science & Engineering

Professor of Organic Geochemistry
 
 
 
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Contact

 

+44 (0)20 7594 6542m.a.sephton Website

 
 
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Location

 

2.34Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

283 results found

Sephton MA, 2013, Pyrolysis, spectroscopy and extraterrestrial organic matter, SpectroscopyEurope, Vol: 25, Pages: 6-11, ISSN: 0966-0941

Journal article

Matthewman R, Martins Z, Sephton MA, 2013, Type IV kerogens as analogues for organic macromolecular materials in aqueously altered carbonaceous chondrites, Astrobiology, Vol: 13, Pages: 324-333, ISSN: 1531-1074

Journal article

Wainipee W, Cuadros J, Sephton MA, Unsworth C, Gill MG, Strekopytov S, Weiss DJet al., 2013, The effects of oil on As(V) adsorption on illite, kaolinite, montmorillonite and chlorite, Geochimica et Cosmochimica Acta, Vol: 121, Pages: 487-502, ISSN: 0016-7037

The effect of oil on As(V) adsorption on clay minerals has been investigated using batch experiments at low and high pH, NaCl concentration and oil contents. Four clay minerals were chosen because of their abundance in sediments and their different crystal chemistry: illite, kaolinite, montmorillonite, and chlorite. The values for pH were 4 and 8 and salt concentrations were 0.001 and 0.7 M NaCl to appreciate the effects of changing salinity, e.g from fresh water to seawater conditions. For the coating experiments, a well-characterised oil was used to survey the main effects of complex organic mixtures on adsorption and oil to clay mineral (w/w) ratios were 0.0325 and 0.3250. As(V) adsorption increased with increasing NaCl concentration, suggesting that the mechanisms of As(V) adsorption are related to the formation of inner-sphere complexes in which Na+ ions act as bridges between the clay surface and the As(V) anions. Cation bridging is also indicated by zeta potential measurements which show that higher NaCl concentrations along with the presence of As(V) can cause the clay particles and adsorbed ions to have a more negative overall charge. Adsorption is lower at higher pH due to the reduced number of positively charged sites on the edge of clay mineral layers. Oil coating reduces As(V) adsorption by decreasing the available surface area of clay minerals, except in the case of oil-coated montmorillonite, where surface area following dispersion in water is increased. The main variables controlling As(V) adsorption are surface area and surface charge density, as confirmed by a simplified quantitative model. These findings advance our ability to predict the effects of complex pollution events in various freshwater and marine settings.

Journal article

Sephton MA, Court RW, Lewis JM, Wright MC, Gordon PRet al., 2013, Selecting samples for Mars sample return: Triage by pyrolysis-FTIR, Planetary and Space Science, Vol: 78, Pages: 45-51, ISSN: 0032-0633

A future Mars Sample Return mission will deliver samples of the red planet to Earth laboratories for detailed analysis. A successful mission will require selection of the best samples that can be used to address the highest priority science objectives including assessment of past habitability and evidence of life. Pyrolysis is a commonly used method for extracting organic information from rocks but is most often coupled with complex analytical steps such as gas chromatography and mass spectrometry. Pyrolysis-Fourier transform infrared spectroscopy is a less resource demanding method that still allows sample characterization. Here we demonstrate how pyrolysis-Fourier transform infrared spectroscopy could be used to triage samples destined to return to Earth, thereby maximising the scientific return from future sample return missions.

Journal article

Howard KT, Bailey MJ, Berhanu D, Bland PA, Cressey G, Howard LE, Jeynes C, Mathewman R, Martins Z, Sephton MA, Stolojan V, Verchovsky Set al., 2013, Biomass preservation in impact melt ejecta, Nature Geoscience

Meteorites can have played a role in the delivery of life to Earth only if organic compounds are able to survive the high pressures and temperatures of an impact event. Although experimental impact studies have reported the survival of organics there are uncertainties in scaling experimental conditions to those of a meteorite impact on Earth and organic matter has not been found in highly shocked impact materials in a natural setting. Impact glass linked to the 1.2-km-diameter Darwin crater in western Tasmania is strewn over an area exceeding 400 km2 and is thought to have been ejected by a meteorite impact about 800 kyr ago into terrain consisting of rainforest and swamp. Here we use pyrolysis–gas chromatography–mass spectrometry to show that biomarkers representative of plant species in the local ecosystem—including cellulose, lignin, aliphatic biopolymer and protein remnants—survived the Darwin impact. We find that inside the impact glass the organic components are trapped in porous carbon spheres.We propose that the organic material was captured within impact melt and preserved when the melt quenched to glass, preventing organic decomposition since the impact. We suggest that organic material can survive capture and transport in products of extreme impact processing, at least for a Darwin-sized impact event.

Journal article

Sephton MA, Hazen RM, 2013, On the origins of deep hydrocarbons, Reviews in Mineralogy & Geochemistry, Vol: 75, Pages: 449-465, ISSN: 1529-6466

Deep deposits of hydrocarbons, including varied reservoirs of petroleum and natural gas,represent the most economically important component of the deep carbon cycle. Yet despitetheir intensive study and exploitation for more than a century, details of the origins of somedeep hydrocarbons remain a matter of vocal debate in some scientific circles. This long andcontinuing history of controversy may surprise some readers, for the biogenic origins of “fossilfuels”—a principle buttressed by a vast primary scientific literature and established as textbookorthodoxy in North America and many other parts of the world—might appear to be settled fact.Nevertheless, conventional wisdom continues to be challenged by some scientists.The principal objectives of this chapter are: (1) to review the overwhelming evidence for thebiogenic origins of most known deep hydrocarbon reservoirs; (2) to present equally persuasiveexperimental, theoretical, and field evidence that components of some deep hydrocarbondeposits appear to have an abiotic origin; and (3) to suggest future studies that might help toachieve a more nuanced resolution of this sometimes polarized topic.

Journal article

Sephton MA, James RH, Fehr MA, Bland PA, Gounelle Met al., 2013, Lithium isotopes as indicators of meteorite parent body alteration, Meteoritics & Planetary Science, Vol: 48, Pages: 872-878, ISSN: 1086-9379

Hydrothermal processing on planetesimals in the early solar system produced new mineral phases, including those generated by the transformation of anhydrous silicates into their hydrated counterparts. Carbonaceous chondrites represent tangible remnants of such alteration products. Lithium isotopes are known to be responsive to aqueous alteration, yet previously recognized variability within whole rock samples from the same meteorite appears to complicate the use of these isotopes as indicators of processing by water. We demonstrate a new way to use lithium isotopes that reflects aqueous alteration in carbonaceous chondrites. Temperature appears to exert a control on the production of acetic acid-soluble phases, such as carbonates and poorly crystalline Fe-oxyhydroxides. Temperature and degree of water-rock interaction determines the amount of lithium isotope fractionation expressed as the difference between whole rock and acetic acid-leachable fractions. Using these features, the type 1 chondrite Orgueil (d7Li(whole rock) = 4.3&; D7Li(acetic-whole) = 1.2&) can be distinguished from the type 2 chondrites Murchison (d7Li(whole rock) = 3.8; D7Li(acetic whole) = 8.8&) and carbonate-poor Tagish Lake (d7Li(whole rock) = 4.3; D7Li(acetic-whole) = 9.4&). This initial study suggests that lithium isotopes have the potential to reveal the role of liquid water in the early solar system.

Journal article

Mustard JF, Adler M, Allwood A, Bass DS, Beaty DW, Bell JF, Brinckerhoff WB, Carr M, Des Marais DJ, Drake B, Edgett KS, Eigenbrode J, Elkins-Tanton LT, Grant JA, Milkovich SM, Ming D, Moore C, Murchie S, Onstott TC, Ruff SW, Sephton MA, Steele A, Treiman Aet al., 2013, Report of the Mars 2020 Science Definition Team, Report of the Mars 2020 Science Definition Team, Publisher: Mars Exploration Analysis Group (MEPAG)

Report

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

Journal article

Lomax BH, Fraser WT, Harrington G, Blackmore S, Sephton MA, Harris NBWet al., 2012, 295 A novel palaeoaltimetry proxy based on spore and pollen wall chemistry, 日本花粉学会会誌, Vol: 58, Pages: 133-134, ISSN: 0387-1851

Journal article

Emmerton S, Muxworthy AR, Sephton MA, 2012, Magnetic characterization of oil sands at Osmington Mills and Mupe Bay, Wessex Basin, UK, Remagnetization and Chemical Alteration of Sedimentary Rocks, Editors: Elmore, Muxworthy, Aldana, Mena, Elmore, Muxworthy, Aldana, Mena, London, Publisher: Geological Society, Pages: 189-198

Book chapter

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

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

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

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

Court RW, Sephton MA, 2012, Insights into the nature of cometary organic matter from terrestrial analogues, International Journal of Astrobiology, Vol: 11, Pages: 83-92, ISSN: 1473-5504

The nature of cometary organic matter is of great interest to investigations involving the formation and distribution of organic matter relevant to the origin of life. We have used pyrolysis–Fourier transform infrared (FTIR) spectroscopy to investigate the chemical effects of the irradiation of naturally occurring bitumens, and to relate their products of pyrolysis to their parent assemblages. The information acquired has then been applied to the complex organic matter present in cometary nuclei and comae. Amalgamating the FTIR data presented here with data from published studies enables the inference of other comprehensive trends within hydrocarbon mixtures as they are progressively irradiated in a cometary environment, namely the polymerization of lower molecular weight compounds; an increased abundance of polycyclic aromatic hydrocarbon structures; enrichment in 13C; reduction in atomic H/C ratio; elevation of atomic O/C ratio and increase in the temperature required for thermal degradation. The dark carbonaceous surface of a cometary nucleus will display extreme levels of these features, relative to the nucleus interior, while material in the coma will reflect the degree of irradiation experienced by its source location in the nucleus. Cometary comae with high methane/water ratios indicate a nucleus enriched in methane, favouring the formation of complex organic matter via radiation-induced polymerization of simple precursors. In contrast, production of complex organic matter is hindered in a nucleus possessing a low methane/water ration, with the complex organic matter that does form possessing more oxygen-containing species, such as alcohol, carbonyl and carboxylic acid functional groups, resulting from reactions with hydroxyl radicals formed by the radiolysis of the more abundant water. These insights into the properties of complex cometary organic matter should be of particular interest to both remote observation and space missions involving in situ an

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.

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

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.

Journal article

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.

Conference paper

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.

Journal article

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)

Report

Ehrenfreund P, Foing BH, Röling WFM, Thiel CS, Quinn R, Sephton MA, Stoker C, Kotler M, Direito SOL, Martins Z, Orzechowska GE, Kidd RDet al., 2011, Habitability studies in preparation for future Mars missions, Pages: 1208-1209

The search for organic material and biosignatures on Mars is a highly complex endeavor. Oxidative and radiation processes on the Martian surface are destructive to any organic and biological compound. However, the cold and dry climate on Mars may preserve organic matter in the subsurface, even in old terrain when spared from regional processing. An interdisciplinary preparation phase for future Mars missions is crucial to better understand the processes that may alter organic matter. Mars simulations that take into account the effects of UV and ionizing radiation, atmospheric reactions, aridity, temperature conditions, surface oxidation, salinity and acidity and aeolian processes need to be undertaken and compiled in a database to determine how the preservation potential of molecules influences the record that can be observed. Instruments on future Mars missions are limited in their capabilities to search for signs of life that conform to our preconceived notions of biomarkers. Field research conducted during the EuroGeoMars 2009 campaigns shows the need to further optimize extraction procedures to analyze biomarkers and organic molecules in future sampling campaigns. Methods have to be developed that can release adsorbed biological compounds such as amino acids and DNA during the extraction process from soils. The successful hunt for extant biosignatures will be a tradeoff between multiple parameters, including accessibility, biomarker concentration, the preservation potential, extractability, and instrument performance. When deploying organic detection instruments on Mars, consideration only of the geological context and the history of regional aqueous processes for landing site selection may be insufficient. The host microenvironment of organics and putative microbes on Mars must be compatible with the capabilities of the instrument payload. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

Conference paper

Sephton MA, Herd CDK, 2011, THE END TO END MARS SAMPLE RETURN CAMPAIGN, 74th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A211-A211, ISSN: 1086-9379

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, Pages: A211-A211, ISSN: 1086-9379

Conference paper

Verchovsky AB, Montgomery W, Sephton MA, 2011, Q NOBLE GASES IN THE ORGUEIL Hf/HCl RESIDUE: A HIGH PRESSURE EXPERIMENT, 74th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A244-A244, ISSN: 1086-9379

Conference paper

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