Imperial College London

ProfessorMarkSephton

Faculty of EngineeringDepartment of Earth Science & Engineering

Head of the Department of Earth Science and Engineering
 
 
 
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Contact

 

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

 
 
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Assistant

 

Ms Daphne Salazar +44 (0)20 7594 7401

 
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Location

 

G30 (via G28)Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

195 results found

Gordon PR, Sephton MA, 2018, A Method for Choosing the Best Samples for Mars Sample Return, Astrobiology, ISSN: 1531-1074

Success of a future Mars Sample Return mission will depend on the correct choice of samples. Pyrolysis-FTIR can be employed as a triage instrument for Mars Sample Return. The technique can thermally dissociate minerals and organic matter for detection. Identification of certain mineral types can determine the habitability of the depositional environment, past or present, while detection of organic matter may suggest past or present habitation. In Mars history, the Theiikian Era represents an attractive target for life search missions and the acquisition of samples. The acidic and increasingly dry Theiikian may have been habitable and followed a lengthy neutral and wet period in Mars history during which life could have originated and proliferated to achieve relatively abundant levels of biomass with a wide distribution. Moreover, the sulfate minerals produced in the Theiikian are also known to be good preservers of organic matter. We have used pyrolysis-FTIR and samples from a Mars analogue ferrous acid stream with a thriving ecosystem to test the triage concept. Pyrolysis-FTIR identifies those samples with the greatest probability of habitability and habitation. A three tier scoring system was developed based on the detection of i) organic signals, ii) carbon dioxide and water and iii) sulfur dioxide. The presence of each component is given a score of A, B or C depending on whether the substance has been detected, tentatively detected or not detected respectively. Single-step (for greatest possible sensitivity) or multi-step (for more diagnostic data) pyrolysis-FTIR methods can inform the assignments. The system allows the highest priority samples to be categorised as AAA (or A*AA if the organic signal is complex) while the lowest priority samples can be categorised as CCC. Our methods provide a mechanism to rank samples and identify those that should take the highest priority for return to Earth during a Mars Sample Return mission.

JOURNAL ARTICLE

Lewis JMT, Najorka J, Watson JS, Sephton MAet al., 2018, The Search for Hesperian Organic Matter on Mars: Pyrolysis Studies of Sediments Rich in Sulfur and Iron, ASTROBIOLOGY, ISSN: 1531-1074

JOURNAL ARTICLE

Mohialdeen IMJ, Mustafa KA, Salih DA, Saeed DA, Sephton MAet al., 2018, Biomarker analysis of the upper Jurassic Naokelekan and Barsarin Formations in the Miran Well-2, Miran oil field, Kurdistan region, Iraq, Arabian Journal of Geosciences, Vol: 11, Pages: 51-51, ISSN: 1866-7538

The Miran oilfield is one of the new oil fields in Kurdistan region, northern Iraq, located in the Sulaimani Governorate. TwelveCuttings samples from the Upper Jurassic Naokelekan and Barsarin formations in well Miran-2 were selected for detailed organicgeochemical investigations. All the samples were subjected to bitumen extraction in order to study any biomarkers present usinggas chromatography-mass spectrometry. The dominance of low-molecular-weight n-alkanes and other calculated parameters indicate a marine source for the organic matter derived from planktonic algal and bacterial precursors deposited under anoxic conditions. The isoprenoids/n-alkanes ratios indicate type II and mixed II/III kerogen for both formations. The type II/III kerogen is characteristic of transitional environment under anoxic to dysoxic conditions as also indicated by the homohopane index for studied samples. More argillaceous carbonate rocks were deposited when reducing conditions were prevalent. Medium to high gammacerane index values in the rock extracts probably indicate a stratified water column during deposition of both formations.The studied samples from both formations have entered peak oil window maturity as reflected from the biomarker ratios fromboth aliphatic and aromatic fractions of the extracts.

JOURNAL ARTICLE

Moreno-Paz M, Gómez-Cifuentes A, Ruiz-Bermejo M, Hosftetter O, Maqueira Á, Morais S, Sephton MA, Knopp D, Parro Vet al., 2018, Detecting non-volatile life- and non-life-derived organics in a carbonaceous chondrite analogue with a new multiplex immunoassay and its relevance for planetary exploration, Astrobiology, ISSN: 1531-1074

Among the potential martian molecular targets are those supplied by meteoritic carbonaceous chondrites such as amino acids and polyaromatic hydrocarbons (PAHs), or true biomarkers by any hypothetical Martian biota (aromatic amino acids, steroid and triterpene molecules, peptides). Heat extraction and pyrolysis based methods currently used in planetary exploration are highly aggressive and very often modify the target molecules making a cumbersome task their identification. We have developed and validated a mild, non-destructive, multiplex competitive/inhibitory microarray immunoassay and its implementation in the SOLID (Signs of Life Detector) instrument for simultaneous detection of several organic molecules relevant for Mars exploration and environmental monitoring. A multiplex inhibitory immunoassay with a set of highly specific and sensitive antibodies capable to distinguish between D and L aromatic amino acids (Phe, Tyr, Trp), benzo[a]pyrene (BAP), pentachlorophenol or sulfone-containing aromatics, was validated in SOLID instrument for the analysis of kerogen samples as analogues of refractory organic material in carbonaceous chondrites or even Mars organics. Most of the antibodies exhibited sensitivities at 1-10 ppb level and some of them even at ppt. The multiplex immunoassay allowed the detection of BAP as well as aromatic sulfones in a water/methanol extract of an early cretaceous sample (c.a. 100 My) enriched in type IV kerogen. No L/D aromatic amino acids were detected, reflecting the high maturity and the absence of chemical groups. The results demonstrated once more the feasibility of multiplex inhibitory immunoassays and its potential use for in situ analytical instruments in planetary exploration and environmental monitoring.

JOURNAL ARTICLE

Schulze-Makuch D, Wagner D, Kounaves SP, Mangelsdorf K, Devine KG, de Vera J-P, Schmitt-Kopplin P, Grossart H-P, Parro V, Kaupenjohann M, Galy A, Schneider B, Airo A, Frösler J, Davila A, Arens F, Caceres L, Cornejo FS, Carrizo D, Dartnell L, DiRuggiero J, Flury M, Ganzert L, Gessner MO, Grathwohl P, Guan L, Heinz J, Hess M, Keppler F, Maus D, McKay CP, Meckenstock RU, Montgomery W, Oberlin EA, Probst A, Saenz J, Sattler T, Schirmack J, Sephton MA, Schloter M, Uhl J, Valenzuela B, Vestergaard G, Wörmer L, Zamorano Pet al., 2018, A transitory microbial habitat in the hyperarid Atacama desert, Proceedings of the National Academy of Sciences, ISSN: 0027-8424

JOURNAL ARTICLE

Sephton MA, 2018, Selecting Mars Samples to Return to Earth, Astronomy and Geophysics, ISSN: 1366-8781

When the search for life on Mars turns to returning samples to Earth for analysis, the choice of what to bring is complex. Mark A Sephton considers how to select the most valuable samples to bring back to Earth from Mars.

JOURNAL ARTICLE

Sephton MA, Waite JH, Brockwell TG, 2018, How to Detect Life on Icy Moons, Astrobiology, Vol: 18, ISSN: 1531-1074

The icy moons of the outer solar system present the possibility of subsurface water, habitable conditions and potential abodes for life. Access to evidence that reveals the presence of life on the icy moons can be facilitated by plumes that eject material from the subsurface out into space. One instrument capable of performing life-search investigations at the icy moons is the MAss SPectrometer for Planetary EXploration/Europa (MASPEX), which constitutes a high-resolution, high sensitivity multibounce time-of-flight mass spectrometer capable of measuring trace amounts (ppb) of organic compounds. MASPEX has been selected for the NASA Europa Clipper mission and will sample any plumes and the surface-sputtered atmosphere to assess any evidence for habitability and life. MASPEX is capable of similar investigations targeted at other icy moons. Data may be forthcoming from direct sampling but also impact dissociation because of the high speed of some analytes. Impact dissociation is analogous to the dissociation provided by modern analytical pyrolysis methods. Radiolytic dissociation on the Europan surface before or during the sputtering process can also induce fragmentation similar to pyrolysis. In this study, we have compiled pyrolysis-mass spectrometry data from a variety of biological and non-biological materials to demonstrate the ability of MASPEX to recognise habitability and detect life in any plumes and atmospheres of icy moons.

JOURNAL ARTICLE

Abrams MA, Gong C, Garnier C, Sephton MAet al., 2017, A new thermal extraction protocol to evaluate liquid rich unconventional oil in place and in-situ fluid chemistry, Marine and Petroleum Geology, Vol: 88, Pages: 659-675, ISSN: 0264-8172

JOURNAL ARTICLE

Georgieva MN, Little CTS, Watson JS, Sephton MA, Ball AD, Glover AGet al., 2017, Identification of fossil worm tubes from Phanerozoic hydrothermal vents and cold seeps, Journal of Systematic Palaeontology, Pages: 1-43, ISSN: 1477-2019

© 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. One of the main limitations to understanding the evolutionary history of hydrothermal vent and cold seep communities is the identification of tube fossils from ancient deposits. Tube-dwelling annelids are some of the most conspicuous inhabitants of modern vent and seep ecosystems, and ancient vent and seep tubular fossils are usually considered to have been made by annelids. However, the taxonomic affinities of many tube fossils from vents and seeps are contentious, or have remained largely undetermined due to difficulties in identification. In this study, we make a detailed chemical (Fourier-transform infrared spectroscopy and pyrolysis gas-chromatography mass-spectrometry) and morphological assessment of modern annelid tubes from six families, and fossil tubes (seven tube types from the Cenozoic, 12 Mesozoic and four Palaeozoic) from hydrothermal vent and cold seep environments. Characters identified from these investigations were used to explore for the first time the systematics of ancient vent and seep tubes within a cladistic framework. Results reveal details of the compositions and ultrastructures of modern tubes, and also suggest that two types of tubes from ancient vent localities were made by the annelid family Siboglinidae, which often dominates modern vents and seeps. Our results also highlight that several vent and seep tube fossils formerly thought to have been made by annelids cannot be assigned an annelid affiliation with any certainty. The findings overall improve the level of quality control with regard to interpretations of fossil tubes, and, most importantly, suggest that siboglinids likely occupied Mesozoic vents and seeps, greatly increasing the minimum age of the clade relative to earlier molecular estimates.

JOURNAL ARTICLE

Potiszil C, Montgomery W, Sephton MA, 2017, Effects of Pressure on Model Compounds of Meteorite Organic Matter, ACS EARTH AND SPACE CHEMISTRY, Vol: 1, Pages: 475-482, ISSN: 2472-3452

JOURNAL ARTICLE

Royle SH, Montgomery W, Kounaves SP, Sephton MAet al., 2017, Effect of Hydration State of Martian Perchlorate Salts on Their Decomposition Temperatures During Thermal Extraction, JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS, Vol: 122, Pages: 2793-2802, ISSN: 2169-9097

JOURNAL ARTICLE

Sephton MA, 2017, Thermal extraction for organic-matter containing materials to answer questions both on Earth and in Space, First Break, Vol: 35, Pages: 113-117, ISSN: 1365-2397

The role of heat in the generation of petroleum has led to the study of organic matter-containing rocks by laboratory heating techniques. In particular, heat is used for the thermal extraction of organic matter in preparation for characterization by a range of detectors. Recently, thermal extraction has been used to answer certain planetary science questions such as the history of habitability for planets in the solar system and the search for evidence of life outside the Earth. The development of new thermal extraction protocols for challenging planetary science objectives provide methods that are readily translatable back to petroleum activities and include new shale screening and assessment techniques.

JOURNAL ARTICLE

Zafar R, Watson JS, Weiss DJ, Sephton MAet al., 2017, Organic compound-mineral interactions: Using flash pyrolysis to monitor the adsorption of fatty acids on calcite, JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS, Vol: 123, Pages: 184-193, ISSN: 0165-2370

JOURNAL ARTICLE

Gordon PR, Sephton MA, 2016, Rapid habitability assessment of Mars samples by pyrolysis-FTIR, Planetary and Space Science, Vol: 121, Pages: 60-75, ISSN: 1873-5088

Pyrolysis Fourier transform infrared spectroscopy (pyrolysis FTIR) is a potential sample selection method for Mars Sample Return missions. FTIR spectroscopy can be performed on solid and liquid samples but also on gases following preliminary thermal extraction, pyrolysis or gasification steps. The detection of hydrocarbon and non-hydrocarbon gases can reveal information on sample mineralogy and past habitability of the environment in which the sample was created. The absorption of IR radiation at specific wavenumbers by organic functional groups can indicate the presence and type of any organic matter present. Here we assess the utility of pyrolysis-FTIR to release water, carbon dioxide, sulphur dioxide and organic matter from Mars relevant materials to enable a rapid habitability assessment of target rocks for sample return. For our assessment a range of minerals were analysed by attenuated total reflectance FTIR. Subsequently, the mineral samples were subjected to single step pyrolysis and multi step pyrolysis and the products characterised by gas phase FTIR.Data from both single step and multi step pyrolysis-FTIR provide the ability to identify minerals that reflect habitable environments through their water and carbon dioxide responses. Multi step pyrolysis-FTIR can be used to gain more detailed information on the sources of the liberated water and carbon dioxide owing to the characteristic decomposition temperatures of different mineral phases. Habitation can be suggested when pyrolysis-FTIR indicates the presence of organic matter within the sample. Pyrolysis-FTIR, therefore, represents an effective method to assess whether Mars Sample Return target rocks represent habitable conditions and potential records of habitation and can play an important role in sample triage operations.

JOURNAL ARTICLE

Gordon PR, Sephton MA, 2016, Organic Matter Detection on Mars by Pyrolysis-FTIR: An Analysis of Sensitivity and Mineral Matrix Effects, ASTROBIOLOGY, Vol: 16, Pages: 831-845, ISSN: 1531-1074

JOURNAL ARTICLE

Jardine PE, Fraser WT, Lomax BH, Sephton MA, Shanahan TM, Miller CS, Gosling WDet al., 2016, Pollen and spores as biological recorders of past ultraviolet irradiance, SCIENTIFIC REPORTS, Vol: 6, ISSN: 2045-2322

JOURNAL ARTICLE

Matthewman R, Crawford IA, Jones AP, Joy KH, Sephton MAet al., 2016, Organic Matter Responses to Radiation under Lunar Conditions, ASTROBIOLOGY, Vol: 16, Pages: 900-912, ISSN: 1531-1074

JOURNAL ARTICLE

Montgomery W, Bromiley GD, Sephton MA, 2016, The nature of organic records in impact excavated rocks on Mars, SCIENTIFIC REPORTS, Vol: 6, ISSN: 2045-2322

JOURNAL ARTICLE

Montgomery W, Potiszil C, Watson JS, Sephton MAet al., 2016, Sporopollenin, a Natural Copolymer, is Robust under High Hydrostatic Pressure, MACROMOLECULAR CHEMISTRY AND PHYSICS, Vol: 217, Pages: 2494-2500, ISSN: 1022-1352

JOURNAL ARTICLE

Montgomery W, Sephton MA, 2016, PRESSURE EFFECTS IN POLYCYCLIC AROMATIC NITROGENATED HETEROCYCLES (PANHs): DIAGNOSTIC QUALITIES AND COSMOBAROMETRY POTENTIAL, ASTROPHYSICAL JOURNAL, Vol: 819, ISSN: 0004-637X

JOURNAL ARTICLE

Najorka J, Lewis JMT, Spratt J, Sephton MAet al., 2016, Single-crystal X-ray diffraction study of synthetic sodium-hydronium jarosite, PHYSICS AND CHEMISTRY OF MINERALS, Vol: 43, Pages: 377-386, ISSN: 0342-1791

JOURNAL ARTICLE

Abubakar R, Muxworthy A, Sephton M, Southern P, Watson J, Fraser A, Almeida Tet al., 2015, Formation of magnetic minerals at hydrocarbon-generation conditions, Marine and Petroleum Geology, Vol: 68, Pages: 509-519, ISSN: 0264-8172

JOURNAL ARTICLE

Lewis JMT, Watson JS, Najorka J, Duy L, Sephton MAet al., 2015, Sulfate Minerals: A Problem for the Detection of Organic Compounds on Mars?, ASTROBIOLOGY, Vol: 15, Pages: 247-258, ISSN: 1531-1074

JOURNAL ARTICLE

Luong D, Sephton MA, Watson JS, 2015, Subcritical water extraction of organic matter from sedimentary rocks, ANALYTICA CHIMICA ACTA, Vol: 879, Pages: 48-57, ISSN: 0003-2670

JOURNAL ARTICLE

Matthewman R, Court RW, Crawford IA, Jones AP, Joy KH, Sephton MAet al., 2015, The Moon as a Recorder of Organic Evolution in the Early Solar System: A Lunar Regolith Analog Study, Astrobiology, Vol: 15, Pages: 154-168, ISSN: 1531-1074

JOURNAL ARTICLE

Montgomery W, Sephton MA, Watson JS, Zeng Het al., 2015, The Effects of Minerals on Heavy-Oil and Bitumen Chemistry When Recovered by Steam-Assisted Methods, Publisher: SPE-SOC PETROLEUM ENGINEERS, CANADA, Pages: 15-17, ISSN: 0021-9487

CONFERENCE PAPER

Montgomery W, Sephton MA, Watson JS, Zeng Het 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.

JOURNAL ARTICLE

Montgomery W, Sephton MA, Watson JS, Zeng H, Rees ACet al., 2015, Minimising hydrogen sulphide generation during steam assisted production of heavy oil, SCIENTIFIC REPORTS, Vol: 5, ISSN: 2045-2322

JOURNAL ARTICLE

Mustafa KA, Sephton MA, Watson JS, Spathopoulos F, Krzywiec Pet al., 2015, Organic geochemical characteristics of black shales across the Ordovician-Silurian boundary in the Holy Cross Mountains, central Poland, MARINE AND PETROLEUM GEOLOGY, Vol: 66, Pages: 1042-1055, ISSN: 0264-8172

JOURNAL ARTICLE

Sephton MA, Carter JN, 2015, The chances of detecting life on Mars, PLANETARY AND SPACE SCIENCE, Vol: 112, Pages: 15-22, ISSN: 0032-0633

JOURNAL ARTICLE

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