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

189 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

Jarosite on Mars is of significant geological and astrobiological interest as it forms in acidic aqueous conditions that are potentially habitable for acidophilic organisms. Jarosite can provide environmental context and may host organic matter. The most common analytical technique used to search for organic molecules on the surface of Mars is pyrolysis. However, thermal decomposition of jarosite produces oxygen, which degrades organic signals. At pH values greater than 3 and high water to rock ratios jarosite has a close association with goethite. Hematite can form by dehydration of goethite or directly from jarosite under certain aqueous conditions. Goethite and hematite are significantly more amenable for pyrolysis experiments searching for organic matter than jarosite. Analysis of the mineralogy and organic chemistry of samples from a natural acidic stream revealed a diverse response for organic compounds during pyrolysis of goethite-rich layers but a poor response for jarosite-rich or mixed jarosite-goethite units. Goethite units that are associated with jarosite but do not contain jarosite themselves should be targeted for organic detection pyrolysis experiments on Mars. These findings are extremely timely as future exploration targets for Mars Science Laboratory include Hematite Ridge, which may have formed from goethite precursors.

JOURNAL ARTICLE

Royle SH, Montgomery W, Kounaves SP, Sephton MAet al., 2018, Effect of hydration state of Martian perchlorate salts on their decomposition temperatures during thermal extraction, Journal of Geophysical Research: Planets, ISSN: 2169-9097

Three Mars missions have analyzed the composition of surface samples using thermal extraction techniques. The temperatures of decomposition have been used as diagnostic information for the materials present. One compound of great current interest is perchlorate, a relatively recently discovered component of Mars' surface geochemistry that leads to deleterious effects on organic matter during thermal extraction. Knowledge of the thermal decomposition behavior of perchlorate salts is essential for mineral identification and possible avoidance of confounding interactions with organic matter. We have performed a series of experiments which reveal that the hydration state of magnesium perchlorate has a significant effect on decomposition temperature, with differing temperature releases of oxygen corresponding to different perchlorate hydration states (peak of O2 release shifts from 500 to 600°C as the proportion of the tetrahydrate form in the sample increases). Changes in crystallinity/crystal size may also have a secondary effect on the temperature of decomposition, and although these surface effects appear to be minor for our samples further investigation may be warranted. A less than full appreciation of the hydration state of perchlorate salts during thermal extraction analyses could lead to misidentification of the number and the nature of perchlorate phases present.

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

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

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

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: 184-203, 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 AR, Sephton MA, Southern P, Watson JS, Fraser AJ, Almeida TPet 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

Sephton MA, Jiao D, Engel MH, Looy CV, Visscher Het al., 2015, Terrestrial acidification during the end-Permian biosphere crisis?, GEOLOGY, Vol: 43, Pages: 159-162, ISSN: 0091-7613

JOURNAL ARTICLE

Sephton MA, Watson JS, Meredith W, Love GD, Gilmour I, Snape CEet al., 2015, Multiple Cosmic Sources for Meteorite Macromolecules?, ASTROBIOLOGY, Vol: 15, Pages: 779-786, ISSN: 1531-1074

JOURNAL ARTICLE

Watson JS, Sephton MA, 2015, Heat, Aromatic Units, and Iron-Rich Phyllosilicates: A Mechanism for Making Macromolecules in the Early Solar System, ASTROBIOLOGY, Vol: 15, Pages: 787-792, ISSN: 1531-1074

JOURNAL ARTICLE

Wright MC, Court RW, Kafantaris F-CA, Spathopoulos F, Sephton MAet al., 2015, A new rapid method for shale oil and shale gas assessment, Fuel, Vol: 153, Pages: 231-239, ISSN: 0016-2361

JOURNAL ARTICLE

Court RW, Sephton MA, 2014, New estimates of the production of volatile gases from ablating carbonaceous micrometeoroids at Earth and Mars during an E-belt-type Late Heavy Bombardment, Geochimica et Cosmochimica Acta, Vol: 145, Pages: 175-205, ISSN: 0016-7037

JOURNAL ARTICLE

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