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
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280 results found

Sims MJE, Sephton MA, Watson JS, Fraser AJ, Vane CHet al., 2024, Biomarker evidence for the depositional environment of basinal UK Mississippian mudstones, Geological Society Special Publication, ISSN: 0305-8719

The regional character of organic matter type and depositional conditions of Pendleian, Brigantian and Arnsbergian mudstones between the Craven Basin and the Widmerpool Gulf was compared through interpretation of biomarker and pyrolysis data from 201 samples recovered from 9 boreholes. The Carboniferous seaways have been determined to commonly host dysoxic conditions, enabling preservation of a mixture of marine and terrestrial organic matter types. Photic zone anoxia evidenced by aryl-isoprenoids was determined to be persistent during ‘marine’ conditions represented by marine band, high sea level and carbonate facies. Observation and correlation of diasteranes and Ts/Tm ratios within the samples and to other maturity parameters highlighted a significant clay mineral catalytic and/or hydrocarbon retention effect in the samples. This influenced both biomarkers as well as Tmax thermal maturity data reducing the reliability of such results in interpreting burial and ultimately reserve potential.

Journal article

Siljeström S, Czaja AD, Corpolongo A, Berger EL, Li AY, Cardarelli E, Abbey W, Asher SA, Beegle LW, Benison KC, Bhartia R, Bleefeld BL, Burton AS, Bykov SV, Clark B, DeFlores L, Ehlmann BL, Fornaro T, Fox A, Gómez F, Hand K, Haney NC, HickmanLewis K, Hug WF, Imbeah S, Jakubek RS, Kah LC, Kivrak L, Lee C, Liu Y, MartínezFrías J, McCubbin FM, Minitti M, Moore K, Morris RV, Núñez JI, Osterhout JT, Phua YY, Randazzo N, Hollis JR, Rodriguez C, Roppel R, Scheller EL, Sephton M, Sharma SK, Sharma S, Steadman K, Steele A, Tice M, Uckert K, VanBommel S, Williams AJ, Williford KH, Winchell K, Wu MK, Yanchilina A, Zorzano Met al., 2024, Evidence of sulfate‐rich fluid alteration in Jezero crater floor, Mars, Journal of Geophysical Research: Planets, Vol: 129, ISSN: 2169-9100

Sulfur plays a major role in martian geochemistry and sulfate minerals are important repositories of water. However, their hydration states on Mars are poorly constrained. Therefore, understanding the hydration and distribution of sulfate minerals on Mars is important for understanding its geologic, hydrologic, and atmospheric evolution as well as its habitability potential. NASA's Perseverance rover is currently exploring the Noachian-age Jezero crater, which hosts a fan-delta system associated with a paleolake. The crater floor includes two igneous units (the Séítah and Máaz formations), both of which contain evidence of later alteration by fluids including sulfate minerals. Results from the rover instruments Scanning Habitable Environments with Raman and Luminescence for Organics and Chemistry and Planetary Instrument for X-ray Lithochemistry reveal the presence of a mix of crystalline and amorphous hydrated Mg-sulfate minerals (both MgSO4·[3–5]H2O and possible MgSO4·H2O), and anhydrous Ca-sulfate minerals. The sulfate phases within each outcrop may have formed from single or multiple episodes of water activity, although several depositional events seem likely for the different units in the crater floor. Textural and chemical evidence suggest that the sulfate minerals most likely precipitated from a low temperature sulfate-rich fluid of moderate pH. The identification of approximately four waters puts a lower constraint on the hydration state of sulfate minerals in the shallow subsurface, which has implications for the martian hydrological budget. These sulfate minerals are key samples for future Mars sample return.

Journal article

Kalaiarasan G, Kumar P, Tomson M, Zavala-Reyes JC, Porter AE, Young G, Sephton MA, Abubakar-Waziri H, Pain CC, Adcock IM, Mumby S, Dilliway C, Fang F, Arcucci R, Chung KFet al., 2024, Particle number size distribution in three different microenvironments of London, Atmosphere, Vol: 15, ISSN: 2073-4433

We estimated the particle number distributions (PNDs), particle number concentrations (PNCs), physicochemical characteristics, meteorological effects, and respiratory deposition doses (RDD) in the human respiratory tract for three different particle modes: nucleation (N6–30), accumulation (N30–300), and coarse (N300–10,000) modes. This study was conducted in three different microenvironments (MEs) in London (indoor, IN; traffic intersection, TI; park, PK) measuring particles in the range of 6 nm–10,000 nm using an electrical low-pressure impactor (ELPI+). Mean PNCs were 1.68 ± 1.03 × 104 #cm−3, 7.00 ± 18.96 × 104 #cm−3, and 0.76 ± 0.95 × 104 #cm−3 at IN, TI, and PK, respectively. The PNDs were high for nucleation-mode particles at the TI site, especially during peak traffic hours. Wind speeds ranging from 0 to 6 ms−1 exhibit higher PNCs for nucleation- and accumulation-mode particles at TI and PK sites. Physicochemical characterisation shows trace metals, including Fe, O, and inorganic elements, that were embedded in a matrix of organic material in some samples. Alveolar RDD was higher for the nucleation and accumulation modes than the coarse-mode particles. The chemical signatures from the physicochemical characterisation indicate the varied sources at different MEs. These findings enhance our understanding of the different particle profiles at each ME and should help devise ways of reducing personal exposure at each ME.

Journal article

Vance SD, Craft KL, Shock E, Schmidt BE, Lunine J, Hand KP, McKinnon WB, Spiers EM, Chivers C, Lawrence JD, Wolfenbarger N, Leonard EJ, Robinson KJ, Styczinski MJ, Persaud DM, Steinbrügge G, Zolotov MY, Quick LC, Scully JEC, Becker TM, Howell SM, Clark RN, Dombard AJ, Glein CR, Mousis O, Sephton MA, Castillo-Rogez J, Nimmo F, McEwen AS, Gudipati MS, Jun I, Jia X, Postberg F, Soderlund KM, Elder CMet al., 2023, Investigating Europa's habitability with the Europa Clipper, Space Science Reviews, Vol: 219, ISSN: 0038-6308

The habitability of Europa is a property within a system, which is driven by a multitude of physical and chemical processes and is defined by many interdependent parameters, so that its full characterization requires collaborative investigation. To explore Europa as an integrated system to yield a complete picture of its habitability, the Europa Clipper mission has three primary science objectives: (1) characterize the ice shell and ocean including their heterogeneity, properties, and the nature of surface-ice-ocean exchange; (2) characterize Europa's composition including any non-ice materials on the surface and in the atmosphere, and any carbon-containing compounds; and (3) characterize Europa's geology including surface features and localities of high science interest. The mission will also address several cross-cutting science topics including the search for any current or recent activity in the form of thermal anomalies and plumes, performing geodetic and radiation measurements, and assessing high-resolution, co-located observations at select sites to provide reconnaissance for a potential future landed mission. Synthesizing the mission's science measurements, as well as incorporating remote observations by Earth-based observatories, the James Webb Space Telescope, and other space-based resources, to constrain Europa's habitability, is a complex task and is guided by the mission's Habitability Assessment Board (HAB).

Journal article

Tan J, Salter T, Watson J, Waite JH, Sephton Met al., 2023, Organic biosignature degradation in hydrothermal and serpentinizing environments: Implications for life detection on Icy Moons and Mars, Astrobiology, Vol: 10, Pages: 1045-1055, ISSN: 1531-1074

Evidence of liquid water is a primary indicator of habitability on the icy moons in our outer solar system as well as on terrestrial planets such as Mars. If liquid water-containing environments host life, some of its organic remains can be fossilized and preserved as organic biosignatures. However, inorganic materials may also be present and water-assisted organic-inorganic reactions can transform the organic architecture of biological remains. Our understanding of the fate of these organic remains can be assisted by experimental simulations that monitor the chemical changes that occur in microbial organic matter due to the presence of water and minerals. We performed hydrothermal experiments between 100–300°C involving lipid-rich microbes and natural serpentinite mineral mixtures generated by the subaqueous hydrothermal alteration of ultramafic rock. The products reveal what the signals of life may look like when subjected to water-organic-inorganic reactions. Straight and branched chain lipids in unaltered samples are joined by cyclization and aromatization products in hydrothermally altered samples. Hydrothermal reactions produce distinct products that are not present in the starting materials including small, single-ring, heteroatomic and aromatic compounds such as indoles and phenols. Hydrothermal reactions in the presence of serpentinite minerals lead to the significant reduction of these organic structures and their replacement by diketopiperazines (DKPs) and dihydropyrazines (DHPs), which may be compounds that are distinct to organic-inorganic reactions. Given that the precursors of DKPs and DHPs are normally lost during early diagenesis, the presence of these compounds can be an indicator of co-existing recent life and hydrothermal processing. However, the thermal stability of these compounds reveals that the formation and preservation of these compounds only occurs within a distinct temperature window. Serpentinite is also found to have a preser

Journal article

Tomson M, Kumar P, Kalaiarasan G, Zavala-Reyes JC, Chiapasco M, Sephton MA, Young G, Porter AE, Klosowski MMet al., 2023, Corrigendum to “Pollutant concentrations and exposure variability in four urban microenvironments of London” [Atmos. Environ. 298 (2023) 119624], Atmospheric Environment, Vol: 310, ISSN: 1352-2310

Journal article

Hausrath EM, Adcock CT, Bechtold A, Beck P, Benison K, Brown A, Cardarelli EL, Carman NA, Chide B, Christian J, Clark BC, Cloutis E, Cousin A, Forni O, Gabriel TSJ, Gasnault O, Golombek M, Gómez F, Hecht MH, Henley TLJ, Huidobro J, Johnson J, Jones MWM, Kelemen P, Knight A, Lasue JA, Le Mouélic S, Madariaga JM, Maki J, Mandon L, Martinez G, MartínezFrías J, McConnochie TH, Meslin P, Zorzano M, Newsom H, Paar G, Randazzo N, Royer C, Siljeström S, Schmidt ME, Schröder S, Sephton MA, Sullivan R, Turenne N, Udry A, VanBommel S, Vaughan A, Wiens RC, Williams Net al., 2023, An examination of soil crusts on the floor of Jezero Crater, Mars, Journal of Geophysical Research: Planets, Vol: 128, ISSN: 2169-9100

Martian soils are critically important for understanding the history of Mars, past potentially habitable environments, returned samples, and future human exploration. This study examines soil crusts on the floor of Jezero crater encountered during initial phases of the Mars 2020 mission. Soil surface crusts have been observed on Mars at other locations, starting with the two Viking Lander missions. Rover observations show that soil crusts are also common across the floor of Jezero crater, revealed in 45 of 101 locations where rover wheels disturbed the soil surface, two out of seven helicopter flights that crossed the wheel tracks, and four of eight abrasion/drilling sites. Most soils measured by the SuperCam laser-induced breakdown spectroscopy (LIBS) instrument show high hydrogen content at the surface, and fine-grained soils also show a visible/near infrared (VISIR) 1.9 μm H2O absorption feature. The Planetary Instrument for X-ray Lithochemistry (PIXL) and SuperCam observations suggest the presence of salts at the surface of rocks and soils. The correlation of S and Cl contents with H contents in SuperCam LIBS measurements suggests that the salts present are likely hydrated. On the “Naltsos” target, magnesium and sulfur are correlated in PIXL measurements, and Mg is tightly correlated with H at the SuperCam points, suggesting hydrated Mg-sulfates. Mars Environmental Dynamics Analyzer (MEDA) observations indicate possible frost events and potential changes in the hydration of Mg-sulfate salts. Jezero crater soil crusts may therefore form by salts that are hydrated by changes in relative humidity and frost events, cementing the soil surface together.

Journal article

Sephton MA, Tan JSW, Watson JS, Hickman-Lewis K, Madariaga JMet al., 2023, Organic geochemistry of in situ thermal-based analyses on Mars: the importance and influence of minerals, Journal of the Geological Society, Vol: 180, Pages: 1-10, ISSN: 0016-7649

A high priority goal for past, present and future missions to Mars is the search for evidence of past or present life. Some of the most information-rich signals are those represented by organic biomarkers. Thermal extraction has historically been the most popular in situ analysis technique employed on Mars owing to its elegance and ability to liberate both small compounds and large macromolecular networks. The geological record of Mars contains a variety of minerals, some of which can interact with organic matter when subjected to thermal extraction. Here we discuss the organic records that may be associated with these mineral hosts and the problems encountered when mineral-organic mixtures are analysed by thermal-based methods. We also suggest potential mitigations for future experiments of a similar nature and note that these mitigating steps can be applied not only in situ on Mars but also after samples are returned to Earth as part of Mars Sample Return where more resources and time for sample preparation are available.

Journal article

Simon JI, HickmanLewis K, Cohen BA, Mayhew LE, Shuster DL, Debaille V, Hausrath EM, Weiss BP, Bosak T, Zorzano M, Amundsen HEF, Beegle LW, Bell JF, Benison KC, Berger EL, Beyssac O, Brown AJ, Calef F, Casademont TM, Clark B, Clavé E, Crumpler L, Czaja AD, Fairén AG, Farley KA, Flannery DT, Fornaro T, Forni O, Gómez F, Goreva Y, Gorin A, Hand KP, Hamran S, Henneke J, Herd CDK, Horgan BHN, Johnson JR, Joseph J, Kronyak RE, Madariaga JM, Maki JN, Mandon L, McCubbin FM, McLennan SM, Moeller RC, Newman CE, Núñez JI, Pascuzzo AC, Pedersen DA, Poggiali G, Pinet P, QuantinNataf C, Rice M, Rice JW, Royer C, Schmidt M, Sephton M, Sharma S, Siljeström S, Stack KM, Steele A, Sun VZ, Udry A, VanBommel S, Wadhwa M, Wiens RC, Williams AJ, Williford KHet al., 2023, Samples collected from the floor of Jezero crater with the Mars 2020 Perseverance rover, Journal of Geophysical Research: Planets, Vol: 128, Pages: 1-42, ISSN: 2169-9097

The first samples collected by the Mars 2020 mission represent units exposed on the Jezero Crater floor, from the potentially oldest Séítah formation outcrops to the potentially youngest rocks of the heavily cratered Máaz formation. Surface investigations reveal landscape-to-microscopic textural, mineralogical, and geochemical evidence for igneous lithologies, some possibly emplaced as lava flows. The samples contain major rock-forming minerals such as pyroxene, olivine, and feldspar, accessory minerals including oxides and phosphates, and evidence for various degrees of aqueous activity in the form of water-soluble salt, carbonate, sulfate, iron oxide, and iron silicate minerals. Following sample return, the compositions and ages of these variably altered igneous rocks are expected to reveal the geophysical and geochemical nature of the planet’s interior at the time of emplacement, characterize martian magmatism, and place timing constraints on geologic processes, both in Jezero Crater and more widely on Mars. Petrographic observations and geochemical analyses, coupled with geochronology of secondary minerals, can also reveal the timing of aqueous activity as well as constrain the chemical and physical conditions of the environments in which these minerals precipitated, and the nature and composition of organic compounds preserved in association with these phases. Returned samples from these units will help constrain the crater chronology of Mars and the global evolution of the planet’s interior, for understanding the processes that formed Jezero Crater floor units, and for constraining the style and duration of aqueous activity in Jezero Crater, past habitability, and cycling of organic elements in Jezero Crater.

Journal article

Tomson M, Kumar P, Kalaiarasan G, Zavala-Reyes JC, Chiapasco M, Sephton MA, Young G, Porter AEet al., 2023, Pollutant concentrations and exposure variability in four urban microenvironments of London, Atmospheric Environment, Vol: 298, Pages: 1-16, ISSN: 1352-2310

We compared various pollutant concentrations (PM1, PM2.5, PM10, PNC, BC) at four different urban microenvironments (MEs) in London (Indoor, IN; Traffic Intersection, TI; Park, PK; and Street Canyon, SC). The physico-chemical characteristics of particles were analysed, and the respiratory deposition doses (RDD) were estimated. Field measurements were conducted over a period of 121 days. The mean PM2.5 (PNC) concentrations were found to be 9.47 ± 7.05 (16366 ± 11815), 8.09 ± 4.57 (10951 ± 6445), 5.11 ± 2.96 (7717 ± 4576), 3.88 ± 3.06 (5672 ± 2934) μg m−3 (# cm−3) at TI, SC, PK and IN, respectively. PM2.5, PM10 and PNC exhibited a trend of TI > SC > PK > IN; higher concentrations for PM1 and BC were observed at IN than PK due to the emissions from printers, producing a trend of TI > SC > IN > PK. We observed 12%–30% higher fine PM concentrations at TI and SC sites during morning peak (07:00–09:30) than the evening peak hours (16:00–19:00); while IN showed a smaller variation in fine PM concentrations compared with outdoor TI, PK and SC sites owing to their prevalence in the IN for a longer time. Fine and ultrafine PM containing potentially toxic trace transition metals including Fe, Ti, Cr, Mn, Al and Mg were detected by high resolution electron microscopy at all sites. There was a similar relative abundance of different elements at the TI, IN and PK sites, which suggests a transport of PM between MEs. RDD for PM1 was highest (2.45 ± 2.27 μg h−1) at TI for females during running; PM2.5 and PM10 were highest at SC (11.23 ± 6.34 and 37.17 ± 20.82 μg h−1, respectively). The results show that the RDD variation between MEs does not follow the PM concentration trend. RDD at PK was found to be 39%–53% lower than TI and SC during running for all the PM fractions. Overall, the study findings show the air quality variation at dif

Journal article

Vaughan A, Minitti ME, Cardarelli EL, Johnson JR, Kah LC, Pilleri P, Rice MS, Sephton M, Horgan BHN, Wiens RC, Yingst RA, Zorzano Mier M, Anderson R, Bell JF, Brown AJ, Cloutis EA, Cousin A, Herkenhoff KE, Hausrath EM, Hayes AG, Kinch K, Merusi M, Million CC, Sullivan R, Siljeström SM, St Clair Met al., 2023, Regolith of the crater floor units, Jezero crater, Mars: textures, composition, and implications for provenance, Journal of Geophysical Research: Planets, Vol: 128, Pages: 1-32, ISSN: 2169-9097

A multi-instrument study of the regolith of Jezero crater floor units by the Perseverance rover has identified three types of regolith: fine-grained, coarse-grained, and mixed-type. Mastcam-Z, Wide Angle Topographic Sensor for Operations and eNgineering, and SuperCam Remote Micro Imager were used to characterize the regolith texture, particle size, and roundedness where possible. Mastcam-Z multispectral and SuperCam laser-induced breakdown spectroscopy data were used to constrain the composition of the regolith types. Fine-grained regolith is found surrounding bedrock and boulders, comprising bedforms, and accumulating on top of rocks in erosional depressions. Spectral and chemical data show it is compositionally consistent with pyroxene and a ferric-oxide phase. Coarse-grained regolith consists of 1–2 mm well-sorted gray grains that are found concentrated around the base of boulders and bedrock, and armoring bedforms. Its chemistry and spectra indicate it is olivine-bearing, and its spatial distribution and roundedness indicate it has been transported, likely by saltation-induced creep. Coarse grains share similarities with the olivine grains observed in the Séítah formation bedrock, making that unit a possible source for these grains. Mixed-type regolith contains fine- and coarse-grained regolith components and larger rock fragments. The rock fragments are texturally and spectrally similar to bedrock within the Máaz and Séítah formations, indicating origins by erosion from those units, although they could also be a lag deposit from erosion of an overlying unit. The fine- and coarse-grained types are compared to their counterparts at other landing sites to inform global, regional, and local inputs to regolith formation within Jezero crater. The regolith characterization presented here informs the regolith sampling efforts underway by Perseverance.

Journal article

Salter TL, Watson JS, Sephton MA, 2023, Effects of minerals (phyllosilicates and iron oxides) on the responses of aliphatic hydrocarbon containing kerogens (Type I and Type II) to analytical pyrolysis, Journal of Analytical and Applied Pyrolysis, Vol: 170, Pages: 1-8, ISSN: 0165-2370

Organic matter in sediments is dominated by kerogen, a high molecular weight geomacromolecule. Kerogen can be subdivided into Types I to IV that provide paleoenvironmental and petroleum potential information. Kerogen typing can be performed by several chemical methods including elemental analysis (H/C and O/C), FTIR and pyrolysis-gas chromatography techniques. However, kerogens occur naturally within mineral matrices and these can influence the chemical responses. We have examined the effects of a range of minerals (namely kaolinite, lizardite, ripidolite, illite, montmorillonite, haematite, goethite, limonite and magnetite) on the responses of kerogen to pyrolysis-gas chromatography-mass spectrometry. We used aliphatic hydrocarbon containing kerogen Types I and II from Carboniferous Midland Valley shales of Scotland and the Jurassic Oxford Clay of southern England, respectively, as well as a pure synthetic aliphatic polymer, polyethylene. We find that the aliphatic organic matter in Type I kerogens is transformed by interaction with minerals during pyrolysis to give a signal incorrectly suggesting more contributions from land plant-containing kerogens, such as a large number of aromatic molecules. Pyrolysis with goethite, limonite and magnetite leads to almost complete destruction of the organic matter. Hence, the mineral composition of sedimentary rocks during pyrolysis should be considered when assigning kerogen types. Failure to consider the effects of minerals can lead to incorrect assignment of kerogen type and, therefore, erroneous interpretations of paleoenvironments and petroleum potential.

Journal article

Sephton M, Chan Q, Watson J, Burchell M, Spathis V, Grady M, Verchovsky A, Abernethy F, Franchi Iet al., 2023, Insoluble macromolecular organic matter in the Winchcombe meteorite, Meteoritics and Planetary Science, ISSN: 1086-9379

The Winchcombe meteorite fell on 28th February 2021 in Gloucestershire, UK. As the most accurately recorded carbonaceous chondrite fall, the Winchcombe meteorite is an opportunity to link a tangible sample of known chemical constitution to a specific region of the solar system whose chemistry can only be otherwise predicted or observed remotely. Winchcombe is a CM carbonaceous chondrite, a group known for their rich and varied abiotic organic chemistry. The rapid collection of Winchcombe provides an opportunity to study a relatively terrestrial contaminant-limited meteoritic organic assemblage. The majority of the organic matter in CM chondrites is macromolecular in nature and we have performed non-destructive and destructive analyses of Winchcombe by Raman spectroscopy, online pyrolysis-gas chromatography (pyrolysis-GC-MS), and stepped combustion. The Winchcombe pyrolysis products were consistent with a CM chondrite, namely aromatic and polycyclic aromatic hydrocarbons, sulfur-containing units including thiophenes, oxygen containing units such as phenols and furans, and nitrogen-containing units such as pyridine; many substituted/alkylated forms of these units were also present. The presence of phenols in the online pyrolysis products indicated only limited influence from aqueous alteration, which can deplete the phenol precursors in the macromolecule when aqueous alteration is extensive. Raman spectroscopy and stepped combustion also generated responses consistent with a CM chondrite. The pyrolysis-GC-MS data is likely to reflect the more labile and thermally sensitive portions of the macromolecular materials while the Raman and stepped combustion data will also reflect the more refractory and non-pyrolyzable component, hence we accessed the complete macromolecular fraction of the recently fallen Winchcombe meteorite and revealed a chemical constitution that is similar to other meteorites of the CM group.

Journal article

Royle S, Cropper L, Watson J, Sinibaldi S, Entwisle M, Sephton Met al., 2023, Solid phase micro extraction for organic contamination control throughout assembly and operational phases of space missions, Astrobiology, Vol: 23, Pages: 127-143, ISSN: 1531-1074

Space missions concerned with life detection contain highly sensitive instruments for the detection of organics. Terrestrial contamination can interfere with signals of indigenous organics in samples and has the potential to cause false positive biosignature detections, which may lead to incorrect suggestions of the presence of life elsewhere in the Solar System. This study assessed the capability of solid phase micro extraction (SPME) as a method for monitoring organic contamination encountered by spacecraft hardware during assembly and operation. SPME-gas chromatography-mass spectrometry (SPME-GC-MS) analysis was performed on potential contaminant source materials, which are commonly used in spacecraft construction. The sensitivity of SPME-GC-MS to organics was assessed in the context of contaminants identified in molecular wipes taken from hardware surfaces on the ExoMars Rosalind Franklin rover. SPME was found to be effective at detecting a wide range of common organic contaminants that include aromatic hydrocarbons, non-aromatic hydrocarbons, nitrogen-containing compounds, alcohols and carbonyls. A notable example of correlation of contaminant with source material was the detection of benzenamine compounds in an epoxy adhesive analyzed by SPME-GC-MS and in the ExoMars rover surface wipe samples. The current form of SPME-GC-MS does not enable quantitative evaluation of contaminants, nor is it suitable for the detection of every group of organic molecules relevant to astrobiological contamination concerns, namely, large and/or polar molecules such as amino acids. However, it nonetheless represents an effective new monitoring method for rapid, easy identification of organic contaminants commonly present on spacecraft hardware and could thus be utilized in future space missions as part of their contamination control and mitigation protocols.

Journal article

Kumar P, Zavala-Reyes JC, Kalaiarasan G, Abubakar-Waziri H, Young G, Mudway I, Dilliway C, Lakhdar R, Mumby S, Kłosowski MM, Pain CC, Adcock IM, Watson JS, Sephton MA, Chung KF, Porter AEet al., 2023, Characteristics of fine and ultrafine aerosols in the London underground., Science of the Total Environment, Vol: 858, ISSN: 0048-9697

Underground railway systems are recognised spaces of increased personal pollution exposure. We studied the number-size distribution and physico-chemical characteristics of ultrafine (PM0.1), fine (PM0.1-2.5) and coarse (PM2.5-10) particles collected on a London underground platform. Particle number concentrations gradually increased throughout the day, with a maximum concentration between 18:00 h and 21:00 h (local time). There was a maximum decrease in mass for the PM2.5, PM2.5-10 and black carbon of 3.9, 4.5 and ~ 21-times, respectively, between operable (OpHrs) and non-operable (N-OpHrs) hours. Average PM10 (52 μg m-3) and PM2.5 (34 μg m-3) concentrations over the full data showed levels above the World Health Organization Air Quality Guidelines. Respiratory deposition doses of particle number and mass concentrations were calculated and found to be two- and four-times higher during OpHrs compared with N-OpHrs, reflecting events such as train arrival/departure during OpHrs. Organic compounds were composed of aromatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) which are known to be harmful to health. Specific ratios of PAHs were identified for underground transport that may reflect an interaction between PAHs and fine particles. Scanning transmission electron microscopy (STEM) chemical maps of fine and ultrafine fractions show they are composed of Fe and O in the form of magnetite and nanosized mixtures of metals including Cr, Al, Ni and Mn. These findings, and the low air change rate (0.17 to 0.46 h-1), highlight the need to improve the ventilation conditions.

Journal article

Chan QHS, Watson JS, Sephton MA, O'Brien ÁC, Hallis LJet al., 2023, The amino acid and polycyclic aromatic hydrocarbon compositions of the promptly recovered CM2 Winchcombe carbonaceous chondrite, Meteoritics and Planetary Science, ISSN: 1086-9379

The rapid recovery of the Winchcombe meteorite offers a valuable opportunity to study the soluble organic matter (SOM) profile in pristine carbonaceous astromaterials. Our interests in the biologically relevant molecules, amino acids—monomers of protein, and the most prevalent meteoritic organics—polycyclic aromatic hydrocarbons (PAHs) are addressed by analyzing the solvent extracts of a Winchcombe meteorite stone using gas chromatography mass spectrometry. The Winchcombe sample contains an amino acid abundance of ~1132 parts-per-billion that is about 10 times lower than other CM2 meteorites. The detection of terrestrially rare amino acids, including α-aminoisobutyric acid (AIB); isovaline; β-alanine; α-, β-, and γ-amino-n-butyric acids; and 5-aminopentanoic acid, and the racemic enantiomeric ratios (D/L = 1) observed for alanine and isovaline indicate that these amino acids are indigenous to the meteorite and not terrestrial contaminants. The presence of predominantly α-AIB and isovaline is consistent with their formation via the Strecker-cyanohydrin synthetic pathway. The L-enantiomeric excesses in isovaline previously observed for aqueously altered meteorites were viewed as an indicator of parent body aqueous processing; thus, the racemic ratio of isovaline observed for Winchcombe, alongside the overall high free:total amino acid ratio, and the low amino acid concentration suggest that the analyzed stone is derived from a lithology that has experienced brief episode(s) of aqueous alteration. Winchcombe also contains 2- to 6-ring alkylated and nonalkylated PAHs. The low total PAHs abundance (6177 ppb) and high nonalkylated:alkylated ratio are distinct from that observed for heavily aqueously altered CMs. The weak petrographic properties of Winchcombe, as well as the discrepancies observed for the Winchcombe SOM content—a low total amino acid abundance comparable to heavily altered CMs, and ye

Journal article

Scheller EL, Hollis JR, Cardarelli EL, Steele A, Beegle LW, Bhartia R, Conrad P, Uckert K, Sharma S, Ehlmann BL, Abbey WJ, Asher SA, Benison KC, Berger EL, Beyssac O, Bleefeld BL, Bosak T, Brown AJ, Burton AS, V Bykov S, Cloutis E, Fairen AG, DeFlores L, Farley KA, Fey DM, Fornaro T, Fox AC, Fries M, Hickman-Lewis K, Hug WF, Huggett JE, Imbeah S, Jakubek RS, Kah LC, Kelemen P, Kennedy MR, Kizovski T, Lee C, Liu Y, Mandon L, McCubbin FM, Moore KR, Nixon BE, Nunez JI, Sanchez-Vahamonde CR, Roppel RD, Schulte M, Sephton MA, Sharma SK, Siljestrom S, Shkolyar S, Shuster DL, Simon JI, Smith RJ, Stack KM, Steadman K, Weiss BP, Werynski A, Williams AJ, Wiens RC, Williford KH, Winchell K, Wogsland B, Yanchilina A, Yingling R, Zorzano M-Pet al., 2022, Aqueous alteration processes in Jezero crater, Mars-implications for organic geochemistry, Science, Vol: 378, Pages: 1105-1110, ISSN: 0036-8075

The Perseverance rover landed in Jezero crater, Mars, in February 2021. We used the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument to perform deep-ultraviolet Raman and fluorescence spectroscopy of three rocks within the crater. We identify evidence for two distinct ancient aqueous environments at different times. Reactions with liquid water formed carbonates in an olivine-rich igneous rock. A sulfate-perchlorate mixture is present in the rocks, which probably formed by later modifications of the rocks by brine. Fluorescence signatures consistent with aromatic organic compounds occur throughout these rocks and are preserved in minerals related to both aqueous environments.

Journal article

King AJ, Daly L, Rowe J, Joy KH, Greenwood RC, Devillepoix HAR, Suttle MD, Chan QHS, Russell SS, Bates HC, Bryson JFJ, Clay PL, Vida D, Lee MR, O'Brien Á, Hallis LJ, Stephen NR, Tartèse R, Sansom EK, Towner MC, Cupak M, Shober PM, Bland PA, Findlay R, Franchi IA, Verchovsky AB, Abernethy FAJ, Grady MM, Floyd CJ, Van Ginneken M, Bridges J, Hicks LJ, Jones RH, Mitchell JT, Genge MJ, Jenkins L, Martin P-E, Sephton MA, Watson JS, Salge T, Shirley KA, Curtis RJ, Warren TJ, Bowles NE, Stuart FM, Di Nicola L, Györe D, Boyce AJ, Shaw KMM, Elliott T, Steele RCJ, Povinec P, Laubenstein M, Sanderson D, Cresswell A, Jull AJT, Sýkora I, Sridhar S, Harrison RJ, Willcocks FM, Harrison CS, Hallatt D, Wozniakiewicz PJ, Burchell MJ, Alesbrook LS, Dignam A, Almeida NV, Smith CL, Clark B, Humphreys-Williams ER, Schofield PF, Cornwell LT, Spathis V, Morgan GH, Perkins MJ, Kacerek R, Campbell-Burns P, Colas F, Zanda B, Vernazza P, Bouley S, Jeanne S, Hankey M, Collins GS, Young JS, Shaw C, Horak J, Jones D, James N, Bosley S, Shuttleworth A, Dickinson P, McMullan I, Robson D, Smedley ARD, Stanley B, Bassom R, McIntyre M, Suttle AA, Fleet R, Bastiaens L, Ihász MB, McMullan S, Boazman SJ, Dickeson ZI, Grindrod PM, Pickersgill AE, Weir CJ, Suttle FM, Farrelly S, Spencer I, Naqvi S, Mayne B, Skilton D, Kirk D, Mounsey A, Mounsey SE, Mounsey S, Godfrey P, Bond L, Bond V, Wilcock C, Wilcock H, Wilcock Ret al., 2022, The Winchcombe meteorite, a unique and pristine witness from the outer solar system., Science advances, Vol: 8, ISSN: 2375-2548

Direct links between carbonaceous chondrites and their parent bodies in the solar system are rare. The Winchcombe meteorite is the most accurately recorded carbonaceous chondrite fall. Its pre-atmospheric orbit and cosmic-ray exposure age confirm that it arrived on Earth shortly after ejection from a primitive asteroid. Recovered only hours after falling, the composition of the Winchcombe meteorite is largely unmodified by the terrestrial environment. It contains abundant hydrated silicates formed during fluid-rock reactions, and carbon- and nitrogen-bearing organic matter including soluble protein amino acids. The near-pristine hydrogen isotopic composition of the Winchcombe meteorite is comparable to the terrestrial hydrosphere, providing further evidence that volatile-rich carbonaceous asteroids played an important role in the origin of Earth's water.

Journal article

Salter TL, Watson J, Waite JH, Sephton MAet al., 2022, Hydrothermal processing of microorganisms: Mass spectral signals of degraded biosignatures for life detection on icy moons, ACS Earth and Space Chemistry, Vol: 6, Pages: 2508-2518, ISSN: 2472-3452

Life detection missions to the outer solar system are concentrating on the icy moons of Jupiter and Saturn and their inferred sub-surface oceans. Access to evidence of habitability, and possibly even life, is facilitated by the ejection of subsurface material in plumes and outgassing fissures. Orbiting spacecraft can intersect the plume material or detect past sputtered remnants of outgassed products and analyse the contents using instruments such as mass spectrometers. Hydrothermalism has been proposed for the subsurface environments of icy moons and the organic remains of any associated life would be expected to suffer some degradation through hydrothermalism, radiolysis, or spacecraft flyby impact fragmentation. Hydrothermalism is treated here for the first time in the context of the Europa Clipper mission.To assess the influence of hydrothermalism on the ability of orbiting mass spectrometers to detect degrading signals of life, we have subjected Earth microorganisms to laboratory hydrothermal processing. The processed microorganism samples were then analysed using gas chromatography-mass spectrometry (GC-MS) and mass spectra were generated. Certain compound classes, such as carbohydrates and proteins are significantly altered by hydrothermal processing, resulting in small one-ring and two-ring aromatic compounds such as indoles and phenols. However, lipid fragments, such as fatty acids, retain their fidelity and their provenance is easily recognised as biological in origin. Our data indicate that mass spectrometry measurements in the plumes of icy moons, using instruments such as the MAss Spectrometer for Planetary Exploration (MASPEX) onboard the upcoming Europa Clipper mission, can reveal the presence of life even after significant degradation by hydrothermal processing has taken place.

Journal article

Peers De Nieuwburgh C, Watson J, Weiss D, Sephton MAet al., 2022, Environmental screening of water associated with shale gas extraction by fluorescence excitation emission matrix, Environmental Science: Water Research & Technology, Vol: 8, Pages: 2196-2206, ISSN: 2053-1400

The shale revolution has involved the production of oil and gas from shale reservoirs enabled by modern techniques such as horizontal drilling and hydraulic fracturing. Large volumes of water-based fluids are required for hydraulic fracturing, some of which return to the surface as produced water. The recycling and effective disposal of produced water reduces water demand and avoids environmental impacts, respectively. Yet risks of water quality degradation surrounding shale oil and gas extraction operations remain highest during produced water treatment and disposal. Risk assessments related to produced water use are difficult to generate due to a lack of standard monitoring methods to characterise produced water and a lack of baseline monitoring data of surrounding water resources. We have performed a study on laboratory shale leachates using fluorescence Excitation Emission Matrix (EEM) spectra and have demonstrated the utility of this spectroscopic technique as a standard method for environmental screening in which the chemical constitution of produced water is monitored. EEM spectra recorded in this work show that dissolved organic matter (DOM) in laboratory shale leachates contains chromophores such as humic acid-like and soluble microbial-like material. Short emission wavelengths (<380 nm) EEM spectra may indicate anthropogenic contamination incidents in future operations, especially as they correspond to fluorescence signatures of some injection fluid additives. Our simple fluorescence method requires little sample preparation and could be coupled with remote sensors for real time, in-situ monitoring of contamination incidents.

Journal article

Farley KA, Stack KM, Shuster DL, Horgan BHN, Hurowitz JA, Tarnas JD, Simon JI, Sun VZ, Scheller EL, Moore KR, McLennan SM, Vasconcelos PM, Wiens RC, Treiman AH, Mayhew LE, Beyssac O, Kizovski TV, Tosca NJ, Williford KH, Crumpler LS, Beegle LW, Bell JF, Ehlmann BL, Liu Y, Maki JN, Schmidt ME, Allwood AC, Amundsen HEF, Bhartia R, Bosak T, Brown AJ, Clark BC, Cousin A, Forni O, Gabriel TSJ, Goreva Y, Gupta S, Hamran S-E, Herd CDK, Hickman-Lewis K, Johnson JR, Kah LC, Kelemen PB, Kinch KB, Mandon L, Mangold N, Quantin-Nataf C, Rice MS, Russell PS, Sharma S, Siljeström S, Steele A, Sullivan R, Wadhwa M, Weiss BP, Williams AJ, Wogsland BV, Willis PA, Acosta-Maeda TA, Beck P, Benzerara K, Bernard S, Burton AS, Cardarelli EL, Chide B, Clavé E, Cloutis EA, Cohen BA, Czaja AD, Debaille V, Dehouck E, Fairén AG, Flannery DT, Fleron SZ, Fouchet T, Frydenvang J, Garczynski BJ, Gibbons EF, Hausrath EM, Hayes AG, Henneke J, Jørgensen JL, Kelly EM, Lasue J, Le Mouélic S, Madariaga JM, Maurice S, Merusi M, Meslin P-Y, Milkovich SM, Million CC, Moeller RC, Núñez JI, Ollila AM, Paar G, Paige DA, Pedersen DAK, Pilleri P, Pilorget C, Pinet PC, Rice JW, Royer C, Sautter V, Schulte M, Sephton MA, Sharma SK, Sholes SF, Spanovich N, St Clair M, Tate CD, Uckert K, VanBommel SJ, Yanchilina AG, Zorzano M-Pet al., 2022, Aqueously altered igneous rocks sampled on the floor of Jezero crater, Mars, Science, Vol: 377, ISSN: 0036-8075

<jats:p>The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater’s sedimentary delta, finding that the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Magnesium-iron carbonates along grain boundaries indicate reactions with carbon dioxide–rich water under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks have been stored aboard Perseverance for potential return to Earth.</jats:p>

Journal article

Cohen BA, Benison KC, Bosak T, Czaja AD, Debaille V, Hausrath EM, Herd CDK, Hickman-Lewis K, Mayhew LE, Sephton MA, Shuster DL, Siljestrom S, Simon JI, Weiss BP, Zorzano M-P, Wadhwa M, Hand KP, Sun VZ, Stack KM, Farley KAet al., 2022, THE JEZERO CRATER FLOOR SAMPLE SUITE COLLECTED BY THE MARS 2020 PERSEVERANCE ROVER., 85th Annual Meeting of the Meteoritical-Society, Publisher: WILEY, ISSN: 1086-9379

Conference paper

Kminek G, Benardini JN, Brenker FE, Brooks T, Burton AS, Dhaniyala S, Dworkin JP, Fortman JL, Glamoclija M, Grady MM, Graham HV, Haruyama J, Kieft TL, Koopmans M, McCubbin FM, Meyer MA, Mustin C, Onstott TC, Pearce N, Pratt LM, Sephton MA, Siljeström S, Sugahara H, Suzuki S, Suzuki Y, van Zuilen M, Viso Met al., 2022, COSPAR Sample Safety Assessment Framework (SSAF)., Astrobiology, Vol: 22, Pages: S186-S216, ISSN: 1531-1074

The Committee on Space Research (COSPAR) Sample Safety Assessment Framework (SSAF) has been developed by a COSPAR appointed Working Group. The objective of the sample safety assessment would be to evaluate whether samples returned from Mars could be harmful for Earth's systems (e.g., environment, biosphere, geochemical cycles). During the Working Group's deliberations, it became clear that a comprehensive assessment to predict the effects of introducing life in new environments or ecologies is difficult and practically impossible, even for terrestrial life and certainly more so for unknown extraterrestrial life. To manage expectations, the scope of the SSAF was adjusted to evaluate only whether the presence of martian life can be excluded in samples returned from Mars. If the presence of martian life cannot be excluded, a Hold & Critical Review must be established to evaluate the risk management measures and decide on the next steps. The SSAF starts from a positive hypothesis (there is martian life in the samples), which is complementary to the null-hypothesis (there is no martian life in the samples) typically used for science. Testing the positive hypothesis includes four elements: (1) Bayesian statistics, (2) subsampling strategy, (3) test sequence, and (4) decision criteria. The test sequence capability covers self-replicating and non-self-replicating biology and biologically active molecules. Most of the investigations associated with the SSAF would need to be carried out within biological containment. The SSAF is described in sufficient detail to support planning activities for a Sample Receiving Facility (SRF) and for preparing science announcements, while at the same time acknowledging that further work is required before a detailed Sample Safety Assessment Protocol (SSAP) can be developed. The three major open issues to be addressed to optimize and implement the SSAF are (1) setting a value for the level of assurance to effectively exclude the presence

Journal article

Royle SH, Salter TL, Watson JS, Sephton Met al., 2022, Mineral matrix effects on pyrolysis products of kerogens infer difficulties in determining biological provenance of macromolecular organic matter at Mars, Astrobiology, Vol: 22, Pages: 1-21, ISSN: 1531-1074

Ancient martian organic matter is likely to take the form of kerogen-like recalcitrant macromolecular organic matter (MOM), existing in close association with reactive mineral surfaces, especially iron oxides. Detecting and identifying a biological origin for martian MOM will therefore be of utmost importance for life detection efforts at Mars. We show that Type I and Type IV kerogens provide effective analogues for putative martian MOM of biological and abiological (meteoric) provenances respectively. We analyse the pyrolytic breakdown products when these kerogens are mixed with mineral matrices highly relevant for the search for life on Mars. We demonstrate that, using traditional thermal techniques as generally used by the Sample Analysis at Mars and Mars Organic Molecule Analyser instruments, even the breakdown products of highly recalcitrant MOM are transformed during analysis in the presence of reactive mineral surfaces, particularly iron. Analytical transformation reduces the diagnostic ability of this technique, as detected transformation products of both biological and abiological MOM may be identical (low molecular weight gas phases and benzene) and indistinguishable. The severity of transformational effects increased through: calcite < kaolinite < haematite < nontronite < magnetite < goethite. Due to their representation of various habitable aqueous environments and the preservation potential of organic matter by iron, it is not advisable to completely avoid iron-rich strata. We conclude that haematite-rich localities, with evidence of extensive aqueous alteration of originally reducing phases, such as the Vera Rubin Ridge, may be relatively promising targets for identifying martian biologically-sourced MOM.

Journal article

Schubotz F, Sephton MA, Derenne S, 2022, Biomarkers in Extreme Environments on Earth and the Search for Extraterrestrial Life in Our Solar System, Elements, Vol: 18, Pages: 100-106, ISSN: 1811-5209

Our appreciation of the potential distribution of life in the Solar System has been impacted by the discovery that organisms are able to occupy the most extreme environments on Earth. The persistence of life in the deepest parts of oceans, the deep sedimentary and crustal biosphere accessed by deep drill holes, hot springs, deserts, and polar regions has led to diverse hypotheses regarding the potential for extraterrestrial life on other planets. This chapter provides an overview on how scientists explore the habitability of other planets and moons of our Solar System and far away in outer space and how future space missions aim to find evidence for extraterrestrial life.

Journal article

Salter TL, Magee BA, Waite JH, Sephton MAet al., 2022, Mass spectrometric fingerprints of Bacteria and Archaea for life detection on icy moons, Astrobiology, Vol: 22, Pages: 143-157, ISSN: 1531-1074

The icy moons of the outer solar system display evidence of subsurface liquid water and therefore potential habitability for life. Flybys of Saturn’s moon Enceladus by the Cassini spacecraft have provided measurements of material from plumes that suggest hydrothermal activity and the presence of organic matter. Jupiter’s moon Europa may have similar plumes and is the target for the forthcoming Europa Clipper mission that carries a high mass resolution and high sensitivity mass spectrometer, called the MAss Spectrometer for Planetary EXploration (MASPEX), with the capability for providing detailed characterisation of any organic materials encountered. We have performed a series of experiments using pyrolysis-gas chromatography-mass spectrometry to characterise the mass spectrometric fingerprints of microbial life. A range of extremophile Archaea and Bacteria have been analysed and the laboratory data converted to MASPEX-type signals. Molecules characteristic of protein, carbohydrate and lipid structures were detected and the characteristic fragmentation patterns corresponding to these different biological structures were identified. Protein pyrolysis fragments included phenols, nitrogen heterocycles and cyclic dipeptides. Oxygen heterocycles, such as furans, were detected from carbohydrates. Our data reveal how mass spectrometry on Europa Clipper can aid in the identification of the presence of life, by looking for characteristic bacterial fingerprints that are similar to those from simple Earthly organisms.

Journal article

Sims M, Fraser A, Neumaier M, Sephton M, Vane Cet al., 2022, NEAR WELLBORE PETROLEUM SYSTEMS MODELLING FOR IDENTIFICATION OF UNCONVENTIONAL TARGETS WITHIN THE LOWER CARBONIFEROUS OF ENGLAND, Pages: 2749-2753

As opposed to regional petroleum systems modelling, 3D modelling tools were employed to investigate resources at the 'near-wellbore' scale. A high resolution model was produced studying hydrocarbon generation and expulsion for Lower Carboniferous shales in the Cheshire Basin, northern England. The model was guided by mineralogy, organic contents and hydrocarbon saturations from petrophysical interpretations, these were calibrated against laboratory derived Rock Eval 6 and XRD measurements. The proposed methodology provides a high resolution method to assess resources which may be optimal in densely populated countries like the UK. Additionally the modelling method could guide future exploration tactics while reducing the requirement for extensive core programmes.

Conference paper

Potiszil C, Montgomery W, Sephton M, 2021, Heterogeneity within refractory organic matter from CM2 carbonaceous chondrites: evidence from Raman spectroscopy, Earth and Planetary Science Letters, Vol: 574, Pages: 1-10, ISSN: 0012-821X

CM2 chondrites experienced widespread aqueous and short term thermal alteration on their parent bodies. Whilst previous Raman spectroscopic investigations have investigated insoluble organic matter (IOM), they have not taken into account the binary nature of IOM. Studies employing mass spectrometry have indicated that IOM also known as macromolecular organic matter (MOM) is in fact composed of two distinct fractions: labile organic matter (LOM) and refractory organic matter (ROM). The ROM component represents the aromatic rich and heteroatom poor component of IOM/MOM, whilst the LOM fraction represents a more heteroatom and aliphatic rich component. Here we report Raman 2D maps and spectroscopic data for Murchison and Mighei, both before and after chemical degradation, which attacks and liberates LOM. The removal of LOM simulates the effects of aqueous alteration, where ester and ether bonds are broken and is thought to release some components to the soluble organic matter (SOM) fraction, also known as the free organic matter fraction (FOM). Raman spectroscopy can be used to reveal the nature of bonding (sp2 and sp3) within carbonaceous materials such as meteoritic organic matter, through evaluation of the D and G band peak centres and FWHM values from the recorded data. The presence of sp3 orbitals indicates that the organic materials contain aliphatic linkages and/or heteroatoms. Statistical analysis of the Raman parameters obtained here indicates that the organic matter originating the Raman response is indistinguishable between the bulk (chemically untreated) and chemically degraded (treated with KOH and HI) samples. Such an observation indicates that the ROM fraction is the major contributor to the Raman response of meteoritic organic matter and thus Raman spectroscopy is unlikely to record any aqueous alteration processes that have affected meteoritic organic matter. Therefore, studies which use Raman to probe the IOM are investigating just one of the compone

Journal article

Royle S, Watson JS, Sephton M, 2021, Transformation of cyanobacterial biomolecules by iron oxides during flash pyrolysis: Implications for Mars life detection missions, Astrobiology, Vol: 21, ISSN: 1531-1074

Answering the question of whether life ever existed on Mars is a key goal of both NASA’s and ESA’s imminent Mars rover missions. The obfuscatory effects of oxidising salts, such as perchlorates and sulfates, on organic matter during thermal decomposition analysis techniques are well established. Less well studied are the transformative effects of iron oxides and (oxy)hydroxides, which are present in great abundances in the martian regolith. We examined the products of flash pyrolysis GC-MS, a technique analogous to the thermal techniques employed by past, current and future landed Mars missions, formed when the cyanobacteria Arthrospira platensis was heated in the presence of a variety of Mars-relevant 16iron bearing minerals. We found that iron oxides/(oxy)hydroxides have transformative effects on the pyrolytic products of cyanobacterial biomolecules. Both the abundance and variety of molecular species detected were decreased as iron substrates transformed biomolecules, by both oxidative and reductive processes, into lower fidelity alkanes, aromatic and aryl-bonded hydrocarbons. Despite the loss of fidelity, a suite containing mid-length alkanes and PAHs and/or aryl-bonded molecules in iron-rich samples subjected to pyrolysis, may allude to the transformation of cyanobacterially-derived mid-long chain length fatty acids (particularly unsaturated fatty acids) originally present in the sample. Haematite was found to be the iron-oxide with the lowest transformation potential and so, because this iron oxide has a high affinity forco-deposition of organic matter and preservation over geological timescales, sampling at Mars should target sediments/strata which have undergone a diagenetic history encouraging the dehydration, dehydroxylation and oxidation of more reactive iron-bearing phases to haematite by looking for (mineralogical) evidence of the activity of oxidising, acidic/neutral and either hot or long-lived fluids.

Journal article

Montgomery W, Schofield E, Sephton MA, Watson JSet al., 2021, The Preservation of English Oak in Marine Environments

<jats:p>&lt;p&gt;This study compares the chemical integrity of English Oak (Quercus robur) samples with an age range of four centuries by analysing the lignin degradation.The samples were collected from four historic British vessels and thusrepresent samples of diverse ages which have nonetheless experienced similar non-arborealenvironments. We conclude that the Mary Rose, the oldest vessel studied and therecipient of the most intensive conservation efforts, has been well-preserved throughtreatment with PEG, and we present a baseline for assessing whether a ship hasbeen biologically degraded.&lt;/p&gt;&lt;p&gt;&lt;br&gt;&lt;/p&gt;&lt;p&gt;The work combines quantitative analytic chemistry techniques (e.g., THM-GC-MS) with the conservation of large historic artifacts.&lt;/p&gt;</jats:p>

Journal article

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