Publications
255 results found
Tomson M, Kumar P, Kalaiarasan G, et 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
Vaughan A, Minitti ME, Cardarelli EL, et al., 2023, Regolith of the Crater Floor Units, Jezero Crater, Mars: Textures, Composition, and Implications for Provenance, Journal of Geophysical Research: Planets, Vol: 128, 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.
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.
Sephton M, Chan Q, Watson J, et 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.
Simon JI, HickmanLewis K, Cohen BA, et al., 2023, Samples collected from the floor of Jezero crater with the Mars 2020 Perseverance rover, Journal of Geophysical Research: Planets, 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.
Royle S, Cropper L, Watson J, et 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.
Kumar P, Zavala-Reyes JC, Kalaiarasan G, et 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.
Chan QHS, Watson JS, Sephton MA, et 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
Scheller EL, Hollis JR, Cardarelli EL, et 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.
King AJ, Daly L, Rowe J, et 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.
Salter TL, Watson J, Waite JH, et 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.
Peers De Nieuwburgh C, Watson J, Weiss D, et 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.
Farley KA, Stack KM, Shuster DL, et 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>
Kminek G, Benardini JN, Brenker FE, et 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
Royle SH, Salter TL, Watson JS, et 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.
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.
Salter TL, Magee BA, Waite JH, et 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.
Sims M, Fraser A, Neumaier M, et 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.
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
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.
Montgomery W, Schofield E, Sephton MA, et al., 2021, The Preservation of English Oak in Marine Environments
<jats:p><p>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.</p><p><br></p><p>The work combines quantitative analytic chemistry techniques (e.g., THM-GC-MS) with the conservation of large historic artifacts.</p></jats:p>
Montgomery W, Schofield E, Sephton MA, et al., 2021, The Preservation of English Oak in Marine Environments
<jats:p>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 thus represent samples of diverse ages which have nonetheless experienced similar non-arboreal environments. We conclude that the Mary Rose, the oldest vessel studied and the recipient of the most intensive conservation efforts, has been well-preserved through treatment with PEG, and we present a baseline for assessing whether a ship has been biologically degraded.</jats:p><jats:p>The work combines quantitative analytic chemistry techniques (e.g., THM-GC-MS) with the conservation of large historic artifacts.</jats:p>
Tan JSW, Sephton MA, 2021, Quantifying preservation potential: lipid degradation in a Mars-analog circumneutral iron deposit, Astrobiology, Vol: 21, Pages: 1-17, ISSN: 1531-1074
Comparisons between the preservation potential of Mars-analog environments have historically been qualitative rather than quantitative. Recently, however, laboratory-based artificial maturation combined with kinetic modeling techniques have emerged as a potential means by which the preservation potential of solvent-soluble organic matter can be quantified in various Mars-analog environments. These methods consider how elevated temperatures, pressures, and organic–inorganic interactions influence the degradation of organic biomarkers post-burial. We used these techniques to investigate the preservation potential of deposits from a circumneutral iron-rich groundwater system. These deposits are composed of ferrihydrite (Fe5HO8 · 4H2O), an amorphous iron hydroxide mineral that is a common constituent of rocks found in ancient lacustrine environments on Mars, such as those observed in Gale Crater. Both natural and synthetic ferrihydrite samples were subjected to hydrous pyrolysis to observe the effects of long-term burial on the mineralogy and organic content of the samples. Our experiments revealed that organic–inorganic interactions in the samples are dominated by the transformation of iron minerals. As amorphous ferrihydrite transforms into more crystalline species, the decrease in surface area results in the desorption of organic matter, potentially rendering them more susceptible to degradation. We also find that circumneutral iron-rich deposits provide unfavorable conditions for the preservation of solvent-soluble organic matter. Quantitative comparisons between preservation potentials as calculated when using kinetic parameters show that circumneutral iron-rich deposits are ∼25 times less likely to preserve solvent-soluble organic matter compared with acidic, iron-rich environments. Our results suggest that circumneutral iron-rich deposits should be deprioritized in favor of acidic iron- and sulfur-rich deposits when searching for evidence o
Royle SH, Tan J, Watson JS, et al., 2021, Pyrolysis of carboxylic acids in the presence of iron oxides: implications for life detection on missions to Mars, Astrobiology, Pages: 1-19, ISSN: 1531-1074
The search for, and characterization of, organic matter on Mars is central to efforts in identifying habitable environments and detecting evidence of life in the martian surface and near surface. Iron oxides are ubiquitous in the martian regolith and are known to be associated with the deposition and preservation of organic matter in certain terrestrial environments, thus iron oxide-rich sediments are potential targets for life-detection missions. The most frequently used protocol for martian organic matter characterization (also planned for use on ExoMars) has been thermal extraction for the transfer of organic matter to gas chromatography-mass spectrometry (GC-MS) detectors. For the effective use of thermal extraction for martian samples, it is necessary to explore how potential biomarker organic molecules evolve during this process in the presence of iron oxides. We have thermally decomposed iron oxides simultaneously with (z)-octadec-9-enoic and n-octadecanoic acids and analyzed the products through pyrolysis-GC-MS. We found that the thermally driven dehydration, reduction, and recrystallization of iron oxides transformed fatty acids. Overall detectability of products greatly reduced, molecular diversity decreased, unsaturated products decreased, and aromatization increased. The severity of this effect increased as reduction potential of the iron oxide and inferred free radical formation increased. Of the iron oxides tested hematite showed the least transformative effects, followed by magnetite, goethite, then ferrihydrite. It was possible to identify the saturation state of the parent carboxylic acid at high (0.5 wt %) concentrations by the distribution of n-alkylbenzenes in the pyrolysis products. When selecting life-detection targets on Mars, localities where hematite is the dominant iron oxide could be targeted preferentially, otherwise thermal analysis of carboxylic acids, or similar biomarker molecules, will lead to enhanced polymerization, aromatiz
Tan J, Royle S, Sephton M, 2021, Artificial maturation of iron- and sulfur-rich Mars analogues: Implications for the diagenetic stability of biopolymers and their detection with pyrolysis gas chromatography–mass spectrometry, Astrobiology, Vol: 21, Pages: 199-218, ISSN: 1531-1074
Acidic iron- and sulfur-rich streams are appropriate analogues for the late Noachian and early Hesperian periods of martian history, when Mars exhibited extensive habitable environments. Any past life on Mars may have left behind diagnostic evidence of life that could be detected at the present day. For effective preservation, these remains must have avoided the harsh radiation flux at the martian surface, survived geological storage for billions of years, and remained detectable within their geochemical environment by analytical instrument suites used on Mars today, such as thermal extraction techniques.We investigated the detectability of organic matter within sulfur stream sediments that had been subjected to artificial maturation by hydrous pyrolysis. After maturation, the samples were analyzed by pyrolysis–gas chromatography–mass spectrometry (py-GC-MS) to determine whether organic matter could be detected with this commonly used technique. We find that macromolecular organic matter can survive the artificial maturation process in the presence of iron- and sulfur-rich minerals but cannot be unambiguously distinguished from abiotic organic matter. However, if jarosite and goethite are present in the sulfur stream environment, they interfere with the py-GC-MS detection of organic compounds in these samples. Clay reduces the obfuscating effect of the oxidizing minerals by providing nondeleterious adsorption sites. We also find that after a simple alkali and acid leaching process that removes oxidizing minerals such as iron sulfates, oxides, and oxyhydroxides, the sulfur stream samples exhibit much greater organic responses during py-GC-MS in terms of both abundance and diversity of organic compounds, such as the detection of hopanes in all leached samples.Our results suggest that insoluble organic matter can be preserved over billions of years of geological storage while still retaining diagnostic organic information, but sample selection strategies mu
Tan J, Sephton M, 2020, Organic records of early life on Mars: the role of iron, burial and kinetics on preservation, Astrobiology, Vol: 20, Pages: 53-72, ISSN: 1531-1074
Samples that are likely to contain evidence of past life on Mars must have been deposited when and where environments exhibited habitable conditions. Mars analogue sites provide the opportunity to study how life could have exploited such habitable conditions. Acidic iron- and sulfur-rich streams are good geochemical analogues for the late Noachian and early Hesperian, periods of Martian history where habitable conditions were widespread. Past life on Mars would have left behind fossilised microbial organic remains and these are often-sought diagnostic evidence, but must be shielded from the harsh radiation flux at the Martian surface and its deleterious effect on organic matter. One mechanism that promotes such preservation is burial, which raises questions about how organic biomarkers are influenced by the post-burial effects of diagenesis. We investigated the kinetics of organic degradation in the subsurface of Mars. Natural mixtures of acidic iron- and sulfur-rich stream sediments and their associated microbial populations and remains were subjected to hydrous pyrolysis, which simulated the increased temperatures and pressures of burial alongside any promoted organic-mineral interactions. Calculations were made to extrapolate the observed changes over Martian history. Our experiments indicate that low carbon contents, high water-to-rock ratios, and the presence of iron-rich minerals combine to provide unfavourable conditions for the preservation of organic matter over the billions of years necessary to produce present day organic records of late Noachian and early Hesperian life on Mars. Successful sample selection strategies must therefore consider the pre-, syn- and post-burial histories of sedimentary records on Mars and the balance between the production of biomass and the long-term preservation of organic biomarkers over geological time.
Abubakar R, Muxworthy A, Fraser A, et al., 2020, Mapping hydrocarbon charge-points in the Wessex Basin using seismic, geochemistry and mineral magnetics, Marine and Petroleum Geology, Vol: 111, Pages: 510-528, ISSN: 1873-4073
This study reports a multidisciplinary approach to determining hydrocarbon charge-points and migration in the Wessex Basin, southern England. Geochemical analysis of reservoir core material (Bridport Sandstone and Inferior Oolite) using gas chromatography-mass spectrometry (GC-MS), suggests that the oil in the Wessex Basin is from a single source, and that small variations in environmentally sensitive biomarkers are likely due to small differences in maturity or depositional conditions during the formation of the oil over millions of years. Using seismic data, basin modelling revealed two potential hydrocarbon migration pathways from the hanging wall of the Purbeck fault into the Sherwood Sandstone reservoir at Wytch Farm. One of these potential pathways is represented by cores termed Creech and the other Bushey Farm. To try to distinguish between the two potential pathways, cores were studied using mineral magnetic techniques. The magnetic signature was characterised using low-temperature (<50 K) magnetic measurements; this is because much of the magnetic signature was dominated by nanoparticles < 30 nm, which are thermally activated at room temperature and magnetically “transparent”. Wells that contained considerable amounts of hydrocarbons were dominated by nanometric magnetite (<30 nm). Such particles are small enough to migrate with the oil, through pore spaces, which are of the order ~100 nm. Wells located at the fringes of large hydrocarbon accumulation had enhanced pyrrhotite-dominated magnetic signals. Of the two potential migration pathways, the mineral magnetic results suggest that the oil migrated through Creech rather than through Bushey Farm.
Royle S, Watson J, Zhang Y, et al., 2019, Solid Phase Micro Extraction: Potential for Organic Contamination Control for Planetary Protection of Life-Detection Missions to the Icy Moons of the Outer Solar System, Astrobiology, Vol: 19, Pages: 1153-1166, ISSN: 1531-1074
Conclusively detecting, or ruling out the possibility of, life on the icy moons of the outer solar system will require spacecraft missions to undergo rigorous planetary protection and contamination control procedures to achieve extremely low levels of organic terrestrial contamination. Contamination control is necessary to avoid forward contamination of the body of interest and to avoid the detection of false positive signals which could either mask indigenous organic chemistry of interest or cause an astrobiological false alarm. Here we test a new method for rapidly and inexpensively assessing the organic cleanliness of spaceflight hardware surfaces using solid phase micro extraction (SPME) fibres to directly swab surfaces. The results suggest that the method is both time and cost efficient. The SPME-gas chromatography mass spectrometry (GC-MS) method is sensitive to common mid-weight, non-polar contaminant compounds, e.g. aliphatic and aromatic hydrocarbons, which are common contaminants in laboratory settings. While we demonstrate the potential of SPME for surface sampling, the GC-MS instrumentation restricts the SPME-GC-MS technique’s sensitivity to larger polar and non-volatile compounds. Although not used in this study, to increase the potential range of detectable compounds, SPME can also be used in conjunction with high performance liquid chromatography/liquid chromatography-mass spectrometry systems suitable for polar analytes [Kataoka et al., 2000]. Thus, our SPME method presents an opportunity to monitor organic contamination in a relatively rapid and routine way that produces information-rich data sets.
Rettberg P, Antunes A, Brucato J, et al., 2019, Biological contamination prevention for outer solar system moons of astrobiological interest: What do we need to know?, Astrobiology, Vol: 19, ISSN: 1531-1074
To ensure that scientific investments in space exploration are not compromised by terrestrial contamination of celestial bodies, special care needs to be taken to preserve planetary conditions for future astrobiological exploration. Significant effort has been made and is being taken to address planetary protection in the context of inner Solar System exploration. In particular for missions to Mars, detailed internationally accepted guidelines have been established. For missions to the icy moons in the outer Solar System, Europa and Enceladus, the planetary protection requirements are so far based on a probabilistic approach and a conservative estimate of poorly known parameters. One objective of the European Commission-funded project, Planetary Protection of Outer Solar System, was to assess the existing planetary protection approach, to identify inherent knowledge gaps, and to recommend scientific investigations necessary to update the requirements for missions to the icy moons.
Kminek G, Fellous J-L, Rettburg P, et al., 2019, The international planetary protection handbook, Space Research Today, Vol: 205, Pages: e1-e120, ISSN: 1752-9298
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