Analysis of single oil-bearing fluid inclusions in mid-Proterozoic sandstones (Roper Group, Australia)

Hydrocarbons and organic biomarkers extracted from black shales and other carbonaceous sedimentary rocks are valuable sources of information on the biodiversity and environment of early Earth. However, many Precambrian hydrocarbons including biomarkers are suspected of being younger contamination. An alternative approach is to study biomarkers trapped in oil-bearing fluid inclusions by bulk crushing samples and subsequently analysing the extracted hydrocarbons with gas chromatography-mass spectrometry. However, this method does not constrain the hydrocarbons to one particular oil inclusion, which means that if several different generations of oil inclusions are present in the sample, a mix of the content from these oil inclusions will be analysed. In addition, samples with few and/or small inclusions are often below the detection limit. Recently, we showed that it is possible to detect organic biomarkers in single oil-bearing fluid inclusions using time-of-flight secondary ion mass spectrometry (ToF-SIMS). In the present study, single fluid inclusion analysis has been performed on Proterozoic samples for the first time. Four individual oil-bearing fluid inclusions, found in 1430. Ma sandstone from the Roper Superbasin in Northern Australia, were analysed with ToF-SIMS. The ToF-SIMS spectra of the oil in the different inclusions are very similar to each other and are consistent with the presence of n-alkanes/branched alkanes, monocyclic alkanes, bicyclic alkanes, aromatic hydrocarbons, and tetracyclic and pentacyclic hydrocarbons. These results are in agreement with those obtained from bulk crushing of inclusions trapped in the same samples. The capability to analyse the hydrocarbon and biomarker composition of single oil-bearing fluid inclusions is a major breakthrough, as it opens up a way of obtaining molecular compositional data on ancient oils without the ambiguity of the origin of these hydrocarbons. Additionally, this finding suggests that it will be possible to analyse minute oil samples beyond the capability of established techniques. This may allow the biomarker record of the biosphere, as preserved in fluid inclusions, to be extended further back in time, and hence makes it possible to more accurately trace the early evolution of life on Earth, and search for life on other planets or moons.16 page(s

Taphonomy of the fossil insects of the middle Eocene Kishenehn Formation

The lacustrine oil shales of the Coal Creek Member of the Kishenehn Formation in northwestern Montana comprise a relatively unstudied middle Eocene fossil insect locality. Herein, we detail the stratigraphic position of the fossiliferous unit, describe the insect fauna of the Coal Creek locality and document its bias towards very small but remarkably pre-served insects. In addition, the depositional environment is examined and the mineral constituents of the laminations that comprise the varves of the Kishenehn oil shale are defined. Fifteen orders of insects have been recorded with the majority of all insects identified as aquatic with the families Chironomidae (Diptera) and Corixidae (Hemiptera) dominant. The presence of small aquatic insects, many of which are immature, the intact nature of >90% of the fossil insects and the presence of Daphnia ephippia, all indicate that the depositional environment was the shallow margin of a large freshwater lake. The fossil insects occur within fossilized microbial mat layers that comprise the bedding planes of the oil shale. Unlike the fossiliferous shales of the Florissant and Okanagan Highlands, the mats are not a product of diatomaceous algae nor are diatom frustules a component of the sediments or the varve structure. Instead, the varves are composed of very fine eolian siliciclastic silt grains overlaid with non-diatomaceous, possibly cyanobacteria-derived microbial mats which contain distinct traces of polyaromatic hydrocarbons. A distinct third layer composed of essentially pure calcite is present in the shale of some exposures and is presumably derived from the seasonal warming-induced precipitation of carbonate from the lake’s waters. The Coal Creek locality presents a unique opportunity to study both very small middle Eocene insects not often preserved as compression fossils in most Konservat-Lagerstätte and the processes that led to their preservation

Composition of cometary particles collected during two periods of the Rosetta mission: multivariate evaluation of mass spectral data

International audienceThe instrument COSIMA (COmetary Secondary Ion Mass Analyzer) onboard of the European Space Agency mission Rosetta collected and analyzed dust particles in the neighborhood of comet 67P/Churyumov-Gerasimenko. The chemical composition of the particle surfaces was characterized by time-of-flight secondary ion mass spectrometry. A set of 2213 spectra has been selected, and relative abundances for CH-containing positive ions as well as positive elemental ions define a set of multivariate data with nine variables. Evaluation by complementary chemometric techniques shows different compositions of sample groups collected during two periods of the mission. The first period was August to November 2014 (far from the Sun); the second period was January 2015 to February 2016 (nearer to the Sun). The applied data evaluation methods consider the compositional nature of the mass spectral data and comprise robust principal component analysis as well as classification with discriminant partial least squares regression, k-nearest neighbor search, and random forest decision trees. The results indicate a high importance of the relative abundances of the secondary ions C + and Fe + for the group separation and demonstrate an enhanced content of carbon-containing substances in samples collected in the period with smaller distances to the Sun. K E Y W O R D S comet 67P/Churyumov-Gerasimenko, KNN classification, random forest classification, time-of-flight secondary ion mass spectrometry, variable importanc

Electrical properties of cometary dust particles derived from line shapes of TOF-SIMS spectra measured by the ROSETTA/COSIMA instrument

International audienceBetween Aug. 2014 and Sept. 2016, while ESA’s cornerstone mission Rosetta was operating in the vicinity of the nucleus and in the coma of comet 67P/Churyumov-Gerasimenko, the COSIMA instrument collected a large number of dust particles with diameters up to a millimeter. Positive or negative ions were detected by a time-of-flight secondary ion mass spectrometer (TOF-SIMS) and the composition of selected particles was deduced. Many of the negative ion mass spectra show, besides mass peaks at the correct position, an additional, extended contribution at the lower mass side caused by partial charging of the dust. This effect, usually avoided in SIMS applications, can in our case be used to obtain information on the electrical properties of the collected cometary dust particles, such as the specific resistivity ( ρr > 1.2 ∙10^10 Ωm) and the real part of the relative electrical permittivity (ε 0.8)

Chemical composition of the first rocks sampled by the Perseverance rover in Jezero crater, Mars

International audienceThe Perseverance rover will collect its first sample in August 2021 by coring low-standing, polygonally fractured rocks associated with the crater-retaining terrain to the southeast of Jezero delta. Future laboratory analyses of this first sample could determine the origin and depositional/emplacement age of the fractured unit in Jezero crater. Depending on the lithology, further analyses can address: 1. the potential utility of this unit for the constraining the age of the delta and possibly calibration of the crater chronology of Mars; 2. the evolution of martian interior, surface and climate. The dusty polygons are flat on a m-to-cm scale, largely lack visible layering and occasionally grade into darker, higher-standing nubs. WATSON and SuperCam Remote Micro-Imager (RMI) images of these rocks reveal mm-scale light and dark patches and specular reflection in a matrix with otherwise difficult-to-see grains. Analyses by SuperCam laser-induced breakdown spectroscopy (LIBS) and visible and infrared spectroscopy (VISIR) do not support a compositional distinction between the low areas and nubs, suggesting two different weathering expressions of the same starting material. The same analyses reveal hydration signals on the surfaces of all these rocks and suggest alteration by fluids, whereas the dark mm-to-cm scale pits, holes and reflective patches on the rock surfaces indicate wind abrasion. The low-standing rocks are compositionally heterogeneous at the scale of LIBS spot raster spacings (2-5 mm), with a bulk composition consistent with basaltic andesite. The major element compositions of some individual ~0.3 mm-diameter LIBS spots are consistent with iron oxides, ilmenite, various pyroxene minerals, feldspars and glass-like phases enriched in SiO2. This supports the presence of pure mineral grains at this scale. VISIR data point to a potential mixture of iron-rich phyllosilicate and iron oxyhydroxide on rock surfaces. These observations are consistent with the interpretations of the polygonally fractured rocks as either fine-grained sandstone or tuff. New constraints on their origin are expected in August 2021, when WATSON, SuperCam, PIXL and SHERLOC will be able to examine the texture and composition of abraded rocks millimeters below the dusty rock surfaces and any rock surface coatings

Chemical composition of the first rocks sampled by the Perseverance rover in Jezero crater, Mars

International audienceThe Perseverance rover will collect its first sample in August 2021 by coring low-standing, polygonally fractured rocks associated with the crater-retaining terrain to the southeast of Jezero delta. Future laboratory analyses of this first sample could determine the origin and depositional/emplacement age of the fractured unit in Jezero crater. Depending on the lithology, further analyses can address: 1. the potential utility of this unit for the constraining the age of the delta and possibly calibration of the crater chronology of Mars; 2. the evolution of martian interior, surface and climate. The dusty polygons are flat on a m-to-cm scale, largely lack visible layering and occasionally grade into darker, higher-standing nubs. WATSON and SuperCam Remote Micro-Imager (RMI) images of these rocks reveal mm-scale light and dark patches and specular reflection in a matrix with otherwise difficult-to-see grains. Analyses by SuperCam laser-induced breakdown spectroscopy (LIBS) and visible and infrared spectroscopy (VISIR) do not support a compositional distinction between the low areas and nubs, suggesting two different weathering expressions of the same starting material. The same analyses reveal hydration signals on the surfaces of all these rocks and suggest alteration by fluids, whereas the dark mm-to-cm scale pits, holes and reflective patches on the rock surfaces indicate wind abrasion. The low-standing rocks are compositionally heterogeneous at the scale of LIBS spot raster spacings (2-5 mm), with a bulk composition consistent with basaltic andesite. The major element compositions of some individual ~0.3 mm-diameter LIBS spots are consistent with iron oxides, ilmenite, various pyroxene minerals, feldspars and glass-like phases enriched in SiO2. This supports the presence of pure mineral grains at this scale. VISIR data point to a potential mixture of iron-rich phyllosilicate and iron oxyhydroxide on rock surfaces. These observations are consistent with the interpretations of the polygonally fractured rocks as either fine-grained sandstone or tuff. New constraints on their origin are expected in August 2021, when WATSON, SuperCam, PIXL and SHERLOC will be able to examine the texture and composition of abraded rocks millimeters below the dusty rock surfaces and any rock surface coatings

Overview and Results From the Mars 2020 Perseverance Rover's First Science Campaign on the Jezero Crater Floor

International audienceThe Mars 2020 Perseverance rover landed in Jezero crater on 18 February 2021. After a 100-sol period of commissioning and the Ingenuity Helicopter technology demonstration, Perseverance began its first science campaign to explore the enigmatic Jezero crater floor, whose igneous or sedimentary origins have been much debated in the scientific community. This paper describes the campaign plan developed to explore the crater floor's Máaz and Séítah formations and summarizes the results of the campaign between sols 100-379. By the end of the campaign, Perseverance had traversed more than 5 km, created seven abrasion patches, and sealed nine samples and a witness tube. Analysis of remote and proximity science observations show that the Máaz and Séítah formations are igneous in origin and composed of five and two geologic members, respectively. The Séítah formation represents the olivine-rich cumulate formed from differentiation of a slowly cooling melt or magma body, and the Máaz formation likely represents a separate series of lava flows emplaced after Séítah. The Máaz and Séítah rocks also preserve evidence of multiple episodes of aqueous alteration in secondary minerals like carbonate, Fe/Mg phyllosilicates, sulfates, and perchlorate, and surficial coatings. Post-emplacement processes tilted the rocks near the Máaz-Séítah contact and substantial erosion modified the crater floor rocks to their present-day expressions. Results from this crater floor campaign, including those obtained upon return of the collected samples, will help to build the geologic history of events that occurred in Jezero crater and provide time constraints on the formation of the Jezero delta. Plain Language Summary The Mars 2020 Perseverance rover, along with the Ingenuity Helicopter technology demonstration, landed in Jezero crater, Mars on 18 February 2021. Here, we detail results from the first science campaign of the mission, the purpose of which was to explore the enigmatic Jezero crater floor. By the end of the campaign, Perseverance traversed more than 5 km, created seven abrasion patches, SUN ET AL

Overview and Results From the Mars 2020 Perseverance Rover's First Science Campaign on the Jezero Crater Floor

The Mars 2020 Perseverance rover landed in Jezero crater on 18 February 2021. After a 100‐sol period of commissioning and the Ingenuity Helicopter technology demonstration, Perseverance began its first science campaign to explore the enigmatic Jezero crater floor, whose igneous or sedimentary origins have been much debated in the scientific community. This paper describes the campaign plan developed to explore the crater floor's Máaz and Séítah formations and summarizes the results of the campaign between sols 100–379. By the end of the campaign, Perseverance had traversed more than 5 km, created seven abrasion patches, and sealed nine samples and a witness tube. Analysis of remote and proximity science observations show that the Máaz and Séítah formations are igneous in origin and composed of five and two geologic members, respectively. The Séítah formation represents the olivine‐rich cumulate formed from differentiation of a slowly cooling melt or magma body, and the Máaz formation likely represents a separate series of lava flows emplaced after Séítah. The Máaz and Séítah rocks also preserve evidence of multiple episodes of aqueous alteration in secondary minerals like carbonate, Fe/Mg phyllosilicates, sulfates, and perchlorate, and surficial coatings. Post‐emplacement processes tilted the rocks near the Máaz‐Séítah contact and substantial erosion modified the crater floor rocks to their present‐day expressions. Results from this crater floor campaign, including those obtained upon return of the collected samples, will help to build the geologic history of events that occurred in Jezero crater and provide time constraints on the formation of the Jezero delta

The potential science and engineering value of samples delivered to Earth by Mars sample return

International audienc