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Carbon with depleted d 13 C (down to - 25.6‰ VPDB) found in > 3.7 billion year old metamorphic sediments from the Isua Supracrustal Belt, Southwestern Greenland, has been proposed to represent the oldest remains of life on Earth. Graphitic inclusions within garnet porphyroblasts from this locality have been shown to associate with elements consistent with biogenic remains. In this report, we focus on certain liquid inclusions found in the Isua garnets, characterizing their chemical composition using atomic force microscopy, AFM-based infrared spectroscopy, optical photothermal infrared spectroscopy, Raman spectroscopy, and time-of-flight secondary ion mass spectrometry. Our results show that the liquid inclusions contain functional groups consisting of carbon, nitrogen, and oxygen in a configuration similar to amide functional groups. We suspect that the amide groups formed from N, O and C-containing volatile components that were released from the original kerogenous material enclosed in the garnets, as this was graphitized during thermal maturation. This is consistent with the observed inclusion assemblage of solid graphitic and viscous fluid inclusions alike. Our observations are compatible with the inclusions forming from biogenic precursor material, and when considered alongside previous reports on the carbonaceous material in the Isua metamorphic sediments, these and our study collectively indicate that the carbonaceous material in the Isua metasediments represents the oldest traces of life on Earth., (© 2024. The Author(s).)

The Perseverance rover landed at Jezero crater, Mars, on 18 February 2021, with a payload of scientific instruments to examine Mars' past habitability, look for signs of past life, and process samples for future return to Earth. The instrument payload includes the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) deep ultraviolet Raman and fluorescence imaging spectrometer designed to detect, characterize, and map the presence of organics and minerals on the Martian surface. Operation and engineering constraints sometimes result in the acquisition of spectra with features near the detection limit. It is therefore important to separate instrumental (background) spectral components and spectral components inherent to Martian surface materials. For SHERLOC, the instrumental background is assessed by collecting spectra in the stowed-arm configuration where the instrument is pointed at the Martian nighttime sky with no surface sample present in its optical path. These measurements reveal weak Raman and fluorescence background spectral signatures as well as charged-coupled device pixels prone to erroneous intensity spikes separate from cosmic rays. We quantitatively describe these features and provide a subtraction procedure to remove the spectral background from surface spectra. By identifying and accounting for the SHERLOC Raman background features within the median Raman spectra of Martian target scans, we find that the undefined silicate spectral feature interpreted to be either amorphous silicate or plagioclase feldspar is ubiquitously found in every Mars target Raman scan collected through Sol 751., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

A major objective of the Mars 2020 mission is to sample rocks in Jezero crater that may preserve organic matter for later return to Earth. Using an ultraviolet Raman and luminescence spectrometer, the Perseverance rover detected luminescence signals with maximal intensities at 330 to 350 nanometers and 270 to 290 nanometers that were initially reported as consistent with organics. Here, we test the alternative hypothesis that the 330- to 350-nanometer and 270- to 290-nanometer luminescence signals trace Ce 3+ in phosphate and silicate defects, respectively. By comparing the distributions of luminescence signals with the rover detections of x-ray fluorescence from P 2 O 5 and Si-bearing materials, we show that, while an organic origin is not excluded, the observed luminescence can be explained by purely inorganic materials. These findings highlight the importance of eventual laboratory analyses to detect and characterize organic compounds in the returned samples.

In this work, we derive a simple method for calibrating Raman bandwidths for the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument onboard NASA's Perseverance rover. Raman bandwidths and shapes reported by an instrument contain contributions from both the intrinsic Raman band (IRB) and instrumental artifacts. To directly correlate bandwidth to sample properties and to compare bandwidths across instruments, the IRB width needs to be separated from instrumental effects. Here, we use the ubiquitous bandwidth calibration method of modeling the observed Raman bands as a convolution of a Lorentzian IRB and a Gaussian instrument slit function. Using calibration target data, we calculate that SHERLOC has a slit function width of 34.1 cm -1 . With a measure of the instrument slit function, we can deconvolve the IRB from the observed band, providing the width of the Raman band unobscured by instrumental artifact. We present the correlation between observed Raman bandwidth and intrinsic Raman bandwidth in table form for the quick estimation of SHERLOC Raman intrinsic bandwidths. We discuss the limitations of using this model to calibrate Raman bandwidth and derive a quantitative method for calculating the errors associated with the calibration. We demonstrate the utility of this method of bandwidth calibration by examining the intrinsic bandwidths of SHERLOC sulfate spectra and by modeling the SHERLOC spectrum of olivine., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument onboard the Mars 2020 Perseverance rover detected so far some of the most intense fluorescence signals in association with sulfates analyzing abraded patches of rocks at Jezero crater, Mars. To assess the plausibility of an organic origin of these signals, it is key to understand if organics can survive exposure to ambient Martian UV after exposure by the Perseverance abrasion tool and prior to analysis by SHERLOC. In this work, we investigated the stability of organo-sulfate assemblages under Martian-like UV irradiation and we observed that the spectroscopic features of phthalic and mellitic acid embedded into hydrated magnesium sulfate do not change for UV exposures corresponding to at least 48 Martian sols and, thus, should still be detectable in fluorescence when the SHERLOC analysis takes place, thanks to the photoprotective properties of magnesium sulfate. In addition, different photoproduct bands diagnostic of the parent carboxylic acid molecules could be observed. The photoprotective behavior of hydrated magnesium sulfate corroborates the hypothesis that sulfates might have played a key role in the preservation of organics on Mars, and that the fluorescence signals detected by SHERLOC in association with sulfates could potentially arise from organic compounds., (© 2024. The Author(s).)

Solar radiation that arrives on the surface of Mars interacts with organic molecules present in the soil. The radiation can degrade or transform the organic matter and make the search for biosignatures on the planet's surface difficult. Therefore, samples to be analyzed by instruments on board Mars probes for molecular content should be selectively chosen to have the highest organic preservation content. To support the identification of organic molecules on Mars, the behavior under UV irradiation of two organic compounds, undecanoic acid and L-phenylalanine, in the presence of vermiculite and two chloride salts, NaCl and MgCl, was studied. The degradation of the molecule's bands was monitored through IR spectroscopy. Our results show that, while vermiculite acts as a photoprotective mineral with L-phenylalanine, it catalyzes the photodegradation of undecanoic acid molecules. On the other hand, both chloride salts studied decreased the degradation of both organic species acting as photoprotectors. While these results do not allow us to conclude on the preservation capabilities of vermiculite, they show that places where chloride salts are present could be good candidates for in situ analytic experiments on Mars due to their organic preservation capacity under UV radiation.

The Mars Sample Return mission intends to retrieve a sealed collection of rocks, regolith, and atmosphere sampled from Jezero Crater, Mars, by the NASA Perseverance rover mission. For all life-related research, it is necessary to evaluate water availability in the samples and on Mars. Within the first Martian year, Perseverance has acquired an estimated total mass of 355 g of rocks and regolith, and 38 μmoles of Martian atmospheric gas. Using in-situ observations acquired by the Perseverance rover, we show that the present-day environmental conditions at Jezero allow for the hydration of sulfates, chlorides, and perchlorates and the occasional formation of frost as well as a diurnal atmospheric-surface water exchange of 0.5-10 g water per m 2 (assuming a well-mixed atmosphere). At night, when the temperature drops below 190 K, the surface water activity can exceed 0.5, the lowest limit for cell reproduction. During the day, when the temperature is above the cell replication limit of 245 K, water activity is less than 0.02. The environmental conditions at the surface of Jezero Crater, where these samples were acquired, are incompatible with the cell replication limits currently known on Earth., (© 2024. The Author(s).)

The presence and distribution of preserved organic matter on the surface of Mars can provide key information about the Martian carbon cycle and the potential of the planet to host life throughout its history. Several types of organic molecules have been previously detected in Martian meteorites 1 and at Gale crater, Mars 2-4 . Evaluating the diversity and detectability of organic matter elsewhere on Mars is important for understanding the extent and diversity of Martian surface processes and the potential availability of carbon sources 1,5,6 . Here we report the detection of Raman and fluorescence spectra consistent with several species of aromatic organic molecules in the Máaz and Séítah formations within the Crater Floor sequences of Jezero crater, Mars. We report specific fluorescence-mineral associations consistent with many classes of organic molecules occurring in different spatial patterns within these compositionally distinct formations, potentially indicating different fates of carbon across environments. Our findings suggest there may be a diversity of aromatic molecules prevalent on the Martian surface, and these materials persist despite exposure to surface conditions. These potential organic molecules are largely found within minerals linked to aqueous processes, indicating that these processes may have had a key role in organic synthesis, transport or preservation., (© 2023. The Author(s).)

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.

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.

Before Perseverance, Jezero crater's floor was variably hypothesized to have a lacustrine, lava, volcanic airfall, or aeolian origin. SuperCam observations in the first 286 Mars days on Mars revealed a volcanic and intrusive terrain with compositional and density stratification. The dominant lithology along the traverse is basaltic, with plagioclase enrichment in stratigraphically higher locations. Stratigraphically lower, layered rocks are richer in normative pyroxene. The lowest observed unit has the highest inferred density and is olivine-rich with coarse (1.5 millimeters) euhedral, relatively unweathered grains, suggesting a cumulate origin. This is the first martian cumulate and shows similarities to martian meteorites, which also express olivine disequilibrium. Alteration materials including carbonates, sulfates, perchlorates, hydrated silicates, and iron oxides are pervasive but low in abundance, suggesting relatively brief lacustrine conditions. Orbital observations link the Jezero floor lithology to the broader Nili-Syrtis region, suggesting that density-driven compositional stratification is a regional characteristic.

Organic molecules preserved in fossils provide a wealth of new information about ancient life. The discovery of almost unaltered complex organic molecules in well-preserved fossils raise the question of how common such occurrences are in the fossil record, how to differentiate between endogenous and exogenous sources for the organic matter and what promotes such preservation. The aim of this study was the in-situ analysis of a well-preserved vertebrate fossil from 48 Ma Eocene sediments in the Messel pit, Germany for preservation of complex biomolecules. The fossil was characterized using a variety of techniques including time-of-flight secondary ion mass spectrometry (ToF-SIMS), scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDX), x-ray diffraction (XRD) and Raman spectroscopy. A suite of organic molecules was detected, including porphyrins, which given the context of the detected signal are most probably diagenetically altered heme originating from the fossil though a microbial contribution cannot be completely ruled out. Diagenetic changes to the porphyrin structure were observed that included the exchange of the central iron by nickel. Further analyses on the geochemistry of the fossil and surrounding sediments showed presence of pyrite and aluminosilicates, most likely clay. In addition, a carbonate and calcium phosphate dominated crust has formed around the fossil. This suggests that several different processes are involved in the preservation of the fossil and the organic molecules associated with it. Similar processes seem to have also been involved in preservation of heme in fossils from other localities., Competing Interests: The authors have declared that no competing interests exist.

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 of martian life in the samples, (2) carrying out an analogue test program, and (3) acquiring relevant contamination knowledge from all Mars Sample Return (MSR) flight and ground elements. Although the SSAF was developed specifically for assessing samples from Mars in the context of the currently planned NASA-ESA MSR Campaign, this framework and the basic safety approach are applicable to any other Mars sample return mission concept, with minor adjustments in the execution part related to the specific nature of the samples to be returned. The SSAF is also considered a sound basis for other COSPAR Planetary Protection Category V, restricted Earth return missions beyond Mars. It is anticipated that the SSAF will be subject to future review by the various MSR stakeholders.

The Mars Organic Molecule Analyzer (MOMA) is a key scientific instrument on the ExoMars Rover mission. MOMA is designed to detect and characterize organic compounds, over a wide range of volatility and molecular weight, in samples obtained from up to 2 m below the martian surface. Thorough analog sample studies are required to best prepare to interpret MOMA data collected on Mars. We present here the MOMA characterization of Mars analog samples, microbial streamer communities composed primarily of oxygenic and anoxygenic phototrophs, collected from an alkaline silica-depositing hot spring in Yellowstone National Park, Wyoming, USA. Samples of partly mineralized microbial streamers and their total lipid extract (TLE) were measured on a MOMA Engineering Test Unit (ETU) instrument by using its laser desorption/ionization mass spectrometry (LDI-MS) mode. MOMA LDI-MS detected a variety of lipids and pigments such as chlorophyll a, monogalactosyldiacylglycerol, digalactosyldiacylglycerol, diacylglycerols, and β-carotene in the TLE sample. Only chlorophyll a was detected in the untreated streamer samples when using mass isolation, which was likely due to the higher background signal of this sample and the relative high ionization potential of the chlorophyll a compared with other compounds in unextracted samples. The results add to the LDI-MS sample characterization database and demonstrate the benefit of using mass isolation on the MOMA instrument to reveal the presence of complex organics and potential biomarkers preserved in a natural sample. This will also provide guidance to in situ analysis of surface samples during Mars operations.

The 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., (© 2020 The Authors. Journal of Chemometrics published by John Wiley & Sons Ltd.)

Fractured rocks of impact craters may be suitable hosts for deep microbial communities on Earth and potentially other terrestrial planets, yet direct evidence remains elusive. Here, we present a study of the largest crater of Europe, the Devonian Siljan structure, showing that impact structures can be important unexplored hosts for long-term deep microbial activity. Secondary carbonate minerals dated to 80 ± 5 to 22 ± 3 million years, and thus postdating the impact by more than 300 million years, have isotopic signatures revealing both microbial methanogenesis and anaerobic oxidation of methane in the bedrock. Hydrocarbons mobilized from matured shale source rocks were utilized by subsurface microorganisms, leading to accumulation of microbial methane mixed with a thermogenic and possibly a minor abiotic gas fraction beneath a sedimentary cap rock at the crater rim. These new insights into crater hosted gas accumulation and microbial activity have implications for understanding the astrobiological consequences of impacts.

The sources and nature of organic carbon on Mars have been a subject of intense research. Steele et al. (2012) showed that 10 martian meteorites contain macromolecular carbon phases contained within pyroxene- and olivine-hosted melt inclusions. Here, we show that martian meteorites Tissint, Nakhla, and NWA 1950 have an inventory of organic carbon species associated with fluid-mineral reactions that are remarkably consistent with those detected by the Mars Science Laboratory (MSL) mission. We advance the hypothesis that interactions among spinel-group minerals, sulfides, and a brine enable the electrochemical reduction of aqueous CO 2 to organic molecules. Although documented here in martian samples, a similar process likely occurs wherever igneous rocks containing spinel-group minerals and/or sulfides encounter brines.

Garnets from disparate geographical environments and origins such as oxidized soils and river sediments in Thailand host intricate systems of microsized tunnels that significantly decrease the quality and value of the garnets as gems. The origin of such tunneling has previously been attributed to abiotic processes. Here we present physical and chemical remains of endolithic microorganisms within the tunnels and discuss a probable biological origin of the tunnels. Extensive investigations with synchrotron-radiation X-ray tomographic microscopy (SRXTM) reveal morphological indications of biogenicity that further support a euendolithic interpretation. We suggest that the production of the tunnels was initiated by a combination of abiotic and biological processes, and that at later stages biological processes came to dominate. In environments such as river sediments and oxidized soils garnets are among the few remaining sources of bio-available Fe2+, thus it is likely that microbially mediated boring of the garnets has trophic reasons. Whatever the reason for garnet boring, the tunnel system represents a new endolithic habitat in a hard silicate mineral otherwise known to be resistant to abrasion and chemical attack., Competing Interests: The authors have declared that no competing interests exist.

The in situ cometary dust particle instrument COSIMA (COmetary Secondary Ion Mass Analyser) onboard ESA's Rosetta mission has collected about 31 000 dust particles in the inner coma of comet 67P/Churyumov-Gerasimenko since August 2014. The particles are identified by optical microscope imaging and analysed by time-of-flight secondary ion mass spectrometry. After dust particle collection by low speed impact on metal targets, the collected particle morphology points towards four families of cometary dust particles. COSIMA is an in situ laboratory that operates remotely controlled next to the comet nucleus. The particles can be further manipulated within the instrument by mechanical and electrostatic means after their collection by impact. The particles are stored above 0°C in the instrument and the experiments are carried out on the refractory, ice-free matter of the captured cometary dust particles. An interesting particle morphology class, the compact particles, is not fragmented on impact. One of these particles was mechanically pressed and thereby crushed into large fragments. The particles are good electrical insulators and transform into rubble pile agglomerates by the application of an energetic indium ion beam during the secondary ion mass spectrometry analysis.This article is part of the themed issue 'Cometary science after Rosetta'., (© 2017 The Author(s).)

The deep biosphere is one of the least understood ecosystems on Earth. Although most microbiological studies in this system have focused on prokaryotes and neglected microeukaryotes, recent discoveries have revealed existence of fossil and active fungi in marine sediments and sub-seafloor basalts, with proposed importance for the subsurface energy cycle. However, studies of fungi in deep continental crystalline rocks are surprisingly few. Consequently, the characteristics and processes of fungi and fungus-prokaryote interactions in this vast environment remain enigmatic. Here we report the first findings of partly organically preserved and partly mineralized fungi at great depth in fractured crystalline rock (-740 m). Based on environmental parameters and mineralogy the fungi are interpreted as anaerobic. Synchrotron-based techniques and stable isotope microanalysis confirm a coupling between the fungi and sulfate reducing bacteria. The cryptoendolithic fungi have significantly weathered neighboring zeolite crystals and thus have implications for storage of toxic wastes using zeolite barriers.Deep subsurface microorganisms play an important role in nutrient cycling, yet little is known about deep continental fungal communities. Here, the authors show organically preserved and partly mineralized fungi at 740 m depth, and find evidence of an anaerobic fungi and sulfate reducing bacteria consortium.

The Mars Organic Molecule Analyzer (MOMA) instrument onboard the ESA/Roscosmos ExoMars rover (to launch in July, 2020) will analyze volatile and refractory organic compounds in martian surface and subsurface sediments. In this study, we describe the design, current status of development, and analytical capabilities of the instrument. Data acquired on preliminary MOMA flight-like hardware and experimental setups are also presented, illustrating their contribution to the overall science return of the mission. Key Words: Mars-Mass spectrometry-Life detection-Planetary instrumentation. Astrobiology 17, 655-685., Competing Interests: No competing financial interests exist.

Dyes currently used to stain carious dentine have a limited capacity to discriminate normal dentine from carious dentine, which may result in overexcavation. Consequently, finding a selective dye is still a challenge. However, there is evidence that hydrazine-based dyes, via covalent bonds to functional groups, bind specifically to carious dentine. The aim of this study was to investigate the possible formation of covalent bonds between carious dentine and 15N2-hydrazine and the hydrazine-based dye, 15N2-labelled Lucifer Yellow, respectively. Powdered dentine from extracted carious and normal teeth was exposed to the dyes, and the staining reactions were analysed using time-of-flight secondary ion mass spectrometry (ToF-SIMS), solid-state 13C-labelled nuclear magnetic resonance (NMR) and 15N-NMR spectroscopy. The results showed that 15N2-hydrazine and 15N2-labelled Lucifer Yellow both bind to carious dentine but not to normal dentine. It can thus be concluded that hydrazine-based dyes can be used to stain carious dentine and leave normal dentine unstained., (© 2017 S. Karger AG, Basel.)

The presence of solid carbonaceous matter in cometary dust was established by the detection of elements such as carbon, hydrogen, oxygen and nitrogen in particles from comet 1P/Halley. Such matter is generally thought to have originated in the interstellar medium, but it might have formed in the solar nebula-the cloud of gas and dust that was left over after the Sun formed. This solid carbonaceous material cannot be observed from Earth, so it has eluded unambiguous characterization. Many gaseous organic molecules, however, have been observed; they come mostly from the sublimation of ices at the surface or in the subsurface of cometary nuclei. These ices could have been formed from material inherited from the interstellar medium that suffered little processing in the solar nebula. Here we report the in situ detection of solid organic matter in the dust particles emitted by comet 67P/Churyumov-Gerasimenko; the carbon in this organic material is bound in very large macromolecular compounds, analogous to the insoluble organic matter found in the carbonaceous chondrite meteorites. The organic matter in meteorites might have formed in the interstellar medium and/or the solar nebula, but was almost certainly modified in the meteorites' parent bodies. We conclude that the observed cometary carbonaceous solid matter could have the same origin as the meteoritic insoluble organic matter, but suffered less modification before and/or after being incorporated into the comet.

Elucidating cardiac evolution has been frustrated by lack of fossils. One celebrated enigma in cardiac evolution involves the transition from a cardiac outflow tract dominated by a multi-valved conus arteriosus in basal actinopterygians, to an outflow tract commanded by the non-valved, elastic, bulbus arteriosus in higher actinopterygians. We demonstrate that cardiac preservation is possible in the extinct fish Rhacolepis buccalis from the Brazilian Cretaceous. Using X-ray synchrotron microtomography, we show that Rhacolepis fossils display hearts with a conus arteriosus containing at least five valve rows. This represents a transitional morphology between the primitive, multivalvar, conal condition and the derived, monovalvar, bulbar state of the outflow tract in modern actinopterygians. Our data rescue a long-lost cardiac phenotype (119-113 Ma) and suggest that outflow tract simplification in actinopterygians is compatible with a gradual, rather than a drastic saltation event. Overall, our results demonstrate the feasibility of studying cardiac evolution in fossils.

Mid-Mesozoic kalligrammatid lacewings (Neuroptera) entered the fossil record 165 million years ago (Ma) and disappeared 45 Ma later. Extant papilionoid butterflies (Lepidoptera) probably originated 80-70 Ma, long after kalligrammatids became extinct. Although poor preservation of kalligrammatid fossils previously prevented their detailed morphological and ecological characterization, we examine new, well-preserved, kalligrammatid fossils from Middle Jurassic and Early Cretaceous sites in northeastern China to unravel a surprising array of similar morphological and ecological features in these two, unrelated clades. We used polarized light and epifluorescence photography, SEM imaging, energy dispersive spectrometry and time-of-flight secondary ion mass spectrometry to examine kalligrammatid fossils and their environment. We mapped the evolution of specific traits onto a kalligrammatid phylogeny and discovered that these extinct lacewings convergently evolved wing eyespots that possibly contained melanin, and wing scales, elongate tubular proboscides, similar feeding styles, and seed-plant associations, similar to butterflies. Long-proboscid kalligrammatid lacewings lived in ecosystems with gymnosperm-insect relationships and likely accessed bennettitalean pollination drops and pollen. This system later was replaced by mid-Cretaceous angiosperms and their insect pollinators., (© 2016 The Authors.)

Precipitation of exceptionally 13C-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in 13C than in the source methane, because of incorporation of C also from other sources, they are far more depleted in 13C (δ13C as light as -69‰ V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely 13C-depleted carbonates ever reported, δ13C down to -125‰ V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane.

Comets are composed of dust and frozen gases. The ices are mixed with the refractory material either as an icy conglomerate, or as an aggregate of pre-solar grains (grains that existed prior to the formation of the Solar System), mantled by an ice layer. The presence of water-ice grains in periodic comets is now well established. Modelling of infrared spectra obtained about ten kilometres from the nucleus of comet Hartley 2 suggests that larger dust particles are being physically decoupled from fine-grained water-ice particles that may be aggregates, which supports the icy-conglomerate model. It is known that comets build up crusts of dust that are subsequently shed as they approach perihelion. Micrometre-sized interplanetary dust particles collected in the Earth's stratosphere and certain micrometeorites are assumed to be of cometary origin. Here we report that grains collected from the Jupiter-family comet 67P/Churyumov-Gerasimenko come from a dusty crust that quenches the material outflow activity at the comet surface. The larger grains (exceeding 50 micrometres across) are fluffy (with porosity over 50 per cent), and many shattered when collected on the target plate, suggesting that they are agglomerates of entities in the size range of interplanetary dust particles. Their surfaces are generally rich in sodium, which explains the high sodium abundance in cometary meteoroids. The particles collected to date therefore probably represent parent material of interplanetary dust particles. This argues against comet dust being composed of a silicate core mantled by organic refractory material and then by a mixture of water-dominated ices. At its previous recurrence (orbital period 6.5 years), the comet's dust production doubled when it was between 2.7 and 2.5 astronomical units from the Sun, indicating that this was when the nucleus shed its mantle. Once the mantle is shed, unprocessed material starts to supply the developing coma, radically changing its dust component, which then also contains icy grains, as detected during encounters with other comets closer to the Sun.

The characterization of any organic molecules on Mars is a top-priority objective for the ExoMars European Space Agency-Russian Federal Space Agency joint mission. The main instrument for organic analysis on the ExoMars rover is the Mars Organic Molecule Analyzer (MOMA). In preparation for the upcoming mission in 2018, different Mars analog samples are studied with MOMA and include samples collected during the Arctic Mars Analog Svalbard Expedition (AMASE) to Svalbard, Norway. In this paper, we present results obtained from two different Mars analog sites visited during AMASE11, Colletthøgda and Botniahalvøya. Measurements were performed on the samples during AMASE11 with a MOMA gas chromatograph (GC) prototype connected to a commercial mass spectrometer (MS) and later in home institutions with commercial pyrolysis-GCMS instruments. In addition, derivatization experiments were performed on the samples during AMASE11 and in the laboratory. Three different samples were studied from the Colletthøgda that included one evaporite and two carbonate-bearing samples. Only a single sample was studied from the Botniahalvøya site, a weathered basalt covered by a shiny surface consisting of manganese and iron oxides. Organic molecules were detected in all four samples and included aromatics, long-chained hydrocarbons, amino acids, nucleobases, sugars, and carboxylic acids. Both pyrolysis and derivatization indicated the presence of extinct biota by the detection of carboxylic acids in the samples from Colletthøgda, while the presence of amino acids, nucleobases, carboxylic acids, and sugars indicated an active biota in the sample from Botniahalvøya. The results obtained with the prototype flight model in the field coupled with repeat measurements with commercial instruments within the laboratory were reassuringly similar. This demonstrates the performance of the MOMA instrument and validates that the instrument will aid researchers in their efforts to answer fundamental questions regarding the speciation and possible source of organic content on Mars.

Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced hydrothermal convection. Impact-generated hydrothermal systems have been suggested to possess the same life supporting capability as hydrothermal systems associated with volcanic activity. However, evidence of fossil microbial colonization in impact-generated hydrothermal systems is scarce in the literature. Here we report of fossilized microorganisms in association with cavity-grown hydrothermal minerals from the 458 Ma Lockne impact structure, Sweden. Based on morphological characteristics the fossilized microorganisms are interpreted as fungi. We further infer the kerogenization of the microfossils, and thus the life span of the fungi, to be contemporaneous with the hydrothermal activity and migration of hydrocarbons in the system. Our results from the Lockne impact structure show that hydrothermal systems associated with impact structures can support colonization by microbial life.

Rationale: Over the last decade, the high lateral resolution and imaging capabilities of time-of-flight secondary ion mass spectrometry (ToF-SIMS) have increasingly stimulated interest in studying organic molecules in complex environmental materials. However, unlike with the established mass spectrometric techniques, the use of ToF-SIMS in the biogeosciences is still hampered by a lack of reference spectra of the relevant biomarker compounds. Here we present and interpret ToF-SIMS reference spectra of ten different cyclic lipids that are frequently used as biological tracers in ecological, organic geochemical and geobiological studies., Methods: Standard compounds of α,β,β-(20R,24S)-24-methylcholestane, (22E)-ergosta-5,7,22-trien-3β-ol, 17α(H),21β-(H)-30-norhopane, hope-17(21)-ene, hop-22(29)-ene, 17β(H),21β(H)-bacteriohopane-32,33,34,35-tetrol, 17β(H),21β(H)-35-aminobacteriohopane-32,33,34-triol, α-tocopherol, β,β-carotene, chlorophyll a, and cryosections of microbial mats and a fungus were analyzed using a ToF-SIMS instrument equipped with a Bi(3)(+) cluster ion source., Results: The spectra obtained from the standard compounds showed peaks in the molecular weight range (molecular ions, protonated and deprotonated molecules, adduct ions) and diagnostic fragment ion peaks in both, positive and negative ion modes. For the cyclic hydrocarbons, however, the positive ion mode spectra typically showed more and stronger characteristic peaks than the negative ion mode spectra. Using real world samples the capability of ToF-SIMS to detect and image selected compounds in complex organic matrices was tested. 17β(H),21β(H)-35-Aminobacteriohopane-32,33,34-triol, carotene and chlorophyll a were successfully identified in cryosections of microbial mats, and the distribution of ergosterol was mapped at µm resolution in a cryosection of a fungus (Tuber uncinatum)., Conclusions: This study further highlights the utility of ToF-SIMS for the identification and localization of lipids within environmental samples and as a technique for biomarker-related research in organic geochemistry and geobiology., (Copyright © 2013 John Wiley & Sons, Ltd.)

The source and nature of carbon on Mars have been a subject of intense speculation. We report the results of confocal Raman imaging spectroscopy on 11 martian meteorites, spanning about 4.2 billion years of martian history. Ten of the meteorites contain abiotic macromolecular carbon (MMC) phases detected in association with small oxide grains included within high-temperature minerals. Polycyclic aromatic hydrocarbons were detected along with MMC phases in Dar al Gani 476. The association of organic carbon within magmatic minerals indicates that martian magmas favored precipitation of reduced carbon species during crystallization. The ubiquitous distribution of abiotic organic carbon in martian igneous rocks is important for understanding the martian carbon cycle and has implications for future missions to detect possible past martian life.

Steranes and hopanes are organic biomarkers used as indicators for the first appearance of eukaryotes and cyanobacteria on Earth. Oil-bearing fluid inclusions may provide a contamination-free source of Precambrian biomarkers, as the oil has been secluded from the environment since the formation of the inclusion. However, analysis of biomarkers in single oil-bearing fluid inclusions, which is often necessary due to the presence of different generations of inclusions, has not been possible due to the small size of most inclusions. Here, we have used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to monitor in real time the opening of individual inclusions trapped in hydrothermal veins of fluorite and calcite and containing oil from Ordovician source rocks. Opening of the inclusions was performed by using a focused C(60)(+) ion beam and the in situ content was precisely analysed for C(27)-C(29) steranes and C(29)-C(32) hopanes using Bi(3)(+) as primary ions. The capacity to unambiguously detect these biomarkers in the picoliter amount of crude oil from a single, normal-sized (15-30 mum in diameter) inclusion makes the approach promising in the search of organic biomarkers for life's early evolution on Earth.