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Clodoré L, Foucher F, Hickman-Lewis K, Sorieul S, Jouve J, Réfrégiers M, Collet G, Petoud S, Gratuze B, Westall F. Multi-Technique Characterization of 3.45 Ga Microfossils on Earth: A Key Approach to Detect Possible Traces of Life in Returned Samples from Mars. ASTROBIOLOGY 2024; 24:190-226. [PMID: 38393828 DOI: 10.1089/ast.2023.0089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2024]
Abstract
The NASA Mars 2020 Perseverance rover is actively exploring Jezero crater to conduct analyses on igneous and sedimentary rock targets from outcrops located on the crater floor (Máaz and Séítah formations) and from the delta deposits, respectively. The rock samples collected during this mission will be recovered during the Mars Sample Return mission, which plans to bring samples back to Earth in the 2030s to conduct in-depth studies using sophisticated laboratory instrumentation. Some of these samples may contain traces of ancient martian life that may be particularly difficult to detect and characterize because of their morphological simplicity and subtle biogeochemical expressions. Using the volcanic sediments of the 3.45 Ga Kitty's Gap Chert (Pilbara, Australia), containing putative early life forms (chemolithotrophs) and considered as astrobiological analogues for potential early Mars organisms, we document the steps required to demonstrate the syngenicity and biogenicity of such biosignatures using multiple complementary analytical techniques to provide information at different scales of observation. These include sedimentological, petrological, mineralogical, and geochemical analyses to demonstrate macro- to microscale habitability. New approaches, some unavailable at the time of the original description of these features, are used to verify the syngenicity and biogenicity of the purported fossil chemolithotrophs. The combination of elemental (proton-induced X-ray emission spectrometry) and molecular (deep-ultraviolet and Fourier transform infrared) analyses of rock slabs, thin sections, and focused ion beam sections reveals that the carbonaceous matter present in the samples is enriched in trace metals (e.g., V, Cr, Fe, Co) and is associated with aromatic and aliphatic molecules, which strongly support its biological origin. Transmission electron microscopy observations of the carbonaceous matter documented an amorphous nanostructure interpreted to correspond to the degraded remains of microorganisms and their by-products (extracellular polymeric substances, filaments…). Nevertheless, a small fraction of carbonaceous particles has signatures that are more metamorphosed. They probably represent either reworked detrital biological or abiotic fragments of mantle origin. This study serves as an example of the analytical protocol that would be needed to optimize the detection of fossil traces of life in martian rocks.
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Affiliation(s)
- Laura Clodoré
- CNRS-Centre de Biophysique Moléculaire, Orléans, France
| | - Frédéric Foucher
- CNRS-Centre de Biophysique Moléculaire, Orléans, France
- CNRS-Conditions Extrêmes et Matériaux: Haute Température et Irradiation, Orléans, France
| | - Keyron Hickman-Lewis
- Natural History Museum, London, United Kingdom
- Dipartimento BiGeA, Università di Bologna, Bologna, Italy
| | | | - Jean Jouve
- University of Bordeaux, CNRS, IN2P3, CENBG, Gradignan, France
| | | | - Guillaume Collet
- CNRS-Centre de Biophysique Moléculaire, Orléans, France
- Chair of Cosmetology, AgroParisTech Innovation, Orléans, France
| | | | - Bernard Gratuze
- CNRS-Institut de Recherche sur les ArchéoMATériaux, Orléans, France
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Barlow EV, House CH, Liu MC, Wetherington MT, Van Kranendonk MJ. Distinctive microfossil supports early Paleoproterozoic rise in complex cellular organisation. GEOBIOLOGY 2024; 22:e12576. [PMID: 37803496 DOI: 10.1111/gbi.12576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 08/14/2023] [Accepted: 09/07/2023] [Indexed: 10/08/2023]
Abstract
The great oxidation event (GOE), ~2.4 billion years ago, caused fundamental changes to the chemistry of Earth's surface environments. However, the effect of these changes on the biosphere is unknown, due to a worldwide lack of well-preserved fossils from this time. Here, we investigate exceptionally preserved, large spherical aggregate (SA) microfossils permineralised in chert from the c. 2.4 Ga Turee Creek Group in Western Australia. Field and petrographic observations, Raman spectroscopic mapping, and in situ carbon isotopic analyses uncover insights into the morphology, habitat, reproduction and metabolism of this unusual form, whose distinctive, SA morphology has no known counterpart in the fossil record. Comparative analysis with microfossils from before the GOE reveals the large SA microfossils represent a step-up in cellular organisation. Morphological comparison to extant micro-organisms indicates the SAs have more in common with coenobial algae than coccoidal bacteria, emphasising the complexity of this microfossil form. The remarkable preservation here provides a unique window into the biosphere, revealing an increase in the complexity of life coinciding with the GOE.
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Affiliation(s)
- Erica V Barlow
- Australian Centre for Astrobiology, School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington, New South Wales, Australia
- Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS), Macquarie University, Sydney, New South Wales, Australia
- Department of Geosciences and the Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Christopher H House
- Department of Geosciences and the Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Ming-Chang Liu
- Department of Earth, Planetary, and Space Sciences, University of California at Los Angeles, Los Angeles, California, USA
- Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Maxwell T Wetherington
- Materials Research Institute and Department of Materials Science & Engineering, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Martin J Van Kranendonk
- Australian Centre for Astrobiology, School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington, New South Wales, Australia
- Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS), Macquarie University, Sydney, New South Wales, Australia
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Runge EA, Mansor M, Kappler A, Duda JP. Microbial biosignatures in ancient deep-sea hydrothermal sulfides. GEOBIOLOGY 2023; 21:355-377. [PMID: 36524457 DOI: 10.1111/gbi.12539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 11/03/2022] [Accepted: 12/03/2022] [Indexed: 06/17/2023]
Abstract
Deep-sea hydrothermal systems provide ideal conditions for prebiotic reactions and ancient metabolic pathways and, therefore, might have played a pivotal role in the emergence of life. To understand this role better, it is paramount to examine fundamental interactions between hydrothermal processes, non-living matter, and microbial life in deep time. However, the distribution and diversity of microbial communities in ancient deep-sea hydrothermal systems are still poorly constrained, so evolutionary, and ecological relationships remain unclear. One important reason is an insufficient understanding of the formation of diagnostic microbial biosignatures in such settings and their preservation through geological time. This contribution centers around microbial biosignatures in Precambrian deep-sea hydrothermal sulfide deposits. Intending to provide a valuable resource for scientists from across the natural sciences whose research is concerned with the origins of life, we first introduce different types of biosignatures that can be preserved over geological timescales (rock fabrics and textures, microfossils, mineral precipitates, carbonaceous matter, trace metal, and isotope geochemical signatures). We then review selected reports of biosignatures from Precambrian deep-sea hydrothermal sulfide deposits and discuss their geobiological significance. Our survey highlights that Precambrian hydrothermal sulfide deposits potentially encode valuable information on environmental conditions, the presence and nature of microbial life, and the complex interactions between fluids, micro-organisms, and minerals. It further emphasizes that the geobiological interpretation of these records is challenging and requires the concerted application of analytical and experimental methods from various fields, including geology, mineralogy, geochemistry, and microbiology. Well-orchestrated multidisciplinary studies allow us to understand the formation and preservation of microbial biosignatures in deep-sea hydrothermal sulfide systems and thus help unravel the fundamental geobiology of ancient settings. This, in turn, is critical for reconstructing life's emergence and early evolution on Earth and the search for life elsewhere in the universe.
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Affiliation(s)
- Eric Alexander Runge
- Sedimentology and Organic Geochemistry, Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Muammar Mansor
- Geomicrobiology, Department of Geosciences, Tübingen University, Tübingen, Germany
| | - Andreas Kappler
- Geomicrobiology, Department of Geosciences, Tübingen University, Tübingen, Germany
- Cluster of Excellence EXC 2124, Controlling Microbes to Fight Infection, Tübingen, Germany
| | - Jan-Peter Duda
- Sedimentology and Organic Geochemistry, Department of Geosciences, Tübingen University, Tübingen, Germany
- Geobiology, Geoscience Center, Göttingen University, Göttingen, Germany
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Tingle KE, Porter SM, Raven MR, Czaja AD, Webb SM, Bloeser B. Organic preservation of vase-shaped microfossils from the late Tonian Chuar Group, Grand Canyon, Arizona, USA. GEOBIOLOGY 2023; 21:290-309. [PMID: 36651474 DOI: 10.1111/gbi.12544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 12/08/2022] [Accepted: 01/05/2023] [Indexed: 06/17/2023]
Abstract
Vase-shaped microfossils (VSMs) are found globally in middle Neoproterozoic (800-730 Ma) marine strata and represent the earliest evidence for testate (shell-forming) amoebozoans. VSM tests are hypothesized to have been originally organic in life but are most commonly preserved as secondary mineralized casts and molds. A few reports, however, suggest possible organic preservation. Here, we test the hypothesis that VSMs from shales of the lower Walcott Member of the Chuar Group, Grand Canyon, Arizona, contain original organic material, as reported by B. Bloeser in her pioneering studies of Chuar VSMs. We identified VSMs from two thin section samples of Walcott Member black shales in transmitted light microscopy and used scanning electron microscopy to image VSMs. Carbonaceous material is found within the internal cavity of all VSM tests from both samples and is interpreted as bitumen mobilized from Walcott shales likely during the Cretaceous. Energy dispersive X-ray spectroscopy (EDS) and wavelength dispersive X-ray spectroscopy (WDS) reveal that VSM test walls contain mostly carbon, iron, and sulfur, while silica is present only in the surrounding matrix. Raman spectroscopy was used to compare the thermal maturity of carbonaceous material within the samples and indicated the presence of pyrite and jarosite within fossil material. X-ray absorption spectroscopy revealed the presence of reduced organic sulfur species within the carbonaceous test walls, the carbonaceous material found within test cavities, and in the sedimentary matrix, suggesting that organic matter sulfurization occurred within the Walcott shales. Our suite of spectroscopic analyses reveals that Walcott VSM test walls are organic and sometimes secondarily pyritized (with the pyrite variably oxidized to jarosite). Both preservation modes can occur at a millimeter spatial scale within sample material, and at times even within a single specimen. We propose that sulfurization within the Walcott Shales promoted organic preservation, and furthermore, the ratio of iron to labile VSM organic material controlled the extent of pyrite replacement. Based on our evidence, we conclude that the VSMs are preserved with original organic test material, and speculate that organic VSMs may often go unrecognized, given their light-colored, translucent appearance in transmitted light.
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Affiliation(s)
- Kelly E Tingle
- Department of Earth Science, University of California, Santa Barbara, California, USA
| | - Susannah M Porter
- Department of Earth Science, University of California, Santa Barbara, California, USA
| | - Morgan R Raven
- Department of Earth Science, University of California, Santa Barbara, California, USA
| | - Andrew D Czaja
- Department of Geology, University of Cincinnati, Cincinnati, Ohio, USA
| | - Samuel M Webb
- Stanford Synchrotron Radiation Lightsource, Stanford University, Menlo Park, California, USA
| | - Bonnie Bloeser
- Department of Geological Sciences, San Diego State University, San Diego, California, USA
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Loron CC, Rodriguez Dzul E, Orr PJ, Gromov AV, Fraser NC, McMahon S. Molecular fingerprints resolve affinities of Rhynie chert organic fossils. Nat Commun 2023; 14:1387. [PMID: 36914650 PMCID: PMC10011563 DOI: 10.1038/s41467-023-37047-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 03/01/2023] [Indexed: 03/16/2023] Open
Abstract
The affinities of extinct organisms are often difficult to resolve using morphological data alone. Chemical analysis of carbonaceous specimens can complement traditional approaches, but the search for taxon-specific signals in ancient, thermally altered organic matter is challenging and controversial, partly because suitable positive controls are lacking. Here, we show that non-destructive Fourier Transform Infrared Spectroscopy (FTIR) resolves in-situ molecular fingerprints in the famous 407 Ma Rhynie chert fossil assemblage of Aberdeenshire, Scotland, an important early terrestrial Lagerstätte. Remarkably, unsupervised clustering methods (principal components analysis and K-mean) separate the fossil spectra naturally into eukaryotes and prokaryotes (cyanobacteria). Additional multivariate statistics and machine-learning approaches also differentiate prokaryotes from eukaryotes, and discriminate eukaryotic tissue types, despite the overwhelming influence of silica. We find that these methods can clarify the affinities of morphologically ambiguous taxa; in the Rhynie chert for example, we show that the problematic "nematophytes" have a plant-like composition. Overall, we demonstrate that the famously exquisite preservation of cells, tissues and organisms in the Rhynie chert accompanies similarly impressive preservation of molecular information. These results provide a compelling positive control that validates the use of infrared spectroscopy to investigate the affinity of organic fossils in chert.
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Affiliation(s)
- C C Loron
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK.
| | - E Rodriguez Dzul
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - P J Orr
- UCD School of Earth Sciences, University College Dublin, Dublin, Ireland
| | - A V Gromov
- EastCHEM and School of Chemistry, University of Edinburgh, Edinburgh, UK
| | - N C Fraser
- Natural Sciences Department, National Museums Scotland, Edinburgh, UK
| | - S McMahon
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK. .,School of Geosciences, University of Edinburgh, Edinburgh, UK.
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Rasmussen B, Muhling JR. Organic carbon generation in 3.5-billion-year-old basalt-hosted seafloor hydrothermal vent systems. SCIENCE ADVANCES 2023; 9:eadd7925. [PMID: 36724225 PMCID: PMC9891697 DOI: 10.1126/sciadv.add7925] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 01/03/2023] [Indexed: 06/18/2023]
Abstract
Carbon is the key element of life, and its origin in ancient sedimentary rocks is central to questions about the emergence and early evolution of life. The oldest well-preserved carbon occurs with fossil-like structures in 3.5-billion-year-old black chert. The carbonaceous matter, which is associated with hydrothermal chert-barite vent systems originating in underlying basaltic-komatiitic lavas, is thought to be derived from microbial life. Here, we show that 3.5-billion-year-old black chert vein systems from the Pilbara Craton, Australia contain abundant residues of migrated organic carbon. Using younger analogs, we argue that the black cherts formed during precipitation from silica-rich, carbon-bearing hydrothermal fluids in vein systems and vent-proximal seafloor sediments. Given the volcanic setting and lack of organic-rich sediments, we speculate that the vent-mound systems contain carbon derived from rock-powered organic synthesis in the underlying mafic-ultramafic lavas, providing a glimpse of a prebiotic world awash in terrestrial organic compounds.
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Coutant M, Lepot K, Fadel A, Addad A, Richard E, Troadec D, Ventalon S, Sugitani K, Javaux EJ. Distinguishing cellular from abiotic spheroidal microstructures in the ca. 3.4 Ga Strelley Pool Formation. GEOBIOLOGY 2022; 20:599-622. [PMID: 35712885 DOI: 10.1111/gbi.12506] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 05/04/2022] [Accepted: 05/20/2022] [Indexed: 06/15/2023]
Abstract
The morphogenesis of most carbonaceous microstructures that resemble microfossils in Archean (4-2.5 Ga old) rocks remains debated. The associated carbonaceous matter may even-in some cases-derive from abiotic organic molecules. Mineral growths associated with organic matter migration may mimic microbial cells, some anatomical features, and known microfossils-in particular those with simple spheroid shapes. Here, spheroid microstructures from a chert of the ca. 3.4 Ga Strelley Pool Formation (SPF) of the Pilbara Craton (Western Australia) were imaged and analyzed with a combination of high-resolution in situ techniques. This provides new insights into carbonaceous matter distributions and their relationships with the crystallographic textures of associated quartz. Thus, we describe five new types of spheroids and discuss their morphogenesis. In at least three types of microstructures, wall coalescence argues for migration of carbonaceous matter onto abiotic siliceous spherulites or diffusion in poorly crystalline silica. The nanoparticulate walls of these coalescent structures often cut across multiple quartz crystals, consistent with migration in/on silica prior to quartz recrystallization. Sub-continuous walls lying at quartz boundaries occur in some coalescent vesicles. This weakens the "continuous carbonaceous wall" criterion proposed to support cellular inferences. In contrast, some clustered spheroids display wrinkled sub-continuous double walls, and a large sphere shows a thick sub-continuous wall with pustules and depressions. These features appear consistent with post-mortem cell alteration, although abiotic morphogenesis remains difficult to rule out. We compared these siliceous and carbonaceous microstructures to coalescent pyritic spheroids from the same sample, which likely formed as "colloidal" structures in hydrothermal context. The pyrites display a smaller size and only limited carbonaceous coatings, arguing that they could not have acted as precursors to siliceous spheroids. This study revealed new textural features arguing for abiotic morphogenesis of some Archean spheroids. The absence of these features in distinct types of spheroids leaves open the microfossil hypothesis in the same rock. Distinction of such characteristics could help addressing further the origin of other candidate microfossils. This study calls for similar investigations of metamorphosed microfossiliferous rocks and of the products of in vitro growth of cell-mimicking structures in presence of organics and silica.
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Affiliation(s)
- Maxime Coutant
- Univ. Lille, CNRS, Univ. Littoral Côte d'Opale, UMR 8187, LOG - Laboratoire d'Océanologie et de Géosciences, Lille, France
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, Liège, Belgium
| | - Kevin Lepot
- Univ. Lille, CNRS, Univ. Littoral Côte d'Opale, UMR 8187, LOG - Laboratoire d'Océanologie et de Géosciences, Lille, France
- Institut Universitaire de France (IUF), France
| | - Alexandre Fadel
- UMR 8207 - UMET - Unité Matériaux et Transformations, Univ. Lille, CNRS, INRAE, Centrale Lille, Lille, France
| | - Ahmed Addad
- UMR 8207 - UMET - Unité Matériaux et Transformations, Univ. Lille, CNRS, INRAE, Centrale Lille, Lille, France
| | - Elodie Richard
- Univ. Lille, CNRS, INSERM, CHU Lille, Institut Pasteur de Lille, US 41 - UAR 2014 - PLBS, Lille, France
| | - David Troadec
- Univ. Lille, CNRS, Centrale Lille, Junia, Univ. Polytechnique Hauts-de-France, UMR 8520 - IEMN - Institut d'Electronique de Microélectronique et de Nanotechnologie, Lille, France
| | - Sandra Ventalon
- Univ. Lille, CNRS, Univ. Littoral Côte d'Opale, UMR 8187, LOG - Laboratoire d'Océanologie et de Géosciences, Lille, France
| | - Kenichiro Sugitani
- Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan
| | - Emmanuelle J Javaux
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, Liège, Belgium
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Sforna MC, Loron CC, Demoulin CF, François C, Cornet Y, Lara YJ, Grolimund D, Ferreira Sanchez D, Medjoubi K, Somogyi A, Addad A, Fadel A, Compère P, Baudet D, Brocks JJ, Javaux EJ. Intracellular bound chlorophyll residues identify 1 Gyr-old fossils as eukaryotic algae. Nat Commun 2022; 13:146. [PMID: 35013306 PMCID: PMC8748435 DOI: 10.1038/s41467-021-27810-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 12/03/2021] [Indexed: 11/09/2022] Open
Abstract
The acquisition of photosynthesis is a fundamental step in the evolution of eukaryotes. However, few phototrophic organisms are unambiguously recognized in the Precambrian record. The in situ detection of metabolic byproducts in individual microfossils is the key for the direct identification of their metabolisms. Here, we report a new integrative methodology using synchrotron-based X-ray fluorescence and absorption. We evidence bound nickel-geoporphyrins moieties in low-grade metamorphic rocks, preserved in situ within cells of a ~1 Gyr-old multicellular eukaryote, Arctacellularia tetragonala. We identify these moieties as chlorophyll derivatives, indicating that A. tetragonala was a phototrophic eukaryote, one of the first unambiguous algae. This new approach, applicable to overmature rocks, creates a strong new proxy to understand the evolution of phototrophy and diversification of early ecosystems.
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Affiliation(s)
- Marie Catherine Sforna
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, Liège, Belgium.
| | - Corentin C Loron
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, Liège, Belgium
| | - Catherine F Demoulin
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, Liège, Belgium
| | - Camille François
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, Liège, Belgium.,Commission for the Geological Map of the World, Paris, France
| | - Yohan Cornet
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, Liège, Belgium
| | - Yannick J Lara
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, Liège, Belgium
| | - Daniel Grolimund
- Paul Scherrer Institut, Swiss Light Source, CH-5232, Villigen PSI, Switzerland
| | | | | | | | - Ahmed Addad
- Unité Matériaux et Transformations (UMR CNRS 8207), Université Lille 1 - Sciences et Technologies, Villeneuve d'Ascq, France
| | - Alexandre Fadel
- Unité Matériaux et Transformations (UMR CNRS 8207), Université Lille 1 - Sciences et Technologies, Villeneuve d'Ascq, France
| | - Philippe Compère
- Functional and Evolutive Morphology, Department of Biology, Ecology and Evolution, UR FOCUS, and Center for Applied Research and Education in Microscopy (CAREM-ULiege), University of Liège, Liège, Belgium
| | - Daniel Baudet
- Geodynamics & Mineral Resources Service, Royal Museum for Central Africa, Tervuren, Belgium
| | - Jochen J Brocks
- Research School of Earth Sciences, The Australian National University, Canberra ACT, Australia
| | - Emmanuelle J Javaux
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, Liège, Belgium.
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