1
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Bergsten P, Vannier P, Klonowski AM, Knobloch S, Gudmundsson MT, Jackson MD, Marteinsson VT. Basalt-Hosted Microbial Communities in the Subsurface of the Young Volcanic Island of Surtsey, Iceland. Front Microbiol 2021; 12:728977. [PMID: 34659155 PMCID: PMC8513691 DOI: 10.3389/fmicb.2021.728977] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 08/30/2021] [Indexed: 01/04/2023] Open
Abstract
The island of Surtsey was formed in 1963–1967 on the offshore Icelandic volcanic rift zone. It offers a unique opportunity to study the subsurface biosphere in newly formed oceanic crust and an associated hydrothermal-seawater system, whose maximum temperature is currently above 120°C at about 100m below surface. Here, we present new insights into the diversity, distribution, and abundance of microorganisms in the subsurface of the island, 50years after its creation. Samples, including basaltic tuff drill cores and associated fluids acquired at successive depths as well as surface fumes from fumaroles, were collected during expedition 5059 of the International Continental Scientific Drilling Program specifically designed to collect microbiological samples. Results of this microbial survey are investigated with 16S rRNA gene amplicon sequencing and scanning electron microscopy. To distinguish endemic microbial taxa of subsurface rocks from potential contaminants present in the drilling fluid, we use both methodological and computational strategies. Our 16S rRNA gene analysis results expose diverse and distinct microbial communities in the drill cores and the borehole fluid samples, which harbor thermophiles in high abundance. Whereas some taxonomic lineages detected across these habitats remain uncharacterized (e.g., Acetothermiia, Ammonifexales), our results highlight potential residents of the subsurface that could be identified at lower taxonomic rank such as Thermaerobacter, BRH-c8a (Desulfallas-Sporotomaculum), Thioalkalimicrobium, and Sulfurospirillum. Microscopy images reveal possible biotic structures attached to the basaltic substrate. Finally, microbial colonization of the newly formed basaltic crust and the metabolic potential are discussed on the basis of the data.
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Affiliation(s)
- Pauline Bergsten
- Exploration & Utilization of Genetic Resources, Matís, Reykjavík, Iceland.,Faculty of Life and Environmental Sciences, University of Iceland, Reykjavík, Iceland
| | - Pauline Vannier
- Exploration & Utilization of Genetic Resources, Matís, Reykjavík, Iceland
| | | | - Stephen Knobloch
- Exploration & Utilization of Genetic Resources, Matís, Reykjavík, Iceland
| | | | - Marie Dolores Jackson
- Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, United States
| | - Viggó Thor Marteinsson
- Exploration & Utilization of Genetic Resources, Matís, Reykjavík, Iceland.,Faculty of Food Science and Nutrition, University of Iceland, Reykjavík, Iceland
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2
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Baucon A, Neto de Carvalho C, Briguglio A, Piazza M, Felletti F. A predictive model for the ichnological suitability of the Jezero crater, Mars: searching for fossilized traces of life-substrate interactions in the 2020 Rover Mission Landing Site. PeerJ 2021; 9:e11784. [PMID: 34631304 PMCID: PMC8466086 DOI: 10.7717/peerj.11784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 06/24/2021] [Indexed: 11/20/2022] Open
Abstract
Ichnofossils, the fossilized products of life-substrate interactions, are among the most abundant biosignatures on Earth and therefore they may provide scientific evidence of potential life that may have existed on Mars. Ichnofossils offer unique advantages in the search for extraterrestrial life, including the fact that they are resilient to processes that obliterate other evidence for past life, such as body fossils, as well as chemical and isotopic biosignatures. The goal of this paper is evaluating the suitability of the Mars 2020 Landing Site for ichnofossils. To this goal, we apply palaeontological predictive modelling, a technique used to forecast the location of fossil sites in uninvestigated areas on Earth. Accordingly, a geographic information system (GIS) of the landing site is developed. Each layer of the GIS maps the suitability for one or more ichnofossil types (bioturbation, bioerosion, biostratification structures) based on an assessment of a single attribute (suitability factor) of the Martian environment. Suitability criteria have been selected among the environmental attributes that control ichnofossil abundance and preservation in 18 reference sites on Earth. The goal of this research is delivered through three predictive maps showing which areas of the Mars 2020 Landing Site are more likely to preserve potential ichnofossils. On the basis of these maps, an ichnological strategy for the Perseverance rover is identified, indicating (1) 10 sites on Mars with high suitability for bioturbation, bioerosion and biostratification ichnofossils, (2) the ichnofossil types, if any, that are more likely to be present at each site, (3) the most efficient observation strategy for detecting eventual ichnofossils. The predictive maps and the ichnological strategy can be easily integrated in the existing plans for the exploration of the Jezero crater, realizing benefits in life-search efficiency and cost-reduction.
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Affiliation(s)
- Andrea Baucon
- DISTAV, University of Genoa, Genova, Italy.,Geology Office of Idanha-a-Nova, Naturtejo UNESCO Global Geopark, Idanha-a-Nova, Portugal
| | - Carlos Neto de Carvalho
- Geology Office of Idanha-a-Nova, Naturtejo UNESCO Global Geopark, Idanha-a-Nova, Portugal.,Instituto D. Luiz, Faculdade de Ciências da Universidade de Lisboa, University of Lisbon, Lisbon, Portugal
| | | | | | - Fabrizio Felletti
- Dipartimento di Scienze della Terra 'Ardito Desio', University of Milan, Milan, Italy
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3
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McMahon S, Ivarsson M, Wacey D, Saunders M, Belivanova V, Muirhead D, Knoll P, Steinbock O, Frost DA. Dubiofossils from a Mars-analogue subsurface palaeoenvironment: The limits of biogenicity criteria. GEOBIOLOGY 2021; 19:473-488. [PMID: 33951268 DOI: 10.1111/gbi.12445] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 03/12/2021] [Accepted: 03/30/2021] [Indexed: 06/12/2023]
Abstract
The search for a fossil record of Earth's deep biosphere, partly motivated by potential analogies with subsurface habitats on Mars, has uncovered numerous assemblages of inorganic microfilaments and tubules inside ancient pores and fractures. Although these enigmatic objects are morphologically similar to mineralized microorganisms (and some contain organic carbon), they also resemble some abiotic structures. Palaeobiologists have responded to this ambiguity by evaluating problematic filaments against checklists of "biogenicity criteria". Here, we describe material that tests the limits of this approach. We sampled Jurassic calcite veins formed through subseafloor serpentinization, a water-rock reaction that can fuel the deep biosphere and is known to have occurred widely on Mars. At two localities ~4 km apart, veins contained curving, branched microfilaments composed of Mg-silicate and Fe-oxide minerals. Using a wide range of analytical techniques including synchrotron X-ray microtomography and scanning transmission electron microscopy, we show that these features meet many published criteria for biogenicity and are comparable to fossilized cryptoendolithic fungi or bacteria. However, we argue that abiotic processes driven by serpentinization could account for the same set of lifelike features, and report a chemical garden experiment that supports this view. These filaments are, therefore, most objectively described as dubiofossils, a designation we here defend from criticism and recommend over alternative approaches, but which nevertheless signifies an impasse. Similar impasses can be anticipated in the future exploration of subsurface palaeo-habitats on Earth and Mars. To avoid them, further studies are required in biomimetic geochemical self-organization, microbial taphonomy and micro-analytical techniques, with a focus on subsurface habitats.
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Affiliation(s)
- Sean McMahon
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
- School of Geosciences, Grant Institute, University of Edinburgh, Edinburgh, UK
| | - Magnus Ivarsson
- Department of Paleobiology, Swedish Museum of Natural History, Stockholm, Sweden
| | - David Wacey
- Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Perth, WA, Australia
| | - Martin Saunders
- Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Perth, WA, Australia
| | - Veneta Belivanova
- Department of Paleobiology, Swedish Museum of Natural History, Stockholm, Sweden
| | - David Muirhead
- School of Geosciences, King's College, University of Aberdeen, Aberdeen, UK
| | - Pamela Knoll
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, USA
| | - Oliver Steinbock
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, USA
| | - Daniel A Frost
- Department of Earth & Planetary Science, University of California, Berkeley, CA, USA
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4
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Mitchell RL, Davies P, Kenrick P, Volkenandt T, Pleydell-Pearce C, Johnston R. Correlative Microscopy: a tool for understanding soil weathering in modern analogues of early terrestrial biospheres. Sci Rep 2021; 11:12736. [PMID: 34140576 PMCID: PMC8211647 DOI: 10.1038/s41598-021-92184-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 05/27/2021] [Indexed: 02/05/2023] Open
Abstract
Correlative imaging provides a method of investigating complex systems by combining analytical (chemistry) and imaging (tomography) information across dimensions (2D-3D) and scales (centimetres-nanometres). We studied weathering processes in a modern cryptogamic ground cover from Iceland, containing early colonizing, and evolutionary ancient, communities of mosses, lichens, fungi, and bacteria. Targeted multi-scale X-ray Microscopy of a grain in-situ within a soil core revealed networks of surficial and internal features (tunnels) originating from organic-rich surface holes. Further targeted 2D grain characterisation by optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (SEM-EDS), following an intermediate manual correlative preparation step, revealed Fe-rich nodules within the tunnels. Finally, nanotomographic imaging by focussed ion beam microscopy (FIB-SEM) revealed coccoid and filamentous-like structures within subsurface tunnels, as well as accumulations of Fe and S in grain surface crusts, which may represent a biological rock varnish/glaze. We attribute these features to biological processes. This work highlights the advantages and novelty of the correlative imaging approach, across scales, dimensions, and modes, to investigate biological weathering processes. Further, we demonstrate correlative microscopy as a means of identifying fingerprints of biological communities, which could be used in the geologic rock record and on extra-terrestrial bodies.
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Affiliation(s)
- R. L. Mitchell
- grid.4827.90000 0001 0658 8800Advanced Imaging of Materials (AIM) Facility, College of Engineering, Bay Campus, Swansea University, Swansea, SA1 8EN UK ,grid.35937.3b0000 0001 2270 9879Earth Sciences Department, The Natural History Museum, Cromwell Road, London, SW7 5BD UK ,grid.11835.3e0000 0004 1936 9262Sheffield Tomography Centre (STC), The University of Sheffield, North Campus, Broad Lane, Sheffield, S3 7HQ UK
| | - P. Davies
- grid.4827.90000 0001 0658 8800Advanced Imaging of Materials (AIM) Facility, College of Engineering, Bay Campus, Swansea University, Swansea, SA1 8EN UK
| | - P. Kenrick
- grid.35937.3b0000 0001 2270 9879Earth Sciences Department, The Natural History Museum, Cromwell Road, London, SW7 5BD UK
| | - T. Volkenandt
- grid.424549.a0000 0004 0379 7801Carl Zeiss Microscopy GmbH, Carl-Zeiss-Straße 22, 73447 Oberkochen, Germany
| | - C. Pleydell-Pearce
- grid.4827.90000 0001 0658 8800Advanced Imaging of Materials (AIM) Facility, College of Engineering, Bay Campus, Swansea University, Swansea, SA1 8EN UK
| | - R. Johnston
- grid.4827.90000 0001 0658 8800Advanced Imaging of Materials (AIM) Facility, College of Engineering, Bay Campus, Swansea University, Swansea, SA1 8EN UK
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5
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Rouillard J, van Zuilen M, Pisapia C, Garcia-Ruiz JM. An Alternative Approach for Assessing Biogenicity. ASTROBIOLOGY 2021; 21:151-164. [PMID: 33544651 PMCID: PMC7876362 DOI: 10.1089/ast.2020.2282] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 09/07/2020] [Indexed: 05/27/2023]
Abstract
The search for signs of life in the ancient rock record, extreme terrestrial environments, and other planetary bodies requires a well-established, universal, and unambiguous test of biogenicity. This is notably true for cellular remnants of microbial life, since their relatively simple morphologies resemble various abiogenic microstructures that occur in nature. Although lists of qualitative biogenicity criteria have been devised, debates regarding the biogenicity of many ancient microfossils persist to this day. We propose here an alternative quantitative approach for assessing the biogenicity of putative microfossils. In this theoretical approach, different hypotheses-involving biology or not and depending on the geologic setting-are put forward to explain the observed objects. These hypotheses correspond to specific types of microstructures/systems. Using test samples, the morphology and/or chemistry of these systems are then characterized at the scale of populations. Morphologic parameters include, for example, circularity, aspect ratio, and solidity, while chemical parameters could include elementary ratios (e.g., N/C ratio), isotopic enrichments (e.g., δ13C), or chirality (e.g., molar proportion of stereoisomers), among others. Statistic trends distinguishing the different systems are then searched for empirically. The trends found are translated into "decision spaces" where the different systems are quantitatively discriminated and where the potential microfossil population can be located as a single point. This approach, which is formulated here on a theoretical level, will solve several problems associated with the classical qualitative criteria of biogenicity. Most importantly, it could be applied to reveal the existence of cellular life on other planets, for which characteristics of morphology and chemical composition are difficult to predict.
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Affiliation(s)
- Joti Rouillard
- Laboratario de Estudios Cristalograficos, Instituto Andaluz de Ciencias de la Tierra, CSIC—Universidad de Granada, Armilla, Spain
| | - Mark van Zuilen
- Institut de Physique du Globe de Paris, Université de Paris, CNRS UMR 7154, Paris, France
| | - Céline Pisapia
- Institut de Physique du Globe de Paris, Université de Paris, CNRS UMR 7154, Paris, France
| | - Juan-Manuel Garcia-Ruiz
- Laboratario de Estudios Cristalograficos, Instituto Andaluz de Ciencias de la Tierra, CSIC—Universidad de Granada, Armilla, Spain
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6
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McLoughlin N, Wacey D, Phunguphungu S, Saunders M, Grosch EG. Deconstructing Earth's oldest ichnofossil record from the Pilbara Craton, West Australia: Implications for seeking life in the Archean subseafloor. GEOBIOLOGY 2020; 18:525-543. [PMID: 32542902 DOI: 10.1111/gbi.12399] [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: 12/18/2019] [Revised: 03/30/2020] [Accepted: 04/26/2020] [Indexed: 06/11/2023]
Abstract
Microtextures of titanite (CaTiSiO5 ) in exceptionally preserved Archean pillow lavas have been proposed as the earliest examples of microbial ichnofossils. An origin from microbial tunneling of seafloor volcanic glass that is subsequently chloritized and the tunnels infilled by titanite has been argued to record the activities of subseafloor microbes. We investigate the evidence in pillow lavas of the 3.35 Ga Euro Basalt from the Pilbara Craton, Western Australia, to evaluate the biogenicity of the microtextures. We employ a combination of light microscopy and chlorite mineral chemical analysis by EPMA (electron probe micro-analysis) to document the environment of formation and analyze their ultrastructure using FIB-TEM (focussed ion beam combined with transmission electron microscopy) to investigate their mode of growth. Petrographic study of the original and re-collected material identified an expanded range of titanite morphotypes along with early anatase growth forming chains and aggregates of coalesced crystallites in a sub-greenschist facies assemblage. High-sensitivity mapping of FIB lamellae cut across the microtextures confirm that they are discontinuous chains of coalesced crystallites that are highly variable in cross section and contain abundant chlorite inclusions, excluding an origin from the mineralization of previously hollow microtunnels. Comparison of chlorite mineral compositions to DSDP/IODP data reveals that the Euro Basalt chlorites are similar to recent seafloor chlorites. We advance an abiotic origin for the Euro Basalt microtextures formed by spontaneous nucleation and growth of titanite and/anatase during seafloor-hydrothermal metamorphism. Our findings reveal that the Euro Basalt microtextures are not comparable to microbial ichnofossils from the recent oceanic crust, and we question the evidence for life in these Archean lavas. The metamorphic reactions that give rise to the growth of the Euro Basalt microtextures could be commonplace in Archean pillow lavas and need to be excluded when seeking traces of life in the subseafloor on the early Earth.
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Affiliation(s)
| | - David Wacey
- Centre for Microscopy, Characterization and Analysis (CMCA), The University of Western Australia (UWA), Perth, WA, Australia
| | | | - Martin Saunders
- Centre for Microscopy, Characterization and Analysis (CMCA), The University of Western Australia (UWA), Perth, WA, Australia
| | - Eugene G Grosch
- Department of Geology, Rhodes University, Grahamstown, South Africa
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7
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Samuels T, Bryce C, Landenmark H, Marie‐Loudon C, Nicholson N, Stevens AH, Cockell C. Microbial Weathering of Minerals and Rocks in Natural Environments. ACTA ACUST UNITED AC 2020. [DOI: 10.1002/9781119413332.ch3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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8
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McMahon S. Earth's earliest and deepest purported fossils may be iron-mineralized chemical gardens. Proc Biol Sci 2019; 286:20192410. [PMID: 31771469 PMCID: PMC6939263 DOI: 10.1098/rspb.2019.2410] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Recognizing fossil microorganisms is essential to the study of life's origin and evolution and to the ongoing search for life on Mars. Purported fossil microbes in ancient rocks include common assemblages of iron-mineral filaments and tubes. Recently, such assemblages have been interpreted to represent Earth's oldest body fossils, Earth's oldest fossil fungi, and Earth's best analogues for fossils that might form in the basaltic Martian subsurface. Many of these putative fossils exhibit hollow circular cross-sections, lifelike (non-crystallographic, constant-thickness, and bifurcate) branching, anastomosis, nestedness within ‘sheaths’, and other features interpreted as strong evidence for a biological origin, since no abiotic process consistent with the composition of the filaments has been shown to produce these specific lifelike features either in nature or in the laboratory. Here, I show experimentally that abiotic chemical gardening can mimic such purported fossils in both morphology and composition. In particular, chemical gardens meet morphological criteria previously proposed to establish biogenicity, while also producing the precursors to the iron minerals most commonly constitutive of filaments in the rock record. Chemical gardening is likely to occur in nature. Such microstructures should therefore not be assumed to represent fossil microbes without independent corroborating evidence.
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Affiliation(s)
- Sean McMahon
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.,School of Geosciences, Grant Institute, University of Edinburgh, James Hutton Road, Edinburgh EH9 3FE, UK
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9
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McMahon S, Ivarsson M. A New Frontier for Palaeobiology: Earth's Vast Deep Biosphere. Bioessays 2019; 41:e1900052. [PMID: 31241200 DOI: 10.1002/bies.201900052] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 04/29/2019] [Indexed: 11/11/2022]
Abstract
Diverse micro-organisms populate a global deep biosphere hosted by rocks and sediments beneath land and sea, containing more biomass than any other biome except forests. This paper reviews an emerging palaeobiological archive of these dark habitats: microfossils preserved in ancient pores and fractures in the crust. This archive, seemingly dominated by mineralized filaments (although rods and coccoids are also reported), is presently far too sparsely sampled and poorly understood to reveal trends in the abundance, distribution, or diversity of deep life through time. New research is called for to establish the nature and extent of the fossil record of Earth's deep biosphere by combining systematic exploration, rigorous microanalysis, and experimental studies of both microbial preservation and the formation of abiotic pseudofossils within the crust. It is concluded that the fossil record of Earth's largest microbial habitat may still have much to tell us about the history of life, the evolution of biogeochemical cycles, and the search for life on Mars.
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Affiliation(s)
- Sean McMahon
- School of Geosciences, University of Edinburgh, Edinburgh, EH8 9XP, UK.,UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, UK
| | - Magnus Ivarsson
- Department of Biology, University of Southern Denmark, DK-5230, Odense, Denmark.,Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, SE-104 05, Sweden
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10
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Purvis G, van der Land C, Sano N, Cockell C, Barlow A, Cumpson P, Lopez-Capel E, Gray N. The organic stratigraphy of Ontong Java Plateau Tuff correlated with the depth-related presence and absence of putative microbial alteration structures. GEOBIOLOGY 2019; 17:281-293. [PMID: 30525281 DOI: 10.1111/gbi.12326] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 10/27/2018] [Accepted: 10/30/2018] [Indexed: 06/09/2023]
Abstract
Structures in geological samples are often interpreted as fossilised life; however, such interpretations are equivocal, as abiotic processes can be invoked to explain their presence. Thus, additional lines of chemical evidence are invaluable in confirming or refuting such morphological evidence. Glass shards in tuff from the Ontong Java Plateau (OJP) contain microtubular structures that are in close proximity to functionalised nitrogen substituted aromatic compounds that may be indicative of the chemical remnants of biological activity. The organic composition of the OJP tuff containing microtubular alteration structures was compared with tuff without such features. In addition, organic matter associated with horizons with compacted remnants of woody material buried in the OJP tuff and overlying pelagic calcareous foraminifer sediment were also characterised, to ascertain the provenance of the organic matter found in the OJP tuff. As a further control, the organic material in submarine and terrestrial basalts from other locations were also characterised providing further evidence to support the view that the organic matter in the OJP tuff is authigenic. Carbon-nitrogen chemistry was detected across all OJP tuff samples irrespective of the presence or absence of microtubular features, but was not detected in either the wood material, the overlying pelagic sediments or in the basalts from other locations. The results indicate no direct link between the OJP nitrogenous organic compounds and the presence or absence of microtubular features.
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Affiliation(s)
- Graham Purvis
- Earth, Ocean & Planetary Science Research, School of Natural and Environmental Sciences, Newcastle University, Newcastle-upon-Tyne, UK
| | - Cees van der Land
- Earth, Ocean & Planetary Science Research, School of Natural and Environmental Sciences, Newcastle University, Newcastle-upon-Tyne, UK
| | - Naoko Sano
- National ESCA and XPS Users' Service (NEXUS), Newcastle University, Newcastle-upon-Tyne, UK
| | - Charles Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - Anders Barlow
- Centre for Materials and Surface Science, Department of Chemistry and Physics, La Trobe University, Melbourne, Victoria, Australia
| | - Peter Cumpson
- Mark Wainwright Analytical Centre, University of New South Wales, Sydney, New South Wales, Australia
| | - Elisa Lopez-Capel
- Earth, Ocean & Planetary Science Research, School of Natural and Environmental Sciences, Newcastle University, Newcastle-upon-Tyne, UK
| | - Neil Gray
- Earth, Ocean & Planetary Science Research, School of Natural and Environmental Sciences, Newcastle University, Newcastle-upon-Tyne, UK
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11
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Abstract
We propose a model whereby microscopic tunnels form in basalt glass in response to a natural proton flux from seawater into the glass. This flux is generated by the alteration of the glass as protons from water replace cations in the glass. In our proton gradient model, cells are gateways through which protons enter and alter the glass and through which cations leave the glass. In the process, tunnels are formed, and cells derive energy from the proton and ion fluxes. Proton flux from seawater into basalt glass would have occurred on Earth as soon as water accumulated on the surface and would have preceded biological redox catalysis. Tunnels in modern basalts are similar to tunnels in Archean basalts, which may be our earliest physical evidence of life. Proton gradients like those described in this paper certainly exist on other planetary bodies where silicate rocks are exposed to acidic to slightly alkaline water.
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Affiliation(s)
- Martin R Fisk
- 1 College of Earth, Ocean, and Atmospheric Sciences, Oregon State University , Corvallis, Oregon, USA
| | - Radu Popa
- 2 Department of Biological Sciences, University of Southern California , Los Angeles, California, USA
| | - David Wacey
- 3 Centre for Microscopy, Characterisation and Analysis, The University of Western Australia , Perth, Australia
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12
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Ivarsson M, Skogby H, Phichaikamjornwut B, Bengtson S, Siljeström S, Ounchanum P, Boonsoong A, Kruachanta M, Marone F, Belivanova V, Holmström S. Intricate tunnels in garnets from soils and river sediments in Thailand - Possible endolithic microborings. PLoS One 2018; 13:e0200351. [PMID: 30089115 PMCID: PMC6082506 DOI: 10.1371/journal.pone.0200351] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 06/25/2018] [Indexed: 11/30/2022] Open
Abstract
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.
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Affiliation(s)
- Magnus Ivarsson
- University of Southern Denmark, Department of Biology and Nordic Center for Earth Evolution, Odense M, Denmark
- Swedish Museum of Natural History, Department of Palaeobiology, Stockholm, Sweden
- * E-mail:
| | - Henrik Skogby
- Swedish Museum of Natural History, Department of Geosciences, Stockholm, Sweden
| | | | - Stefan Bengtson
- Swedish Museum of Natural History, Department of Palaeobiology, Stockholm, Sweden
| | - Sandra Siljeström
- RISE Research Institutes of Sweden, Bioscience and Materials/Chemistry and Materials, Stockholm, Sweden
| | - Prayote Ounchanum
- Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
| | - Apichet Boonsoong
- Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
| | - Mingkhwan Kruachanta
- Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
| | - Federica Marone
- Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland
| | - Veneta Belivanova
- Swedish Museum of Natural History, Department of Palaeobiology, Stockholm, Sweden
| | - Sara Holmström
- Stockholm University, Department of Geological Sciences, Stockholm, Sweden
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13
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Kraus EA, Beeler SR, Mors RA, Floyd JG, Stamps BW, Nunn HS, Stevenson BS, Johnson HA, Shapiro RS, Loyd SJ, Spear JR, Corsetti FA. Microscale Biosignatures and Abiotic Mineral Authigenesis in Little Hot Creek, California. Front Microbiol 2018; 9:997. [PMID: 29887837 PMCID: PMC5981138 DOI: 10.3389/fmicb.2018.00997] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 04/27/2018] [Indexed: 11/13/2022] Open
Abstract
Hot spring environments can create physical and chemical gradients favorable for unique microbial life. They can also include authigenic mineral precipitates that may preserve signs of biological activity on Earth and possibly other planets. The abiogenic or biogenic origins of such precipitates can be difficult to discern, therefore a better understanding of mineral formation processes is critical for the accurate interpretation of biosignatures from hot springs. Little Hot Creek (LHC) is a hot spring complex located in the Long Valley Caldera, California, that contains mineral precipitates composed of a carbonate base (largely submerged) topped by amorphous silica (largely emergent). The precipitates occur in close association with microbial mats and biofilms. Geological, geochemical, and microbiological data are consistent with mineral formation via degassing and evaporation rather than direct microbial involvement. However, the microfabric of the silica portion is stromatolitic in nature (i.e., wavy and finely laminated), suggesting that abiogenic mineralization has the potential to preserve textural biosignatures. Although geochemical and petrographic evidence suggests the calcite base was precipitated via abiogenic processes, endolithic microbial communities modified the structure of the calcite crystals, producing a textural biosignature. Our results reveal that even when mineral precipitation is largely abiogenic, the potential to preserve biosignatures in hot spring settings is high. The features found in the LHC structures may provide insight into the biogenicity of ancient Earth and extraterrestrial rocks.
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Affiliation(s)
- Emily A Kraus
- Geo- Environmental- Microbiology Laboratory, Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO, United States
| | - Scott R Beeler
- Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, United States
| | - R Agustin Mors
- Laboratorio de Paleobiología y Geomicrobiología Experimental, Centro de Investigaciones en Ciencias de la Tierra (CONICET-UNC), Córdoba, Argentina
| | - James G Floyd
- Department of Microbiology and Plant Biology, The University of Oklahoma, Norman, OK, United States
| | | | - Blake W Stamps
- Geo- Environmental- Microbiology Laboratory, Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO, United States
| | - Heather S Nunn
- Department of Microbiology and Plant Biology, The University of Oklahoma, Norman, OK, United States
| | - Bradley S Stevenson
- Department of Microbiology and Plant Biology, The University of Oklahoma, Norman, OK, United States
| | - Hope A Johnson
- Department of Biological Sciences, California State University, Fullerton, Fullerton, CA, United States
| | - Russell S Shapiro
- Geological and Environmental Sciences, California State University, Chico, Chico, CA, United States
| | - Sean J Loyd
- Department of Geological Sciences, California State University, Fullerton, Fullerton, CA, United States
| | - John R Spear
- Geo- Environmental- Microbiology Laboratory, Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO, United States
| | - Frank A Corsetti
- Department of Earth Sciences, University of Southern California, Los Angeles, CA, United States
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Türke A, Ménez B, Bach W. Comparing biosignatures in aged basalt glass from North Pond, Mid-Atlantic Ridge and the Louisville Seamount Trail, off New Zealand. PLoS One 2018; 13:e0190053. [PMID: 29466353 PMCID: PMC5821312 DOI: 10.1371/journal.pone.0190053] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 12/07/2017] [Indexed: 11/18/2022] Open
Abstract
Microbial life can leave various traces (or biosignatures) in rocks, including biotic alteration textures, biominerals, enrichments of certain elements, organic molecules, or remnants of DNA. In basalt glass from the ocean floor, microbial alteration textures as well as chemical and isotopic biosignatures have been used to trace microbial activity. However, little is known about the relationship between the physical and chemical nature of the habitat and the prevalent types of biosignatures. Here, we report and compare strongly variable biosignatures from two different oceanic study sites. We analyzed rock samples for their textural biosignatures and associated organic molecules. The biosignatures from the 8 Ma North Pond Region, which represents young, well-oxygenated, and hydrologically active crust, are characterized by little textural diversity. The organic matter associated with those textures shows evidence for the occurrence of remnants of complex biomolecules like proteins. Comparably the biosignatures from the older Louisville Seamount Trail (~70 Ma) are more texturally diverse, but associated with organic molecules that are more degraded. The Louisville Seamount has less fresh glass left and decreased permeability, which metabolic pathways may dominate that only leave molecular biosignatures without textural evidence of glass alteration. We propose that diverse biosignatures in oceanic crust may form during different stages of crustal evolution.
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Affiliation(s)
- Andreas Türke
- Department of Geosciences and MARUM, University of Bremen, Klagenfurter Str. GEO, Bremen, Germany
- * E-mail:
| | - Bénédicte Ménez
- Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ Paris Diderot, CNRS, France
| | - Wolfgang Bach
- Department of Geosciences and MARUM, University of Bremen, Klagenfurter Str. GEO, Bremen, Germany
- Centre of Excellence in Geobiology and the Department of Earth Sciences, Realfagbygget, University of Bergen, Allegaten 41, Bergen, Norway
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Fungus-like mycelial fossils in 2.4-billion-year-old vesicular basalt. Nat Ecol Evol 2017; 1:141. [PMID: 28812648 DOI: 10.1038/s41559-017-0141] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 03/15/2017] [Indexed: 11/09/2022]
Abstract
Fungi have recently been found to comprise a significant part of the deep biosphere in oceanic sediments and crustal rocks. Fossils occupying fractures and pores in Phanerozoic volcanics indicate that this habitat is at least 400 million years old, but its origin may be considerably older. A 2.4-billion-year-old basalt from the Palaeoproterozoic Ongeluk Formation in South Africa contains filamentous fossils in vesicles and fractures. The filaments form mycelium-like structures growing from a basal film attached to the internal rock surfaces. Filaments branch and anastomose, touch and entangle each other. They are indistinguishable from mycelial fossils found in similar deep-biosphere habitats in the Phanerozoic, where they are attributed to fungi on the basis of chemical and morphological similarities to living fungi. The Ongeluk fossils, however, are two to three times older than current age estimates of the fungal clade. Unless they represent an unknown branch of fungus-like organisms, the fossils imply that the fungal clade is considerably older than previously thought, and that fungal origin and early evolution may lie in the oceanic deep biosphere rather than on land. The Ongeluk discovery suggests that life has inhabited submarine volcanics for more than 2.4 billion years.
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Affiliation(s)
- Nicola McLoughlin
- Department of Geology and Albany Museum, Rhodes University, Grahamstown, 6140, South Africa
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Wacey D, Saunders M, Kong C, Kilburn MR. A new occurrence of ambient inclusion trails from the ~1900-million-year-old Gunflint Formation, Ontario: nanocharacterization and testing of potential formation mechanisms. GEOBIOLOGY 2016; 14:440-456. [PMID: 27185586 DOI: 10.1111/gbi.12186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 03/09/2016] [Indexed: 06/05/2023]
Abstract
Ambient inclusion trails (AITs) are tubular microstructures thought to form when a microscopic mineral crystal is propelled through a fine-grained rock matrix. Here, we report a new occurrence of AITs from a fossilized microbial mat within the 1878-Ma Gunflint Formation, at Current River, Ontario. The AITs are 1-15 μm in diameter, have pyrite as the propelled crystal, are infilled with chlorite and have been propelled through a microquartz (chert) or chlorite matrix. AITs most commonly originate at the boundary between pyrite- and chlorite-rich laminae and chert-filled fenestrae, with pyrite crystals propelled into the fenestrae. A subset of AITs originate within the fenestrae, rooted either within the chert or within patches of chlorite. Sulphur isotope data ((34) S/(32) S) obtained in situ from AIT pyrite have a δ(34) S of -8.5 to +8.0 ‰, indicating a maximum of ~30 ‰ fractionation from Palaeoproterozoic seawater sulphate (δ(34) S ≈ +20 ‰). Organic carbon is common both at the outer margins of the fenestrae and in patches of chlorite where most AITs originate, and can be found in smaller quantities further along some AITs towards the terminal pyrite grain. We infer that pyrite crystals now found within the AITs formed via the action of heterotrophic sulphate-reducing bacteria during early diagenesis within the microbial mat, as pore waters were becoming depleted in seawater sulphate. Gases derived from this process such as CO2 and H2 S were partially trapped within the microbial mat, helping produce birds-eye fenestrae, while rapid microquartz precipitation closed porosity. We propose that propulsion of the pyrite crystals to form AITs was driven by two complementary mechanisms during burial and low-grade metamorphism: firstly, thermal decomposition of residual organic material providing CO2 , and potentially CH4 , as propulsive gases, plus organic acids to locally dissolve the microquartz matrix; and secondly, reactions involving clay minerals that potentially led to enhanced quartz solubility, plus increases in fluid and/or gas pressure during chlorite formation, with chlorite then infilling the AITs. This latter mechanism is novel and represents a possible way to generate AITs in environments lacking organic material.
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Affiliation(s)
- D Wacey
- Australian Research Council Centre of Excellence for Core to Crust Fluid Systems, The University of Western Australia, Crawley, WA, Australia
- Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Crawley, WA, Australia
- School of Earth Sciences, University of Bristol, Bristol, UK
| | - M Saunders
- Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Crawley, WA, Australia
| | - C Kong
- Electron Microscopy Unit, University of New South Wales, Kingsford, NSW, Australia
| | - M R Kilburn
- Australian Research Council Centre of Excellence for Core to Crust Fluid Systems, The University of Western Australia, Crawley, WA, Australia
- Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Crawley, WA, Australia
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Grosch EG, Hazen RM. Microbes, Mineral Evolution, and the Rise of Microcontinents-Origin and Coevolution of Life with Early Earth. ASTROBIOLOGY 2015; 15:922-939. [PMID: 26430911 DOI: 10.1089/ast.2015.1302] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Earth is the most mineralogically diverse planet in our solar system, the direct consequence of a coevolving geosphere and biosphere. We consider the possibility that a microbial biosphere originated and thrived in the early Hadean-Archean Earth subseafloor environment, with fundamental consequences for the complex evolution and habitability of our planet. In this hypothesis paper, we explore possible venues for the origin of life and the direct consequences of microbially mediated, low-temperature hydrothermal alteration of the early oceanic lithosphere. We hypothesize that subsurface fluid-rock-microbe interactions resulted in more efficient hydration of the early oceanic crust, which in turn promoted bulk melting to produce the first evolved fragments of felsic crust. These evolved magmas most likely included sialic or tonalitic sheets, felsic volcaniclastics, and minor rhyolitic intrusions emplaced in an Iceland-type extensional setting as the earliest microcontinents. With the further development of proto-tectonic processes, these buoyant felsic crustal fragments formed the nucleus of intra-oceanic tonalite-trondhjemite-granitoid (TTG) island arcs. Thus microbes, by facilitating extensive hydrothermal alteration of the earliest oceanic crust through bioalteration, promoted mineral diversification and may have been early architects of surface environments and microcontinents on young Earth. We explore how the possible onset of subseafloor fluid-rock-microbe interactions on early Earth accelerated metavolcanic clay mineral formation, crustal melting, and subsequent metamorphic mineral evolution. We also consider environmental factors supporting this earliest step in geosphere-biosphere coevolution and the implications for habitability and mineral evolution on other rocky planets, such as Mars.
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Affiliation(s)
- Eugene G Grosch
- 1 Department of Earth Science, University of Bergen , Bergen, Norway
| | - Robert M Hazen
- 2 Geophysical Laboratory, Carnegie Institution of Washington , Washington, DC, USA
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McLoughlin N, Grosch EG. A Hierarchical System for Evaluating the Biogenicity of Metavolcanic- and Ultramafic-Hosted Microalteration Textures in the Search for Extraterrestrial Life. ASTROBIOLOGY 2015; 15:901-921. [PMID: 26496528 DOI: 10.1089/ast.2014.1259] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The low-temperature alteration of submarine volcanic glasses has been argued to involve the activity of microorganisms, and analogous fluid-rock-microbial-mediated alteration has also been postulated on Mars. However, establishing the extent to which microbes are involved in volcanic glass alteration has proven to be difficult, and the reliability of resulting textural biosignatures is debated, particularly in the early rock record. We therefore propose a hierarchical scheme to evaluate the biogenicity of candidate textural biosignatures found in altered terrestrial and extraterrestrial basaltic glasses and serpentinized ultramafic rocks. The hierarchical scheme is formulated to give increasing confidence of a biogenic origin and involves (i) investigation of the textural context and syngenicity of the candidate biosignature; (ii) characterization of the morphology and size range of the microtextures; (iii) mapping of the geological and physicochemical variables controlling the occurrence and preservation of the microtextures; (iv) in situ investigation of chemical signatures that are syngenetic to the microtexture; and (v) identification of growth patterns suggestive of biological behavior and redox variations in the host minerals. The scheme results in five categories of candidate biosignature as follows: Category 1 indicates preservation of very weak evidence for biogenicity, Categories 2 through 4 indicate evidence for increasing confidence of a biogenic origin, and Category 5 indicates that biogenic origin is most likely. We apply this hierarchical approach to examine the evidence for a biogenic origin of several examples, including candidate bacterial encrustations in altered pillow lavas, granular and tubular microtextures in volcanic glass from the subseafloor and a Phanerozoic ophiolite, mineralized microtextures in Archean metavolcanic glass, and alteration textures in olivines of the martian meteorite Yamato 000593. The aim of this hierarchical approach is to provide a framework for identifying robust biosignatures of microbial life in the altered oceanic crust on Earth, and in extraterrestrial altered mafic-ultramafic rocks, particularly on Mars.
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Affiliation(s)
| | - Eugene G Grosch
- Department of Earth Sciences, University of Bergen , Bergen, Norway
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Zhou X, Chen D, Tang D, Dong S, Guo C, Guo Z, Zhang Y. Biogenic Iron-Rich Filaments in the Quartz Veins in the Uppermost Ediacaran Qigebulake Formation, Aksu Area, Northwestern Tarim Basin, China: Implications for Iron Oxidizers in Subseafloor Hydrothermal Systems. ASTROBIOLOGY 2015; 15:523-537. [PMID: 26168395 DOI: 10.1089/ast.2014.1234] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Fe-(oxyhydr)oxide-encrusted filamentous microstructures produced by microorganisms have been widely reported in various modern and ancient extreme environments; however, the iron-dependent microorganisms preserved in hydrothermal quartz veins have not been explored in detail because of limited materials available. In this study, abundant well-preserved filamentous microstructures were observed in the hydrothermal quartz veins of the uppermost dolostones of the terminal-Ediacaran Qigebulake Formation in the Aksu area, northwestern Tarim Basin, China. These filamentous microstructures were permineralized by goethite and hematite as revealed by Raman spectroscopy and completely entombed in chalcedony and quartz cements. Microscopically, they are characterized by biogenic filamentous morphologies (commonly 20-200 μm in length and 1-5 μm in diameter) and structures (curved, tubular sheath-like, segmented, and mat-like filaments), similar to the Fe-oxidizing bacteria (FeOB) living in modern and ancient hydrothermal vent fields. A previous study revealed that quartz-barite vein swarms were subseafloor channels of low-temperature, silica-rich, diffusive hydrothermal vents in the earliest Cambrian, which contributed silica to the deposition of the overlying bedded chert of the Yurtus Formation. In this context, this study suggests that the putative filamentous FeOB preserved in the quartz veins might have thrived in the low-temperature, silica- and Fe(II)-rich hydrothermal vent channels in subseafloor mixing zones and were rapidly fossilized by subsequent higher-temperature, silica-rich hydrothermal fluids in response to waning and waxing fluctuations of diffuse hydrothermal venting. In view of the occurrence in a relatively stable passive continental margin shelf environment in Tarim Block, the silica-rich submarine hydrothermal vent system may represent a new and important geological niche favorable for FeOB colonization, which is different from their traditional habitats reported in hydrothermal vent systems at oceanic spreading centers or volcanic seamounts. Thus, these newly recognized microfossils offer a new clue to explore the biological signatures and habitat diversity of microorganisms on Earth and beyond.
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Affiliation(s)
- Xiqiang Zhou
- 1 Key Lab of Petroleum Resources Research, Institute of Geology and Geophysics , Chinese Academy of Sciences, Beijing, China
- 2 University of Chinese Academy of Sciences , Beijing, China
| | - Daizhao Chen
- 1 Key Lab of Petroleum Resources Research, Institute of Geology and Geophysics , Chinese Academy of Sciences, Beijing, China
| | - Dongjie Tang
- 3 School of Geosciences and Resources, China University of Geosciences , Beijing, China
| | - Shaofeng Dong
- 1 Key Lab of Petroleum Resources Research, Institute of Geology and Geophysics , Chinese Academy of Sciences, Beijing, China
| | - Chuan Guo
- 1 Key Lab of Petroleum Resources Research, Institute of Geology and Geophysics , Chinese Academy of Sciences, Beijing, China
- 2 University of Chinese Academy of Sciences , Beijing, China
| | - Zenghui Guo
- 1 Key Lab of Petroleum Resources Research, Institute of Geology and Geophysics , Chinese Academy of Sciences, Beijing, China
- 2 University of Chinese Academy of Sciences , Beijing, China
| | - Yanqiu Zhang
- 1 Key Lab of Petroleum Resources Research, Institute of Geology and Geophysics , Chinese Academy of Sciences, Beijing, China
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21
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The Deep Biosphere of the Subseafloor Igneous Crust. THE HANDBOOK OF ENVIRONMENTAL CHEMISTRY 2015. [DOI: 10.1007/698_2015_5014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Reassessing the biogenicity of Earth's oldest trace fossil with implications for biosignatures in the search for early life. Proc Natl Acad Sci U S A 2014; 111:8380-5. [PMID: 24912193 DOI: 10.1073/pnas.1402565111] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Microtextures in metavolcanic pillow lavas from the Barberton greenstone belt of South Africa have been argued to represent Earth's oldest trace fossil, preserving evidence for microbial life in the Paleoarchean subseafloor. In this study we present new in situ U-Pb age, metamorphic, and morphological data on these titanite microtextures from fresh drill cores intercepting the type locality. A filamentous microtexture representing a candidate biosignature yields a U-Pb titanite age of 2.819 ± 0.2 Ga. In the same drill core hornfelsic-textured titanite discovered adjacent to a local mafic sill records an indistinguishable U-Pb age of 2.913 ± 0.31 Ga, overlapping with the estimated age of intrusion. Quantitative microscale compositional mapping, combined with chlorite thermodynamic modeling, reveals that the titanite filaments are best developed in relatively low-temperature microdomains of the chlorite matrix. We find that the microtextures exhibit a morphological continuum that bears no similarity to candidate biotextures found in the modern oceanic crust. These new findings indicate that the titanite formed during late Archean ca. 2.9 Ga thermal contact metamorphism and not in an early ca. 3.45 Ga subseafloor environment. We therefore question the syngenicity and biogenicity of these purported trace fossils. It is argued herein that the titanite microtextures are more likely abiotic porphyroblasts of thermal contact metamorphic origin that record late-stage retrograde cooling in the pillow lava country rock. A full characterization of low-temperature metamorphic events and alternative biosignatures in greenstone belt pillow lavas is thus required before candidate traces of life can be confirmed in Archean subseafloor environments.
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Cooper GJT, Boulay AG, Kitson PJ, Ritchie C, Richmond CJ, Thiel J, Gabb D, Eadie R, Long DL, Cronin L. Osmotically driven crystal morphogenesis: a general approach to the fabrication of micrometer-scale tubular architectures based on polyoxometalates. J Am Chem Soc 2011; 133:5947-54. [PMID: 21446750 DOI: 10.1021/ja111011j] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The process of osmotically driven crystal morphogenesis of polyoxometalate (POM)-based crystals is investigated, whereby the transformation results in the growth of micrometer-scale tubes 10-100 μm in diameter and many thousands of micrometers long. This process initiates when the crystals are immersed in aqueous solutions containing large cations and is governed by the solubility of the parent POM crystal. Evidence is presented that indicates the process is general to all types of POMs, with solubility of the parent crystal being the deciding parameter. A modular approach is adopted since different POM precursor crystals can form tubular architectures with a range of large cationic species, producing an ion-exchanged material that combines the large added cations and the large POM-based anions. It is also shown that the process of morphogenesis is electrostatically driven by the aggregation of anionic metal oxides with the dissolved cations. This leads to the formation of a semi-permeable membrane around the crystal. The osmotically driven ingress of water leads to an increase in pressure, and ultimately rupture of the membrane occurs, allowing a saturated solution of the POM to escape and leading to the formation of a "self-growing" microtube in the presence of the cation. It is demonstrated that the growth process is sustained by the osmotic pressure within the membrane surrounding the parent crystal, as tube growth ceases whenever this pressure is relieved. Not only is the potential of the modular approach revealed by the fact that the microtubes retain the properties of their component parts, but it is also possible to control the direction of growth and tube diameter. In addition, the solubility limits of tube growth are explored and translated into a predictive methodology for the fabrication of tubular architectures with predefined physical properties, opening the way for real applications.
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Affiliation(s)
- Geoffrey J T Cooper
- School of Chemistry, WestCHEM, The University of Glasgow, University Avenue, Glasgow G12 8QQ, UK
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Fliegel D, Wirth R, Simonetti A, Furnes H, Staudigel H, Hanski E, Muehlenbachs K. Septate-tubular textures in 2.0-Ga pillow lavas from the Pechenga Greenstone Belt: a nano-spectroscopic approach to investigate their biogenicity. GEOBIOLOGY 2010; 8:372-390. [PMID: 20698893 DOI: 10.1111/j.1472-4669.2010.00252.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Pillow lava rims and interpillow hyaloclastites from the upper part of the Pechenga Greenstone Belt, Kola Peninsula, N-Russia contain rare tubular textures 15-20 μm in diameter and up to several hundred μm long in prehnite-pumpellyite to lower greenschist facies meta-volcanic glass. The textures are septate with regular compartments 5-20 μm across and exhibit branching, stopping and no intersecting features. Synchrotron micro-energy dispersive X-ray was used to image elemental distributions; scanning transmission X-ray microscopy, Fe L-edge and C K-edge were used to identify iron and carbon speciation at interfaces between the tubular textures and the host rock. In situ U-Pb radiometric dating by LA-MC-ICP-MS (laser ablation multicollector inductively coupled plasma mass spectrometry) of titanite from pillow lavas yielded a metamorphic age of 1790 ± 89 Ma. Focused ion-beam milling combined with transmission electron microscopy was used to analyze the textures in three dimensions. Electron diffraction showed that the textures are mineralized by orientated pumpellyite. On the margins of the tubes, an interface between mica or chlorite and the pumpellyite shows evidence of dissolution reactions where the pumpellyite is replaced by mica/chlorite. A thin poorly crystalline Fe-phase, probably precipitated out of solution, occurs at the interface between pumpellyite and mica/chlorite. This sequence of phases leads to the hypothesis that the tubes were initially hollow, compartmentalized structures in volcanic glass that were mineralized by pumpellyite during low-grade metamorphism. Later, a Fe-bearing fluid mineralized the compartments between the pumpellyite and lastly the pumpellyite was partially dissolved and replaced by chlorite during greenschist metamorphism. The most plausible origin for a septate-tubular texture is a progressive etching of the host matrix by several generations of microbes and subsequently these tubes were filled by authigenic mineral precipitates. This preserves the textures in the rock record over geological time. The micro textures reported here thus represent a pumpellyite-mineralized trace fossil that records a Paleoproterozoic sub-seafloor biosphere.
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Affiliation(s)
- D Fliegel
- Department of Earth Science and Center for Geobiology, Allegaten, Bergen, Norway.
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