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Sirantoine E, Wacey D, Bischoff K, Saunders M. Authigenic anatase within 1 billion-year-old cells. GEOBIOLOGY 2021; 19:3-17. [PMID: 32997387 DOI: 10.1111/gbi.12417] [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: 02/04/2020] [Revised: 08/13/2020] [Accepted: 08/23/2020] [Indexed: 06/11/2023]
Abstract
The siliciclastic ~1 Ga-old strata of the Torridon Group, Scotland, contain some of the most exquisitely preserved three-dimensional organic-walled microfossils (OWMs) of the Precambrian. A very diverse microfossil assemblage is hosted in a dominantly phosphatic and clay mineral matrix, within the Diabaig and the Cailleach Head (CH) Formations. In this study, we report on several microfossil taxa within the CH Formation (Leiosphaeridia minutissima, Leiosphaeridia crassa, Synsphaeridium spp. and Myxococcoides spp.) that include populations of cells containing an optically transparent and highly refringent mineral, here identified using electron microscopy as anatase (TiO2 ). Most anatase crystals occur entirely within individual cells, surrounded by unbroken carbonaceous walls. Rarely, an anatase crystal may protrude outside a cell, interpreted to correspond to zones where the cell wall had broken down prior to anatase precipitation. Where an anatase crystal entombs an organic intracellular inclusion (ICI), the ICI is large and well preserved. These combined observations indicate that the intracellular anatase is an authigenic sedimentary phase, making this the first report of in situ precipitated anatase intimately associated with microfossils. The ability of anatase to preserve relatively large volumes of intracellular and cell wall organic material in these cells suggests that the crystallisation of anatase entombed cellular contents particularly quickly, soon after the death of the cell. This is consistent with the strong affinity of Ti for organic material, the low solubility of TiO2 , and reports of Ti occurring in living organisms. With the data currently available, we propose a mineralisation pathway for anatase involving Ti complexation with organic ligands within specific cells, leading to localised post-mortem anatase nucleation inside these cells as the complexes broke down. Further overgrowth of the anatase crystals was likely fuelled by very early diagenetic mobilisation of Ti that had been bound to more labile organic material nearby in the sediments.
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Affiliation(s)
- Eva Sirantoine
- School of Earth Sciences, The University of Western Australia, Perth, WA, Australia
- Centre for Microscopy, Characterisation, and Analysis, The University of Western Australia, Perth, WA, Australia
| | - David Wacey
- Centre for Microscopy, Characterisation, and Analysis, The University of Western Australia, Perth, WA, Australia
| | - Karl Bischoff
- School of Earth Sciences, The University of Western Australia, Perth, WA, Australia
| | - Martin Saunders
- Centre for Microscopy, Characterisation, and Analysis, The University of Western Australia, Perth, WA, Australia
- School of Molecular Sciences, The University of Western Australia, Perth, WA, Australia
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Onstott T, Ehlmann B, Sapers H, Coleman M, Ivarsson M, Marlow J, Neubeck A, Niles P. Paleo-Rock-Hosted Life on Earth and the Search on Mars: A Review and Strategy for Exploration. ASTROBIOLOGY 2019; 19:1230-1262. [PMID: 31237436 PMCID: PMC6786346 DOI: 10.1089/ast.2018.1960] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Accepted: 04/25/2019] [Indexed: 05/19/2023]
Abstract
Here we review published studies on the abundance and diversity of terrestrial rock-hosted life, the environments it inhabits, the evolution of its metabolisms, and its fossil biomarkers to provide guidance in the search for life on Mars. Key findings are (1) much terrestrial deep subsurface metabolic activity relies on abiotic energy-yielding fluxes and in situ abiotic and biotic recycling of metabolic waste products rather than on buried organic products of photosynthesis; (2) subsurface microbial cell concentrations are highest at interfaces with pronounced chemical redox gradients or permeability variations and do not correlate with bulk host rock organic carbon; (3) metabolic pathways for chemolithoautotrophic microorganisms evolved earlier in Earth's history than those of surface-dwelling phototrophic microorganisms; (4) the emergence of the former occurred at a time when Mars was habitable, whereas the emergence of the latter occurred at a time when the martian surface was not continually habitable; (5) the terrestrial rock record has biomarkers of subsurface life at least back hundreds of millions of years and likely to 3.45 Ga with several examples of excellent preservation in rock types that are quite different from those preserving the photosphere-supported biosphere. These findings suggest that rock-hosted life would have been more likely to emerge and be preserved in a martian context. Consequently, we outline a Mars exploration strategy that targets subsurface life and scales spatially, focusing initially on identifying rocks with evidence for groundwater flow and low-temperature mineralization, then identifying redox and permeability interfaces preserved within rock outcrops, and finally focusing on finding minerals associated with redox reactions and associated traces of carbon and diagnostic chemical and isotopic biosignatures. Using this strategy on Earth yields ancient rock-hosted life, preserved in the fossil record and confirmable via a suite of morphologic, organic, mineralogical, and isotopic fingerprints at micrometer scale. We expect an emphasis on rock-hosted life and this scale-dependent strategy to be crucial in the search for life on Mars.
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Affiliation(s)
- T.C. Onstott
- Department of Geosciences, Princeton University, Princeton, New Jersey, USA
- Address correspondence to: T.C. Onstott, Department of Geosciences, Princeton University,, Princeton, NJ 008544
| | - B.L. Ehlmann
- Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- B.L. Ehlmann, Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
| | - H. Sapers
- Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- Department of Earth Sciences, University of Southern California, Los Angeles, California, USA
| | - M. Coleman
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- NASA Astrobiology Institute, Pasadena, California, USA
| | - M. Ivarsson
- Department of Biology, University of Southern Denmark, Odense, Denmark
| | - J.J. Marlow
- Department of Organismic & Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - A. Neubeck
- Department of Earth Sciences, Uppsala University, Uppsala, Sweden
| | - P. Niles
- Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, Texas, USA
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Lalla E, Sanz-Arranz A, Lopez-Reyes G, Cote K, Daly M, Konstantinidis M, Rodriguez-Losada JA, Groemer G, Medina J, Martínez-Frías J, Rull-Pérez F. A micro-Raman and X-ray study of erupted submarine pyroclasts from El Hierro (Spain) and its' astrobiological implications. LIFE SCIENCES IN SPACE RESEARCH 2019; 21:49-64. [PMID: 31101155 DOI: 10.1016/j.lssr.2019.04.003] [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: 11/23/2018] [Revised: 04/12/2019] [Accepted: 04/14/2019] [Indexed: 06/09/2023]
Abstract
The pumice volcanic samples could have possible connections to the evolution of life and give us insight about their bio-geochemical processes related. In this regard, the samples from the volcanic eruption from La Restinga (El Hierro, Spain) in 2011 have been mainly studied by means of Raman spectroscopy. The research also includes analysis of XRD, Scanning Electron Microscopy and Optical Microscopy to support the Raman analysis. The results show that the Raman methods and mineral analyses are in strong agreement with the results obtained from other authors and techniques. The internal white foamy core (WFC) of the studied pumice samples shows amorphous silica, Fe-oxides, Ti-oxides, quartz, certain sulfates, carbonates, zeolites and organics. On the other hand, the external part (dark crust - DC) of these samples mainly presents primary-sequence mineralogy combined with some secondary alteration minerals such as olivine, feldspar, pyroxene, amorphous silica, and Fe-oxide. Raman spectroscopy detected other minerals not yet reported on these samples like barite, celestine and lepidocrocite. Also, the different chemometric and calibration methods for Raman spectroscopy in elemental composition, mineral classification and structural characterization has been successfully applied. From the astrobiological perspective, the research was also complemented with comparisons to other similar samples from terrestrial analogs. The main consideration was taking into account the proposed hypothesis regarding the potential behavior of the pumice as a substrate for the evolution of life. Furthermore, the detailed analysis from La Restinga eruption is coherent with the mineral phases and processes discussed from previous literature. The white internal part fulfills the conditions to work as an organic reservoir, confirmed by the detection of organic matter and selected minerals that could be used as energy sources for bacterial communities. The external layers of the samples work as a shielding layer to protect the organics from decay in extreme conditions. Finally, here we have demonstrated that the characteristics and advantages of Raman spectroscopy could help to assess and understand the possible biogenicity and alteration processes of any geological sample to be found on Mars.
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Affiliation(s)
- E Lalla
- Centre for Research in Earth and Space Science, York University, Petrie Science Building, 4700 Keele St, Toronto, M3J 1P3, ON, Canada; Austrian Space Forum, Sillufer 3a, Innsbruck, 6020, Austria.
| | - A Sanz-Arranz
- Departamento de Física de la Materia Condensada, Cristalografía y Mineralogía. Universidad de Valladolid, P de Belén 7, 47011, Valladolid, Spain
| | - G Lopez-Reyes
- Departamento de Física de la Materia Condensada, Cristalografía y Mineralogía. Universidad de Valladolid, P de Belén 7, 47011, Valladolid, Spain
| | - K Cote
- Centre for Research in Earth and Space Science, York University, Petrie Science Building, 4700 Keele St, Toronto, M3J 1P3, ON, Canada
| | - M Daly
- Centre for Research in Earth and Space Science, York University, Petrie Science Building, 4700 Keele St, Toronto, M3J 1P3, ON, Canada
| | - M Konstantinidis
- Centre for Research in Earth and Space Science, York University, Petrie Science Building, 4700 Keele St, Toronto, M3J 1P3, ON, Canada
| | - J A Rodriguez-Losada
- Departamento de Biología Animal, Edafología y Geología, Universidad de La Laguna, Tenerife, C/ Astrofisco Sanchez s/n, 38211, La Laguna, Santa Cruz de Tenerife, Spain
| | - G Groemer
- Austrian Space Forum, Sillufer 3a, Innsbruck, 6020, Austria
| | - J Medina
- Departamento de Física de la Materia Condensada, Cristalografía y Mineralogía. Universidad de Valladolid, P de Belén 7, 47011, Valladolid, Spain
| | - J Martínez-Frías
- Dinámica Terrestre y Observación de la Tierra, Instituto de Geociencias, C/Severo Ochoa 7, Ed Entrepabellones 7 y 8, Ciudad Universitaria, 28040 Madrid, Spain
| | - F Rull-Pérez
- Austrian Space Forum, Sillufer 3a, Innsbruck, 6020, Austria
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Neveu M, Hays LE, Voytek MA, New MH, Schulte MD. The Ladder of Life Detection. ASTROBIOLOGY 2018; 18:1375-1402. [PMID: 29862836 PMCID: PMC6211372 DOI: 10.1089/ast.2017.1773] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 03/23/2018] [Indexed: 05/04/2023]
Abstract
We describe the history and features of the Ladder of Life Detection, a tool intended to guide the design of investigations to detect microbial life within the practical constraints of robotic space missions. To build the Ladder, we have drawn from lessons learned from previous attempts at detecting life and derived criteria for a measurement (or suite of measurements) to constitute convincing evidence for indigenous life. We summarize features of life as we know it, how specific they are to life, and how they can be measured, and sort these features in a general sense based on their likelihood of indicating life. Because indigenous life is the hypothesis of last resort in interpreting life-detection measurements, we propose a small but expandable set of decision rules determining whether the abiotic hypothesis is disproved. In light of these rules, we evaluate past and upcoming attempts at life detection. The Ladder of Life Detection is not intended to endorse specific biosignatures or instruments for life-detection measurements, and is by no means a definitive, final product. It is intended as a starting point to stimulate discussion, debate, and further research on the characteristics of life, what constitutes a biosignature, and the means to measure them.
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Affiliation(s)
- Marc Neveu
- NASA Postdoctoral Management Program Fellow, Universities Space Research Association, Columbia, Maryland
- NASA Headquarters, Washington, DC
| | - Lindsay E. Hays
- NASA Headquarters, Washington, DC
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
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McMahon S, Bosak T, Grotzinger JP, Milliken RE, Summons RE, Daye M, Newman SA, Fraeman A, Williford KH, Briggs DEG. A Field Guide to Finding Fossils on Mars. JOURNAL OF GEOPHYSICAL RESEARCH. PLANETS 2018; 123:1012-1040. [PMID: 30034979 PMCID: PMC6049883 DOI: 10.1029/2017je005478] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 03/28/2018] [Accepted: 04/23/2018] [Indexed: 05/05/2023]
Abstract
The Martian surface is cold, dry, exposed to biologically harmful radiation and apparently barren today. Nevertheless, there is clear geological evidence for warmer, wetter intervals in the past that could have supported life at or near the surface. This evidence has motivated National Aeronautics and Space Administration and European Space Agency to prioritize the search for any remains or traces of organisms from early Mars in forthcoming missions. Informed by (1) stratigraphic, mineralogical and geochemical data collected by previous and current missions, (2) Earth's fossil record, and (3) experimental studies of organic decay and preservation, we here consider whether, how, and where fossils and isotopic biosignatures could have been preserved in the depositional environments and mineralizing media thought to have been present in habitable settings on early Mars. We conclude that Noachian-Hesperian Fe-bearing clay-rich fluvio-lacustrine siliciclastic deposits, especially where enriched in silica, currently represent the most promising and best understood astropaleontological targets. Siliceous sinters would also be an excellent target, but their presence on Mars awaits confirmation. More work is needed to improve our understanding of fossil preservation in the context of other environments specific to Mars, particularly within evaporative salts and pore/fracture-filling subsurface minerals.
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Affiliation(s)
- S. McMahon
- Department of Geology and GeophysicsYale UniversityNew HavenCTUSA
- UK Centre for Astrobiology, School of Physics and AstronomyUniversity of EdinburghEdinburghUK
| | - T. Bosak
- Department of Earth, Atmospheric and Planetary SciencesMassachusetts Institute of TechnologyCambridgeMAUSA
| | - J. P. Grotzinger
- Division of Geological and Planetary SciencesCalifornia Institute of TechnologyPasadenaCAUSA
| | - R. E. Milliken
- Department of Earth, Environmental and Planetary SciencesBrown UniversityProvidenceRIUSA
| | - R. E. Summons
- Department of Earth, Atmospheric and Planetary SciencesMassachusetts Institute of TechnologyCambridgeMAUSA
| | - M. Daye
- Department of Earth, Atmospheric and Planetary SciencesMassachusetts Institute of TechnologyCambridgeMAUSA
| | - S. A. Newman
- Department of Earth, Atmospheric and Planetary SciencesMassachusetts Institute of TechnologyCambridgeMAUSA
| | - A. Fraeman
- Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaCAUSA
| | - K. H. Williford
- Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaCAUSA
| | - D. E. G. Briggs
- Department of Geology and GeophysicsYale UniversityNew HavenCTUSA
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Mergelov N, Mueller CW, Prater I, Shorkunov I, Dolgikh A, Zazovskaya E, Shishkov V, Krupskaya V, Abrosimov K, Cherkinsky A, Goryachkin S. Alteration of rocks by endolithic organisms is one of the pathways for the beginning of soils on Earth. Sci Rep 2018; 8:3367. [PMID: 29463846 PMCID: PMC5820250 DOI: 10.1038/s41598-018-21682-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 02/07/2018] [Indexed: 12/03/2022] Open
Abstract
Subaerial endolithic systems of the current extreme environments on Earth provide exclusive insight into emergence and development of soils in the Precambrian when due to various stresses on the surfaces of hard rocks the cryptic niches inside them were much more plausible habitats for organisms than epilithic ones. Using an actualistic approach we demonstrate that transformation of silicate rocks by endolithic organisms is one of the possible pathways for the beginning of soils on Earth. This process led to the formation of soil-like bodies on rocks in situ and contributed to the raise of complexity in subaerial geosystems. Endolithic systems of East Antarctica lack the noise from vascular plants and are among the best available natural models to explore organo-mineral interactions of a very old “phylogenetic age” (cyanobacteria-to-mineral, fungi-to-mineral, lichen-to-mineral). On the basis of our case study from East Antarctica we demonstrate that relatively simple endolithic systems of microbial and/or cryptogamic origin that exist and replicate on Earth over geological time scales employ the principles of organic matter stabilization strikingly similar to those known for modern full-scale soils of various climates.
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Affiliation(s)
- Nikita Mergelov
- Institute of Geography, Russian Academy of Sciences, Department of Soil Geography and Evolution, Moscow, 119017, Russia.
| | - Carsten W Mueller
- TU München, Lehrstuhl für Bodenkunde, Freising-Weihenstephan, 85354, Germany
| | - Isabel Prater
- TU München, Lehrstuhl für Bodenkunde, Freising-Weihenstephan, 85354, Germany
| | - Ilya Shorkunov
- Institute of Geography, Russian Academy of Sciences, Department of Soil Geography and Evolution, Moscow, 119017, Russia
| | - Andrey Dolgikh
- Institute of Geography, Russian Academy of Sciences, Department of Soil Geography and Evolution, Moscow, 119017, Russia
| | - Elya Zazovskaya
- Institute of Geography, Russian Academy of Sciences, Department of Soil Geography and Evolution, Moscow, 119017, Russia
| | - Vasily Shishkov
- Institute of Geography, Russian Academy of Sciences, Department of Soil Geography and Evolution, Moscow, 119017, Russia
| | - Victoria Krupskaya
- Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences, Laboratory of Crystal Chemistry of Minerals, Moscow, 119017, Russia
| | - Konstantin Abrosimov
- V.V. Dokuchaev Soil Science Institute, Russian Academy of Sciences, Department of Soil Physics, Hydrology and Erosion, Moscow, 119017, Russia
| | - Alexander Cherkinsky
- Center for Applied Isotope Studies, University of Georgia, Athens, 30602, United States
| | - Sergey Goryachkin
- Institute of Geography, Russian Academy of Sciences, Department of Soil Geography and Evolution, Moscow, 119017, Russia
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Ivarsson M, Bengtson S, Drake H, Francis W. Fungi in Deep Subsurface Environments. ADVANCES IN APPLIED MICROBIOLOGY 2018; 102:83-116. [PMID: 29680127 DOI: 10.1016/bs.aambs.2017.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The igneous crust of the oceans and the continents represents the major part of Earth's lithosphere and has recently been recognized as a substantial, yet underexplored, microbial habitat. While prokaryotes have been the focus of most investigations, microeukaryotes have been surprisingly neglected. However, recent work acknowledges eukaryotes, and in particular fungi, as common inhabitants of the deep biosphere, including the deep igneous provinces. The fossil record of the subseafloor igneous crust, and to some extent the continental bedrock, establishes fungi or fungus-like organisms as inhabitants of deep rock since at least the Paleoproterozoic, which challenges the present notion of early fungal evolution. Additionally, deep fungi have been shown to play an important ecological role engaging in symbiosis-like relationships with prokaryotes, decomposing organic matter, and being responsible for mineral weathering and formation, thus mediating mobilization of biogeochemically important elements. In this review, we aim at covering the abundance and diversity of fungi in the various igneous rock provinces on Earth as well as describing the ecological impact of deep fungi. We further discuss what consequences recent findings might have for the understanding of the fungal distribution in extensive anoxic environments and for early fungal evolution.
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Affiliation(s)
- Magnus Ivarsson
- Nordic Center for Earth Evolution, University of Southern Denmark, Odense, Denmark; Swedish Museum of Natural History, Stockholm, Sweden.
| | | | | | - Warren Francis
- Nordic Center for Earth Evolution, University of Southern Denmark, Odense, Denmark
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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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10
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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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11
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Chatzitheodoridis E, Haigh S, Lyon I. A conspicuous clay ovoid in Nakhla: evidence for subsurface hydrothermal alteration on Mars with implications for astrobiology. ASTROBIOLOGY 2014; 14:651-693. [PMID: 25046549 PMCID: PMC4126275 DOI: 10.1089/ast.2013.1069] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2013] [Accepted: 05/19/2014] [Indexed: 06/03/2023]
Abstract
Abstract A conspicuous biomorphic ovoid structure has been discovered in the Nakhla martian meteorite, made of nanocrystalline iron-rich saponitic clay and amorphous material. The ovoid is indigenous to Nakhla and occurs within a late-formed amorphous mesostasis region of rhyolitic composition that is interstitial to two clinopyroxene grains with Al-rich rims, and contains acicular apatite crystals, olivine, sulfides, Ti-rich magnetite, and a new mineral of the rhoenite group. To infer the origin of the ovoid, a large set of analytical tools was employed, including scanning electron microscopy and backscattered electron imaging, wavelength-dispersive X-ray analysis, X-ray mapping, Raman spectroscopy, time-of-flight secondary ion mass spectrometry analysis, high-resolution transmission electron microscope imaging, and atomic force microscope topographic mapping. The concentric wall of the ovoid surrounds an originally hollow volume and exhibits internal layering of contrasting nanotextures but uniform chemical composition, and likely inherited its overall shape from a preexisting vesicle in the mesostasis glass. A final fibrous layer of Fe-rich phases blankets the interior surfaces of the ovoid wall structure. There is evidence that the parent rock of Nakhla has undergone a shock event from a nearby bolide impact that melted the rims of pyroxene and the interstitial matter and initiated an igneous hydrothermal system of rapidly cooling fluids, which were progressively mixed with fluids from the melted permafrost. Sharp temperature gradients were responsible for the crystallization of Al-rich clinopyroxene rims, rhoenite, acicular apatites, and the quenching of the mesostasis glass and the vesicle. During the formation of the ovoid structure, episodic fluid infiltration events resulted in the precipitation of saponite rinds around the vesicle walls, altered pyrrhotite to marcasite, and then isolated the ovoid wall structure from the rest of the system by depositing a layer of iron oxides/hydroxides. Carbonates, halite, and sulfates were deposited last within interstitial spaces and along fractures. Among three plausible competing hypotheses here, this particular abiotic scenario is considered to be the most reasonable explanation for the formation of the ovoid structure in Nakhla, and although compelling evidence for a biotic origin is lacking, it is evident that the martian subsurface contains niche environments where life could develop.
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Affiliation(s)
- Elias Chatzitheodoridis
- Department of Geological Sciences, School of Mining and Metallurgical Engineering, National Technical University of Athens, Athens, Greece
| | - Sarah Haigh
- School of Materials, The University of Manchester, Manchester, UK
| | - Ian Lyon
- School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester, UK
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Grosch EG, McLoughlin N, Lanari P, Erambert M, Vidal O. Microscale mapping of alteration conditions and potential biosignatures in basaltic-ultramafic rocks on early Earth and beyond. ASTROBIOLOGY 2014; 14:216-228. [PMID: 24588497 DOI: 10.1089/ast.2013.1116] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Subseafloor environments preserved in Archean greenstone belts provide an analogue for investigating potential subsurface habitats on Mars. The c. 3.5-3.4 Ga pillow lava metabasalts of the mid-Archean Barberton greenstone belt, South Africa, have been argued to contain the earliest evidence for microbial subseafloor life. This includes candidate trace fossils in the form of titanite microtextures, and sulfur isotopic signatures of pyrite preserved in metabasaltic glass of the c. 3.472 Ga Hooggenoeg Formation. It has been contended that similar microtextures in altered martian basalts may represent potential extraterrestrial biosignatures of microbe-fluid-rock interaction. But despite numerous studies describing these putative early traces of life, a detailed metamorphic characterization of the microtextures and their host alteration conditions in the ancient pillow lava metabasites is lacking. Here, we present a new nondestructive technique with which to study the in situ metamorphic alteration conditions associated with potential biosignatures in mafic-ultramafic rocks of the Hooggenoeg Formation. Our approach combines quantitative microscale compositional mapping by electron microprobe with inverse thermodynamic modeling to derive low-temperature chlorite crystallization conditions. We found that the titanite microtextures formed under subgreenschist to greenschist facies conditions. Two chlorite temperature groups were identified in the maps surrounding the titanite microtextures and record peak metamorphic conditions at 315 ± 40°C (XFe3+(chlorite) = 25-34%) and lower-temperature chlorite veins/microdomains at T = 210 ± 40°C (lower XFe3+(chlorite) = 40-45%). These results provide the first metamorphic constraints in textural context on the Barberton titanite microtextures and thereby improve our understanding of the local preservation conditions of these potential biosignatures. We suggest that this approach may prove to be an important tool in future studies to assess the biogenicity of these earliest candidate traces of life on Earth. Furthermore, we propose that this mapping approach could also be used to investigate altered mafic-ultramafic extraterrestrial samples containing candidate biosignatures.
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Affiliation(s)
- Eugene G Grosch
- 1 Department of Earth Science and Centre for Geobiology, University of Bergen , Bergen, Norway
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Marshall CP, Olcott Marshall A. Raman hyperspectral imaging of microfossils: potential pitfalls. ASTROBIOLOGY 2013; 13:920-31. [PMID: 24088070 PMCID: PMC3807534 DOI: 10.1089/ast.2013.1034] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 08/23/2013] [Indexed: 05/24/2023]
Abstract
Initially, Raman spectroscopy was a specialized technique used by vibrational spectroscopists; however, due to rapid advancements in instrumentation and imaging techniques over the last few decades, Raman spectrometers are widely available at many institutions, allowing Raman spectroscopy to become a widespread analytical tool in mineralogy and other geological sciences. Hyperspectral imaging, in particular, has become popular due to the fact that Raman spectroscopy can quickly delineate crystallographic and compositional differences in 2-D and 3-D at the micron scale. Although this rapid growth of applications to the Earth sciences has provided great insight across the geological sciences, the ease of application as the instruments become increasingly automated combined with nonspecialists using this techique has resulted in the propagation of errors and misunderstandings throughout the field. For example, the literature now includes misassigned vibration modes, inappropriate spectral processing techniques, confocal depth of laser penetration incorrectly estimated into opaque crystalline solids, and a misconstrued understanding of the anisotropic nature of sp² carbons.
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Westall F. Microbial Scale Habitability on Mars. HABITABILITY OF OTHER PLANETS AND SATELLITES 2013. [DOI: 10.1007/978-94-007-6546-7_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Cockell CS, Cady SL, McLoughlin N. Introduction. Volcanism and astrobiology: life on earth and beyond. ASTROBIOLOGY 2011; 11:583-584. [PMID: 21895441 DOI: 10.1089/ast.2011.8080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Affiliation(s)
- Charles S Cockell
- UK Centre for Astrobiology, SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
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