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  • 1.
    Kring, David A.
    et al.
    Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, USA..
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Schmieder, Martin
    Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, USA.;HNU–Neu-Ulm University of Applied Sciences, Neu-Ulm, Germany..
    Microbial Sulfur Isotope Fractionation in the Chicxulub Hydrothermal System2021In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070Article in journal (Refereed)
  • 2. Onstott, T.C.
    et al.
    Ehlmann, Bethany
    Sapers, Haley
    Coleman, Max
    Ivarsson, Magnus
    Swedish Museum of Natural History, Department of Paleobiology.
    Marlow, J.J.
    Neubeck, Anna
    Niles, P
    Paleo-rock-hosted life on Earth and the search on Mars: a review and strategy for exploration2019In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 19, no 10, p. 1230-1262Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    Qu, Yuangao
    et al.
    Department of Earth Science and Centre for Geobiology, University of Bergen, Norway.
    Engdahl, Anders
    MAX IV Laboratory, Lund University, Sweden.
    Zhu, Shixing
    Tianjin Institute of Geology and Mineral Resources, CGS, China.
    Vajda, Vivi
    Swedish Museum of Natural History, Department of Paleobiology. Department of Geology, Lund University, Sweden.
    McLoughlin, Nicola
    Department of Geology, Lund University, Sweden.
    Ultrastructural heterogeneity of carbonaceous material in ancient cherts: investigating biosignature origin and preservation2015In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 15, no 10, p. 825-842Article in journal (Refereed)
    Abstract [en]

    Opaline silica deposits on Mars may be good target sites where organic biosignatures could be preserved. Potential analogues on Earth are provided by ancient cherts containing carbonaceous material (CM) permineralized by silica. In this study, we investigated the ultrastructure and chemical characteristics of CM in the Rhynie chert (c. 410 Ma, UK), Bitter Springs Formation (c. 820 Ma, Australia), and Wumishan Formation (c. 1485 Ma, China). Raman spectroscopy indicates that the CM has experienced advanced diagenesis or lowgrade metamorphism at peak metamorphic temperatures of 150–350C. Raman mapping and micro-Fourier transform infrared (micro-FTIR) spectroscopy were used to document subcellular-scale variation in the CM of fossilized plants, fungi, prokaryotes, and carbonaceous stromatolites.

    In the Rhynie chert, ultrastructural variation in the CM was found within individual fossils, while in coccoidal and filamentous microfossils of the Bitter Springs and formless CM of the Wumishan stromatolites ultrastructural variation was found between, not within, different microfossils. This heterogeneity cannot be explained by secondary geological processes but supports diverse carbonaceous precursors that experienced differential graphitization. Micro-FTIR analysis found that CM with lower structural order contains more straight carbon chains (has a lower R3/2 branching index) and that the structural order of eukaryotic CM is more heterogeneous than prokaryotic CM.

    This study demonstrates how Raman spectroscopy combined with micro-FTIR can be used to investigate the origin and preservation of silica-permineralized organics. This approach has good capability for furthering our understanding of CM preserved in Precambrian cherts, and potential biosignatures in siliceous deposits on Mars. Key

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  • 4.
    Qu, Yuangao
    et al.
    Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, China..
    Yin, Zongjun
    State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China..
    Kustatscher, Evelyn
    Museum of Nature South Tyrol, Bozen/Bolzano, Italy.;Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Ludwig-Maximilians-Universität, München, Germany.;SNSB-Bayerische Staatssammlung für Paläontologie und Geobiologie, München, Germany..
    Nützel, Alexander
    Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Ludwig-Maximilians-Universität, München, Germany.;SNSB-Bayerische Staatssammlung für Paläontologie und Geobiologie, München, Germany.;GeoBio-Center, Ludwig-Maximilians-Universität München, München, Germany..
    Peckmann, Jörn
    Institute für Geologie, Centrum für Erdsystemforschung und Nachhaltigkeit, Universität Hamburg, Hamburg, Germany..
    Vajda, Vivi
    Swedish Museum of Natural History, Department of Paleobiology.
    Ivarsson, Magnus
    Swedish Museum of Natural History, Department of Paleobiology.
    Traces of Ancient Life in Oceanic Basalt Preserved as Iron-Mineralized Ultrastructures: Implications for Detecting Extraterrestrial Biosignatures2023In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 23, no 7, p. 769-785Article in journal (Refereed)
    Abstract [en]

    Benefiting from their adaptability to extreme environments, subsurface microorganisms have been discovered in sedimentary and igneous rock environments on Earth and have been advocated as candidates in the search for extraterrestrial life. In this article, we study iron-mineralized microstructures in calcite-filled veins within basaltic pillows of the late Ladinian Fernazza group (Middle Triassic, 239 Ma) in Italy. These microstructures represent diverse morphologies, including filaments, globules, nodules, and micro-digitate stromatolites, which are similar to extant iron-oxidizing bacterial communities. In situ analyses including Raman spectroscopy have been used to investigate the morphological, elemental, mineralogical, and bond-vibrational modes of the microstructures. According to the Raman spectral parameters, iron minerals preserve heterogeneous ultrastructures and crystallinities, coinciding with the morphologies and precursor microbial activities. The degree of crystallinity usually represents a microscale gradient decreasing toward previously existing microbial cells, revealing a decline of mineralization due to microbial activities. This study provides an analog of possible rock-dwelling subsurface life on Mars or icy moons and advocates Raman spectroscopy as an efficient tool for in situ analyses. We put forward the concept that ultrastructural characteristics of minerals described by Raman spectral parameters corresponding to microscale morphologies could be employed as carbon-lean biosignatures in future space missions. Key Words: Ultrastructures—Iron minerals—Oceanic basalt—Subsurface biosignatures.

  • 5. Tulej, Marek
    et al.
    Neubeck, Anna
    Ivarsson, Magnus
    Swedish Museum of Natural History, Department of Paleobiology.
    Riedo, Andreas
    Neuland, M.
    Meyer, Stephan
    Wurz, Peter
    Chemical composition of micrometer-sized filaments in an aragonite host by a miniature laser ablation/ionization mass spectrometer2015In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 15, p. 669-682Article in journal (Refereed)
  • 6.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Fedo, C.M.
    Kamber, B.S.
    Does a Heavy Fe-Isotope Composition of Akilia Quartz-Amphibole-Pyroxene Rocks Necessitate a BIF Origin?2015In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 15, p. 816-824Article in journal (Refereed)
    Abstract [en]

    The age and origin of the quartz-amphibole-pyroxene (qap) gneiss from the island of Akilia, southern West Greenland, has been the subject of intense debate since the light C-isotope composition of graphite inclusions in apatite was interpreted to indicate the presence of Earth’s earliest biological activity.  Although this claim for biogenic relicts has been vigourously challenged, the possibility that the rocks might represent some of the Earth’s earliest water lain sediments and, hence, a suitable repository for life, remains an open question. While some workers have suggested that the entire sequence represents an originally mafic-ultramafic igneous precursor subsequently modified by metasomatism, quartz injection, high-grade metamorphism and extreme ductile deformation, others maintain that at least a small part of the sequence retains geochemical characteristics indicative of a chemical sedimentary origin. Fractionated Fe isotopes with d56Fe values similar to those observed in Isua BIF reported from high-SiO2 units of qap have been used to support a chemical sedimentary protolith for the qap unit. Here we present new Fe isotope data from all lithological variants in the quartz-amphibole-pyroxene gneiss on Akilia, including layers of undisputed ultramafic igneous origin. Since the latter require introdution of fractionated Fe into at least part of the qap unit, we argue that Fe isotopes must therefore be treated with considerable caution when used to infer BIF for part or all of the qap protolith.

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  • 7.
    Wiesendanger, Reto
    et al.
    Research and Planetary Sciences Physics Institute University of Bern Sidlerstrasse 5Bern CH-3012 Switzerland.
    Wacey, David
    Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Perth, Australia.
    Tulej, Marek
    Space Research and Planetary Sciences, Physics Institute, University of Bern, Bern, Switzerland.
    Neubeck, Anna
    Swedish Museum of Natural History, Department of Paleobiology.
    Ivarsson, Magnus
    Swedish Museum of Natural History, Department of Paleobiology. University of Southern Denmark, Department of Biology and Nordic Center for Earth Evolution, Campusvej 55, Odense M, DK-5230, Denmark.
    Grimaudo, V.
    Department of Chemistry and Biochemistry, Interfacial Electrochemistry Group, University of Bern, Bern, Switzerland.
    Moreno-Garcia, P.
    Department of Chemistry and Biochemistry, Interfacial Electrochemistry Group, University of Bern, Bern, Switzerland.
    Cedeῆo López, A.
    Department of Chemistry and Biochemistry, Interfacial Electrochemistry Group, University of Bern, Bern, Switzerland.
    Riedo, Andreas
    Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, The Netherlands.
    Wurz, Peter
    Space Research and Planetary Sciences, Physics Institute, University of Bern, Bern, Switzerland.
    Chemical and optical identification of micrometer sized 1.9 Ga old fossils with a miniature LIMS system combined with an optical microscope2018In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 18, no 8, p. 1071-1080Article in journal (Refereed)
    Abstract [en]

    The recognition of biosignatures on planetary bodies requires the analysis of the putative microfossil with a set of complementary analytical techniques. This includes localized elemental and isotopic analysis of both the putative microfossil and its surrounding host matrix. If the analysis can be performed with spatial resolution at the micrometer level and part-per-million detection sensitivities, valuable information on the (bio)chemical and physical processes that influenced the sample material can be gained. Our miniaturized laser ablation ionization mass spectrometry (LIMS)-time-of-flight mass spectrometer instrument is a valid candidate for performing the required chemical analysis in situ. However, up until now it was limited by the spatial accuracy of the sampling. In this contribution, we introduce a newly developed microscope system with micrometer accuracy for ultra high vacuum application, which allows a significant increase in the measurement capabilities of our miniature LIMS system. The new enhancement allows identification and efficient and accurate sampling of features of micrometer-sized fossils in a host matrix. The performance of our system is demonstrated by the identification and chemical analysis of signatures of micrometer-sized fossil structures in the 1.9 billion-year-old Gunflint chert.

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