Assessing the formation and preservation of organic signatures in extreme environments in the context of the ExoMars 2020 rover mission Dissertation zur Erlangung des mathematisch-naturwissenschaftlichen Doktorgrades „Doctor rerum naturalium“ der Georg-August-Universität Göttingen im Promotionsprogramm Geowissenschaften der Georg-August University School of Science (GAUSS) vorgelegt von Manuel Reinhardt aus Coburg Göttingen, 2019 Betreuungsausschuss: Prof. Dr. Volker Thiel Georg-August-Universität Göttingen, Geowissenschaftliches Zentrum, Abteilung Geobiologie PD Dr. Walter Goetz Max-Planck-Institut für Sonnensystemforschung, Göttingen Mitglieder der Prüfungskommission: Referent: Prof. Dr. Volker Thiel Georg-August-Universität Göttingen, Geowissenschaftliches Zentrum, Abteilung Geobiologie 1. Korreferent: PD Dr. Walter Goetz Max-Planck-Institut für Sonnensystemforschung, Göttingen 2. Korreferent: Prof. Dr. Lorenz Schwark Christian-Albrechts-Universität zu Kiel, Institut für Geowissenschaften, Abteilung Organische Geochemie Weitere Mitglieder der Prüfungskommission: Prof. Dr. Gernot Arp Georg-August-Universität Göttingen, Geowissenschaftliches Zentrum, Abteilung Geobiologie Dr. Martin Blumenberg Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover Dr. Fred Goesmann Max-Planck-Institut für Sonnensystemforschung, Göttingen Prof. Dr. Joachim Reitner Georg-August-Universität Göttingen, Geowissenschaftliches Zentrum, Abteilung Geobiologie Tag der mündlichen Prüfung: 17.05.2019 In memory of my grandmother, Leni Reinhardt, the most optimistic and supportive person in my life. Contents Acknowledgements ................................................................................................................... ix Preface ....................................................................................................................................... xi Abstract ................................................................................................................................... xiii Zusammenfassung .................................................................................................................... xv 1 Introduction ............................................................................................................................. 1 1.1 ExoMars 2020 and the search for traces of life on Mars .............................................................................. 1 1.2 Life as we know it ......................................................................................................................................... 2 1.3 Emergence of life on the early Earth and habitability of Mars ..................................................................... 2 1.3.1 Emergence of life on the early Earth ..................................................................................................... 2 1.3.2 Mars, also a habitable planet? ............................................................................................................... 3 1.4 Molecular biosignatures and their preservational fate .................................................................................. 4 1.5 Thesis objectives and study approaches........................................................................................................ 6 References .......................................................................................................................................................... 7 2 Organic signatures in Pleistocene cherts from Lake Magadi (Kenya), analogs for early Earth hydrothermal deposits.......................................................................................................... 13 2.1 Introduction ................................................................................................................................................ 14 2.2 Materials and Methods................................................................................................................................ 15 2.2.1 Sample material, petrographic and bulk geochemical analyses ........................................................... 15 2.2.2 Organic-geochemical preparation........................................................................................................ 15 2.2.3 Catalytic hydropyrolysis (HyPy) ......................................................................................................... 15 2.2.4 Gas chromatography–mass spectrometry (GC–MS) ........................................................................... 16 2.2.5 Gas chromatography–combustion–isotope ratio mass spectrometry (GC–C–IRMS) ......................... 16 2.2.6 Raman spectroscopy ............................................................................................................................ 16 2.3 Results ........................................................................................................................................................ 16 2.3.1 Petrography, bulk-geochemistry and Raman spectroscopy ................................................................. 16 2.3.2 Bitumen ............................................................................................................................................... 18 2.3.2.1 Functionalized lipids .................................................................................................................... 18 2.3.2.2 Aliphatic hydrocarbons ................................................................................................................ 22 2.3.2.3 Polycyclic aromatic hydrocarbons (PAHs) .................................................................................. 23 2.3.3 Kerogen (high temperature HyPy step, up to 520 °C) ......................................................................... 23 2.3.3.1 Aliphatic hydrocarbons ................................................................................................................ 23 2.3.3.2 PAHs ............................................................................................................................................ 24 2.4 Discussion ................................................................................................................................................... 25 2.4.1 Thermal maturity and syngeneity of the organic matter ...................................................................... 25 2.4.2 Geobiology of the Lake Magadi during chert deposition .................................................................... 26 2.4.2.1 Prokaryotes................................................................................................................................... 26 2.4.2.2 Eukaryotes .................................................................................................................................... 26 2.4.2.3 Hydrothermal impact on organic matter ...................................................................................... 28 2.4.3 Organic signatures from the Magadi cherts: implications for the Archean ......................................... 29 2.5 Conclusions ................................................................................................................................................ 29 Acknowledgements........................................................................................................................................... 30 References ........................................................................................................................................................ 30 3 Ideas and perspectives: hydrothermally driven redistribution and sequestration of early Archean biomass—the “hydrothermal pump hypothesis” .................................................. 37 3.1 Introduction ................................................................................................................................................ 38 3.2 Material and methods ................................................................................................................................. 38 3.2.1 Sample preparation .............................................................................................................................. 38 3.2.2 Petrography and Raman spectroscopy ................................................................................................. 38 3.2.3 Raman-derived H/C data ..................................................................................................................... 39 3.2.4 Molecular analysis of the Dresser kerogen .......................................................................................... 39 3.2.5 Molecular analysis of pre-extracted cyanobacterial biomass (Anabaena cylindrica) ......................... 41 3.2.6 Fischer–Tropsch-type synthesis of organic matter under hydrothermal conditions ............................ 41 3.2.7 Gas chromatography–mass spectrometry ............................................................................................ 41 3.2.8 Polyaromatic hydrocarbon ratios ......................................................................................................... 41 3.2.9 Total organic carbon (TOC) and δ13C analyses (TOC and compound specific) ................................. 41 3.3 Results .......................................................................................................................................................