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Project Reports

• Life Underground

  Our multi-disciplinary team from the University of Southern California, California Institute of Technology, Jet Propulsion Lab, Desert Research Institute, Rensselaer Polytechnic Institute, and Northwestern University is developing and employing field, laboratory, and modeling approaches aimed at detecting and characterizing microbial life in the subsurface—the intraterrestrials. We posit that if life exists, or ever existed, on Mars or other planetary body in our solar system, evidence thereof would most likely be found in the subsurface. This study takes advantage of unique opportunities to explore the subsurface ecosystems on Earth through boreholes, mine shafts, sediment coring, marine vents and seeps, and deeply-sourced springs. Access to the subsurface—both continental and marine—and broad characterization of the rocks, fluids, and microbial inhabitants is central to this study. Our focused research themes require subsurface samples for laboratory and in situ experiments. Specifically, we are carrying out in situ life detection, culturing and isolation of heretofore unknown intraterrestrial archaea and bacteria using numerous novel and traditional techniques, and incorporating new and existing data into regional and global metabolic energy models.

  ROADMAP OBJECTIVES: 2.1 2.2 3.1 3.2 3.3 4.1 5.1 5.2 5.3 6.1 6.2 7.2

• Inv 1 – Geochemical Reactor: Energy Production at Water-Rock Interfaces

  INV 1 examines water-rock interactions in the lab and in the field, to characterize the geochemical gradients that could be present at water-rock interfaces on Earth and other worlds, taking into account different ocean and crustal chemistries. We have fully investigated serpentinization as the most likely of all possible environments for life’s emergence on Earth as well as other water-rich worlds – a key goal for astrobiology as stated in the NASA Astrobiology Roadmap 2008. (Russell, 2015). Serpentinization is now recognized as fundamental to delivering the appropriate chemical disequilibria at the emergence of life. And the fact that this process is likely inevitable on any icy, wet and rocky planet makes its study fundamental to emergence of life, habitability and habitancy. Nevertheless, notwithstanding the thermodynamic drives to CO₂ reduction during the process, great uncertainty exists over just what kind of organic molecules (if any) are delivered to the submarine springs and consequential precipitate mounds. In attempts to clarify what these might be we have undertaken thermodynamic modelling and experimental investigations of the serpentinization process.

  ROADMAP OBJECTIVES: 2.2 3.1 3.2 3.3 3.4 4.1

• ALTERNATIVE EARTH 1 – Atmospheric Traces of Oxygenic Photosynthesis

  The precise timing of the onset of oxygenic photosynthesis is a matter of intense debate. Current estimates span over a billion years of Earth history, ranging from prior to 3.7 billion years ago (Ga), the age of the oldest sedimentary rocks, to 2.4—2.3 Ga, coincident with the first permanent rise of atmospheric oxygen at the so-called “Great Oxidation Event” (GOE). Even without consensus on when biological oxygen production emerged, pinpointing the evolution of this process is essential for understanding Earth’s planetary evolution. If oxygenic photosynthesis evolved early, well before the permanent rise of atmospheric oxygen, the transition to a more oxidizing world in the Proterozoic is likely to be a reflection of Earth’s tectonic history, such as the emergence and stabilization of continents and related shifts in the temporal patterns of volcanism and associated fluxes of reduced gas. Alternatively, biological evolution (specifically, the emergence of oxygenic photosynthesizers) may have directly triggered this switch in Earth states. We are exploring these alternative models and their implications for the systematics of planetary oxygenation on Earth from a combined experimental, empirical and theoretical perspective.

  ROADMAP OBJECTIVES: 4.1 7.2

• Mars Analog Studies: Reflectance Spectroscopy of Organics in Ancient Rocks and Meteorites

  Aside from laboratory analyses of meteorites and in situ measurements by mass spectrometers on rover and lander platforms, the search for extraterrestrial organic material on Mars, carbonaceous© chondrite parent bodies, and other planetary surfaces is primarily limited to remote sensing techniques. Our team has been exploring the use of visible and near-infrared reflectance spectros-copy for assessing the presence and abundance of organic materials preserved in ancient terrestrial rocks and C chondrite meteorites. We have continued a series of controlled laboratory experiments to analyze (1) a suite of isolated kerogens and ancient terrestrial sedimentary rocks from various depositional environments and (2) several suites of synthetic clay-organic mixtures. Our goal is to better characterize the potential of reflectance spectroscopy as a method for organic detection and quantification in planetary environments, with the benefits that this technique is rapid, non-destructive, and applicable at laboratory, rover and orbital scales. The spectral models we are de-veloping will provide a foundation for quantifying organics that may be observed in spectroscopic data returned by the Hayabusa2 and OSIRIS-REx missions, laboratory spectra of C chondrites, and future Mars missions equipped with imaging spectrometers.

  ROADMAP OBJECTIVES: 2.1 4.1 4.3 6.1

• Project 1: The Origin of Homochirality

  Small biological molecules are frequently chiral, meaning that they can exist in both right-handed and left-handed forms. The two forms are identical except for the mirror symmetry that they break, and so would be expected to participate in chemical reactions in a way that does not depend on their chirality. When assembled into polymers, the resulting chains would therefore be expected to consist of a mixture of right and left-handed forms of the small molecules, a so-called racemic state. The surprise is that this is not true for the molecules of life. All chiral amino acids used by biology are left-handed and all chiral sugars are right-handed. That is, they are homochiral. This project is concerned with trying to find an explanation for this ubiquitous phenomenon, a universal aspect of all life on Earth. The specific question that is addressed is whether homochirality is a generic phenomenon of living systems, one that would be anticipated to arise if life were found elsewhere in the universe. Or is it instead some frozen accident related to the specific way that life arose on Earth? This question has been hotly debated in one form or other for over a hundred years, certainly since the time that Lord Kelvin coined the term “homochirality”. It is important for the Illinois NASA Astrobiology Institute for Universal Biology, because it is one of the two most evident universal phenomena of all life on Earth, the other being the universal genetic code. The phenomenon is important for another reason. The magnitude of the homochirality is 100%. It is not a slight imbalance in the abundance of right-handed vs. left-handed molecules. Thus, it is an unambiguous signal to measure, either from biological samples or remotely due to the effects of homochirality on the scattering of light waves. Specifically, homochiral solutions or suspensions will affect the polarization plane of electromagnetic waves, and so can readily be detected through optical means. The most exciting possibility in this regard is that if homochirality can be firmly established as a biological phenomenon, then its presence can be used as a biosignature of non-terrestrial life.

  ROADMAP OBJECTIVES: 1.2 3.2 3.4 4.1 4.2 7.1 7.2

• Inv 2 – From Geochemistry to Biochemistry

  INV 2 focuses on experimentally simulating the geological disequilibrium in hydrothermal systems, and determining the role of minerals in harnessing these gradients toward the emergence of metabolism. Biology utilizes metals (to speed up reactions) and “engines” (such as electron bifurcators, to couple endergonic and exergonic reactions); these components in modern metabolism strongly resemble specific minerals found in hydrothermal environments. We focus on simulating these primordial geological components and processes that might have led to the beginning of metabolism in a seafloor system on a wet rocky planet.

  ROADMAP OBJECTIVES: 3.1 3.2 3.3 4.1 7.1

• ALTERNATIVE EARTH 2 – Dramatic Oxygen Fluctuations

  Our studies of the middle portion of the Paleoproterozoic (2.2 to 2.0 Ga) are focused on whether Earth’s surface experienced a unidirectional oxygen rise or instead rose to high levels (potentially near-modern) and then crashed dramatically. More specifically, we are rigorously testing the idea that the middle Paleoproterozoic Earth was marked by high oxygen levels—in strong contrast to traditional arguments for far lower values. The resolution of this question is perhaps one of the most important issues in Earth history, as it points to the likelihood that the much later development of complex life was not solely contingent on high levels of oxygen at Earth’s surface. Work to date has focused on trying to place empirical constraints on ocean-atmosphere O₂ levels during the Paleoproterozoic and developing quantitative theoretical tools for understanding the dynamics of large shifts in ocean-atmosphere oxygen levels.

  ROADMAP OBJECTIVES: 4.1 7.2

• Understanding Past Environments on Earth and Mars

  In this task we performed research to understand the evolution of habitable environments on Earth and Mars, both of which serve as potential analogs for habitable environments on extrasolar planets. We are expanding this line of work from past reports to span the entire histories of both planets. On Earth, we have sought to understand environments and time periods spanning the origins of life to the effects of human-generated greenhouse gas emissions on modern-day climate cycles. On Mars, we focus on the ancient conditions that could have allowed liquid water to be stable at the surface; on modern Mars, we focus on the debate on the presence, amount, and variability of methane in the Martian atmosphere.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.2 5.1 5.2 6.1

• Mars Analog Studies: Mineral Assemblages in Terrestrial Settings

  It is now widely recognized that hydrated minerals, including clays, sulfates, chlorides and other salts, are important components of the martian crust. Such minerals and assemblages of minerals have the potential to record important information about past interactions between sediment, surface and groundwaters, and the atmosphere. The overarching theme of this project is to examine terrestrial analog sites to better understand how martian mineral assemblages may be used to infer these processes. Current sites include Rio Tinto, Spain and Lake Towuti, Indonesia. We have studied samples from the former and have determined that it may provide an appropriate mineralogical analog for enigmatic hydrous mineral-bearing terrains observed in Valles Marineris, Mars by orbiting spacecraft. Over the past year we have also begun to study mafic and ultramafic sediments in Lake Towuti to examine stratigraphic variations in Fe and Si-bearing mineral phases. Current results indicate these sediments and this lake system may be an appropriate mineralogical and/or chemical analog for ancient lacustrine sediments observed by the Curiosity rover in Gale Crater.

  ROADMAP OBJECTIVES: 2.1 4.1 4.3 6.1

• Project 3: Theory for the Darwinian Transition

  One of the key puzzles of astrobiology concerns the precision, uniqueness and rapidity of early evolution. In order for life to have evolved the main components of the modern cell as early 3.8 billion years ago, with a unique genetic code that is virtually optimal in terms of minimizing translational errors, the mode of evolution would have had to be different from the current vertical transmission of genes. We had shown in 2006 that the collective mechanism of horizontal gene transfer (HGT) is the only one capable of solving the puzzle of early evolution. The HGT means that the evolutionary process before LUCA can be thought of as a network of interactions rather than a tree, as would be the case in vertical gene transfer. The multiple connectivity of the network accelerates the evolution and allows rapid convergence to a unique, near-optimal genetic code. With all these advantages of HGT, why would it ever stop? Our project uses computer simulation of digital organisms in order to address these generic questions about the exit of life from the collective, progenote phase to the current era of vertically dominated evolution.

  This project is potentially important for understanding biosignatures of life. Even on Earth, we are familiar with the tree-like structure of individual organismal lineages. If life were a network, as we believe that it once was, the usual phylogenetic pattern of individuality and species would not apply. If we encounter life on other planets, we cannot be sure if it will be in the collective (progenote) phase or the vertical-dominated phase. Thus it is interesting to understand better the inexorability and timing of the Darwinian Transition.

  ROADMAP OBJECTIVES: 3.2 3.4 4.1 4.2 5.1 6.2

• Project 1C: Analysis of Dissimilatory Iron-Reducing Microbial Communities in Chocolate Pots Hot Spring, Yellowstone National Park

  This study represents the first targeted exploration of the active microbial community at source vent of Chocolate Pots hot springs (CP), a warm, circumneutral pH hot spring in Yellowstone National Park. This work was motivated by previous in vitro dissimilatory iron reducing (DIR) incubations of the native microbial community present in the Fe(III) oxide deposits (hereafter referred to as “CP oxides”) near the vent. DIR has the potential to generate distinct signatures of microbial Fe redox metabolism, and identification of the microbial assemblages involved in this metabolism is important for making a concrete linkage between biological metabolism and the generation of geochemical and isotopic biosignatures in relation to redox gradients on Earth and other rocky planets. The central goal of this study was to obtain a phylogenetic and metagenomic characterization of the active acetate-oxidizing DIR community at CP using ¹³C stable isotope probing (SIP) techniques. CP oxide sediments and spring water were collected from the CP vent source and used to initiate in vitro SIP incubations using labeled (¹³C) and unlabeled acetate. Incubations targeted the active microbial community which is capable of coupling the oxidation of acetate to DIR. The SIP results allowed us to clearly separate the active acetate-metabolizing microbial community from the rest of the community and identify which organisms native to CP make up this population. The role of some members of this community can be inferred with reasonable confidence from the phylogeny of the OTUs from the amplicon libraries (e.g. Geobacter, Ignavibacteria), and the design of the incubations. The metabolic role of other dominant taxa is less well understood at this point and we are preparing to submit samples for shotgun metagenomic sequencing to address these questions.

  ROADMAP OBJECTIVES: 2.1 4.1 5.1 5.3

• Astronomical Biosignatures, False Positives for Life, and Implications for Future Space Telescopes

  In this task, we identify novel biosignatures and also identify “false positives” for life, which are ways for non-biological processes to mimic proposed biosignatures. Of primary concern are false positives that could mimic easier to detect biosignatures like O₂, which we plan to search for with future space-based telescopes. This is a growing area of research that VPL’s past work has motivated, leading to multiple research teams across the planet following our example. Our work continues to be at the forefront of this area of work, as we have identified new non-biological mechanisms for mimicking signs of life. Further, we explained the ways in which these non-biological mechanisms could be identified, and “true positives” from biology confirmed with secondary measurements. Finally, we communicated these lessons to various teams that are studying concepts for future missions that would search for these signs of life. This connection to missions will ensure that our research is incorporated into those missions, so that they will not be “tricked” by these false positives.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.3 5.2 5.3 7.2

• ALTERNATIVE EARTH 3 – Oxygen Stasis and the Rise of Eukaryotes

  The importance of a full understanding of the controls on ocean-atmosphere O₂ levels during the mid-Proterozoic is difficult to overstate. The evolution of O₂ levels in the mid-Proterozoic ocean-atmosphere system forms the backdrop for the initial emergence and subsequent evolutionary stasis of eukaryotic life. Furthermore, it provides the possibility of a remarkably long period of Earth’s history during which many of the links among tectonics, climate, and life may have been short-circuited and/or amplified in unusual ways. Finally, it provides the preface that is essential reading for any story about the proximate causes of the subsequent emergence of complex life in the late Neoproterozoic. The central question in this regard is whether ocean-atmosphere O₂ levels were low enough to inhibit the evolution and ecological emergence of complex multicellular life, or must we seek mechanisms strictly associated with internal biology to explain this event—or both? Our developing framework for very low oxygen levels during the mid-Proterozoic in the deep ocean, shallow ocean, and atmosphere is the baseline against which the dramatic environmental, climatic, and biotic events and triggers of the later Proterozoic should be assessed.

  ROADMAP OBJECTIVES: 4.1 4.2 7.2

• Project 1D: Comparative Genomic Analysis of Chemolithotrophic Fe(II)-Oxidizing Bacteria

  A comparative genomic analysis was performed to identify candidate genes involved in extracellular electron transfer (EET) by Fe(II)-oxidizing bacteria (FeOB). The analysis included a variety of publically-available FeOB genomes, together with genomes from FeOB isolated from subsurface sediments, previously-isolated marine basalt-associated FeOB, and metagenomes from chemolithoautotrophic aerobic pyrite-oxidizing and nitrate-reducing Fe(II)-oxidizing enrichment cultures. We identified outer membrane multi-copper oxidase (MCO) genes homologous to proteins known to be involved in EET in several of the FeOB genomes, as well as homologs to the outer membrane c-type cytochrome (ctyc) Cyc2 known to be involved in bacterial Fe(II) oxidation by Acidithiobacillus ferrooxidans under acidic conditions. Further, we found gene clusters that may potentially encode novel “porin-cytochrome-c protein complex” (PCC) in the well-known neutral-pH FeOB S. lithotrophicus ES-1, and homologous operons were found in other recognized FeOB (Leptothrix cholodnii SP-6 and Leptothrix ochracea L12. Another gene cluster consisting of a porin and three periplasmic multiheme cytc was identified in Hyphomicrobium sp. genome retrieved from a pyrite-oxidizing enrichment culture, and its homologous gene clusters are also present in five marine Zetaproteobacterial FeOB genomes. Overall, this analysis, which is based on our current understanding of bacterial EET in Fe redox reactions, provides a list of candidate genes for further experimental and genomic studies.

  ROADMAP OBJECTIVES: 2.1 3.2 4.1 5.1 5.3

• Subsurface Serpentinization Processes and In-Situ Microbial Life in Oman

  The Rock-Powered Life team has initiated several field-based efforts in Oman focused on characterizing the geochemistry and microbial community structure and activity within massive exposures of peridotites undergoing low-temperature serpentinization. In this project, we are using deep wells drilled hundreds of meters into peridotite catchments to access waters stored in the deep subsurface, and to capture the mineralogical and biological processes that give rise to hyperalkaline fluids rich in dissolved H₂ and CH₄. In particular we extract biomass from the fluids for genetic sequencing in order to identify the types of life that can live within the extreme conditions of low energy and carbon availability, and to infer the metabolisms that sustain in-situ life activity. These analyses are paired with mineralogical analyses of the subsurface rocks and isotopic analyses of the dissolved gases in order to quantify the water/rock reactions occurring in the modern system that give rise to energy transfer from the rocks to living ecosystems.

  ROADMAP OBJECTIVES: 3.1 4.1 5.3 7.2

• ALTERNATIVE EARTH 4 – the Rise of Complexity Amid Environmental Turmoil

  Climatic turmoil and major upheavals in global biogeochemical cycles characterize the latter part of the Proterozoic Eon, during the so-called Neoproterozoic (1,000–541 million years ago). The Neoproterozoic was marked by pronounced shifts in atmospheric composition—especially increased oxygen levels. This environmental instability provided the backdrop for the rise of complex life, including animals; however, limited empirical constraints have hindered attempts to untangle the cause-and-effect relationships among biological innovations, shifts in ecosystem complexity, and biogeochemical evolution. Likewise, still sparse coupled geochemical and paleontological records make it difficult to gauge whether the Neoproterozoic unfolded as a unidirectional march toward greater organismal complexity and higher oxygen levels, as traditionally envisioned, or whether dramatic swings in surface oxygen levels accompanied non-unidirectional ecological shifts. To resolve this debate, we are producing extensive, high-resolution records of oxygen levels and tracking the distribution, abundance, and impact of eukaryotic phytoplankton over this critical interval. Our central goal is to work synergistically with the Origins of Complexity NAI Team to better understand how the rise of complex life shaped planetary-scale biosignatures.

  ROADMAP OBJECTIVES: 4.1 4.2 7.2

• Project 1E: Studies of Early-Evolved Enzymes in Modern Organisms May Reveal the History of Earth’s Ambient Temperature Over Geological Time

  By addressing a focused question — “Does the thermal stability of the reconstructed ancient enzymes of modern organisms provide evidence of the temperature of the environment in which the enzymes originated?” — this study asks a much broader question, namely, “can the biochemistry of extant life provide evidence of ancient environments?” In the geological record, there is virtually no mineralogical evidence to determine ambient surface temperature and data from other sources are ambiguous, contradictory and contentious. By analyzing the thermal stability of ancient reconstructed ancient enzymes, this work may pave the way to solve this fundamental problem and, by doing so, demonstrate a new way to understand the co-evolution of life and its planetary environment.

  ROADMAP OBJECTIVES: 4.1 6.1

• Evolution of Precambrian Life and Primary Producers

  Life on Earth is sustained by photosynthesis, both on land and in the sea. New research provides novel perspectives on the evolution of diatoms, responsible for 25% of all photosynthesis in today’s oceans. Also, new fossils from Russia strengthen the relationship between early eukaryotes and environmental conditions in Proterozoic oceans.

  ROADMAP OBJECTIVES: 4.1 4.2 6.1

• Exploring the Evolution of the Water and Organic Reservoirs in the Solar System

  This project investigates the evolution and stability of water and organic reservoirs in our Solar System, with particular emphasis on the characterization of the current and ancient habitability of planet Mars. We employ extremely powerful observatories (e.g., ALMA, Keck, VLT, future JWST) to acquire high spatial and spectral resolution maps of the isotopic and organic signatures on several bodies in the Solar System. These maps allow us to investigate the stability and evolution of their atmospheres, while localized plumes can be used to identify regions of active release. In this reporting period, we emphasized three areas:

  1. We advanced our pioneering work on characterizing the evolution of water on Mars, by developing a new observational plan that combines the power of ALMA, of Keck and of MAVEN to obtain maps of the water D/H signatures on Mars.

  2. We identified previously unknown chemical processes affecting singlet-O₂ and odd-oxygen on Mars, which may be indicative of a much more active photochemical cycle (with the possible intervention of heterogeneous processes).

  3. We provided science leadership in the investigation of Mars with the James Webb Space Telescope (JWST), and established a variety of observing modes and scientific opportunities.

  ROADMAP OBJECTIVES: 1.1 2.1 3.1 3.2 4.1 7.1

• High Temperature W/R Hosted Microbial Ecosystems in Yellowstone

  Geochemical data indicate that life on early Earth was dependent on chemical forms of energy. This attribute, when coupled with phylogenetic data indicating that early evolving forms of life were thermophilic, lead many astrobiologists to believe that life evolved in a high temperature environment and was dependent on chemical forms of energy to sustain its metabolism.

  Hydrothermal environments with temperatures >70ᵒC exclude life dependent on light energy, leaving only those life forms that can sustain themselves using chemical energy. The >14,000 hot springs in Yellowstone National Park therefore provide a unique field-based early Earth analog environment to examine the processes that sustain life dependent on chemical energy and to investigate the metabolic processes that sustain this life. Moreover, the chemical and physical variation present in these environments affords the opportunity to examine how this variation drove the diversification of life in these early Earth analog environments. RPL investigations in hot spring environments in Yellowstone in 2015 centered on answering questions related to the array of energy and carbon sources available to chemosynthetic life, the preferred carbon sources supporting this life, and the role of hydrogen transformation in the metabolisms of these organisms. By answering these interrelated questions, we will provide a framework by which we can use to begin to understand the processes that most likely sustained microbial life on the early Earth. Since it is possible, if not likely, that such processes would also sustain early life on other planetary bodies, this research has the potential to guide the search for life in non-Earth environments.

  ROADMAP OBJECTIVES: 3.2 3.3 4.1 5.2 5.3 6.1

• Early Animals: Evolution of Complex Multicellularity

  Oxygen availability has long been viewed as a principal deriver of Ediacaran-Cambrian animal diversification, yet quantitative constraints on oxygen history and physiological constraints on animal function at low pO2 have been limited. New statistical analyses of iron-sepciation data for Proterozoic and Paleozoic shales indicate that end-Proterozoic oxygen increase was limited, but physiologial insights from present day oxygen minimum zones indicate that oxygen levels may well have crossed the theshold reuqired from large diverse animals that include carnivores.

  ROADMAP OBJECTIVES: 4.1 4.2

• Planetary Surface and Interior Models and SuperEarths

  We use computational and theoretical models to simulate the evolution of the interior and the surface of real and hypothetical planets around other stars. Our goal is to determine the characteristics that are most likely to contribute to making a planet habitable in the long run. Observations in our own Solar System show us that water and other essential materials are continuously consumed via weathering (and other processes: e.g., subduction, sediment burial) and must be replenished from the planet’s interior via volcanic activity to maintain a biosphere. The surface models we are developing will be used to predict how gases and other materials will be trapped through weathering and biological processes over time. Our interior models are designed to predict tidal effects, heat flow, and how much and what sort of materials will come to a planet’s surface through resurfacing and volcanic activity throughout its history.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 5.2 6.1

• Project 2A: Application of the 13C-18O Clumped Isotope Thermometer to the Ancient Earth

  Application of the clumped isotope thermometer in carbonates, which is based on preferential bonding between ¹³C and ¹⁸O, offers the possibility of testing controversial proposals based on conventional stable isotope thermometry that the early Earth’s oceans were hot. In this project, we report on the results of a study of clumped isotope thermometry of the Neoarchean Campbellrand carbonate platform of South Africa. This platform is the best preserved Archean carbonate sequence known and was subjected to only very low grades of metamorphism, and hence offers the best opportunity to determine seawater temperature for the late Archean oceans. Comparison of clumped isotope temperatures retrieved from co-existing calcite and dolomite confirm that resetting of clumped isotope temperatures occurs at different rates for these minerals, where dolomite is closest to preserving primary temperatures. Despite slower re-equilibration rates for dolomite, however, the fact that the Campbellrand platform was buried at temperatures up to 170 oC for ~2 b.y., prevents use of clumped isotope thermometry from preserving Archean seawater temperatures. This would likely not be the case for carbonates on Mars, where early Mars carbonates would have had a relatively low temperature thermal history, suggesting that clumped isotope thermometry for Mars carbonates is a promising approach for determining ancient surface temperatures on Mars.

  ROADMAP OBJECTIVES: 4.1 5.2 7.1

• Global Surface Biosignatures: Reflectance Spectra of Anoxygenic Phototrophs and Cyanobacteria

  This project investigates the spectral reflectance signature of anoxygenic photosynthetic bacteria, as an alternative to the “biosignature” of the vegetation “red-edge.” The vegetation red-edge is so called due to the sharp contrast in visible light absorbance by light harvesting pigments in plant leaves versus their high reflectance in the near-infrared (NIR). This contrast occurs around 700 nm in the red/far-red. This signature is ubiquitous among plants, which all utilize chlorophyll a. However, anoxygenic phototrophs contain a diverse array primary photopigments, including bacterichlorophylls (Bchl) a, b, d, e, and g. These Bchl pigments display different absorption maxima with peaks primarily in the NIR. There is an abundance of data on plant spectral reflectance thanks to the Earth remote sensing field. However, there is a dearth of data on anoxygenic phototrophs and cyanobacteria. For this project, we measured the reflectance spectra of pure cultures as well as environmental samples of laminated microbial mats to characterize their detectable biosignature features. This work will help inform the search for life on exoplanets at a similar stage of evolution or biogeochemical state as the pre-oxic Earth.

  ROADMAP OBJECTIVES: 4.1 5.2 7.2

• Project 7: Mining Archaeal Genomes for Signatures of Early Life: Comparison of Metabolic Genes in Methanogens

  Methanogens represent the largest diversity among the archaea and have the unique ability to generate methane from simple compounds such as carbon dioxide, acetate and methylamines which were common in the anaerobic environments of early Earth and perhaps Mars. Methane biosynthesis also requires the presence/uptake of important ions such as sulfates, sulfides, carbonates, phosphates, and various light metal ions. In this project, we are attempting to analyze the evolution of the methanogens’ central cellular functions of translation, transcription, replication, and metabolism. To accomplish this, we are constructing the metabolic and regulatory networks of Methanosarcina acetivorans, the most complex methanogen known, and using these models to establish a framework for studying the evolution of methanogens. Results will be tested through microfluidic studies using varying carbon and ion sources.

  ROADMAP OBJECTIVES: 1.1 2.1 3.1 3.2 3.3 3.4 4.1 4.2 5.1 5.2 5.3 6.1 6.2 7.1

• Advances in Gene Sequencing From Low-Biomass Water-Rock Hosted Ecosystems

  One of the approaches our team is taking to explore rock-powered life is to study microorganisms hosted within rocks that are undergoing potentially life-supporting reactions with water. The chemistry of the rock microenvironments shapes the abundance, diversity and distribution of microbial life. In turn, that microbial life locally affects the in-situ geochemistry. This project is currently focusing on the successful extraction and sequencing of the exceedingly small amounts of DNA that accumulates within rocks, in order to successfully detect and characterize the rock-hosted life. Ultimately our improved approaches will support the application of next-generation DNA sequencing technology in the study of natural microbial ecosystems that are key for understanding the mechanisms of rock-powered life.

  ROADMAP OBJECTIVES: 3.2 4.1 5.1 5.2 5.3 6.1 7.2

• Early Animals: Taphonomic Controls on Fossil Record

  This project has focused on Neoproterozoic life with an emphasis on factors influencing fossil preservation. A combination of field and experimental approaches has been used to study preservation of Ediacara-type fossils and to test the prevailing ‘death-mask’ hypothesis that considers iron sulfides to have been a primary agent. Results so far indicate that ferruginization was a late-stage process and not consistent with this model suggesting an important role for early silicification. Initial experimental results show that microbial mats are prone to silicification and that their presence in association with invertebrate carcasses inhibits decay and enhances the preservation of soft-bodied organisms. An investigation of factors controlling the preservation of eukaryotic microfossils in Proterozoic rocks is also underway. Experimental data indicate that certain clays inhibit the growth of decay bacteria such as Pseudoaltermonas.

  New fossil assemblages from grey shales and cherts have been discovered from this same interval – a significant development because very few fossils have been described from rocks between the two Snowball Earth ice ages. The preponderance of exceptional preservations in the Cambrian and subsequent early Paleozoic may be explained in part by a delay in intense mixing of marine shelf sediments by bioturbators, which did not develop until the Devonian. This slow onset of thorough mixing may also have contributed to the late rise of sulfate in the oceans and a mid-Paleozoic drop in oxygen levels.

  ROADMAP OBJECTIVES: 4.1 4.2

• Characterization of Habitability and Biosignature Preservation in Cold Springs

  In an increasingly colder Mars where permafrost was thickening, mineralizing cold springs could have provided extant subsurface habitats and a means to transport evidence of subsurface life to the surface. Depending on conditions and geochemistry, these precipitates could have encapsulated a record of past life, and the residual remnants of such spring mounds could still be exposed at the martian surface. On Earth, high latitude spring systems are rare due to the relatively impermeable permafrost. However, several groups of perennial springs are located at Axel Heiberg Island in the Canadian High Arctic (~80°N). With mean annual air temperatures of -17°C and permafrost depths ≥ 600 meters, these springs flow throughout the year despite minimum air temperatures reaching <-50°C during winter. Thick residual icing pastes form as a result of evaporation, sublimation and freeze fractionation, the mineralogy being dominated by halite, hydrohalite, calcite, gypsum, elemental sulfur, thenardite, and mirabilite. These springs provide an environment where prokaryotes thrive despite extreme conditions and their presence suggests that such systems could have been present throughout Mars history, and activated during cyclical climate changes.The primary goal of this investigation is to evaluate the potential of spring deposits in regions with thick, continuous permafrost and define their taphonomic window and biogeological context. Samples of icing pastes, travertine and other mineral precipitates have been sampled to understand the relationships between geochemistry, environment, presence of biosignatures and their potential preservation.

  ROADMAP OBJECTIVES: 2.1 4.1 7.1

• Rock Powered Life: Education and Communications

  The central theme of the Rock Powered Life research effort is to define how, where and when water/rock interactions release energy and how this energy is harvested to support microbial communities. These studies are of fundamental importance for improving understanding of how microbial life was supported on early Earth. Moreover, since similar reactions can be expected on any rocky planet with liquid water, these studies provide new constraints for predicting the distribution of life on other planetary bodies.

  The focus of our team – rock-hosted microbial ecosystems that are dependent on chemical rather than light energy – provides novel avenues to engage the next generation of astrobiologists and to disseminate knowledge to the broader public. Here we describe current and ongoing efforts by members of Rock Powered Life that are aimed at improving engagement and training in astrobiology. Of particular relevance are efforts to provide opportunities to provide underrepresented high school and undergraduate students hands on training opportnities in astrobiology-focused studies. We also describe advancements in Rock Powered Life’s digital-based information sharing technologies. Through these integrated team efforts we aim to attract and train future generations of astrobiologists and to provide greater access to the current knowledge base with which to understand the potential for life elsewhere on other planetary bodies.

  ROADMAP OBJECTIVES: 3.2 4.1 4.2 5.1 5.2 5.3 6.1 6.2

• Lake Sediment Habitats; Lake Habitability and Sediment Biosignatures

  Regions where lakes and ponds existed once existed on Mars martian are among the highest priority environments for exploration. The physicochemical and biological characteristics of the unique of perennially ice-covered lake ecosystems found on earth in Antarctica, the High Arctic, and in high altitude environments (Altiplano and High Andes) serve as important analogs of earily Mars. Active and abundant microbial communities live in these extreme environments, suggesting the presence of habitable conditions on early on Mars. Unlike temperate lakes, these ecosystems are largely dominated and constrained by their physical environment (e.g., mean annual temperatures near or well below 0°C, with arid or hyper-arid conditions year-round). In these environments, lake sediments accumulate organic biosignatures due to relatively low metabolic rates and cold water. Less understood is their preservation potential once the water evaporates, and sediments are exposed to extreme cold and hyper-arid conditions. Perennially ice-covered lakes are rare on Earth. Their dry, paleo-counterparts are even more exotic, and biosignature preservation in such lake deposits remains largely unstudied. Lake Untersee, one of the largest perennially ice-covered surface lakes in East Antarctica hosts a robust microbial ecosystem including the presence of photosynthetic microbial mats that colonize the lake bottom to depths greater than 100m. These mats are primarily composed of filamentous cyanophytes and form two distinct macroscopic structures – cm-scale cuspate pinnacles dominated by Leptolyngbya spp. and laminated, large conical stromatolites that rise up to 0.5 m above the lake floor, dominated by Phormidium spp. (Andersen et al. 2011). Adjacent to Lake Untersee is the Aurkjosen Cirque, a basin that was once inundated by a large lake which has since evaporated. Desiccated, buried microbial mats have been recovered from this paleo- lacustrine site, and they provide material for the identification of biosignatures and their preservation in and extremely cold setting. Our investigations include the studies of the physical and biogeochemical characteristics of the two lakes, deposition and preservation of biomarkers, and in situ analytical techniques (IR reflectance, Raman, XRD/XRF) to identify organic signatures within a mineralogical context while developing synergistic operational concepts for in situ analyses in paleolake analogs.

  ROADMAP OBJECTIVES: 2.1 4.1 7.1

• Mars Analog Studies: Ice Covered Lakes on Earth and Mars

  Ice-covered lakes in Antarctica provide models for sedimentary processes on ancient Mars and microbial ecosystems for early Earth. Ice affects sedimentation because sand grains can be blown onto the ice, where they can eventually go through the ice into the lake below. Understanding the details of these processes and resulting sediments will allow us to better reconstruct details of lake environments and their implications for climate on early Mars. Early Earth ecosystems, and those on early Mars if life ever existed there, consist exclusively of microorganisms, which is also true for many Antarctic lakes. Thus, these lakes provide the opportunities to investigate ecological principles for early ecosystems. Data from the microbial mats in these lakes are providing insights into the growth of stromatolite, the geochemical impacts of oxygen-producing photosynthesis, and environments that may have promoted the early diversification of animals.

  ROADMAP OBJECTIVES: 2.1 4.1 4.2 5.1 5.2 6.1

• Global Surface Biosignatures: Circular Polarization Spectra of Anoxygenic Phototrophs and Cyanobacteria

  This new project focuses on characterizing the chiral signature of biological molecules. The phenomenon of chirality is a powerful biosignature and, in principle, can be remotely observed on planetary scales using circular polarization spectroscopy. Molecules such as photosynthetic pigments are optically active and have several chiral centers, and influence the polarization of light. This can be measured using full Stokes spectropolarimetry. The goal of this interdisciplinary project is to characterize the circular polarization spectra of chiral photosynthetic pigments in anoxygenic phototrophs and cyanobacteria as global surface biosignatures.

  ROADMAP OBJECTIVES: 4.1 5.2 7.2

• Project 3A: Apatitic Latest Precambrian and Early Cambrian Fossils Provide Direct Evidence of Concentrations of Environmental Oxygen

  Means are not currently available to asses either quantitatively or semi-quantitatively the concentration of oxygen in Earth’s atmosphere over geological time. Despite this, the environmental availability of O₂ has been repeatedly postulated to be a cause of major changes in Earth’s biota, most particularly at the Precambrian-Cambrian boundary-defining “Cambrian Explosion of Life,” a time in Earth history when large deposits of phosphate-rich apatite were deposited in shallow basins worldwide. This study shows that substitution of Sm+3 in the Ca I and Ca II sites of fossil-permineralizing, -infilling, and -encrusting apatite can differentiate between oxic, dysoxic, an anoxic settings of apatite formation. Further studies are underway to date such apatite and establish its REE-substitution as a quantitative O₂ paleobarometer.

  ROADMAP OBJECTIVES: 4.1 4.2

• Eva Stüeken NPP Postdoc Report

  I study the non-marine sedimentary rock record to determine if lakes and rivers could have been important habitats for the early evolution of life on Earth. Our results suggest that the greater environmental diversity found in non-marine settings may enhance biological diversity. However, we cannot confirm previous conclusions that lakes were particularly suited for eukaryotic life. These findings may provide clues about potential biodiversity of other worlds that are characterized by smaller lake basins (e.g. early Mars) versus a global ocean (e.g. Europa).

  ROADMAP OBJECTIVES: 4.1 4.2 6.1

• Physiology of Microbial Populations From W/R Hosted Ecosystems

  Microbial communities supported by chemical energy (chemotrophic communties) released through water / rock interactions are widespread in contemporary Earth environments, including the subsurface where light is excluded and in surface environments where physical or chemical conditions preclude photosynthetic metabolisms. Chemotrophic microorganisms are key targets of astrobiological investigation due to the strong likelihood that they predate photosynthetic metabolisms and because they can be physiologically tested to define the habitable limits for life on Earth, including those associated with extremes of temperature, pH, salinity, and energy availability. Research by RPL scientists is focused on identifying and characterizing the physiological strategies or mechanisms that allow life to persist under extreme conditions at the habitable limits. By combining this information with phylogenetic approaches, we aim to determine how and when these mechanisms evolved and what role they played in the diversification of early life. As such, this research effort is highly interdisciplinary and employs both traditional (e.g., activity assays, cultivation) and contemporary (genomics, transcriptomics, metabolomics) microbiological approaches in combination with geochemical approaches. In addition, RPL investigators are studying the evolution of these communities to hone in on the nature of key physiological processes (e.g., central carbon metabolism, nitrogen metabolism, and iron-sulfur metabolism) in chemotrophs prior to the onset of photosynthetic metabolisms. Field-based RPL investigations of microbial physiology in water/rock ecosystems to date have focused on populations inhabiting subglacial environments (cold-adaptation), hot springs (adaptation to acidity, high temperature), and subsurface peridotite environments (adapation to energy stress, nutrient stress, alkalinity).

  ROADMAP OBJECTIVES: 3.1 3.2 3.3 4.1 5.1 5.2 5.3

• Project 3B: Biologically Recycled Continental Iron Is a Major Component in Banded Iron Formations

  Combined Fe- and Nd-isotope signatures suggest that banded iron formations (BIFs) contain a major component of continentally derived iron that was mobilized by microbial iron reduction followed by transport through an iron shuttle to the site of BIF formation in deep basin environments. This Fe source is in addition to the widely accepted submarine hydrothermal source of Fe in BIFs, and the two sources of Fe may be comparable in importance, although their proportions change over time dependent on basin-scale circulation. These results document a vigorous, basin-scale biological cycle for Fe at least 2.5 b.y. ago.

  ROADMAP OBJECTIVES: 4.1 5.2 7.1

• Project 3C: A Redox-Stratified Ocean 3.2 Billion Years Ago

  A novel combination of stable Fe and radiogenic U–Th–Pb isotope data that demonstrate that significant oxygen contents existed in the shallow oceans at 3.2 Ga, based on analysis of the Manzimnyama Banded Iron Formation (BIF), Fig Tree Group, South Africa. This unit is exceptional in that proximal, shallow-water and distal, deep-water facies are preserved. When compared to the distal, deep-water facies, the proximal samples show elevated U concentrations and moderately positive 56Fe values, indicating vertical stratification in dissolved oxygen contents. Confirmation of oxidizing conditions using U abundances is robustly constrained using samples that have been closed to U and Pb mobility using U–Th–Pb geochronology. This documents the oldest known preserved marine redox gradient in the rock record. The relative enrichment of O₂ in the upper water column is likely due to the existence of oxygen-producing microorganisms such as cyanobacteria. These results provide a new approach for identifying free oxygen in Earth’s ancient oceans, including confirming the age of redox proxies, and indicate that cyanobacteria evolved prior to 3.2 Ga.

  ROADMAP OBJECTIVES: 4.1 5.2 7.1

• Charnay NAI NPP PostDoc Report

  My project focuses on the modeling of clouds and photochemical haze in the atmospheres of the early Earth and exoplanets. I use a 3D model, developed to simulate any kind of atmosphere, to study the formation, dynamics, climatic impact and observational features of clouds/haze. My first object of interest is GJ1214b, a mini-Neptune whose observations by HST revealed a cloudy/hazy atmosphere. The formation of such high and thick clouds is not understood. My second object of interest is the Archean Earth for periods with a methane-rich atmosphere leading to the formation of organic haze.

  ROADMAP OBJECTIVES: 1.2 4.1

• Biogenic Gases From Anoxygenic Photosynthesis in Microbial Mats

  This lab and field project aims to measure biogenic gas fluxes in engineered and natural microbial mats composed of anoxygenic phototrophs and anaerobic chemotrophs, such as may have existed on the early Earth prior to the advent of oxygenic photosynthesis. The goal is to characterize the biogeochemical cycling of S, H, and C in an effort to constrain the sources and sinks of gaseous biosignatures that may be relevant to the detection of life in anoxic biospheres on habitable exoplanets.

  ROADMAP OBJECTIVES: 4.1 5.2 6.1 7.2

• Project 3D: SIMS Analyses of Filamentous Fossil Microbes From the ~3,465 Ma-Old Apex Chert May Reveal Their Physiology

  Permineralized carbonaceous filamentous fossils of the ~3465 Ma Apex chert of Western Australia are among the oldest known in the geological record. Eleven taxa of Bacteria Incertae Sedis (microbes of uncertain systematic affinities) have been described from this assemblage, defined on the basis of the medial and terminal cell size and shape of 200 specimens. To assess their physiology and, thus, their biological affinities, 20 additional specimens, referable to six of the taxa, have been prepared in thin section. Samples will be cut out and repolished to expose each microfossil individually for δ¹³C analyses by use of secondary ion mass spectroscopy (SIMS). Their carbonaceous composition has been mapped by Raman spectroscopy and, as applicable, by confocal laser scanning microscopy, CLSM. This is the first study to use optical microscopy, Raman spectroscopy, SIMS and CLSM, to analyze multiple individual microscopic fossils from a single deposit — applied here to among the oldest fossils now known in the geological record.

  ROADMAP OBJECTIVES: 4.1

• Early Animals: Modeling the Biotic-Abiotic Interface in the Early Evolution of Multicellular Form

  Multicellular organisms in the sea modify their local hydraulic environment. Modeling of the earliest-known multicellular communities of frond-like forms demonstrated that they were large enough and closely spaced enough to generate a distinctive canopy flow-regime. In this context diffusion at the surface of organism was limiting and height and attendant velocity exposure permitted escape from these limits (Ghisalberti et al. 2014). Building on these results, we are developing models of abiotic/biotic interactions at organismal surfaces, relevant to the morphology, development and orientation of other Neoproterozoic fossils. A subset of these are flat-lying forms such as Dickinsonia. These may interact with the sediment modifying redox gradients. Ultimately, this work will help illuminate how forms initially dependent on passive diffusion became more trophically, morphologically and behaviorally complex, during the diversification of animals.

  ROADMAP OBJECTIVES: 4.1 4.2 5.2 6.1

• Project 3E: Genesis of High-δ18O Archean Chert, Pilbara Craton, Australia

  The cherts of the Strelley Pool formation host the oldest generally accepted evidence of life, stromatolites, organic matter and microfossils. Oxygen isotope ratios provide independent evidence to evaluate conditions when quartz formed. These results support habitable conditions during formation of early quartz and late alteration for genesis of late high δ¹⁸O-quartz.

  ROADMAP OBJECTIVES: 1.1 4.1 7.1

• Early Animals: Sensory Systems and Combinatorial Codes

  Understanding the evolution of integrated sensory organs—such as the eyes, ears and nose that develop in concert on our heads—is fundamental to understanding animal complexity. These are the features that permit movement and the environmental responses that characterize animals. We examine understudied early branches of the animal family tree, with a focus on the jellyfish Aurelia, to understand how the genetic regulation of sensory organs is conserved in some cases and evolves in others. Comparison of developmental regulation reveals how similar gene networks can be differentially modified and deployed, permitting the evolution of complex sensory systems. Jellyfish provide an ideal study system for the examination of the evolution of such sensory systems in animal evolution, as they are the most basal branch of the animal tree with multiple sensory modes, and these develop at multiple stages in a complex life history. This provides us the ability to compare and contrast within the broader cnidarian group to which jellyfish belong, and to the bilaterians, the broad group containing humans and most other animals. The application of genomic methods greatly enhances our ability to pursue these questions.

  ROADMAP OBJECTIVES: 4.1 4.2

• Project 3F: Searching for Ancient Impact Events Through Detrital Shocked Zircons

  Understanding how quickly planetary surface environments evolve on newly accreted worlds is critical for predicting when habitable conditions are established. The meteorite impact history of the inner solar system strongly indicates that the Earth was subject to a global impact bombardment during the first few hundred million years after accretion. The scope, timing, and consequences of this profound process are hotly debated. This project investigated populations of detrital zircons in Archean sedimentary rocks to search for tell-tale signs of impact processes in the form of shock-induced microstructures that are diagnostic of impact. Such features have been shown to survive in detrital shocked zircons eroded from known impact structures on Earth, including the Vredefort, Sudbury, and Santa Fe craters. We have investigated populations of 1,000 zircons per sample using backscattered electron imaging of grain exteriors with a scanning electron microscope. Thus far we have surveyed zircons separated from rocks collected from the Yilgarn craton (Australia), North China craton (China), Wyoming craton (USA), the Superior craton (Canada). While intriguing microstructures have been observed, thus far no confirmed shock microstructures have been encountered in our Archean sample suites. Our inability the identify shocked grains in populations of 1,000 zircons (per sample) does not necessarily mean shocked grains are absent; our results provide constraints that if they are present, they are in abundances of <0.1% in the detrital population of the rocks investigated. We are currently in the process of more in-depth surveying (e.g., >1000 grains/sample) to test for very low frequency occurrency events. Our detailed search continues…

  ROADMAP OBJECTIVES: 1.1 4.1 4.3

• Taphonomy of Microbial Ecosystems

  We perform experiments to understand shapes, molecules and isotopic signals of microbial processes in modern and old sediments. Experimental studies of microbial interactions with sediments, ions in the solution and the flow help us elucidate mechanisms that may have shaped sandy surfaces and preserved fossils on these surfaces at the dawn of animal life. Culture-based studies of isotopic fractionations produced by microbial processes and microbial membrane lipids help us interpret corresponding signals in the rock record and modern environments.

  ROADMAP OBJECTIVES: 2.1 4.1 4.2 5.1 5.2 6.1 7.1 7.2

• Early Animals: The Origins of Biological Complexity

  We seek to understand the interactions of ecological, environmental and developmental processes that generate biological novelty and innovation, with particular emphasis on the events associated with the origin and early evolution of animals. The larger goal is to develop a general model of novelty (the origin of new organismal characters) and innovation (the ecological and evolutionary success of these novelties) and determine whether it applies through the history of life. Alternatively episodes of novelty and innovation may be dominated by historical contingency so that no general model can be developed.

  ROADMAP OBJECTIVES: 4.1 4.2

• Project 3G: A 3,400 Ma-Old Shallow Water Anaerobic Sulfuretum Evidences the Anoxic Archean Atmosphere

  Carbonaceous cherts of the ~3430 Ma Strelley Pool Formation contain innumerable “swirls” of fossilized sulfuretum bacteria encompassing quartz-replaced anhydrite nodules intermixed with layered assemblages of phototrophic filamentous fossil microbes. The geologic setting of the fossil-hosting unit, the preservation of the sulfuretum swirls adpressed to quartz pseudomorphs of precipitated anhydrite or gypsum, and the lack of physical disruption of the assemblage document its near-surface quiescent marine environment. The anaerobic physiology of the sulfuretum microbes indicates that Earth’s surface was anoxic. This exceedingly ancient biota is therefore interpreted to be composed of anaerobic H2S-producing sulfuretum microbes and H₂S-using anoxygenic phototrophic bacteria. As such, this first-identified fossil microbial consortium provides firm evidence of the anoxia of Earth’s early environment.

  ROADMAP OBJECTIVES: 4.1 5.2 6.2 7.2

• Earth’s Evolving Nitrogen Cycle – Implications for Community Complexity and Stability

  This project examines nitrogen isotope patterns in Proterozoic and Paleozoic rocks, as part of a broader effort to understand the co-evolution of Earth’s redox cycles and marine ecosystems. The results are being incorporated into a growing framework of data and models that have as their primary objective to show how planetary geochemical cycles evolve with and/or help to record signatures of living systems – both microbial and complex. The project aims to yield a better understanding of the transition from primarily anoxic to primarily oxic deep oceans, and how that transition is mirrored in nutrient budgets (i.e., nitrogen) and the marine ecosystems that depend on the stability of these cycles. Understanding N-cycling throughout Earth’s history has critical implications for the evolution of complex marine ecosystems on geologic timescales.

  ROADMAP OBJECTIVES: 4.1 4.2 5.2 5.3 6.1

• Paleontological, Sedimentological, and Geochemical Investigations of the Mesoproterozoic-Neoproterozoic Transition

  As we learn more about the earliest evolutionary history of animals and other complex multicellular organisms, it becomes clearer that a satisfactory understanding of these events have to be set within the broader context of late Mesoproterozoic and Neoproterozoic biological and environmental change. To this end, several labs within our team have focused research effort of Mesoproterozoic and Neoproterozoic sedimentary successions. Over the reporting period, this has included stratigraphic and sedimentological fieldwork on rocks of this age in northwestern Canada, Death Valley, Mongolia, Peru, and anaylsis of drill cores from Russia, Congo and Zambia. Progress has also been made in new techniques for the discovery, description, and interpretation of Proterozoic microfossils, and several-fold improvements in the precision of oxygen-17 measurements, which can record the balance of atmospheric oxygen and carbon dioxide.

  ROADMAP OBJECTIVES: 4.1 4.2 5.2 6.1

• Project 4B: New Standards for Analysis of O and C Isotope Ratios in Ca-Mg-Fe Carbonates

  Stable isotope ratios are a powerful tool for determining the temperature and fluid conditions during formation of carbonates that host evidence for early life on Earth. However, sedimentary carbonates are often zoned at μm-scale and conventional analysis yields average values. We developed a suite of standards for the dolomite-ankerite series that allow us to make the first accurate SIMS (Secondary ion mass spectrometry) analyses oxygen and carbon isotope ratios at 1-10 μm-scale for these important carbonate minerals.

  ROADMAP OBJECTIVES: 1.1 4.1 4.3 7.1