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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

• 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

• Field Activities at the Coast Range Ophiolite Microbial Observatory (CROMO)

  CROMO provides ongoing excellent exposure to samples of ophiolite-hosted serpentinites and associated rocks, access to monitoring wells important for observing serpentinization-related groundwater flow regimes, and serves as a community-building platform that fosters new scientific collaboration. CROMO has served as a test-bed for refining new experimental approaches, and progressing from basic observations to more complex, multi-disciplinary science.

  Within the past year, studies at CROMO have focused on the subsurface hydrogeochemical dynamics, by monitoring groundwater hydrology, measuring the concentrations and composition dissolved iron, sulfur, dissolved inorganic carbon, major inorganic anions and cations, dissolved hydrogen, carbon monoxide and methane gases, and organic compounds, in addition to time-series analyses.

  CROMO datasets are being incorporated into an exploratory database project aimed at addressing NASA’s public data requirements. Once developed, this database will help to address data sharing plans for collaborators and serve as a valuable tool for CROMO data management across collaborating labs.

  In 2015, project members Dawn Cardace, Masako Tominaga, Michael Kubo, Lauren Seyler, Mary Sabuda, Abigail Johnson, Ken Wilkinson, & Cameron Hearne participated in a field trip to CROMO from August 21-27, to continue seasonal bio/geo/chemical monitoring of the wells, as well as assessing the site for future geophysical measurements.

  ROADMAP OBJECTIVES: 5.1 5.2 5.3 6.1 6.2 7.1 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: Consequences of recA Duplication for Recombination, Genome Stability and Fitness

  Homologous recombination (HR) – the exchange of genetic information between similar DNA molecules – is an ancient process that is central to the emergence of biological complexity, diversity and stability. Yet, it must be tightly regulated, as it is likewise an important source of destabilizing genomic rearrangements. Despite the importance of HR, we still have a poor understanding of the balance of these creative, stabilizing and destabilizing contributions to organismal fitness, complexity and genome evolution. We are using the extraordinary genome evolutionary dynamics and duplicated copies of the HR gene recA in the cyanobacterium Acaryochloris as a model to gain novel insights on the fitness consequences that emerge from the interplay between HR-mediated maintenance of genome stability, selectively favored gene duplications and non-adaptive genomic rearrangements.

  ROADMAP OBJECTIVES: 4.2 5.1 5.3 6.1 6.2

• Insights Into Geochemical and Biological Processes in Serpentinizing Systems From Hyperalkaline Seeps in Oman

  Rock-powered life makes its living from reactions between rocks and water as part of the overall processes of rock weathering. There can be energy available because rocks from deep in the Earth are moved by tectonic forces into regions populated by microbes faster than chemical weathering processes alone can act. Under the right conditions, energy left behind can be consumed by microbial communities, and resulting biogeochemical reactions expedite overall weathering processes. In many cases, these energy sources and the communities they support are independent of sunlight. Instead, their energy and nutrient requirements are met by a combination of slow tectonic and rapid fluid mixing processes. One particularly dramatic example of how the combination of these processes support microbial communities is found in an area of Oman called the Samail ophiolite. Owing to unusual geologic proceses, tectonic forces moved rocks normally in the Earth’s mantle to the surface of the continent on the Arabian peninsula about 65 million years ago. Ever since, the introduction of mantle rocks into the surface hydrosphere has been a source of energy tapped by microbes. At present, in the arid climate of Oman, small amounts of annual precipitation infiltrate these rocks, react, and reappear at springs. Owing to the unusual rock compositions, these springs have remarkably unusual compositions. Not only does the pH go to extremely basic values, nearly reaching 12, but the solutions are so reduced that they can bubble with escaping hydrogen and methane. Although these springs are not hot, they can look like they are boiling in places with lots of escaping gas.

  ROADMAP OBJECTIVES: 5.2 5.3 6.1

• Biomarker Profiling Using the Life Detector Chip (LDChip)

  We have worked on the detection of molecular biomarkers in three relevant environments: Dry (Atacama), acidic (Río Tinto) and deep lake sediments (Andean lakes). Samples have been analyzed in situ by using a powerful biomarker detection chip with and antibody microarray sensor as well in the laboratory with other geomicrobiological tools.

  ROADMAP OBJECTIVES: 5.3 6.1 7.1

• Mars Analogs: Habitability and Biosignatures in the Atacama Deser

  This project focuses on the study of habitability in the Atacama Desert of northern Chile, one of the driest regions on Earth. We want to understand how life adapts and survives in an environment where liquid water is exceedingly rare, and how biosignatures are preserved in that environment after microorganisms die. These studies can become a very useful guide for future robotic missions to Mars. This year we focused on microbial communities that inhabit the interior of salt nodules in evaporitic lake deposits. These are the only known active microbial comunities in the driest parts of the Atacama. We wanted to understand how these microbial communities survive in an environment that excludes every other form of life. We suspected that the salt communities use atmospheric water vapor as a source of water to run their metabolic processes. We showed that this is indeed the case with a combination of field and laboratory tools. Our results suggest that the salt substrate could be one of the last possible habitats for life in extremely dry environments.

  ROADMAP OBJECTIVES: 2.1 5.1 5.3 6.1 6.2 7.1 7.2

• 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

• Project 5: Adaptation, Mutation Supply, and Evolution of Synergy in Biofilm Communities

  We will quantify the dynamics of adaptation and identify the mutational causes in evolving biofilms with high precision, and therefore illustrate how microbes colonizing a new surface can transform their environment and set the stage for primitive multicellularity. Biofilms resemble tissues in their subdivided labor, varied physical structure and shared metabolism. We predict that the stability of this ecological cooperation rests on population-genetic controls on selfish lineages associated with mutators, much as tissues are liable to selfish invasion by cancers.

  ROADMAP OBJECTIVES: 4.2 5.1 5.2 6.1 6.2

• 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

• 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

• 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

• Biosphere-Geosphere Stability and the Evolution of Complex Life

  Five times in the past 500 million years, mass extinctions have resulted in the loss of greater than three-fourths of living species. Each of these events is associated with a significant perturbation of Earth’s carbon cycle. But there are also many such environmental events in the geologic record that are not associated with mass extinctions. What makes them different? We hypothesize that mass extinctions are associated with an instability in the carbon cycle. This project attempts to specify, both theoretically and empirically,the conditions that result in such an instability.

  ROADMAP OBJECTIVES: 4.3 5.1 5.2 6.1

• Subglacial Environments as Water‐Rock Hosted Microbial Ecosystems

  Glaciers, ice sheets and ice caps cover ~11% of the earth’s surface, and likely covered up to 100% during Neoproterozoic glaciations. The beds of these ice masses can have significant sectors at the pressure melting point. The resulting water lubricates ice sliding and accelerates erosion, provides habitat for subglacial microbial ecosystems, and may have acted as refugia during past global glaciations on Earth. Such environments may also act as habitats for life on other planetary bodies.

  Grinding of bedrock by glaciers exposes fresh mineral surfaces capable of sustaining microbial metabolism. The foci of RPL investigations on subglacial environments are categorized into two key areas of relevance to habitability studies: i) determine the extent to which minerals support chemotrophic metabolism and the production of biosignatures (e.g., weathering products), and ii) quantifying the influence of water-rock interactions in supplying substrates to support energy metabolism. Through these interdisciplinary and collaborative studies, we aim to characterize the active microbial processes in subglacial environments and to define the sources of energy that sustains this microbial life.

  ROADMAP OBJECTIVES: 2.1 5.1 5.2 5.3 6.1 6.2 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

• 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

• 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

• Project 10: Evolution Through the Lens of Codon Usage

  The sequences of protein encoding genes are subject to multiple levels of selection. First, amino acid changes that adversely alter protein function are unlikely to survive. In addition, the genetic code is degenerate; it includes alternative (synonymous) codons for most of the amino acids. The codon usages of genes reflect a balance between drift and selection for rapid and accurate translation of mRNAs into proteins, and in the case of horizontally transferred genes, the codon usages of their sources. Our studies of genes and their codon usages have led us to discover that: (i) most of the recently acquired genes come from such closely related organisms that their distinctive codon usages cannot be attributed to a phylogenetically distant source; (ii) the transfers commonly exceed recognized boundaries of microbial species; (iii) some genes do not drift to match the native codon usage of their current genome, but resemble the most recently acquired genes; (iv) many of the genes that are most up-regulated under starvation conditions also have this codon usage; and (v) a distinctive stress/starvation-associated codon usage is a recurring theme that is observed in diverse Bacteria and Archaea.

  These results have changed our understanding of the dynamics with which genetic novelties are shared in the biosphere, and revealed that there are selective forces on codon usage beyond those currently appreciated in the field.

  ROADMAP OBJECTIVES: 5.1 5.2 5.3 6.1

• Project 2D: Carbonate-Associated Sulfate (CAS) as a Tracer of Ancient Microbial Ecosystems

  Our aim is to investigate and understand microbial communities that flourished much earlier in the Earth’s history. We have adapted a method used to investigate the isotopic compositions of ancient oceans, by analyzing rocks formed at those times, but applied it to the pore-waters present in ancient sediments inhabited by in the contemporaneous microbial communities. The isotopic compositions we measure tell us about the extent and progress of microbial metabolic processes. We have applied this method very successfully to 12 million year old sediments. Most recently in order to test and calibrate the approach most fully, we have been examining recent deposits in which we can analyze microbiological communities, the pore-waters in which they live and the rocks forming there.

  ROADMAP OBJECTIVES: 5.2 6.1 7.1

• Environmental and Biological Signatures in Yellowstone National Park Silica Precipitating Hot Springs

  Radiation from the Sun potentially affects solids, liquids, and gases found on the surfaces of planets. Radiation exposure could change the chemical and mineralogical make-up of the surface materials. Sample-return missions aim to collect samples, cache them for a period of time, and then return them to Earth for additional analysis. We have performed field experiments to document environmental radiation levels and exposures and their impact on recently formed materials and associated organic matter.

  ROADMAP OBJECTIVES: 1.1 2.1 6.1 7.1 7.2

• Project 11: Culturing Microbial Communities in Controlled Stress Micro-Environments

  This project explores the adaptation and evolution of organisms under controlled environmental conditions, and compares the behavior across two Domains of Life in order to identify and quantify universal aspects of evolutionary response.

  ROADMAP OBJECTIVES: 6.1 6.2

• 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

• Progress in the Elucidation of Microbial Biosignatures

  A number of discrete individual investigations have contributed to improved knowledge about the occurrence and interpretation of microbial molecular biosignatures across all geological timescales.

  A new analytical approach enabled a revised geologic distributions of fossilized biomarkers for anoxygenic sulfur bacteria. The prevalence of okenane and chlorobactane suggests that marine photic zone euxinia (PZE) was more intense and frequent in the geologic past. However, the presence of these compounds in some sediments and oils may also be a signature for basin restriction rather than one indicating more widespread marine anoxia.

  In a related work, pervasive photic zone euxinia and disruption of biogeochemical cycles was demonstrated for a sequence of rocks deposited on the northeastern Panthalassic Ocean during the end-Triassic extinction.

  A study of lipids and their isotopic compositions, combined with stable isotope probing experiments, demonstrated that streamer biofilm communities, which are a present in the high temperature zones of hydrothermal features of the Lower Geyser Basin of Yelowstone National Park, can alternate their metabolism between autotrophy and heterotrophy depending on substrate availability.

  Other collaborations with numerous colleagues resulted in documentation of lipid and isotopic biosignatures in cultured bacteria.

  ROADMAP OBJECTIVES: 3.2 4.2 5.1 5.2 5.3 6.1

• 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

• 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

• 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

• 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