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Project Reports

• Advancing Methods for the Analyses of Organics Molecules in Sediments

  Eigenbrode’s astrobiological research focuses on understanding the formation and preservation of organic and isotopic sedimentary records of ancient Earth, Mars, and icy bodies. To this end, and as part of GCA’s Theme IV effort, Eigenbrode seeks to overcome sampling and analytical challenges associated with organic analyses of astrobiology relevant samples with modification and development of contamination tracking, sampling, and analytical methods (primarily GCMS) that improve the recovery of meaningful observations and provide protocol guidance for future astrobiological missions.

  ROADMAP OBJECTIVES: 2.1 4.1 7.1

• Amino Acid Alphabet Evolution

  A genetically encoded alphabet of just 20 amino acids has produced the universe of protein structures and functions found throughout Earth’s biosphere. Relationships within this amino acid alphabet are responsible for fundamental biological phenomena, such as protein folding and patterns of molecular evolution. In attempting to unravel these relationships, considerable scientific ingenuity has been spent developing systems to simplify the genetically encoded alphabet of 20 amino acids while minimizing the associated loss of chemical diversity. These efforts present an opportunity to generate a composite picture of the properties that link the amino acids as a set. We are therefore investigating whether different simplification schemes (“simplified amino acid alphabets”), including those derived from very different approaches, can be combined to create a coherent description of amino acid similarity. By understanding the organization and relationships between amino acids on Earth, we hope to shed light on the chemical logic to be expected as a product of evolution in extraterrestrial environments.

  An extensive scientific literature has converged on surprisingly clear agreement that a subset of only around half of the 20 genetically encoded amino acids was likely present from the inception of genetic coding (the “early” amino acids), and an equal sized subset was incorporated through subsequent evolution (the “late” amino acids). A further widespread assumption is that, as the set expanded, natural selection favored the addition of amino acids that extended the range of protein structures and functions. We initiated a quantitative investigation for consilience between these two important ideas.

  ROADMAP OBJECTIVES: 3.2 4.1 4.2 6.2 7.1 7.2

• Habitability of Icy Worlds

  Habitability of Icy Worlds investigates the habitability of liquid water environments in icy worlds, with a focus on what processes may give rise to life, what processes may sustain life, and what processes may deliver that life to the surface. Habitability of Icy Worlds investigation has three major objectives. Objective 1, Seafloor Processes, explores conditions that might be conducive to originating and supporting life in icy world interiors. Objective 2, Ocean Processes, investigates the formation of prebiotic cell membranes under simulated deep-ocean conditions, and Objective 3, Ice Shell Processes, investigates astrobiological aspects of ice shell evolution.

  ROADMAP OBJECTIVES: 1.1 2.1 2.2 3.1 3.2 3.3 3.4 4.1 5.1 6.1 6.2 7.1 7.2

• Biosignatures in Ancient Rocks

  The Biosignatures in Ancient Rocks group investigates the co-evolution of life and environment on early Earth using a combination of geological field work, geochemical analysis, genomics, and numerical simulation.

  ROADMAP OBJECTIVES: 1.1 3.2 4.1 4.2 4.3 5.1 5.2 5.3 6.1 6.2 7.1 7.2

• Atmospheric Oxygen and Complex Life

  Our team is working to understand what the world looked like just before and just after the evolution of animals. This encompasses field geology (identifying rocks of that age), chemical analysis of those rocks, and close examination of the small, enigmatic fossilized forms within those same geologic units. To synthesize these interdisciplinary approaches, our team also works to contribute overview/review papers that speak to the contribution from each field.

  ROADMAP OBJECTIVES: 4.1 4.2 6.1 6.2

• Delivery of Volatiles to Terrestrial Planets

  We are investigating the mechanisms by which terrestrial planets obtain water and organic compounds. By understanding how these crucial constituents for life came to Earth, we can determine whether these mechanisms also operate in exoplanetary systems. When an earth-like planet is finally discovered in an exoplanetary system, it will be difficult to directly measure the composition of that planet. However, VPL scientists will use the observable properties of the system to determine whether that planet has a history that allowed water and organics to have been transported to it. One of the important questions is the initial state of the organic compounds, which sets stringent limits on the ability of the earth-like planets to acquire carbon.

  ROADMAP OBJECTIVES: 1.1 1.2 3.1 4.1 4.3

• Ecology of Extreme Environments: Characterization of Energy Flow, Bioenergetics, and Biodiversity in Early Earth Analog Ecosystems

  The distribution of organisms and their metabolic functions on Earth is rooted, at least in part, to the numerous adaptive radiations that have resulted in the ability to occupy new ecological niches through evolutionary time. Such responses are recorded in extant organismal geographic distribution patterns (e.g., habitat range), as well as in the genetic record of organisms. The extreme variation in the geochemical composition of present day hydrothermal environments is likely to encompass many of those that were present on early Earth, when key metabolic processes are thought to have evolved. Environments such Yellowstone National Park (YNP), Wyoming harbor >12,000 geothermal features that vary widely in temperature and geochemical composition. Such environments provide a field laboratory for examining the tendency for guilds of organisms to inhabit particular ecological niches and to define the range of geochemical conditions tolerated by that functional guild (i.e., habitat range or zone of habitability). In this aim, we are examining the distribution and diversity of genes that encode for target metalloproteins in YNP environments that harbor geochemical properties that are thought to be similar to those that characterize early Earth. Using a number of newly developed computational approaches, we have been able to deduce the primary environmental parameters that constrain the distribution of a number of functional processes and which underpin their diversity. Such information is central to constraining the parameter space of environment types that are likely to have facilitated the emergence of these metal-based biocatalysts.

  ROADMAP OBJECTIVES: 3.2 3.3 3.4 4.1 4.2 5.1 5.2 5.3

• Deconstruction of the Ribosome

  In the ribosome, RNA and protein are fully interdependent, part of the highly complex system of translation. We demonstrate here that isolated Domain III of 23S rRNA from Thermus thermophilus retains function after being split essentially in half. Chemical footprinting shows that a core of Domain III (DIII^core), obtained replacement of helices 54-59 with a simple stem-loop, folds to a near-native state in the presence of Mg²⁺ ions. Both DIII and DIII^core form specific complexes with ribosomal protein L23 in vivo, as indicated with a yeast three-hybrid experiment. L23 has a globular domain on the LSU surface and an extension (L23peptide) that penetrates into the ribosomal large subunit. In the assembled LSU, L23peptide (amino acids 58-79) traverses the surface of DIII^core. In solution, DIII^core forms a stable 1:1 complex with L23peptide, as observed with spectroscopic assay. The experiments described here are intended to recapitulate steps in early ribosomal evolution. We have previously proposed that some of the extensions of ribosomal proteins are molecular fossils that predate the globular protein domains in evolution. In our favored model of ribosomal origins, small independently-folding RNA elements associated with short peptides. Such complexes assembled to form a primitive peptidyl transferase center. The PTC evolved into the modern LSU, in a series of cooptions that left unaltered the basic structure and function of the PTC. This model predicts a continuous size distribution of folding and assembly elements within the LSU. We anticipate autonomy and specificity of folding and interaction of small, mid-sized and large rRNA and protein components.

  ROADMAP OBJECTIVES: 3.2 4.1 4.2

• Biosignatures in Extraterrestrial Settings

  Exploring the prospects for biosignatures in extraterrestrial settings is a multi

  ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 4.1 4.3 6.2 7.1 7.2

• Project 3: The Origin, Evolution, and Volatile Inventories of Terrestrial Planets

  Project 3 focuses on understanding the nature of volatiles (principally water and gase like carbon dioxide and methane) in planetary interiors. The origin of Earth’s oceans and the initiation of plate tectonics may have related through the retention of water deep in Earth’s mantle. In this project scientists study how volatiles behave in silicate melts and Earth’s deep interior. They also study other rock planets, e.g. Mars and Mercury to understand how the presence or absence of volatiles may have lead to such disparate outcomes relative to Earth.

  ROADMAP OBJECTIVES: 1.1 3.1 4.1

• Detectability of Biosignatures

  In this project VPL team members explore the nature and detectability of biosignatures, global signs of life in the atmosphere or on the surface of a planet. This year we submitted for publication modeling work that explores the potential for non-biological generation of oxygen and ozone in early Earth-like atmospheres, which could result in a “false positives” for photosynthetic life. In parallel, we worked with three simulators for telescopes that will one day be able to observe and determine the properties of extrasolar terrestrial planets, and used these simulators to calculate the relative detectability of gases produced by life.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 7.2

• Experimental Evolution and Genomic Analysis of an E. Coli Containing a Resurrected Ancestral Gene

  We have previously described a paleo-experimental evolution system that combines Ancestral Sequence Reconstruction (ASR) with experimental evolution in the laboratory. Briefly, we designed a system that is composed of an organism with a short generation time and a protein under strong selective constraints in the modern host but whose ancestral genotype and phenotype, if genomically integrated, causes the modern host to be less fit than a modern population hosting the modern form of the protein. The modern organism hosting the resurrected protein would obviously need to be viable, but sick. E. coli and a protein, whose ancestral sequences are available termed Elongation Factor-Tu (EF-Tu), turned out to be ideal for this type of experiment.

  ROADMAP OBJECTIVES: 3.4 4.1

• Project 1C: Absorption of Amino Acids on Minerals

  The role of mineral surfaces in extraterrestrial organic synthesis, pre-biotic chemistry, and the early evolution of life remains an open question. Mineral surfaces could promote synthesis, preservation, or degradation of chiral excesses of organic small molecules, polymers, and cells. Different minerals, crystal faces of a mineral, or defects on a face may selectively interact with specific organics, providing an enormous range of chemical possibilities. It has also been suggested in the literature that amino acids may have been delivered to early Earth by meteorite impacts. We focused here on amino-acid adsorption and conformation on model mineral, γ-Al₂O₃.

  We measured adsorption of the acidic amino-acids, glutamate and aspartate, on model nanparticulate oxide mineral, γ-Al₂O₃. Our results should help provide an estimate of the amount of amino-acids delivered. Using bulk adsorption isotherms our results showed similar amounts of adsorption of both amino-acids and FTIR spectroscopy revealed similar bonding configurations for the adsorbed species, over a range of pHs and concentrations.

  The project addresses NASA Astrobiology Institute’s (NAI) Roadmap Goal 3 of understanding how life emerges from cosmic and planetary precursors, and Goal 4 of understanding organic and biosignature preservation mechanisms. The work is relevant to NASA’s Strategic Goal of advancing scientific knowledge on the origin and evolution life on Earth and potentially elsewhere, and of planning future Missions by helping to identify promising targets for the discovery of organics.

  ROADMAP OBJECTIVES: 3.1 3.2 4.1

• Molecular Evolution: A Top Down Approach to Examine the Origin of Key Biochemical Processes

  The emergence of metalloenzymes capable of activating substrates such as CO, N2, and H2, were significant advancements in biochemical reactivity and in the evolution of complex life. Examples of such enzymes include [FeFe]- and [NiFe]-hydrogenase that function in H2 metabolism, Mo-, V-, and Fe-nitrogenases that function in N2 reduction, and CO dehydrogenases that function in the oxidation of CO. Many of these metalloenzymes have closely related paralogs that catalyze distinctly different chemistries, an example being nitrogenase and its closely related paralog protochlorophyllide reductase that functions in the biosynthesis of bacteriochlorophyll (photosynthesis). By specifically focusing on the origin and subsequent evolution of these metallocluster biosynthesis proteins in relation to paralogous proteins that have left clear evidence in the geological record (photosynthesis and the rise of O2), we have been able to obtain significant insight into the origin and evolution of these functional processes, and to place these events in evolutionary time.

  The genomes of extant organisms provide detailed histories of key events in the evolution of complex biological processes such as CO, N2, and H2 metabolism. Advances in sequencing technology continue to increase the pace by which unique (meta)genomic data is being generated. This now makes it possible to seamlessly integrate genomic information into an evolutionary context and evaluate key events in the evolution of biological processes (e.g., gene duplications, fusions, and recruitments) within an Earth history framework. Here we describe progress in using such approaches in examining the evolution of CO, N2, and H2 metabolism.

  ROADMAP OBJECTIVES: 3.2 4.1 5.1

• Biosignatures in Relevant Microbial Ecosystems

  PSARC is investigating microbial life in some of Earth’s most mission-relevant modern ecosystems. These environments include the extremely salty Dead Sea, the impact-fractured crust of the Chesapeake Bay impact structure, methane seeps on the ocean floor, deep ice in the Greenland ice sheet, and oxygen-free waters including deep subsurface groundwater. We target environments that, when studied, provide fundamental information that can serve as the basis for future solar system exploration. Combining our expertise in molecular biology, geochemistry, microbiology, and metagenomics, and in collaboration with some of the planet’s most extreme explorers, we are deciphering the microbiology, fossilization processes, and recoverable biosignatures from these mission-relevant environments.

  ROADMAP OBJECTIVES: 4.1 4.3 5.1 5.2 5.3 6.1 7.1 7.2

• Detectability of Life

  Detectability of Life investigates the detectability of chemical and biological signatures on the surface of icy worlds, with a focus on spectroscopic techniques, and on spectral bands that are not in some way connected to photosynthesis.Detectability of life investigation has three major objectives: Detection of Life in the Laboratory, Detection of Life in the Field, and Detection of Life from Orbit.

  ROADMAP OBJECTIVES: 1.2 2.1 2.2 4.1 5.3 6.1 6.2 7.1 7.2

• Developing New Biosignatures

  The Developing New Biosignatures project is aimed at creating innovative approaches for the analyses of cells and other organic material, finding ways in which metal abundances and isotope systems reflect life, and developing creative approaches for using environmental DNA to study present and past life.

  ROADMAP OBJECTIVES: 4.1 5.1 7.1

• Biomechanics of Rangeomorph Fauna

  The oldest evidence of complex communities of lifeforms come from Newfoundland, Canada. The fossil beds discovered there are dominated by rangeomorphs, which look superficially like underwater plants, but probably got their nutrition by direct uptake of dissolved resources in the water. Here, we use models of water flow in the community to see how these complex organisms could have competed with bacteria for organic matter or reduced compounds in the water. Ultimately, we have determined that by sticking up off the sea floor, rangeomorphs could take advantage of sheer forces created by moving water, and gain an advantage over bacteria in competition for nutrients. The benefits of sticking up into water flow may have driven the early evolution of complex life on earth. Ongoing work seeks to clarify the transitions between flow regimes across stages of community succession from prokaryotic mats to eukaryotic communities

  ROADMAP OBJECTIVES: 4.1 4.2 5.2 6.1

• Project 1D: Establishing Biogenicity and Environmental Setting of Precambrian Kerogen and Microfossils

  This study demonstrates new abilities to use in situ measurements of carbon isotope ratios in microfossil kerogen as a biosignature and to establish taxonomic and micro-structural correlations.

  ROADMAP OBJECTIVES: 2.1 4.1 5.1 5.2 6.1 7.1

• Project 4: Survival of Sugars in Ice/Mineral Mixtures on High Velocity Impact

  Understanding the delivery and preservation of organic molecules in meteoritic material is important to understanding the origin of life on Earth. Though we know that organic molecules are abundant in meteorites, comets, and interplanetary dust particles, few studies have examined how impact processes affect their chemistry and survivability under extreme temperatures and pressures. We are investigating how impact events may change the structure of simple sugars, both alone and when combined with ice mixtures. The experiments will allow us to understand how sugar chemistry is affected by high pressure events and to contrast the survival probabilities of sugars in meteorite and comet impacts. This will lead to a better understanding of how organic molecules are affected during their delivery to Earth. This project leverages expertise in two different NAI nodes, increasing collaborative interaction among NAI investigators.

  ROADMAP OBJECTIVES: 1.1 3.1 4.1 4.3

• Ironing Out the RNA World

  In RNA World models of evolution, RNA was once the primary biopolymer of genetics and catalysis (1). Ancient RNA-based life would have inhabited an earth with abundant soluble iron and no free oxygen (2,3). Anoxic life persisted for around 1.0-1.5 billion years before photosynthesis began producing substantial free oxygen. The ‘great oxidation’ led to Fe²⁺/O₂ mediated cellular damage (4) and depletion of soluble iron from the biosphere (5). We hypothesize that Fe2²⁺ was an RNA cofactor when iron was benign and abundant and that Fe²⁺ was replaced by Mg²⁺ during the great oxidation. The RNA-Fe²⁺ to RNA-Mg²⁺ hypothesis is in close analogy with known metal substitutions in some metalloproteins (6-11). An ancestral ribonucleotide reductase (RNR), for example, spawned di-iron, di-manganese, and iron-manganese RNRs (12). Our hypothesis is supported by observations (13) that (i) RNA folding is conserved between complexes with Fe2+ and Mg²⁺ and (ii) at least some phosphoryl transfer ribozymes are more active in the presence of Fe²⁺ than Mg²⁺. Here, we demonstrate that reversing the putative metal substitution in an anoxic environment, by removing Mg²⁺ and adding Fe²⁺, expands the catalytic repertoire of some RNAs. Fe²⁺ can confer on RNA a previously uncharacterized ability to catalyze single electron transfer. Catalysis is specific, in that it is dependent on the type of RNA. The 23S rRNA and tRNA, some of the most abundant and ancient RNAs (14), are found to be efficient electron transfer ribozymes in the presence of Fe²⁺. Therefore, the catalytic competence of ancient RNAs may have been greater in early earth conditions than in extant conditions, and the experiments described here may be reviving latent function.

  ROADMAP OBJECTIVES: 4.1 4.2

• Project 5: Geological-Biological Interactions

  This project seeks to better understand the interplay between microbes and extreme environments. Towards this end our NAI supported scientists study hot spring environments, both continental and sub marine, environments of active serpentinization where pH may exceed 11, and in the high Arctic. We use molecular, isotopic, and molecular biological approaches to get at the core of the relationship between the microbial world and the natural energy provided by geological processes.

  ROADMAP OBJECTIVES: 4.1 5.1 6.1 6.2 7.1

• Planetary Surface and Interior Models and SuperEarths

  We use computer models to simulate the evolution of the interior and the surface of real and hypothetical planets around other stars. Our goal is to work out what sorts of initial characteristics 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) 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 over time. Our interior models are designed to predict how much and what sort of materials will come to a planet’s surface through volcanic activity throughout its history.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 5.2 6.1

• Project 2A: Inorganic Growth of Mg-Calcite From Dilute Solutions: Understanding Temperature, Composition and pCO2 Effects

  The magnesium content of calcite has been successfully used in the past as a paleotemperature indicator for both inorganic and biological systems. More recently, the magnesium isotope ratio of Mg-bearing calcite has been suggested to display a temperature dependence, lending itself as an additional potential proxy for temperature. While these systems provide a valuable function to place geological materials within an environmental context, it is important to understand the physicochemical factors that control the incorporation of magnesium in calcite. Toward this end, a series of laboratory experiments were conducted to better understand the effect of solution chemistry and precipitation kinetics on the temperature dependence of the incorporation of magnesium isotopes in calcite. The results suggest that solution Mg/Ca ratio plays a subtle but important role in the use of magnesium as a paleotemperature indicator for calcite.

  ROADMAP OBJECTIVES: 4.1 7.1

• Geochemical Signals for Low Oxygen Worlds

  We are studying the physiology of sulfate reducing bacteria, organisms that perform a key microbial metabolism in anoxic worlds. By calibrating microbial sulfur isotope effects, we can infer the redox level of paleoenvironments in the geologic past by studying sedimentary records. The sulfur cycle is intimately linked to the redox budget of the Earth’s surface, such that this study will help inform us about the evolution of aerobic environments, a key process that set the stage for animal evolution. Similarly, we also are studying the role of oxygen in controlling the budget and transformations of nitrogen in the ocean. Nitrogen is a critical nutrient limiting marine production, and the balance of its redox cycling controls how much nitrogen is added or removed from the ocean by redox-sensitive processes.

  ROADMAP OBJECTIVES: 1.1 4.1 4.2 5.1 7.1

• Project 6: The Environment of the Early Earth

  This project involves the development of capabilities that will allow scientists to obtain information about the conditions on early Earth (3.0 to 4.5 billion years ago) by performing chemical analyzes of crystals (minerals) that have survived since that time. When they grow, minerals incorporate trace concentrations of ions and gaseous molecules from the local environment. We are conducting experiments to calibrate the uptake of these “impurities” that we expect to serve as indicators of temperature, moisture, oxidation state and atmosphere composition. To date, our focus has been mainly on zircon (ZrSiO₄), but we have recently turned our attention to quartz as well.

  ROADMAP OBJECTIVES: 1.1 4.1 4.3

• Project 2B: The Influence of Temperature, Composition and pCO2 on the Fractionation of Iron Isotopes in the Calcite-Siderite System

  While siderite is a relatively common constituent of the sedimentary rock record, little is known about how solution composition and precipitation kinetics affect the trace element and Fe-isotope composition of siderite that forms at temperatures conducive to life (< 100°C). With this knowledge, siderite deposits may be placed within a more meaningful environmental context and the origin and diagenetic history of siderite can be better understood. In this study, inorganic siderite was precipitated under tightly controlled physicochemical conditions using the chemo-stat technique to better understand the factors that influence Fe-isotope fractionation in aqueous systems that contain siderite. Preliminary results suggest that siderite may be grown heterogeneously on pre-existing calcite surfaces but the resulting solids are highly susceptible to oxidation. These factors need to be better understood before inorganic precipitation experiments can be used with confidence to assess factors that influence the Fe-isotope composition of Fe-bearing carbonates.

  ROADMAP OBJECTIVES: 4.1 7.1

• Stellar Radiative Effects on Planetary Habitability

  Habitable environments are most likely to exist in close proximity to a star, and hence a detailed and comprehensive understanding of the effect of the star on planetary habitability is crucial in the pursuit of an inhabited world. We looked at how the Sun’s brightness would have changed with time providing wavelength-dependent scaling factors for solar flux anywhere in the solar system from 0.6 to 6.7Gyr. Extrasolar planetary systems can only be determined through studying the host star; therefore we have also worked on determining the ages of Kepler planet host stars. We have constructed far ultraviolet to mid-infrared stellar spectra for 44 stars for being used as input in climate and photochemical models that are applied for determining habitable zones and possible characteristics of habitable planets. We have looked into the effect of methane (CH₄) and hydrogen (H₂) on the outer edge of the habitable zone for F, G, and M stars. We have studied the effect of host star stellar energy distribution (SED) and ice-albedo feedback on the climate of extrasolar planets.

  ROADMAP OBJECTIVES: 1.1 1.2 2.1 4.1 4.3 7.2

• Habitability of Extrasolar Planets

  We model if and under what conditions some of the recently detected Super-Earths – small, Earth-sized planets that have been discovered in in the classical Habitable Zone Sun-like stars – could be habitable. These models explore the underlying physics of planetary atmospheres and their remotely detectable features.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.2 6.2 7.2

• Stromatolites in the Desert: Analogs to Other Worlds

  In this task biologists go to field sites in Mexico to better understand the environmental effects on growth rates for freshwater stromatolites. Stromatolites are microbial mat communities that have the ability to calcify under certain conditions. They are believed to be an ancient form of life, that may have dominated the planet’s biosphere more than 2 billion years ago. Our work focuses on understanding these communities as a means of characterizing their metabolisms and gas outputs, for use in planetary models of ancient environments.

  ROADMAP OBJECTIVES: 4.1 4.2 5.2 5.3 6.1 6.2

• Ice Chemistry of the Solar System

  We are currently in the process of establishing a research program at the University of Hawai’i at Manoa to investigate the evolution of Solar System and interstellar ices; these grains are chemically processed continuously by radiation from either our Sun, or galactic cosmic radiation (GCR). The nature of the chemistry that occurs here is an important component of understanding the origin of complex biomolecules that could have seeded the primordial Earth, helping to kick-start the origin of life. We have constructed one of the leading laboratory facilities in the world capable of carrying out this research, and we focus on establishing the underlying chemical pathways.

  ROADMAP OBJECTIVES: 1.1 2.2 3.1 3.2 3.3 4.1 7.1 7.2

• Interdisciplinary Studies of Earth’s Seafloor Biosphere

  The remote deep sediment-buried ocean basaltic crust is Earth’s largest aquifer and host to the least known and potentially one of the most significant biospheres on Earth. CORK observatories have provided unparalleled access to this remote environment. They are enabling groundbreaking research in crustal fluid flow, (bio)geochemical fluid/crustal alteration, and the emerging field of deep crustal biosphere

  ROADMAP OBJECTIVES: 4.1 4.2 5.1 5.2 5.3 6.1 6.2 7.1 7.2

• Understanding Past Earth Environments

  For much of the history Earth, life on the planet existed in an environment very different than that of modern-day Earth. Thus, the ancient Earth represents a planet with a biosphere that is both dramatically different than the one in which we live, but that is also accessible to detailed study. As such, it serves as a model for what types of biospheres we may find on other planets. A particular focus of our work was on the “Early Earth” (formation through to about 500 million years ago), a timeframe poorly represented in the geological and fossil records but comprises the majority of Earth’s history. We have studied the composition and pressure of the ancient atmosphere; modeled the effects of clouds on such a planet; studied the sulfur, oxygen and nitrogen cycles; and explored atmospheric formation of molecules that were likely important to the origins of life on Earth.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.2 5.1 5.2 6.1

• Project 3A: Stable Isotope and Mineralogical Studies of Banded Iron Formations – O Isotopes by SIMS

  During the past year, we have made advances in technique development for analysis of mineral chemistry and stable isotope ratios in minerals. Applications to magnetite in Banded Iron Formation (BIF) have lead to the proposal that silician magnetite forms only in low oxygen fugacity conditions and are thus a signature for the former presence of reduced organic matter. Petrography and in situ analysis of δ¹⁸O by SIMS has shown that the earliest quartz cements in 1.85 Ga Granular Iron formation (GIF) consistently have high δ¹⁸O showing that earlier reports of more variable compositions included altered material.

  ROADMAP OBJECTIVES: 4.1 4.2 7.2

• Reconstruction of Ancient Proteins

  The genetic code is one of the most ancient and universal aspects of biology on Earth, and determines how specific DNA sequences get interpreted as peptide sequences, which then fold into all the proteins necessary for the growth and function of living cells. To a large extent, this code is determined by a class of proteins that specify which RNA adaptor molecules (tRNA) become attached to which amino acids, aminoacyl-tRNA synthetases. Therefore, reconstructing the amino acid sequences of the ancestors of these synthetases, existing ~4 billion years ago, can tell us the mechanisms by which the genetic code arose, and how it evolved to the modern form inherited by all known living organisms.

  ROADMAP OBJECTIVES: 3.2 3.4 4.1 4.2

• Measuring Interdisciplinarity Within Astrobiology Research

  To integrate the work of the diverse scientists working on astrobiology, we have harvested and analyzed thousands of astrobiology documents to reveal areas of potential connection. This framework allows us to identify crossover documents that guide scientists quickly across vast interdisciplinary libraries, suggest productive interdisciplinary collaborations, and provide a metric of interdisciplinary science.

  ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 3.2 3.3 3.4 4.1 4.2 4.3 5.1 5.2 5.3 6.1 6.2 7.1 7.2

• Project 3B: In Situ S Isotope Studies in Archean-Proterozoic Sulfides

  Studies of sulfur isotopes constrain atmospheric and marine conditions in the Paleoproterozoic and Archean. We have developed capabilities for analysis of all four sulfur isotopes, including the rarest isotope (36-S) in situ by ion microprobe. In general sulfur 4 isotope data from Archean sulfides fall on the reference array for mass independent fractionation that was established by earlier bulk measurements. Small deviations from the array are resolved and likely result from biological or environmental forcings.

  ROADMAP OBJECTIVES: 2.1 4.1 5.2 6.1 7.1

• Project 3C: In Situ Fe Isotope Analysis of Iron Formations

  The Fe isotope composition of magnetite from the oldest (~3.8 Ga) sedimentary banded iron formations of Isua Greenland provide important constraints on the amount of Fe oxidation and its possible pathways. Iron isotope compositions of individual magnetite layers have been measured at the millimeter scale by micromilling and conventional mass spectrometry analysis and at the micrometer scale using femtosecond laser ablation (fs-LA). There is limited variability in the iron isotope composition of magnetite within a layer as would be expected for these amphibolites grade rocks. Within an individual hand sample there is at most a 0.3 ‰ difference in δ⁵⁶Fe values between different layers. Over a scale of tens of kilometers, the δ⁵⁶Fe values between magnetite layers in different samples range from +1.1 to +0.4 ‰. These high positive δ⁵⁶Fe values are noteworthy, and as a whole, Isua iron formations have higher and less variable δ⁵⁶Fe values as compared to the more massive 2.5 Ga iron formations from the Hamersley basin in Australia and the Transvaal basin in South Africa. This contrast in measured Fe isotope composition is best interpreted as having been produced by differing pathways of Fe cycling. The Isua BIFs most likely formed by small amounts of Fe oxidation from a water column caused by anoxygenic phototrophs with limited diagenetic alteration, whereas the younger 2.5 Ga Australian and South African BIFs were most likely formed by higher proportions of Fe oxidation and considerable diagenetic reactions that took place between pore fluids and iron oxide gels

  ROADMAP OBJECTIVES: 4.1

• VPL Databases, Model Interfaces and the Community Tool

  The Virtual Planetary Laboratory (VPL) develops computer models of planetary environments, including planets orbiting other stars (exoplanets) and provides a collaborative framework for scientists from many disciplines to coordinate their research. As part of this framework, VPL develops easier to use interfaces to its models, and provides model output datasets, so that they can be used by more researchers. We also collect and serve to the community the scientific data required as input to the models. These input data include spectra of stars, data files that tell us how atmospheric gases interact with incoming stellar radiation, and plant photosynthetic pigments. We also develop tools that allow users to search and manipulate the scientific input data. This year we provided Earth model datasets, new tools for searching the molecular spectroscopic database, and a new database of biological pigments. All of these products and others are published on the VPL Team Website at: http://depts.washington.edu/naivpl/content/models-spectra.

  ROADMAP OBJECTIVES: 1.1 1.2 3.2 4.1 6.1 7.1 7.2

• The Development of Sensory and Nervous Systems in the Basal Branches of the Animal Tree

  Animals interact with the world through complex sensory structures (eyes, ears, antennas, etc.), which are coordinated by collections of neurons. While the nervous and sensory systems of animals are incredibly diverse, a growing body of evidence suggests that many of these systems are controlled by similar sets of genes. We are looking at early branching and understudied lineages of the animal family tree (using the jellyfish Aurelia and the worm Neanthes respectively) to see if these animals use similar genes during neurosensory development as the better-studied fruit fly and mouse. This research is critical for determining which structures are shared between animals because of common ancestry (known as homologous structures) and those that evolved independently in different lineages. Ultimately, such research informs how morphologically and behaviorally complex animals evolve.

  ROADMAP OBJECTIVES: 4.1 4.2

• The Neoproterozoic Carbon Cycle

  We are studying the dynamics of the rise of oxygen during the Neoproterozoic (1 billion years ago to 543 million years ago) through culturing experiments, models and observations (see the progress report on the Unicellular Protists). We are testing the predictions of the following “anti-priming” hypothesis: if more easily degradable organic matter was degraded in oxic environments, this may have slowed down the degradation of organic matter in anaerobic environments and the overall degradation of organic matter, increasing the concentration of oxygen in the atmosphere and the surface ocean. We are currently developing theoretical predictions and testing these ideas by laboratory enrichment cultures of anaerobic microbes that degrade complex substrates in the presence and absence of labile organic compounds.

  ROADMAP OBJECTIVES: 1.1 4.1 4.2 5.2 6.1 6.2

• Project 3D: Constraints on Oxygen Contents in Earth’s Early Atmosphere and Implications for Evolution of Photosynthesis

  The oxidation state of the atmosphere and oceans on the early Earth remains controversial. Although it is accepted by many workers that the Archean atmosphere and ocean were anoxic, hematite in the 3.46 billion-year-old (Ga) Marble Bar Chert (MBC) from Pilbara Craton, NW Australia has figured prominently in arguments that the Paleoarchean atmosphere and ocean was fully oxygenated. In this study, we report the Fe isotope compositions and U concentrations of the MBC, and show that the samples have extreme heavy Fe isotope enrichment. Collectively, the Fe and U data indicate a reduced, Fe(II)-rich, U-poor environment in the Archean oceans at 3.46 billion years ago. Given the evidence for photosynthetic communities provided by broadly coeval stromatolites, these results suggests that an important photosynthetic pathway in the Paleoarchean oceans may have been anoxygenic photosynthetic Fe(II) oxidation.

  ROADMAP OBJECTIVES: 4.1 6.1 7.1 7.2

• Timescales of Events in the Evolution and Maintenance of Complex Life

  We are using natural occurring isotopes produced by long-lived radioactive decay to: provide high-precision dates on geological and biological processes and to trace the geochemical evolution of the oceans during key times in Earth history.

  ROADMAP OBJECTIVES: 4.1 5.3 6.1

• Stoichiometry of Life – Task 2c – Field Studies – Other

  We continued analyses of organic matter in samples of porewaters from a deep ocean hydrothermal mound; concluded a study on element acquisition by biological soil crusts, and initiated a new study that may shed light on a recent hypothesis that floating pumice may have been a site for the origin of life. In this new study, the eruption of the Puyehue / Cordon Caulle volcano on 4 June 2011 near Bariloche, Argentina, provided a unique opportunity to investigate floating pumice as a unique habitat for microbial life. To assess this, we sampled floating pumice from various regional lakes to assess the make-up of the associated microbial communities using genomic techniques and to evaluate the use of key elements (nitrogen, phosphorus) by these microbes using chemical and isotopic methods.

  ROADMAP OBJECTIVES: 4.1 5.2 5.3 6.1

• Stoichiometry of Life, Task 3a: Ancient Records – Geologic

  Fossil and chemical fingerprints of animal life first appear in the geologic record around 600 million years ago. The four billion years of Earth history before this milestone were marked by dramatic changes that we take for granted today but that set the stage for our existence. Among the key events recorded in very old rocks is the first rise of oxygen in the atmosphere and ocean about 2.5 billion years ago following two billion years of a virtually oxygen-free world. And this evolving chemical state was the backdrop against which photosynthesis first evolved; simple, single-celled organisms appeared and diversified; and the first eukaryotic life evolved as a forerunner to the complex animals that would follow one-to-two billion years later. Our work is exploring the evolving compositions of the early atmosphere and ocean and their cause-and-effect relationships with the evolution of life—spanning the middle 50% of Earth history from the first production of oxygen via photosynthesis to the first appearance of animals. Darwin would have been pleased to know that early rocks tell us a convincingly strong: long before the animals, the oceans were teeming with life and that this life set the stage, in so many ways, for the later evolution of animals. Our sophisticated geochemical tracers are changing our view of the early environmental conditions that facilitated, and just as often throttled, the rise of life and the ways life can passively and intentionally modify its own environment—not unlike the lessons we are learning about our relationship with the changing ocean, atmosphere, and climate today.

  ROADMAP OBJECTIVES: 4.1 4.2

• Understanding the Shuram Excursion

  The Shuram carbon isotopic excursion – one of the largest deviations in Earth history- was first discovered in Oman before being found in deposits across the planet. While the causes of this isotopic excursion are as yet unknown, one hypothesis implicates major changes in Ediacaran carbon cycling that occurred simultaneously with the advent of complex life. Alternative hypotheses posit that it is simply a diagenetic anomaly. This research demonstrated that the Shuram Formation carbonates were formed in equilibrium with a fluid with the same oxygen isotopic composition as seawater and at ~50C.

  ROADMAP OBJECTIVES: 4.1 4.2

• Unicellular Protists of the Neoproterozoic

  We investigated 1) how microbial processes shape some sedimentary rocks, 2) how microbial processes influence the isotopic composition of sulfur-rich minerals that are used to understand the evolution of oxygen and the cycling of carbon in the past, 3) searched for fossils of organisms that lived between 716 and 635 million years ago, surviving times when ice covered entire oceans, even at the equator and 4) used these fossils, recovered from limestone rocks, to understand the cycling of carbon during this unusual time.

  ROADMAP OBJECTIVES: 4.1 4.2 5.1 6.1 7.1

• Project 5A: Improvement in the Accuracy of Stable Isotope Analysis by Laser Ablation

  In-situ isotopic analyses are critical for documenting spatial heterogeneities that can be related to the petrography of a sample. In the last decade, recognition of the power of in-situ analysis has spurred development of instrumentation that has improved the precision of in-situ isotopic analysis to unprecedented levels. With this improved precision, it is necessary to critically re-evaluate accuracy in order to identify true heterogeneities form analytical artifacts. We have evaluated the accuracy of in-situ Fe isotope analyses by femto second laser ablation (fs-LA) by evaluating the size and Fe isotope composition of aerosol particles generated by fs-LA, and to evaluate if fs-LA isotope analysis is free of matrix effects. Aerosols produced by fs-LA are small with ~70% of the particles, by mass of Fe, less than 100 nm in aerodynamic diameter, highlighting that the fs-LA particles can be effectively ionized by the plasma. By isotopic mass balance, the aerosols are a stoichiometric sample of the substrate, however, the smallest sized particles have light 56Fe/54Fe isotope compositions and the larger sized particles have heavy 56Fe/54Fe isotope compositions, which highlights the importance of quantitative transport of the aerosol by the ICP source. Matrix studies that include introduction of elements into the fs-LA aerosol by a desolvating nebulizer coupled with isotope analysis of iron oxide standards with variable chemical compositions suggest that matrix effects are driven by space charge processes where elements with low atomic Z relative to Fe such as Mg, and Si have no effects on the accuracy of the analysis but elements with a similar or higher Z such as Mn or U can produce accuracy issues on the order of +0.5 ‰ in δ56Fe.

  ROADMAP OBJECTIVES: 2.1 4.1 7.1 7.2