Notice: This is an archived and unmaintained page. For current information, please browse

2011 Annual Science Report

Astrobiology Roadmap Objective 4.1 Reports Reporting  |  SEP 2010 – AUG 2011

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. Advances have been made in five sub-studies and manuscript writing is in progress. Studies include: 1 & 2. Advancing protocols for organic molecular studies of iron-oxide rich sediments and sediments laden with perchlorate, 3. Carbon Isotopic Records of the Neoarchean, 4. Solid-phase sorbtive extraction of organic molecules in glacial ice, and 5. Amino acid composition of glacial ice.

    ROADMAP OBJECTIVES: 2.1 4.1 5.1 5.2 5.3 6.1
  • 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
  • AIRFrame Technical Infrastructure and Visualization Software Evaluation

    We have analyzed over four thousand astrobiology articles from the scientific press, published over ten years to search for clues about their underlying connections. This information can be used to build tools and technologies that guide scientists quickly across vast, interdisciplinary libraries towards the diverse works of most relevance to them.

    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
  • 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 5.3 6.1 6.2 7.1 7.2
  • Atmospheric Oxygen and Complex Life

    The biosynthesis of sterols requires oxygen but only in vanishingly low concentrations. Oxygen could be used by algae to make sterols in the surface ocean and, yet, at the same time, it would not be in sufficient concentration to destroy the mass-independent sulfur isotope signal for atmospheric oxygenation.

    Large sulfur isotope fractionations have been observed in sulfate reducing bacteria grown in a 'starvation’ regime, much as most natural populations experience. This casts doubt on the hypothesis that the large sulfur isotope fractionations seen in the Neoproterozoic rock record herald an increase in atmospheric oxygen and the inception of a new form of oxidative sulfur cycling.

    ROADMAP OBJECTIVES: 4.1 4.2 6.1
  • Project 1B: U-Th-Pb Geochronology and Fe Isotopes of the 3.4 Ga Marble Bar Chert Indicates Early Anoxygenic Photosynthesis

    The origin of the spectacular red jasper (hematite+chert) at Marble Bar, Australia, has been a subject of debate for decades. Previous work has argued that oxidation occurred at the time of deposition 3.5 b.y. ago, and that the mechanism of oxidation was free oxygen in the atmosphere. This in turn would indicate that oxygenic photosynthesis had evolved by 3.4 Ga. By measuring Fe isotopes in the jasper, we can show that oxidation was extremely limited, and U-Th-Pb isotope geochronology on the same samples shows that the jasper precipitated form U-poor ocean water. This in turn indicates that there was no free oxygen in seawater at the time of deposition of the jasper. This in turn suggests that the mechanism was more likely to have been an anaerobic process, such as anoxygenic photosynthetic Fe(II) oxidation.

    ROADMAP OBJECTIVES: 4.1 6.1 7.1
  • Delivery of Volatiles to Terrestrial Planets

    This project uses computer models and laboratory work to better understand how volatile materials that are important for life, like water, methane, and other organic molecules, are delivered to terrestrial planets. Habitable planets are too small to gravitationally trap these volatiles directly from the gas disk from which they formed, and instead they must be delivered as solids or ices at the time of the planet’s formation, or ongoing as the planet evolves. These trapped volatiles are eventually released to form our oceans and atmosphere. In this task we use computer models of planet formation and migration to understand how the asteroid belt, which is believed to be the source of the Earth’s oceans, was formed. We also use models to understand what happens to meteoritic material as it enters a planet’s atmosphere, especially where it gets deposited in the atmosphere, what happens to it chemically, and how it interacts with the light from the parent star. .

    ROADMAP OBJECTIVES: 1.1 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
  • Amino Acid Alphabet Evolution

    We study the question why did life on this planet “choose” a set of 20 standard building blocks (amino acids) for converting genetic instructions into living organisms? The evolutionary step has since been used to evolve organisms of such diversity and adaptability that modern biologists struggle to discover the limits to life-as-we-know-it. Yet the standard amino acid alphabet has remained more or less unchanged for 3 billion years.
    During the past year, we have found that the sub-set of amino acids used by biology exhibits some surprisingly simple, strikingly non-random properties. We are now building on this finding to solidify a new insight into the emergence of life here, and what it can reveal about the distribution and characteristics of life elsewhere in the universe.

    ROADMAP OBJECTIVES: 3.1 3.2 4.1 4.2 4.3 5.2 5.3 6.2 7.1
  • Biosignatures in Relevant Microbial Ecosystems

    In this project, PSARC team members explore the isotope ratios, gene sequences, minerals, organic molecules, and other signatures of life in modern environments that have important similarities with early earth conditions, or with life that may be present elsewhere in the solar system and beyond. Many of these environments are “extreme” by human standards and/or have conditions that are at the limit for microbial life on Earth.

    ROADMAP OBJECTIVES: 4.1 4.3 5.1 5.2 5.3 6.1 7.1 7.2
  • Project 3: The Origin, Evolution, and Volatile Inventories of Terrestrial Planets

    This research project brings together a large team of scientists with a unified goal understanding the origin and evolution of volatiles (C, H, O, and N) in planetary interiors. It includes a theoretical study of planet formation with focus of addressing the abundance of volatiles in objects that ultimately combine to form the terrestrial planets. The project gains from information being currently revealed through the NASA Messenger mission in orbit around Mercury. The project has an experimental component that focuses on studying volatiles deep in planetary interiors using ultra-high pressure devices and molecular spectroscopy for species interrogation. Finally, it includes a systematic study of the chemistry of mineral inclusions in diamonds, where diamond serves to trap minerals in a natural high pressure container. These studies allow CIW NAI scientists probe the chemistry of Earth’s deep mantle and help reveal how Earth’s plate tectonics may have started.

    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 completed and published our work on the build up and detectability of sulfur-based biosignatures in early Earth-like atmospheres, especially for planets orbiting stars cooler than our Sun. We also continued to explore the potential 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
  • Analogue Environment Deployments on the Big Island

    We are using the saddle region on the Big Island of Hawaii, in collaboration with NASA teams and the Canadian Space Agency in order to test technology related to sustainable living on the moon. My group will evaluate the utility of 3-D visualization in robotic navigation, in particular for the ex-ploration of lava tubes.

    ROADMAP OBJECTIVES: 1.1 2.1 4.1 4.3 6.1 6.2 7.1
  • Biosignatures in Ancient Rocks

    The Earth’s Archean and Proterozoic eons offer the best opportunity for investigating a microbial world, such as might be found elsewhere in the cosmos. The ancient record on Earth provides an opportunity to see what geochemical signatures are produced by microbial life and how these signatures are preserved over geologic time. As part of our integrated plan, we will study geochemical, isotopic, and sedimentary signatures of life in order to understand the context in which these biosignatures formed.

    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
  • Project 1C: U-Th-Pb Geochronology of the 3.4 Ga Apex Basalt Suggests an Anoxic Early Earth Atmosphere

    Direct determination of the age of oxidative weathering in ancient rocks is difficult, but bears on when the surface environments of the Earth contained free oxygen, which in turn constrain when oxygenic photosynthesis was sufficient to overwelm reduced sinks for oxygen. It has been proposed that oxidized zones of the 3.4 Ga Apex Basalt in the Pilbara Craton formed in the Archean, at least 2.8 b.y. ago, and possibly as old at 3.4 b.y. ago. However, application of U-Th-Pb geochronology to these rocks indicate that oxidation was recent, probably within the last 200 m.y., reflecting deep Phanerozoic weathering that occurred across Australia. The oxidized zones therefore do not reflect the presence of free oxygen in the Archean.

  • 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). While the amino acid composition of these closely related paralogs are often quite similar, their biochemical reactivity and substrate specificity are often very different. This phenomenon is a direct consequence of the composition and molecular structure of the active site metallocluster, which requires a number of accessory proteins to synthesize. 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 Extraterrestrial Settings

    The focus of this project is to explore indicators of life outside of Earth, both within the Solar System and on extrasolar planets. The work includes studies of the chemistry and composition of the Solar System, and the past history of conceivable sites for life in the Solar System. We also look for habitable planets outside the Solar System; work on developing new techniques to find and observe potentially habitable planets; and model the dynamics, evolution and current status of a variety of extrasolar planets.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 4.1 4.3 6.2 7.1 7.2
  • Project 1D: Evolution of Life Related to the Development of the Earth’s Core

    We investigated the effect of evolution of the Earth’s core on the magnetic field, which bears on the extent of magnetic shielding of cosmic radiation, which in turn has implications for the evolution of life. We hypothesize that extensive magnetic shielding likely occurred only after turbulent flow in the liquid outer core subsided, which would have occurred after 1 or 2 b.y. of inner core solidification, allowing differential rotation of the inner and outer core. These results suggest that life which evolved in the first 1 to 2 b.y. of Earth history would have had to develop strategies to cope with high cosmic radiation. The most effective strategy is to use shielding by absorption of radiation by water. Consequently evolution of life on the surface of the Earth occurred much later in the Earth’s history.

  • Evolution and 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.

  • Project 2A: Estimation of Pre-Biotic Amino Acids Delivery to Earth by Carbonaceous Chondrite Meteorites

    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. We focus here on amino-acid isomer adsorption, conformation, and racemization on minerals representing primitive and altered peridotite found in chondritesand on planetary bodies. The study is inspired by the discovery of an excess of L-isovaline, a non-biologic amino acid, in a few carbonaceous meteorites by (Glavin and Dworkin, 2009), which suggests that the chiral nature of biology may have been due to excess L-amino acids delivered pre-biotically by meteorites.

    In the present year of funding, we expanded our study to determine the conformation and binding modes of the acidic amino-acids, glutamate (Glu) and aspartate (Asp), adsorbed on model oxide, γ-Al2O3, using Attenuated Total Reflectance-Fourier Transform Infra-Red Spectroscocpy (ATR-FTIR) and the Triple Layer surface complexation model fits to bulk adsorption data over a wide range of pHs and amino-acid concentrations.

    We also examined adsorption of L- and D- Glu, Asp, and a non-biological; amino acid, iso-valine on peridotite and serpentinte as pristine and altered analogs of carbonaceous chondrites, using LC-FD/ToF-MS. Preliminary results do not indicate preferential adsorption of either L- or D-amino-acids on peridotite and serpentinite, within detection limits. More detailed studies are required to improve the sensitivity and accuracy of the experiments involving the chiral amino-acids adsorption on chondritic analog materials.

    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
  • Composition of Parent Volatiles in Comets

    During the period covered by this progress report we conducted an extensive observing campaign on the Jupiter-family comet 103P/Hartley-2 – the target of the EPOXI fly-by mission. We studied the volatile composition of two other Jupiter-family comets – 10P/Tempel-2 and 21P/Giacobini-Zinner. We continued our multi-comet surveys of spin temperatures and searches for deuterated species. We characterized the abundances of several prebiotic molecules in comet C/2007 N3 Lulin. We also organized NAI-funded “Workshop on cometary taxonomies” held in Annapolis, MD

    ROADMAP OBJECTIVES: 2.2 3.1 4.1
  • Project 5: Geological-Biological Interactions

    This project involves multiple researchers exploring life in extreme environments, the signature of life (chemical, isotopic and mineralogical), and the adaption of life. All together the many sub-topics of this project seek to inform us about where to search for life on other worlds and how to seek evidence that life once existed on other worlds.

    ROADMAP OBJECTIVES: 4.1 5.1 6.1 6.2 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
  • Metabolic Networks From Single Cells to Ecosystems

    Members of the Segre’ group use systems biology approaches to study the complex network of metabolic reactions that allow microbial cells to survive and reproduce under varying environmental conditions. The resource allocation problem that underlies these fundamental processes changes dramatically when multiple cells can compete or cooperate with each other, for example through metabolic cross-feeding. Through mathematical models of microbial ecosystems and computer simulations of spatially structured cell populations, the Segre’ team aims at understanding the environmental conditions and evolutionary processes that favor the emergence of multicellular organization in living systems.

    ROADMAP OBJECTIVES: 4.1 4.2 5.1 5.2 6.1
  • Deep (Sediment-Buried Basement) Biosphere

    The ocean crust comprises the largest aquifer on earth. Deep sediment cover provides an environ-ment for a unique biosphere hosting microorganisms surviving under extreme conditions. Frac-tured rock provides abundant surfaces that can be colonized by diverse microbes and water-rock reactions promote chemical conditions that influence key geochemical cycles within the Earth’s crust and oceans. Team members participated in a 14-day research cruise to study the sediment-buried basement (basaltic crust) biosphere, to provide unprecedented and unique insight into the mobility and origin of microorganisms within this remote biosphere.

    ROADMAP OBJECTIVES: 4.1 4.2 5.2 5.3 6.1 6.2 7.1 7.2
  • Modelling Planetary Albedo & Biomarkers in Rocky Planets’/moons Spectra

    Using data from Kepler and new ground-based detections, Lisa Kaltenegger and Dimitar Sasselov have identified which confirmed and candidate planets orbit within the Habitable Zone and could provide environments for basic and complex life to develop. They have also developed atmosphere models for extrasolar planetary environments for different geological cycles and varied environments for the advent of complex life. The team modeled detectable spectral features that identify such planetary environments for future NASA missions like the James Webb Space Telescope.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.2 6.2 7.2
  • 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 2D: Establishing Biogenicity and Environmental Setting of Precambrian Kerogen and Microfossils

    Stable carbon isotope ratios preserved in ancient organic matter provide valuable information about the origin and evolution of metabolic pathways, and the evolution of the carbon cycle in general. In situ carbon isotope analysis allows organic matter to be measured in petrographic context. The microtexture and spatial relationship of sedimentary organic matter and its mineral matrix offers clues about source and diagenetic history – essential elements in the interpretation of isotopic data. We have developed protocols with the IMS-1280 ion microprobe to analyze carbon isotope ratios in organic matter with a spot size of 1–10 μm. A suite of new standards allows correction of matrix effects due to variable chemical composition. Four suites of Proterozoic microfossils of uncontested biogenicity have been analyzed, showing distinct values of δ13C that correlate with taxonomy and metabolism (Williford et al. 2011a in prep). Studies of kerogen and pyrobitumen from 2.7–2.5 Ga sediments support prior conclusions about differential impacts of aerobiosis and methane metabolisms in shallow versus deep-water depositional environments and reveal a degree of isotopic heterogeneity obscured by conventional, bulk analyses (Williford et al, 2011b in prep). Analysis of organic matter from the 3.35 Ga Strelley Pool Chert yield low and consistent values of δ13C, consistent with a biogenic origin (Lepot et al. 2011, in prep).

  • Project 8: 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 the collaborative interaction among the NAI investigators

    ROADMAP OBJECTIVES: 1.1 3.1 4.1 4.3
  • Postdoctoral Fellow Report: Mark Claire

    I have studied how biology might have impacted Earth’s early atmosphere, and how the Sun’s light has changed with time. More specifically, I’ve modeled how enhanced release of biogenic sulfur gases in earlier periods of Earth history may have left clues in the geologic record, and compared these predictions to the data. Furthermore, I have made a model of what how the light from the Sun would appear at any planet or any time in the solar system.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 4.1 7.2
  • Project 3A: Stable Isotope and Mineralogical Studies of Banded Iron Formations – O and Si Isotopes by SIMS

    We have studied the mineralogy and microscopic textures of four banded iron formations (BIFs): Isua, Greenland (3.8 Ga); Hamersley, Western Australia (2.5 Ga); Transvaal, South Africa (2.5 Ga), and Biwabik, Minnesota, USA (1.9 Ga). These rocks have been interpreted to preserve records of conditions and chemistry of Precambrian oceans. This hypothesis is evaluated with in situ SIMS analysis of oxygen (δ18O) and silicon isotope ratios (δ30Si) in chert domains within the BIFs. The paragenesis of magnetite and hematite is important to understanding the fluid and thermal history of unmetamorphosed or low-temperature (sub-greenschist facies) oxide-facies BIFs. We identified silician (up to 3 wt% SiO2) magnetite overgrowths in samples of the Dales Gorge BIF from Wittenoom. We hypothesize that silician magnetite is stabilized by organic matter and thus is a biosignature. We investigated the distribution of δ18O values in quartz, magnetite, silician magnetite, and hematite by SIMS and found that while quartz is homogeneous (average δ18O = 22.0 ±1.3‰ 2SD, VSMOW), values of δ18O for magnetite and hematite vary by 13‰ (-5 to +7‰) and are correlated with different generations of magnetite and hematite.

    ROADMAP OBJECTIVES: 4.1 5.2 7.1
  • Ironing Out the RNA World

    Life originated during the early Archean, which was characterized by a non-oxidative atmosphere and abundant soluble Fe2+. Current theories on the origin of life focus on RNA-based genetic and metabolic systems. Here we show, by theory and experiment, that critical roles of Mg2+ in extant RNA folding and function can be better served by Fe2+ in the absence of oxygen. The results of our high-level quantum mechanical calculations show that the geometry of coordination of Fe2+ by RNA phosphates is similar to that of Mg2+. The conformation of Tetrahymena Group I intron P4-P6 domain is conserved between complexes of Fe2+ and Mg2+. Additionally, a ribozyme obtained previously by in vitro selection in the presence of Mg2+ and a natural ribozyme both have significantly greater catalytic competence in the presence of Fe2+ than in Mg2+. The combined biochemical and paleogeological data are consistent with an RNA-Fe2+ world that could have supported an array of RNA structures and catalytic functions far more diverse that of an RNA-Mg2+ world.

  • 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. We used models to study the effect of one very big flare on a planet with a carbon dioxide dominated atmosphere, like the early Earth’s, and found that these types of planets are well protected from the UV flux from the flaring star. We have also looked at the first quarter of Kepler data to study flare activity on “ordinary” cool stars, that have not been preselected for their tendency to have large flares. We find that these cool stars fall into two categories: stars that have long duration flares of several hours, but flare less frequently overall, and stars that have short duration flares, but more of them. In future work we will explore the comparative effect on a habitable planet of these two patterns of flaring activity.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 4.1 4.3 7.2
  • Project 3B: In Situ Sulfur Isotope Studies in Archean-Proterozoic Sulfides

    Using new protocols developed at WiscSIMS, we made in situ measurements of three stable isotopes of sulfur (32S, 33S and 34S) in pyrite from the Meteorite Bore Member with unprecedented small spot sizes and accuracy (Williford et al. 2011). We have found a moderate range of S-MIF (> 1‰) in authigenic pyrite before, during and after the Early Proterozoic glaciation as well as a 90‰ range of mass dependent sulfur isotope fractionation (δ34S) larger than any observed in sediments older than 700 Ma. Furthermore, abundant detrital pyrite preserved in one glacial sandstone unit from the Meteorite Bore Member exhibits a range of mass-independent sulfur isotope fractionation slightly larger than the largest published range, from 2.5 Ga sediments of the Hamersley and Transvaal Basins (> 15‰), suggesting that these detrital grains may have originated in rocks of similar age. Taken together, these data imply that the Meteorite Bore Member was deposited during the transitional interval when atmospheric oxygen had risen sufficiently for enhanced continental weathering and ocean sulfate to occur, yet remained low enough to permit the preservation of detrital pyrite and moderate S-MIF.

    ROADMAP OBJECTIVES: 1.1 4.1 4.2 7.1
  • 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
  • Project 3C: Integration of Multiple Isotope Proxies to Study the Pre-GOE Oxygenation of the Earth

    The period 2.7 to 2.5 b.y. ago, the period leading you to the Great Oxidation Event (GOE), is becoming increasingly recognized as a time of major environmental change. A holistic understanding of the changes that occurred in microbial ecology, and their effects of the environment, are only possible by integrating multiple geochemical proxies. By simultaneously looking at C, O, S, Fe, Mo, and Sr isotopes, we develop a picture of extensive oxygenic photosynthesis, but approximate balance with reduced resevoirs such as reduced Fe and reduced volcanic gases, such that free oxygen did not yet become abundant on the planet. Although many workers have questioned a rise in oxygenic photosynthesis significantly before the GOE, these new data clearly indicate that this metabolism was widespread at least 400 m.y. before the GOE.

    ROADMAP OBJECTIVES: 4.1 5.3 6.1 7.1 7.2
  • Protists of the Neoproterozoic

    T. Bosak (MIT), S. Pruss (Smith College), F. Macdonald (Harvard U.) and D. Lahr (U. Sao Paolo) discovered fossils of microscopic eukaryotes in limestone and dolostone strata deposited between the two Neoproterozoic low-latitude glaciations (between ~ 716 and 635 million years ago). These fossils include amoeba-like organisms that incorporated mineral-rich particles from the environment into their shells, mineral-rich shells of the oldest putative foraminiferans, and thick flask-shaped organic envelopes of the first putative ciliates, representatives of a major group of modern eukaryotes. These fossils demonstrate a previously unrecognized record of body fossils during the ~ 70 million years between the two “Snowball Earth” episodes and document the increasing diversity of morphologically and compositionally modern eukaryotes before the rise of complex animals.

    ROADMAP OBJECTIVES: 4.1 4.2 5.2 6.1
  • Proxies for Ocean Anoxia

    Episodes of widespread anoxia in past oceans are known as “Ocean Anoxic Events”. The ecosystem consequences of these events are actively debated. In this project, we are examining the chemical and isotopic signatures of the photosynthetic pigment, chlorophyll, to understand changes in ecosystems and the nutrients that fueled them. The seasonal oxygen minimum zone (OMZ) offshore Chile is being used as a modern analog.

    ROADMAP OBJECTIVES: 4.1 4.2 5.2 5.3 6.1
  • Project 4B: Iron Isotope Biosignatures – Synthesis of Abiotic and Biotic Laboratory Experiments

    Experimental studies in geochemical systems analogous to ancient rock precursors are required to gain insight into the biogeochemical processes responsible for generating unique chemical or isotopic compositions in ancient rocks. We conducted a synthesis of prior and ongoing laboratory studies of Fe isotope fractionation during abiotic and biologically catalyzed (by dissimilatory microbial iron reduction, DIR) interaction between Fe(II) and Fe(III) oxide phases in the presence of dissolved silica, which was likely abundant in Precambrian oceans. In particular, previous studies of iron isotope fractionation during microbial reduction of an amorphous iron oxide-silica coprecipitate in high-silica, low-sulfate artificial Archean seawater were analyzed in combination with fractionation during abiotic Fe(II)-Fe(III) interaction to assess the rates and mechanisms of Fe isotope fractionation. The results show that although isotopic exchange rates were a function of solid and solution compositions, in all cases they were much higher than that determined in previous studies of aqueous Fe(III) and ferrihydrite interaction, highlighting the importance of electron exchange in promoting Fe atom exchange. When compared to analogous microbial reduction experiments with overlapping Fe(II) to Fe(III) ratios, isotopic exchange rates are faster in the biological experiments, likely due to promotion of atom exchange by the solid-phase Fe(II) produced during DIR. These findings provide constraints on the range of equilibrium iron isotope fractionations that may be produced by different geochemical processes. In addition, when interpreted in a Fe mass-balance context, our findings provide strong support for DIR as a mechanism for producing Fe isotope variations observed in Neoarchean and Paleoproterozoic marine sedimentary rocks.

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

    For the first time, a precise and detailed chronology has been developed for numerous factors associated with the great mass extinction that ended to Paleozoic Era

  • Project 4C: Iron Isotope Geochemistry in Biogenic Magnetite-Bearing Lake Sediments

    The production of magnetite as a byproduct of dissimilatory microbial iron oxide reduction (DIR) has been hypothesized to be an important pathway in the early diagenesis of chemically-precipitated sediments on early Earth, leading ultimately to the preservation of large quantities of magnetite in banded iron formations (BIFs). A significant fraction of the magnetite (and other Fe-bearing minerals such as siderite and pyrite) in BIFs is isotopically light, likely due to Fe isotope fractionation between biogenic Fe(II) and residual Fe(III) oxides. Only one modern environmental setting has reported possible in situ magnetite formation resulting from DIR: the Bay of Vidy in Lake Geneva, Switzerland. Previous work has characterized a widespread magnetic susceptibility anomaly in the Bay of Vidy sediments stemming from an influx of amorphous Fe(III) oxide from a nearby sewage treatment plant, and determined the presence of fine-grained magnetite apparently produced via DIR. In this study, we examined the Fe isotope composition of distinct pools of solid-phase Fe contained in sediments from the Bay of Vidy. Significant Fe(III) reduction has taken place, resulting in the reduction of nearly all reactive (non-silicate) Fe. Very little Fe isotope variation was observed within sediment Fe pools, including magnetite. The lack of sediment heterogeneity, along with the highly reduced nature of the sediments, suggests that DIR has carried through to completion in this deposit. The absence of spatial Fe redox gradients accompanying complete Fe(III) reduction has prevented the segregation of Fe isotopes during microbial reduction. This case study provides a basis for interpreting instances in the rock record where DIR was active but no Fe isotope fractionation was preserved.

  • Understanding Past Earth Environments

    For much of the history Earth, life on the planet existed in an environment dramatically 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 and is accessible to detailed study. As such, is 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 of the ancient atmosphere, modeled the effects of clouds on such a planet, studied the sulfur, oxygen and nitrogen cycles, and the 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 5A: Production of Mixed Cation Carbonates in Abiologic and Biologic Systems

    In the fourth year of our NAI project, a series of free drift experiments and one chemo-stat experiment were completed to determine the effect of temperature, chemical composition, pCO2, pH and precipitation rate on the incorporation of Mg in calcite in relatively dilute solutions. These experiments will permit geochemical relationships to be established between carbonate minerals and the solutions from which they form to gain a better understanding of the origin and occurrence of carbonates in ancient terrestrial and extraterrestrial environments.

  • Stoichiometry of Life – Task 2c – Biological Soil Crusts: Metal Use and Acquisition

    Desert biological soil crusts (BSCs) are a complex consortia of microorganisms including cyanobacteria, algae, and fungi. BSCs are the primary colonizers of desert soils, supplying both carbon and nitrogen to these arid-land ecosystems. As such, they may represent an analog for soil development on the early Earth. BSCs occupy an extremely nutrient-poor niche, and meet their nutrient and metal requirements by manipulating their surroundings via the production of metal-binding ligands called siderophores. The soil crust’s metabolism affects the chemical composition of soil porewaters and soil solid phases; these alterations to soil metal contents may represent a biosignature for biological soil crusts that can be preserved over long time scales.

    ROADMAP OBJECTIVES: 4.1 5.3 6.1 6.2 7.1
  • Remote Sensing of Organic Volatiles in Planetary and Cometary Atmospheres

    We developed state-of-the-art spectroscopic methods to analyze our extensive infrared database of Mars and cometary spectra. In the last two years, we acquired the deepest and most comprehensive search for biomarkers on Mars using powerful infrared high-resolution spectrometers (CRIRES, NIRSPEC, CSHELL) at high-altitude observatories (VLT, Keck-II, NASA-IRTF respectively). In order to analyze this unprecedented wealth of data, we developed highly automated and advanced processing techniques that correct for bad-pixels/cosmic-rays and perform spatial and spectral straightening of anarmophic optics data with milli-pixel precision. We also constructed line-by-line models of the ν7 band of ethane (C2H6), the ν3 and ν2 bands of methanol (CH3OH), we compiled spectral information for H2O and HDO using 5 databases (BT2, VTT, HITEMP, HITRAN and GEISA), and compiled spectral information NH3 using 4 databases (BYT2, TROVE, HITRAN and GEISA). These great advancements have allowed us to understand the infrared spectrum of planetary bodies with unprecedented precision.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 4.1 7.1 7.2
  • Project 5B: Magnesium Isotope Fractionation Between Calcite and Aqueous Mg

    The isotopic composition of Mg in carbonate is of interest to studies on paleo environments because of the potential for constraining temperatures, vital effects, and Mg fluxes associated with precipitation of carbonate minerals. Indeed, Mg isotope fractionation during inorganic carbonate precipitation is important because this serves as the baseline for interpreting the Mg isotope variations and inferred fluid isotope compositions for both abiogenic and biogenic carbonate. We report the results of Mg-bearing calcite synthesis studies used to constrain the fractionation of Mg isotopes during calcite precipitation. The results provide the baseline data needed to interpret Mg-bearing carbonates from the early Earth, as well as carbonates that are likely to be found on Mars.

    ROADMAP OBJECTIVES: 4.1 7.1 7.2
  • Stoichiometry of Life, Task 3a: Ancient Records – Geologic

    We have generated and are interpreting a wide range of geochemical data from rocks that are over 1.5 billion years old. The data indicate that the ancient ocean was very different than today and had regions that were full of toxic hydrogen sulfide. These extreme conditions in the ocean were the backdrop against which early organisms appeared and evolved—and perhaps struggled.

  • Stoichiometry of Life, Task 4: Biogeochemical Impacts on Planetary Atmospheres

    Oxygenation of Earth’s early atmosphere must have involved an efficient mode of carbon burial. In the modern ocean, carbon export of primary production is dominated by fecal pellets and aggregates produced by the animal grazer community. But during most of Earth history the oceans were dominated by unicellular, bacteria-like organisms (prokaryotes) causing a substantially altered biogeochemistry. In this task we experiment with the marine cyanobacterium Synechococcus sp. as a model organism and test its aggregation and sinking speed as a function of nutrient (nitrogen, phosphorus, iron) limitation. We have found so far that aggregation and sinking of these minute cyanobacteria is influenced by the concentration of nutrients in the growth medium.

    ROADMAP OBJECTIVES: 4.1 4.2 5.2 6.1 7.2
  • Project 7C: Improving Accuracy of in Situ Stable Isotope Analysis by SIMS

    Isotopic analysis of biologically important elements in petrographic context is a fundamental tool for astrobiology. Secondary ion mass spectrometry (SIMS) is a powerful tool used to understand biogeochemical processes at the spatial scale of the individual microorganisms that drive them. The benefits of the extremely high spatial resolution offered by SIMS do not come without costs, however. Unconstrained physical and chemical variables in the sample of interest can introduce biases leading to inaccurate measurements. Understanding and constraining these barriers to accuracy as we move towards ever finer spatial resolution and analytical precision is a primary focus at WiscSIMS.

    ROADMAP OBJECTIVES: 4.1 5.1 5.2 5.3 7.1