2010 Annual Science Report

Astrobiology Roadmap Objective 4.1 Reports Reporting  |  SEP 2009 – AUG 2010

Project Reports

  • Biosignatures in Ancient Rocks

    This team of geologists, geochemists, paleontologists and biologists seeks signs of early life in ancient rocks from Earth. Working mostly on that part of Earth history before the advent of skeletons and other preservable hard parts in organisms, our group focuses on geochemical traces of life and their activities. We also investigate how life has influenced, and has been influenced by changes in the surface environment, including the establishment of an oxygen-rich environment and the initiation of extreme climate states including global glaciations. For this we use a combination of observations from modern analogous environments, studies of ancient rocks, and numerical modeling.

    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
  • AIRFrame Technical Infrastructure and Visualization Software Evaluation

    The Astrobiology Integrative Research Framework (AIRFrame) analyzes published and unpublished documents to identify and visualize implicit relationships between astrobiology’s diverse constituent fields. The main goal of the AIRFrame project is to allow researchers and the public to discover and navigate across related information from different disciplines.

    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
  • AbGradCon 2010

    The Astrobiology Graduate Student conference is a conference organized by astrobiology graduate students for astrobiology grad students. It provides a comfortable peer forum in which to communicate and discuss research progress and ideas.

    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
  • Advancing Methods for the Analyses of Organics Molecules in Microbial Ecosystems

    Eigenbrode’s GCA work over the past year has largely focused on developing thermochemolysis methodologies for extracting components of complex organics molecules from samples that pose unique analytical challenges because of their mineral composition. These include iron-oxide rich samples regarded as analogs to ancient aqueous environments on Mars and ancient Earth, as well as perchlorate-laden samples. Eigenbrode is making progress with the method development and has observed some interesting biosignatures relevant to understanding microbial contributions and sedimentary preservation. In addition, Eigenbrode has begun a new collaboration with MIT and Wisconsin teams with the intention of applying innovative techniques to understanding the distribution of stable carbon isotopes in the Archean rock record.

    ROADMAP OBJECTIVES: 4.1 5.1 5.2
  • 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
  • Amino Acid Alphabet Evolution

    A standard “alphabet” of just 20 amino acids builds the proteins that interact to form metabolism of all life on Earth (rather like the English of 26 letters can be linked into words that interact in sentences and paragraphs to produce meaningful writing). However, considerable research from many scientific disciplines points to the idea that many other amino acids are made by non-biological processes throughout the universe. A natural question is why did life on our planet “choose” the members of its standard alphabet?

    Our project seeks to gather and organize the diverse information that describes these non-biological amino acids, to understand their properties and potential for making proteins and thus to understand better whether the biology that we know is a clever, predictable solution to making biology – or just one of countless possible solutions that may exist elsewhere.

    ROADMAP OBJECTIVES: 1.1 3.1 3.2 3.4 4.1 4.3 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
  • Biosignatures in Extraterrestrial Settings

    The team will investigate the abundance of sulfur gases and elucidate how these gases can be expected to evolve with time on young terrestrial planets. They will continue studies of planet formation in the presence of migration and model radial transport of volatiles in young planetary systems, and will be involved with searches for M star planetary companions and planets around K-giant stars.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 4.1 4.3 6.2 7.1
  • Delivery of Volatiles to Terrestrial Planets

    Habitable planets are too small to trap gases from the planet-forming disk. Their oceans and atmospheres must originate in the planetesimals from which the planet is built. In this task, we explore how, when, and from where Earth, Mars and habitable worlds around other stars can accumulate water and organic carbon. The main challenge is that water and organic carbon are relatively volatile elements (compared to rock and metal). Therefore, during the period of time in which solids condensed at the current position of Earth, water and carbon would have been mainly in the gas phase. Getting these materials to the habitable zone requires that material from further out in the disk would be transported inward. Another challenge is that upon reaching the Earth, both large and small suffer severe heating during atmospheric entry. We also have investigated the fate of these compounds upon release into the atmosphere.

    ROADMAP OBJECTIVES: 1.1 3.1 4.1 4.3
  • Project 3: The Origin, Evolution, and Volatile Inventories of Terrestrial Planets

    The origin and Sustenance of life on Earth strongly depends on the fact that volatile elements H-C-O-N where retained in sufficient abundance to sustain an ocean-atmosphere. The research in this project involves studies of how terrestrial planets form, why differences exist among the terrestrial planets, how volatiles behave deep within the Earth, and how volatiles and life influence the large and small scale composition of the near surface Earth.

    ROADMAP OBJECTIVES: 1.1 3.1 4.1
  • 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
  • Environmental Oxygen and the Rise (And Fall) of Metazoans

    The viability of complex animals is intimately linked to the availability of molecular oxygen. This project looks at the environmental signatures of oxygen production and availability on a range of timescales and the connection between the stages of Precambrian oxygenation and biological complexity. Increasingly, it is becoming clear that the major mass extinction events of the Phanerozoic are strongly correlated to episodes of deoxygenation.

  • Developing New Biosignatures

    The development and experimental testing of potential indicators of life is essential for providing a critical scientific basis for the exploration of life in the cosmos. In microbial cultures, potential new biosignatures can be found among isotopic ratios, elemental compositions, and chemical changes to the growth media. Additionally, life can be detected and investigated in natural systems by directing cutting-edge instrumentation towards the investigation of microbial cells, microbial fossils, and microbial geochemical products. Our efforts are focused on 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: 2.1 2.2 3.1 3.2 3.4 4.1 5.2 5.3 7.1 7.2
  • 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.

  • 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. Work this year focused 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 explored 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 on acquiring and getting running two simulators for telescopes that will one day be able to observe and determine the properties of extrasolar terrestrial planets.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 6.2
  • Bioastronomy 2007 Meeting Proceedings

    This is the published volume of material from an astrobiology meeting hosted by our lead team in 2007 in San Juan Puerto Riceo. The book includes 60 papers covering the breadth of astrobiology, and developed a new on-line astrobiology glossary.

    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 5: Geological-Biological Interactions

    This project focuses on a wide range of questions spanning understanding microbial diversity in extreme environments to the identification of biosignatures in modern and ancient rocks. In terms of environments, research in this project focuses on research at deep sea hydrothermal vents, desert sulfate deposits, arctic hydrothermal fields, as well as Paleoproterozoic terrains of Australia, Canada, and India. By learning more how life adapts to extreme environments on Earth, we hope to gain a better understanding of the limits of life on other worlds. By understanding better the signature of life recorded in ancient rocks, we hope to better refine our search stategies for the presence of life on other worlds.

    ROADMAP OBJECTIVES: 4.1 5.1 6.1 6.2 7.1
  • Molecular Paleontology of Iron-Sulfur Enzymes

    In this project we are attempting to trace back in the evolutionary record using specific genetic events as markers. We are using specific gene fusion and gene duplication events in the genetic record to place a chronological sequence to the advent of nitrogen fixation, certain modes of hydrogen metabolism, and both anoxygenic and oxygenic photosynthesis.

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 3.4 4.1 5.1 5.2 5.3 6.1
  • PHL 278: A Gateway Course for a Minor in Astrobiology

    We have recently developed obtained Montana Board of Regents for an undergraduate minor in Astrobiology at Montana State University. The Minor includes courses in Earth Sciences, Physics, Astronomy, Microbiology, Ecology, Chemistry, and Philosophy. Two new courses have been developed as part of the minor, one of which is a gateway or introductory course examines the defining characteristics of life on earth as well as the challenges of a science that studies life and its origin. The other course which will be offered fall 2011 is the capstone course for the minor which will delved into the science of Astrobiology in more detail and targeted for Juniors and Seniors that have fulfilled the majority of the requisite course requirements for the curriculum.

    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
  • Computational Astrobiology Summer School

    The Computational Astrobiology Summer School (CASS) is an excellent opportunity for graduate students in computer science and related areas to learn about astrobiology, and to carry out substantial projects related to the field.

    The two-week on-site part of the program is an intensive introduction to the field of astrobiology. NASA Astrobiology Institute scientists present their work, and the group discusses ways in which computational tools (e.g. models, simulations, data processing applications, sensor networks, etc.) could improve astrobiology research. Also during this time, participants define their projects, with the help of the participating NAI researchers. On returning to their home institutions, participants work on their projects, under the supervision of a mentor, with the goal of presenting their completed projects at an astrobiology-related conference the following year.

    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 2B: Production of Mixed Cation Carbonates in Abiologic and Biologic Systems

    Carbonate minerals commonly occur on Earth and they are found in extraterrestrial materials such as meteorites and interplanetary dust particles. The chemistry of carbonates provides clues about their formation and alteration of over time. For example, carbonate minerals that form inorganically have chemical compositions that are highly constrained by the environmental conditions under which they grow, however, it is now known that microorganisms can produce carbonates that deviate from these generally accepted patterns. When carbonate minerals are placed in the appropriate environmental context, certain compositions may represent a biosignature for microbially mediated formation. The goal of this project is to develop a broader understanding of how carbonate minerals grow so that we may formulate explicit criteria for their origin based on their chemical and isotopic composition.

  • 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

    We use mathematical and computational approaches to study the dynamics and evolution of metabolism in individual microbes and in microbial ecosystems. In particular, we take advantage of sequenced genomes to study the complete network of biochemical reactions present in an organism. We have been extending these approaches from single genomes to multiple genomes, generating ecosystem-level models of metabolism, which can help us understand some of the key transitions in the history of life on our planet.

    ROADMAP OBJECTIVES: 4.1 4.2 5.1 5.2 6.1
  • Project 2D: Tectonic Hydrogen Production Through Piezoelectrochemical Effect, a New Mechanism for the Direct Conversion of Mechanical Energy to Chemical Energy by Deforming Piezoelectric Minerals in Water

    A decade ago, environmental microbiologists put forth the radical proposal that the Earth may contain a deep biosphere, where microorganisms may live several kilometers deep within the Earth, effectively isolated from the surface biosphere. This in turn has important implications for our search for life elsewhere in the universe. A key issue of this proposal is how could such life sustain itself? We propose a mechanism of Piezoelectrochemical Effect for the direct conversion of mechanical energy to chemical energy. This phenomenon is capable of hydrogen and oxygen via direct-water decomposition by means of as-synthesized quartz and other piezoelectric micro-crystals. Deformation of the piezoelectric crystals will lead to strain-induced electric charges development on crystals surfaces. With sufficient electric potential, strained piezoelectric crystals in water triggered the redox reaction of water to produce hydrogen and oxygen gases. This study provides a new insight for generating tectonic hydrogen for sustaining sub-surface microorganisms through deforming piezoelectric minerals like quartz in geological environments, and it may be an important process for sustaining the deep biosphere on Earth.

  • Deep (Sediment-Buried Basement) Biosphere

    The ocean crust comprises the largest aquifer on earth and there is increasing evidence that supports the presence of actively growing microbial communities within basaltic porewaters.

    Advanced Integrated Ocean Drilling Program (IODP) circulation obviation retrofit kit (CORK) observatories provide a unique opportunity to sample these otherwise inaccessible deep subseafloor habitats at the basalt-sediment transition zone. Aging porewaters remain isolated within this sediment-buried upper oceanic basement, subjected to increasing temperatures and pressures as plates move away from spreading ridges.

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

    The recent discovery of several potentially habitable Super-Earths (planets up to about 10x the mass of our own Earth that could be rocky) and the first nearby super-Earth planets around the habitable Zone of Gl581, has proven that we can already detect potentially habitable planets and makes this research extremely relevant. We model atmospheric spectral signatures, including biosignatures, of known and hypothetical exoplanets that are potentially habitable.
    The atmospheric characterization of such Super-Earths and potentially habitable Moons, will allow us to explore the condition on the first detectable rocky exoplanets and potentially characterize the first detectable Habitable Exoplanet.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.2 6.2 7.2
  • Structure, Reactivity, and Biosynthesis of Cataylic Iron-Sulfur Clusters

    We are examining the biosynthesis of complex iron-sulfur cluster to determine the specific chemistry associated with modifying iron-sulfur motifs in biology for different functions. We then relate the chemistry associated with these modifying reactions to reactions that could potentially modify iron-sulfur mineral motifs in the early non-living Earth to promote analogous reactivity.

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 3.4 4.1 7.1 7.2
  • Postdoctoral Fellow Report: Mark Claire

    I am interested in how biological gases affect the atmosphere of Earth (and possibly other planets.) Specifically, I use computer models to investigate how biogenic sulfur gases might build up in a planetary atmosphere, and if this would lead to observable traces in Earth’s rock record or in the atmospheres of planets around other stars. I’ve also worked on how perchlorate formed in Earth’s Atacama desert as an attempt to explain how perchlorate formed on Mars

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 4.1 7.2
  • Project 3A: Quantifying the Amount of Free Oxygen in the Neoarchean Photic Zone Through Combined Fe and Mo Isotopes

    The history of Earth’s atmospheric evolution is critical for understanding the interplay between life and the physical environment, both here on Earth, and potentially on other worlds. The majority of models for Earth’s atmospheric evolution, and evidence from the geologic record, suggest that the atmosphere was virtually devoid of free oxygen through the Archean and into the earliest Proterozoic, and became more oxygen-rich over time in a punctuated fashion. The earliest significant increase in atmospheric oxygen has been termed the “Great Oxidation Event” (GOE), and is commonly considered to have occurred between ~2.4 and 2.2 Ga (Holland, 1984, 2006 and references therein). However, some geologic evidence indicates that the free oxygen content of the atmosphere-hydrosphere system may have been similar to that of the modern Earth since prior to 3.5 Ga (e.g., Hoashi et al. 2009), or that it may have had a more complex history with numerous instances of oxygen production and consumption prior to the GOE, but perhaps on a more localized scale (Anbar et al., 2007; Frei et al., 2009; Godfrey and Falkowski, 2009). Additionally, evidence from biomarkers (Brocks et al., 1999; Eigenbrode et al., 2008; Waldbauer et al., 2009) and carbon isotopes (Hayes, 1983; Eigenbrode and Freeman, 2006) suggest that both oxygen producers and consumers existed by ~2.7 Ga.

    ROADMAP OBJECTIVES: 4.1 5.2 6.1 7.1
  • Project 3B: Do Iron-Rich Carbonates From Banded Iron Formations Record Ancient Seawater?

    Carbonates are ubiquitous in the geologic record over Earth’s history, and their chemical and isotopic compositions have been key to discussions on the compositions of the ancient oceans, as well as the evolution of life. Moreover, the abundance of Fe-carbonates, common in banded iron formations (BIFs), and the Archean sedimentary rock record in general, has led many workers to use such carbonates as a proxy for surface conditions and to provide insights into seawater chemistry of the ancient Earth. For carbonates to yield information about ancient ocean compositions, however, they must be demonstrated to have been a direct precipitate from ocean water and not subsequently modified. One approach to test if ancient carbonates record seawater is through studies of the isotopic compositions of elements that usually reflect seawater compositions in carbonate minerals.

    ROADMAP OBJECTIVES: 4.1 4.3 5.2 7.1
  • Stellar 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 also model how stars with different masses, temperatures and flare activity affect the habitability of planets, including looking at the effect of a very big flare on a planet’s atmosphere and surface. We find that a planet with an atmosphere like Earth orbiting around a cool red star is fairly well protected from UV radiation, but particles associated with the flare can produce damaging chemistry in the planetary atmosphere that severely depletes the planet’s ozone layer.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 4.1 4.3 5.3 6.1 7.2
  • Project 3C: Iron Isotope Biosignatures: Laboratory Studies and Modern Environments

    Ancient rocks often carry chemical and isotopic signatures of ancient microbiological processes. However, fluids important in the generation of these signatures are lost upon lithification. Experimental studies in geochemical systems analogous to ancient rock precursors are therefore critical to gain insight into the biogeochemical processes responsible for generating unique chemical or isotopic compositions in ancient rocks. New laboratory studies were conducted to extend our recent work on Fe isotope fractionation during microbial dissimilatory iron reduction (DIR) in the presence of dissolved silica, which was likely abundant in Precambrian oceans. Iron isotope fractionation was investigated during microbial reduction of an amorphous iron oxide-silica coprecipitate in high-silica, low-sulfate artificial Archean seawater to determine if such conditions alter the extent of reduction, or the isotopic fractionations relative to those previously observed in simple systems. These new results show that, relative to simiple systems, significantly larger quantities of low-isotopically-light reduced iron were produced during reduction of the Fe-Si coprecipitate. These findings provide strong support for DIR as a mechanism for producing Fe isotope variations observed in Neoarchean and Paleoproterozoic marine sedimentary rocks.

    ROADMAP OBJECTIVES: 2.1 4.1 5.2 6.1 7.1 7.2
  • Timscales of Events in the Evolution and Maintenance of Complex Life

    We are establishing geological histories for different parts of each history (namely 252 and 720 million years ago) using a combination of dating of volcanic ash beds and correlating rocks between continents using the variation in isotopic signatures.

  • 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 3D: Stable Isotope and Mineralogical Studies of Banded Iron Formations: O & Si Isotopes by SIMS

    The oxygen isotope ratio of modern seawater is 0‰ (δ18O, VSMOW) and the oceans are thought to partly balance high δ18O crustal rocks relative to a primary mantle δ18O value of 5.5‰. Isotope ratios of O and Si from cherts up to 3.5 Ga have been controversially interpreted to reflect either a hot Archean ocean of 50-70°C or a low δ18O Archean ocean of -10 to -13‰. These interpretations assume that cherts record the primary seawater δ18O. We have conducted in situ SIMS analysis of oxygen and silicon isotope ratios in cherts from banded iron formations (BIFs) at Isua, Greenland (3.8 Ga); Hamersley, Western Australia (2.5 Ga); Transvaal, South Africa (2.5 Ga), and Biwabik, Minnesota, USA (1.9 Ga). Correlated values of δ18O and δ30Si are used to test assumptions about the degree to which these isotope ratios record ocean compositions, or exchange during diagenesis or metamorphism. Silicon isotopes may also have the potential to distinguish between continental (δ30Si > -0.4‰) and hydrothermal sources of Si in BIF cherts.

    Oxide facies BIFs are essentially composed of equal parts quartz and iron oxides. Magnetite and hematite are the dominant Fe-oxides and the paragenesis of these minerals is important to understanding the fluid and thermal history of unmetamorphosed or low-temperature (sub-greenschist facies) BIFs. We identified silician magnetite overgrowths by BSE-SEM and used three diffraction techniques to verify that silicon is structural in magnetite. Silician magnetite overgrowths may form in reducing alkaline conditions during BIF diagenesis and metamorphism. We have observed silician magnetite in several low-temperature BIFs from 2.6 to 1.9 Ga and hypothesize that the former presence of organic matter may be required to attain the low oxygen fugacity necessary to stabilize silicon in magnetite. Silician magnetite is thus proposed as a novel biosignature.

  • Project 3E: In Situ Sulfur Isotope Studies in in Archean-Proterozoic Sulfides

    Sulfur is an essential element for life on Earth, and it participates in a diverse array of chemical reactions as it moves through the lithosphere, atmosphere, hydrosphere and biosphere. The sulfur isotopic composition of sulfide minerals integrates these processes and thus provides useful information about changing Earth systems. Sulfur isotope studies are vital components of current knowledge about the evolution of habitable environments on early Earth, the antiquity of microbial metabolisms, the evolution of photosynthesis, the oxygenation of the atmosphere, and the mass extinctions of the Phanerozoic, and they are likely to play just as critical a role in the discovery and detection of biosignatures in extraterrestrial materials. Recent developments have made it possible to measure sulfur isotope ratios in situ with analytical precision and accuracy approaching that of “conventional” bulk techniques which are more destructive, remove samples from their petrologic context, and mask variability on small spatial scales. Using the CAMECA ims-1280 at the WiscSIMS laboratory, we have explored the limiting factors for precision and accuracy of SIMS sulfur isotope measurements in various sulfide minerals, used the findings to develop techniques that optimize precision and accuracy, and applied these techniques in several contexts relevant to astrobiology. In the near future, these developments will support paired, in situ sulfur, carbon and iron isotope analyses on the same samples in an effort to understand the co-evolution of microbial communities and biogeochemical cycles in early Earth environments.

    ROADMAP OBJECTIVES: 1.1 4.1 4.2 7.1
  • Project 4A: Improving Accuracy of in Situ Stable Isotope Analysis by SIMS

    In situ analysis of isotope ratios of oxygen, sulfur, and iron by SIMS provides a new record of biological, sedimentary, and hydrothermal processes in banded iron formations (BIFs). BIFs formed throughout several broad secular changes in atmospheric and oceanic conditions during the Archean and Proterozoic and provide a non-uniformitarian example of biogeochemical cycling on the early Earth. We have focused on the well-known BIF from the Dales Gorge member of the Brockman Iron Formation, Hamersley Group, Western Australia; alternations of Si- and Fe-rich microlaminae are alternately interpreted as annual varves, formed by oscillations in hydrothermal activity, or due to the internal dynamics of Fe and Si complexes during diagenesis. The question of whether these models are mutually exclusive or act in combination to form the characteristic banding of BIFs is relevant to interpreting the role of microbial life in precipitation of the Fe-oxides. Isotope ratios of oxygen and sulfur from coexisting mineral pairs can provide a temperature estimate of the rock, or the composition of pore fluids during diagenesis and subsequent metamorphism of BIFs. However, many BIF oxides are chemically zoned and/or in cross-cutting relationships. For these textures, oxygen isotope ratios of iron oxides reflect the changing thermal and fluid history of BIFs. Precision and accuracy of in situ stable isotope analysis of ultra-small spots by SIMS have been improved by careful evaluation of sample relief, X-Y effects, crystal orientation, and standardization. Small spot oxygen and sulfur isotope analyses down to 1 μm diameter are pushing the analytical limit for accurate SIMS analysis.

  • Stoichiometry of Life – Task 1b – Experimental Studies – Microbial Production of Exopolymeric Subtances (EPS)

    One way that microscopic plankton affect the Earth system is by producing carbon compounds that can sink to the bottom of the ocean, thus burying C for extended periods. The production of “exopolymeric substances” (EPS), sticky molecules often made from sugars, is such a mechanism. This project seeks to determine some of the basic parameters that affect the production of EPS by marine phytoplankton.

  • Understanding Past Earth Environments

    We study the chemical and climate evolution of the Earth as the best available proxy for what other inhabited planets might be like. A particular focus is on the “Early Earth” (formation through to the 1.6 billion years ago) which is poorly represented in the geological record but comprises half of Earth’s history. We have studied the total pressure of the Archean atmosphere (prior to 2.5 billion years ago), developed constraints on CO2 concentration, studied the oxygen and nitrogen cycles, the fractionation of sulfur isotopes and explored the effect of hazes on early Earth climate.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.2 5.1 5.2 6.1
  • Stoichiometry of Life – Task 1d – Experimental Studies – the Role of Molybdenum in the Nitrogen Cycle, Past and Present

    The element molybdenum (Mo) is critical for key processes in the cycling of nitrogen (N); for example, it is essential for the enzyme nitrogenase which bacteria use to convert gaseous N to “fixed” N that can be used in biological processes. This project seeks to understand how Mo might limit N processing in modern ecosystems (lakes and oceans) and infer its potential role in the past.

    ROADMAP OBJECTIVES: 4.1 5.1 6.1
  • Project 5C: Fluid-Mineral Fractionation of Mg Isotopes and Tracing the Origin of Sulfate Minerals

    We are developing an experimental program to characterize the Mg isotope fractionation between fluids and minerals in order to use the Mg isotope system to characterize the paleoenvironmental conditions of ancient terrestrial rocks and samples from Mars. Our initial work has focused on Mg isotope fractionation between aqueous Mg and epsomite. Magnesium sulfate is present on the surface of Mars, where, for example, up to 36 wt. % sulfate has been found in some outcrops on the Martian surface, of which Mg-sulfate is the most abundant (Clark et al., 2005). Sulfates are a major water reservoir for the Martian surface and thus it is inferred that there was a period of aqueous alteration on Mars (e.g., Wang et al., 2008). Knowledge of the controls on Mg isotope fractionation in the system fluid and Mg sulfate will allow us to ultimately characterize the evaporation rates and Mg fluxes that occurred during one of the wettest periods in Mars History.

    ROADMAP OBJECTIVES: 2.1 4.1 7.1 7.2
  • Stoichiometry of Life – Task 1f – Concept Studies – Nickel-Molybdenum Co-Limitation and Evolution of Mo-Nitrogenase

    The element molybdenum (Mo) is critical for key processes in the cycling of nitrogen (N); for example, it is essential for the enzyme nitrogenase which bacteria use to convert gaseous N to “fixed” N that can be used in biological processes. However, this process costs a lot of energy. In some microbes, this energy can be captured and used via enzymes that involve both Mo and nickel (Ni). This project investigates the role of these Ni-Fe enzymes in making nitrogenase-driven processes more energetically efficient and how these enzymes may have evolved in the deep past when Ni concentrations were lower.

    ROADMAP OBJECTIVES: 4.1 5.1 5.2 6.1
  • Oxygen Isotopes of Apatites in Precambrian Banded Iron Formations

    Dominic Papineau from the Carnegie team, received an NAI research scholarship to come work with team member Gary Huss to use the ion microprobe to look at apatite grains in a suite of Precambrian banded iron formations in order to document the ranges of d18O values dot see if this technique could be used for biosignature studies in banded iron formations.

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

    We are analyzing, at high resolution, Mid-Proterozoic drill core and outcrop samples in an effort to fingerprint the evolving redox state of the atmosphere and ocean at critical intervals in Earth history. This refined view of biospheric oxygenation provides the key backdrop for measuring and inferring abundances of diverse bioessential elements. Within this context we can better understand the distribution and evolution of early eukaryotic organisms at a variety of spatial and temporal scales.

  • 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. The NASA Ocean Biogechemical Model (NOBM) is applied using cyanobacteria (blue-green algae) as the only photosynthetic group in the oceans. The analyses showed that the early Earth ocean had 19% less primary production and 35% more nitrate due to slower growth by the cyanobacteria, and reduced nutrient uptake efficiency relative to modern phytoplankton Additionally there was 8% more total carbon in the oceans as a result of higher atmospheric pCO2. We plan to optimize this early Proterozoic ocean model in combination with a 1 D model to account for changes in aggregate formation and sinking speed in response to varying nutrients.

    ROADMAP OBJECTIVES: 1.1 4.1 4.2 5.2 6.1 7.2
  • Quantification of the Disciplinary Roots of Astrobiology

    While astrobiology is clearly an interdisciplinary science, this project seeks to address the question of how interdisciplinary it is. We are reviewing published works across a broad range of scholarly databases, comparing disciplinary indicators such as subject terms, journal titles and author affiliations, and creating a computational model to identify and compare the makeup of astrobiological research literature in terms of the proportion of work that come from constituent fields.

    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