2010 Annual Science Report

Astrobiology Roadmap Objective 7.1 Reports Reporting  |  SEP 2009 – AUG 2010

Project Reports

  • Cosmic Distribution of Chemical Complexity

    This project is aimed to improve our understanding of the connection between chemistry in space and the origin of life on Earth, and its possibility on other worlds. Our approach is to trace the formation and development of chemical complexity in space, with particular emphasis on understanding the evolution from simple to complex species. The work focuses upon molecular species that are interesting from a biogenic perspective and also upon understanding their possible roles in the origin of life on habitable worlds. We do this by first measuring the spectra and chemistry of materials under simulated space conditions in the laboratory. We then use these results to interpret astronomical observations made with ground-based and orbiting telescopes. We also carry out experiments on simulated extraterrestrial materials to analyze extraterrestrial samples returned by NASA missions or that fall to Earth in meteorites.

    ROADMAP OBJECTIVES: 1.1 2.1 2.2 3.1 3.2 3.4 4.3 7.1 7.2
  • Biomineralization

    Minerals formed by biological systems such as bones, teeth, and seashells can be used to identify the organism from which they came. Thus these mineral structures are unique biosignatures. Our efforts are focused on trying to identify the key underlying factors that are responsible for the subtle differences in the structure of these biominerals imparted by the organic biological components of the organism. We therefore study the interface between the mineral and the organic components with a particular focus on very early events in the mineral growth process.

    ROADMAP OBJECTIVES: 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
  • 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
  • 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
  • Project 2: Origin and Evolution of Organic Matter in the Solar System

    Through telescopic observations of remote objects, we are learning about the distribution of organic matter in the outer Solar System and how it is thermally processed, as well as about dynamic processes that .could have delivered such organic-rich material to be incorporated into terrestrial planets. Extraterrestrial samples like primitive meteorites and interplanetary dust particles contain significant amounts of carbonaceous material and were likely a source of organic matter to the early Earth. By using a wide variety of advanced techniques to study organic matter in meteorites and other extraterrestrial samples, we are trying to learn how and where it formed, and how it has been modified during 4.5 billion years of solar system evolution. We also perform laboratory experiments to simulate formation of complex organic matter and how it is modified on planetary surfaces.

    ROADMAP OBJECTIVES: 2.2 3.1 7.1
  • 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
  • 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 1C: Extra-Cellular Polymeric Substances as Armor Against Cell Membrane Rupture on Mineral Surfaces

    Our interdisciplinary project examined the hypotheses that bacterial cell membranes are ruptured in contact with specific mineral surfaces, and that biofilm-forming extra-cellular polymeric substances (EPS) may have evolved to shield against membrane rupture (cell lysis). Furthermore, we proposed that mineral reactivity towards membranolysis should depend on its surface properties such as charge, reactive area, or free radicals generated by radiation and impacts on early Earth, Mars, and other worlds. The effect of EPS on preservation in the rock record will also be examined. By understanding the mechanisms for membranolysis, especially under the extreme conditions of high radiation and heavy impacts during early planetary history, the project addresses the NASA Astrobiology Institute’s (NAI) Roadmap goals of understanding the origins of cellularity, the evolution of mechanisms for survival at environmental limits, and preservation of biosignatures, and NASA’s Strategic Goal of advancing scientific knowledge of the origin and evolution of the Earth’s biosphere and the potential for life elsewhere.

    ROADMAP OBJECTIVES: 3.4 5.1 7.1
  • Path to Flight

    Our technology investigation, a Path to Flight for astrobiology, utilizes instrumentation built with non-NAI funding to carry out three science investigations namely habitability, survivability and detectability of life. The search for life requires instruments and techniques that can detect biosignatures from orbit and in-situ under harsh conditions. Advancing this capacity is the focus of our Technology Investigation.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 3.2 7.1 7.2
  • Survivability of Icy Worlds

    As part of our Survivability of icy Worlds investigation, we examine the similarities and differences between the abiotic chemistry of planetary ices irradiated with ultraviolet photons (UV), electrons, and ions, and the chemistry of biomolecules exposed to similar conditions. Can the chemical products resulting from these two scenarios be distinguished? Can viable microbes persist after exposure to such conditions? These are motivating questions for our investigation.

    ROADMAP OBJECTIVES: 2.2 3.2 5.1 5.3 7.1 7.2
  • 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
  • Minerals to Enzymes: The Path to CO Dehydrogenase/Acetyl – CoA Synthase

    The relationship between structure and reactivity of iron-sulfur minerals and the active sites of iron-sulfur enzymes is too strong to be coincidental. We and others have proposed that the emergence and genesis of iron-sulfur cluster enzymes occurred by a stepwise process in which mineral motifs were first nested in simple organic polymers and then in response to selective pressure evolved specific gene encoded protein nest that confer high specific enzyme activities. We are examining this hypothesis through nesting NiFeS motifs in a variety of organic nest and examining the structural determinants of reactivity.

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 3.4 7.1 7.2
  • 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
  • Project 1D: Dolomite Precipitation From Solutions Containing Agar or Carboxymethyl Cellulose, Synthetic Analogs for Extracellular Polymeric Substances (EPS)

    A major paradox in the study of ancient sedimentary rocks is that dolomite is ubiquitous in the rock record, and yet is nearly impossible to form dolomite in the laboratory. A common proposal to this dilemma is that microorganisms, especially anaerobic microorganisms, can overcome kinetic barriers to facilitate dolomite precipitation, although their specific role in dolomite formation and nucleation is still unclear. Our experiments demonstrate that disordered dolomite can be synthesized abiotically from solutions containing agar or carboxymethyl cellulose at room temperature. It is now recognized that dehydration / desolvation of hydrated surface Mg(II) is a critical kinetic barrier to dolomite nucleation. Our work shows that dissolving a low dielectric constant solvent in water will lower the dielectric constant of the solution, and thus can reduce the solvation energies of dissolved cations. Tis work therefore provides insight into the mechanisms by which microorganisms may catalyze dolomite formation.

    ROADMAP OBJECTIVES: 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
  • Project 2A: Chemolithotrophic Microbial Oxidation of Basalt Glass

    Ferrous iron (Fe(II)) can serve as an energy source for a wide variety of chemolithotrophic microorganisms (organisms that gain energy from metabolism of inorganic compounds). Fe(II) oxidation may have played a role in past (and possibly, present) life on Mars, whose crust is rich in Fe(II)-bearing silicate minerals (e.g. ultramafic basalt rocks). The goal of this project is to determine whether an established chemolithoautotrophic Fe(II)-oxidizing, nitrate-reducing culture can grow by oxidation of Fe(II) in basalt glass. Experiments showed that the culture is able to oxidize a significant portion (approximately 1%) of the Fe(II) content of fresh basalt glass from Kilauea, a shield volcano in Hawaii that represents an analog for ancient volcanic activity on Mars. The ratio of Fe(II) oxidized to nitrate reduced was consistent with the expected 1:5 stoichiometry, suggesting that the culture oxidized Fe(II) with nitrate in a manner analogous to its metabolism of other (e.g. aqueous) Fe(II) forms.

    ROADMAP OBJECTIVES: 2.1 6.2 7.1
  • Project 5: Vistas of Early Mars: In Preparation for Sample Return

    To understand the history of life in the solar system requires knowledge of how hydrous minerals form on planetary surfaces, and the role these minerals play in the development of potential life forms. One hydrous mineral found on Earth and inferred from in situ measurements on Mars, is the mineral Jarosite, KFe3(SO4)2(OH)6. We are investigating whether radiometric ages, specifically 40Ar/39Ar ages on jarosite can be interpreted to accurately record climate change events on Mars. This project not only requires understanding the conditions required for jarosite formation and preservation on planetary surfaces, but also assessing under what conditions its “radiometric clock” can be reset (e.g., during changes in environmental conditions such as temperature). By studying jarosites formed by a variety of processes on Earth, we will be prepared to analyze and properly interpret ages measured from jarosite obtained from future Mars sample return missions.

    ROADMAP OBJECTIVES: 1.1 2.1 7.1
  • 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.

    ROADMAP OBJECTIVES: 4.1 7.1
  • 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
  • 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
  • Project 2C: Computational Studies of Calcium Mineralization (Calcium Phosphate Nucleation and Dolomite Formation) as Model Systems for Biomineral Signatures on Earth and Other Solid Planetary Bodies

    The unique morphologies of biominerals produced by organisms, when complemented by other chemical and isotopic signals, may serve as a potential biosignature for life on Mars and other solid planets. The mechanisms by which biology promotes organic-mediated biomineralization must be understood in order to distinguish them from look-alike minerals formed by the interaction of non-biological organic molecules or by inorganic physical-chemical processes. We have used the Molecular Dynamics and Bioinformatics computational chemistry approaches to determine the potential role of soluble proteins, commonly found in the organic part of biominerals, in controlling nucleation of the earliest solid Ca-PO4 inorganic precursor in hydroxyapatite (Ca5(PO4)3OH) biomineralization, and whether and how the conformation of a peptide (alpha-helix versus random coil) influences the nucleation pathway of hydroxyapatite compared to the inorganic system. We have found that the random coil conformation of the peptide promotes formation of an amorphous Ca-PO4 cluster, which ultimately transforms into crystalline hydroxyapatite. Identification of bioorganic molecule-promoted pathway of rapid amorphous solid formation, rather than direct mineral crystal templation, could help determine potential biomineral biosignatures on Mars and other solid worlds. Our project addresses NASA Astrobiology Institute’s (NAI) Roadmap goals of recognizing and preserving biosignatures and NASA’s Strategic Goal of advancing scientific knowledge of the origin and evolution of the Earth’s biosphere and the potential for life elsewhere.

    ROADMAP OBJECTIVES: 7.1
  • 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
  • Rationalized Chemical Surface Modifications

    Using biological examples such as nitrogen fixation by nitrogenase, hydrogen evolution and uptake by hydrogenases, and reversible CO/CO2 conversion by CO dehydrogenase, we began to study the effect of heterometal (Mo, V, Ni) substitution in iron-sulfur minerals and particles. We have successfully bound molybdenum sulfide on pyrite mineral surfaces and exploring the synthetic feasibility of doping Ni into freshly precipitated FeS particles. Preliminary reactivity studies indicated higher yields in formation of ammonia from nitrogen oxides at hydrothermal conditions relative to the pure iron-sulfur systems.

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 7.1 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
  • 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
  • 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
  • Subglacial Methanogenesis and Implications for Planetary Carbon Cycling

    Methanogens are thought to be among the earliest emerging life forms. Today, the distribution of methanogens is narrowly constrained, due in part to the energetics of the reactions which support this functional class of organism (namely carbon dioxide reduction with hydrogen and acetate fermentation). Methanogens utilize a number of metalloenzymes that have active site clusters comprised of a unique array of metals. The goals of this project are 1) identifying a suite of biomarkers indicative of biological CH4 production 2). quantifying the flux of CH~4~ from sub-ice systems and 3). developing an understanding how life thrives at the thermodynamic limits of life. This project represents a unique extension of the ABRC and bridges the research goals of several nodes, namely the JPL-Icy Worlds team and the ASU-Follow the Elements team.

    ROADMAP OBJECTIVES: 2.1 5.1 5.2 5.3 7.1 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
  • Surface Chemistry on Iron-Sulfur Minerals

    Progress has been made in defining competitive abiotic pathways for reducing nitrogen compounds to ammonia from nitrogen oxides relative to the dinitrogen. Using pyrite mineral surfaces and freshly precipitated Fe-S particles, we showed that under hydrothermal conditions nitrite (NO2-), nitrate (NO3-), as well as nitric oxide (NO) can be converted to ammonia to comparable yields than starting from dinitrogen (N2). Formation of ammonia or ammonium ion in aqueous solution is considered as an essential step toward creating amino acids that are key building blocks of life.

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 7.1 7.2
  • 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.

    ROADMAP OBJECTIVES: 4.1 7.1
  • Research Activities in the Astrobiology Analytical Laboratory

    We are a laboratory dedicated to the study of organic compounds derived from Stardust and future sample return missions, meteorites, lab simulations of Mars, interstellar, proto-planetary, and cometary ices and grains, and instrument development. Like forensic crime shows, the Astrobiology Analytical Laboratory employs commercial analytical instruments. However, ours are configured and optimized for small organics of astrobiological interest instead of blood, clothing, etc.

    ROADMAP OBJECTIVES: 2.1 3.1 3.2 7.1
  • 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
  • Virtual Catalysis From Molecular Beam Scattering

    Molecular beam/surface scattering experiments provide a controlled environment for modeling abiotic processes at the interface of lytho- and atmosphere. Specifically, it has been proposed that exposed rock surfaces may have played a role in modifying activated atmospheric molecules in the presence of UV radiation toward the building blocks of life. We have found that extended exposure of pyrite mineral surfaces to hydrogen atoms creates a reduced iron surface. The reduced state and the modified geometric structure of the surface iron atoms were confirmed by X-ray spectroscopy. Furthermore, this modified pyrite surface shows remarkable chemical reactivity in converting the hyperthermal beam of N2 to ammonia.

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 7.1 7.2
  • 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.

    ROADMAP OBJECTIVES: 4.1 7.1
  • Stoichiometry of Life, Task 1a: Experimental Studies – Cellular Stoichiometry Under Nutrient Limitation in Chemostats

    In this project we are raising several species of “extremophile” microbes at different growth rates under different kinds of element limitation (N, P, and Fe) in order to determine how their “elemental recipes” (in terms of C, N, P, Fe, and other metals) change with environmental conditions. These data will help us understand similar data to be obtained from microbes in natural ecosystems.

    ROADMAP OBJECTIVES: 5.1 5.2 5.3 6.1 6.2 7.1
  • X-Ray Characterization of Modified Fe-S Mineral Surfaces

    High energy X-ray radiations generated by tunable synchrotron lightsources were used to characterize both the location of the electrons and the atomic centers in modified Fe-S minerals and particles. We have exploited the complementary information content of three different detections techniques in both soft and hard X-ray energy range. We confirmed the formation of a reduced pyrite structure from hydrogen atom exposure experiments. The formation of a reduced pyrite surface is relevant to small molecule activation processes of abiotic molecules toward formation of more complex molecules, such as amino and nucleic acids.

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 7.1 7.2
  • Project 5B: Detection of Biosignatures in Extreme Environments, Analogs for Mars

    The planet Mars may have been warmer in the past and at one time probably had an acidic, wet environment but currently it is cold and dry. Past conditions and maybe even present ones, although extreme, could support microbial life and we have investigated life in two extreme analog environments. The Río Tinto is an acid river is Spain where from an airborne remote survey we have monitored the progress of a metabolic process in which iron, rather than carbon, is oxidized by bacteria. At the site of a former munitions factory in Israel we have shown that bacteria can live off the chemical energy of the chemical compound perchlorate (recently found on Mars), despite adverse conditions and negligible amounts of water in the environment.

    ROADMAP OBJECTIVES: 2.1 7.1
  • 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
  • Project 5D: The Rock That Started It All: Geochronology of Mars Meteorite ALH84001

    The possible biosignatures that were discovered in Martian meteorite ALHA84001 by McKay et al. (1996) can be significantly credited with establishing the NAI. Despite the importance of this sample in spurring a variety of research efforts to evaluate how one could determine if there was ancient life on other planets, we still do not convincingly know the age of this sample. Original geochronologic work indicated that this sample crystallized soon after planetary accretion at ~4.5 Ga (e.g., Nyquist et al., 2001). We have begun re-evaluating the crystallization age of this meteorite using new geochronologic techniques, and based on these new results the crystallization age for this sample is in need of revision and we suggest that an age of 4.09 Ga is more appropriate (Lapen et al., 2010). This younger age fits much better into generally accepted models for the early evolution of Mars.

    ROADMAP OBJECTIVES: 2.1 7.1
  • 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
  • The Deep Hot Biosphere: Expedition 331 of the Integrated Ocean Drilling Program (IODP)

    Hydrothermal systems on the seafloor, and their associated submarine hot springs, are one of the leading candidates for the setting in which life originated on planet Earth some 4 billion years ago. Today these systems are known to harbor active and diverse communities of microbes, both bacteria and archaea, which thrive on the high temperatures and the abundant sources of chemical energy supplied by reduced chemical species generated from magma and by water-rock reactions within the hydrothermal system. From September 1 through October 4, 2010, we drilled into an active high-temperature hydrothermal system in the Okinawa Trough, an actively rifting back-arc basin that lies in a transitional region between continental and oceanic crust, northwest of the island of Okinawa in the western Pacific Ocean. The objectives of this drilling were to investigate microbial communities with the hydrothermal system and their geochemical and geophysical setting.

    ROADMAP OBJECTIVES: 5.3 7.1