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2012 Annual Science Report

Astrobiology Roadmap Objective 7.1 Reports Reporting  |  SEP 2011 – AUG 2012

Project Reports

  • Habitability of Icy Worlds

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

    ROADMAP OBJECTIVES: 1.1 2.1 2.2 3.1 3.2 3.3 3.4 4.1 5.1 6.1 6.2 7.1 7.2
  • Biosignatures in Ancient Rocks

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

    ROADMAP OBJECTIVES: 1.1 3.2 4.1 4.2 4.3 5.1 5.2 5.3 6.1 6.2 7.1 7.2
  • Advancing Methods for the Analyses of Organics Molecules in Sediments

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

    ROADMAP OBJECTIVES: 2.1 4.1 7.1
  • Amino Acid Alphabet Evolution

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

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

    ROADMAP OBJECTIVES: 3.2 4.1 4.2 6.2 7.1 7.2
  • BioInspired Mimetic Cluster Synthesis: Bridging the Structure and Reactivity of Biotic and Abiotic Iron-Sulfur Motifs

    Bioinspired synthetic techniques are bridging the gap between iron sulfur (FeS) mineral surfaces that demonstrate chemical reactivity and the highly evolved FeS cluster centers observed in biological metalloenzymes. An emerging paradigm in biology relating to the synthesis of certain complex iron sulfur clusters involves the modification of standard FeS clusters through radical chemistry catalyzed by radical S-adenosylmethionine (SAM) enzymes. In our attempts to examine potential sources for prebiotic and/or early biotic catalysts, we have initiated a new experimental line that probes the ability of short conserved FeS amino acid motifs that are present in modern day enzymes for their ability to coordinate FeS clusters capable of initiating small molecule radical reactions.

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 3.4 7.1 7.2
  • Cosmic Distribution of Chemical Complexity

    The three tasks of this project explore the connections between chemistry in space and the origin of life. We start by tracking the formation and evolution of chemical complexity in space, from simple carbon-rich molecules such as formaldehyde and acetylene to complex species including amino acids, nucleic acids and polycyclic aromatic hydrocarbons. The work focuses on carbon-rich species that are interesting from a biogenic perspective and on understanding their possible roles in the origin of life on habitable worlds. We do this by measuring the spectra and chemistry of analog materials in the laboratory, by remote sensing with small spacecraft, and by analysis of extraterrestrial samples returned by spacecraft or that fall to Earth as meteorites. We then use these results to interpret astronomical observations made with ground-based and orbiting telescopes.

    ROADMAP OBJECTIVES: 1.1 2.1 2.2 3.1 3.2 3.4 4.3 7.1 7.2
  • Project 2: Origin and Evolution of Organic Matter in the Solar System

    Extraterrestrial organic matter as is found in comets and certain meteorites has the potential to tell us much about the origin of the solar system, the origin of planetary volatiles, and possible the origins of life. In this project, we bring a powerful array of analytical methods to bare on understanding extraterrestrial organic matter at the molecular level. Our work links astronomy, chemistry, physics, and planetary science.

    ROADMAP OBJECTIVES: 2.2 3.1 7.1
  • Survivability of Icy Worlds

    Survivability of Icy worlds (Investigation 2) focuses on survivability. As part of our Survivability 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
  • Biosignatures in Extraterrestrial Settings

    Exploring the prospects for biosignatures in extraterrestrial settings is a multi

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 4.1 4.3 6.2 7.1 7.2
  • Biosignatures in Relevant Microbial Ecosystems

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

    ROADMAP OBJECTIVES: 4.1 4.3 5.1 5.2 5.3 6.1 7.1 7.2
  • Charting the Universe of Amino Acid Structures

    More than 3.5 billion years ago, life on our planet evolved a precise alphabet of 20 amino acids to function as building blocks which cells use to construct proteins according to genetic instructions. However, the twenty genetically encoded amino acids are but a tiny fraction of the chemical structures that could plausibly play such a role. Any science of the origins, distribution and future of life in the universe must take into account this larger context of chemical structures. But while astrochemistry, prebiotic chemistry, and bioengineering all hint at the chemical structures it contains, until now this amino acid universe has remained largely unexplored. Efforts to describe the structures it contains, or even estimate their number, have been hampered by the complexity inherent to the combinatorial properties of organic molecules. We have formed a new collaboration to combine European (DLR) advances in computational chemistry with NAI expertise in organic chemistry and amino acid biology to address this gap in current scientific understanding. Our early results have provided the first ever sketch of the amino acid structure universe, showing it to be far larger and more complex than previously supposed. This forms an important milestone in defining and exploring the principles of “universal biology”

    ROADMAP OBJECTIVES: 3.1 3.2 6.2 7.1 7.2
  • Detectability of Life

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

    ROADMAP OBJECTIVES: 1.2 2.1 2.2 4.1 5.3 6.1 6.2 7.1 7.2
  • Developing New Biosignatures

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

    ROADMAP OBJECTIVES: 4.1 5.1 7.1
  • Project 1D: Establishing Biogenicity and Environmental Setting of Precambrian Kerogen and Microfossils

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

    ROADMAP OBJECTIVES: 2.1 4.1 5.1 5.2 6.1 7.1
  • Path to Flight

    The (Field Instrumentation and) Path to Flight investigation’s purpose is to enable in-situ measurements of organics and biological material with field instrumentation that have high potential for future flight instrumentation. The preceding three Investigations (Habitability, Survivability and Detectability) provide a variety of measurable goals that are used to modify or “tune” instrumentation that can be placed in the field. In addition the members involved with Investigation provide new measurement capabilities that have been developed with the specific goal of life-detection and organic detection using both non-contact/non-destructive means and ingestion based methods. The developments under this investigation (Inv 4) incorporate state-of-the-art laboratory instruments and next generation in-situ instrumentation that have been developed under programs that include NASA as well as NSF and DOD. These include mass-spectrometers, gas analyzers, and fluorescence/Raman spectrometry instruments.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 3.2 7.1 7.2
  • Astrochemistry Theory and Observation Group NAI Report

    We have continued observational programs designed to explore the chemical composition of comets and establishing their potential for delivering pre-biotic organic materials and water to the young Earth and other planets. State of the art, international facilities are being employed to conduct multiwavelength, simultaneous, studies of comets in order to gain more accurate abundances, distributions, temperatures, and other physical parameters of various cometary species. Additionally, observational programs designed to test current theories of the origins of isotopically fractionated meteorite (and cometary) materials are currently underway. Recent chemical models have suggested that in the cold dense cores of star forming regions, significant isotope enrichment can occur for nitrogen and possibly vary between molecular species and trace an object’s chemical evolution. Observations are being conducted at millimeter and submillimeter wavelengths of HCN and HNC isotopologues for comparison to other nitrogen-bearing species to measure fractionation in cold star forming regions.

    ROADMAP OBJECTIVES: 2.2 3.1 3.2 7.1
  • Nitrate and Nitrate Conversion to Ammonia on Iron-Sulfur Minerals

    Conversion of nitrate and nitrite may have contributed to the formation of ammonia—a key reagent in the formation of amino acids—on the prebiotic Earth. Results suggest that the presence of iron mono sulfide facilitates the conversion of nitrate and nitrite. Nitrite conversion is, however, much faster than the conversion of nitrate.

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 7.1 7.2
  • Radical SAM Chemistry and Biological Ligand Accelerated Catalysis

    Iron sulfur (FeS) clusters are thought to be among the most ancient cofactors in living systems. The FeS enzyme thrust is focused on examining the structure, mechanism, and biosynthesis of the complex FeS enzymes nitrogenase and hydrogenase. Exciting recent results have identified important links between the biosynthesis of the H-cluster and FeMo-co and have outlined a new paradigm for the biosynthesis of complex FeS clusters. The observations made have provided direct links to the evolution of FeS biocatalysts from their mineral-based precursors.

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 7.1 7.2
  • Project 5: Geological-Biological Interactions

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

    ROADMAP OBJECTIVES: 4.1 5.1 6.1 6.2 7.1
  • Earth as an Extrasolar Planet

    Earth is the only known planet that can support life on its surface, and often serves as the typical example of what a habitable planet looks like. In anticipation of future discoveries of observable, potentially habitable worlds around other stars, this task seeks to understand how we would characterize and understand the distant Earth. To accomplish this, we have developed several tools and approaches for simulating and investigating the Pale Blue Dot. In particular, we have demonstrated how an airless moon can affect observations of a habitable planet, developed new metrics to measure atmospheric pressure, and modeled light reflected off liquid water surfaces.

    ROADMAP OBJECTIVES: 1.2 7.1 7.2
  • 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 minerals may play in the development of potential life forms. The minerals hematite and jarosite have been identified on Mars and presented as in situ evidence for aqueous activity. This project seeks to understand (i) the conditions required for jarosite and hematite formation and preservation on planetary surfaces, and (ii) the conditions under which their “radiometric clocks” can be reset (e.g., during changes in environmental conditions such as temperature). By investigating the kinetics of noble gases in minerals, known to occur on Mars and Earth, we will be prepared to analyze and properly interpret ages measured on samples from future Mars sample return missions.

    ROADMAP OBJECTIVES: 1.1 2.1 7.1
  • Geochemical Signals for Low Oxygen Worlds

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

    ROADMAP OBJECTIVES: 1.1 4.1 4.2 5.1 7.1
  • Project 2A: Inorganic Growth of Mg-Calcite From Dilute Solutions: Understanding Temperature, Composition and pCO2 Effects

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

  • Surface Chemistry of Iron-Sulfur Minerals

    The exposure of pyrite surfaces to energetic particle beams creates an activated surface that is capable of facilitating the reduction of nitrogen molecules to ammonia. Experimental results and complementary theoretical calculations indicates that the exposure of pyrite surfaces creates anomalously reduced iron atoms. The chemical state of the surface iron atoms is somewhat similar to iron in the active center of several key enzymes. The triple bond in dinitrogen sorbed onto these reduced surface iron atoms weakens, which is a key step in the conversion to ammonia, a key reagent in the formation of amino acids on the prebiotic Earth

    ROADMAP OBJECTIVES: 3.1 3.2 3.3 7.1 7.2
  • Project 2B: The Influence of Temperature, Composition and pCO2 on the Fractionation of Iron Isotopes in the Calcite-Siderite System

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

  • Project 2C: Roles of EPS Excreted From Anaerobic Microorganism in Governing Dolomite Composition and Crystallization

    EPS from anaerobic microorganisms of sulfate-reducing bacteria, fermentation bacteria, and methanogen can catalyze dolomite nucleation and growth. Compositions of dolomite and Ca-Mg-carbonates is related to the amount of dissolved EPS. Polysaccharide in the EPS is the key to the dehydration of surface water and dolomite crystallization at room temperature. Low temperature dolomite / sedimentary dolomite can be a potential biosignature. The discovery also provides key to solving the “Dolomite Problem” that has puzzled geologists for decades.

  • The Subglacial Biosphere – Insights Into Life-Sustaining Strategies in an Extraterrestrial Analog Environment

    Sub-ice environments are prevalent on Earth today and are likely to have been more prevalent the Earth’s past during episodes of significant glacial advances (e.g., snow-ball Earth). Numerous metabolic strategies have been hypothesized to sustain life in sub-ice environments. Common among these hypotheses is that they are all independent of photosynthesis, and instead rely on chemical energy. Recently, we demonstrated the presence of an active assemblage of methanogens in the subglacial environment of an Alpine glacier (Boyd et al., 2010). 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. During the course of this study, we identified other features that were suggestive of other active and potentially relevant metabolic strategies in the subglacial environment, such as nitrogen cycling. The goals of this project are 1) identifying a suite of biomarkers indicative of biological CH4 production 2). quantifying the flux of CH4 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 2.2 5.1 5.2 5.3 6.1 6.2 7.1 7.2
  • Project 2D: Catalytic Role of Adsorbed Hydrogen Sulfide in Dolomite Crystallization: Density Functional Theory Study

    The key kinetic barrier in dolomite crystal formation is believed to be the surface Mg2+-H2O complex which hinder the accessibility of surface Mg2+ ions to the CO32+ ions in the solution. Our recent experiments demonstrated that hydrogen sulfide acting as a catalyst can overcome the barrier and promote dolomite nucleation and growth. Our results from ab initio simulations based on density functional theory (DFT) show that hydrogen sulfide can be adsorbed on (104) surface of dolomite from solution. Aqueous hydrogen sulfide produced by sulfate-reducing bacteria adsorbed on the surface can also increase the surrounding surface Mg2+-H2O distances and thus weaken the electrostatic interactions between surface Mg2+ and water molecules.

  • Project 2E: Preferential Dolomitization of Carbonate Microbialites From a Modern Hypersaline Lake and in Ancient Dolomite

    Modern stromatolite from a hypersaline lake displays micro-laminated layers of calcite and protodolomite high-Mg calcite. The oscillatory layers indicate variations of microbial activity. The dolomite layers with micro-crystals are rich in organic. Extracellular polymeric substance (EPS) from photosynthetic microbes enhance precipitation of high-Mg calcite, and EPS from anaerobic bacteria catalyzes the transformation from high-Mg calcite into protodolomite. Atomic resolution Z-contrast images indicate that protodolomite is consisted of very weakly ordered dolomite domains ranging from 3 to 10 nm and disordered dolomite.

  • Ice Chemistry of the Solar System

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

    ROADMAP OBJECTIVES: 1.1 2.2 3.1 3.2 3.3 4.1 7.1 7.2
  • Interdisciplinary Studies of Earth’s Seafloor Biosphere

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

    ROADMAP OBJECTIVES: 4.1 4.2 5.1 5.2 5.3 6.1 6.2 7.1 7.2
  • Measuring Interdisciplinarity Within Astrobiology Research

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

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 3.2 3.3 3.4 4.1 4.2 4.3 5.1 5.2 5.3 6.1 6.2 7.1 7.2
  • Project 3B: In Situ S Isotope Studies in Archean-Proterozoic Sulfides

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

    ROADMAP OBJECTIVES: 2.1 4.1 5.2 6.1 7.1
  • Remote Sensing of Organic Volatiles in Planetary and Cometary Atmospheres

    In the last year, we have greatly advanced our capabilities to model spectra of cometary and planetary atmospheres (Villanueva et al. 2012a, 2012b). Using these newly developed analytical methods, we derived the most comprehensive search for biomarkers on Mars (Villanueva et al. 2012, submitted) from our extensive database of high-quality Mars spectra. Furthermore, we retrieved molecular abundances of several comets (Villanueva et al. 2012c, Gibb et al. 2012, Paganini et al. 2012a/b), and of several young circumstellar disks (Mandell et al. 2012). These great advancements have allowed us to understand the infrared spectrum of planetary bodies and their composition with unprecedented precision.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 3.2 7.1 7.2
  • VPL Databases, Model Interfaces and the Community Tool

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

    ROADMAP OBJECTIVES: 1.1 1.2 3.2 4.1 6.1 7.1 7.2
  • Project 3D: Constraints on Oxygen Contents in Earth’s Early Atmosphere and Implications for Evolution of Photosynthesis

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

    ROADMAP OBJECTIVES: 4.1 6.1 7.1 7.2
  • Research Activities in the Astrobiology Analytical Laboratory

    We are a laboratory dedicated to the study of organic compounds derived from past and future sample return missions, meteorites, lab simulations of Mars, interstellar, proto-planetary, and cometary ices and grains, and instrument development. This year, we continued our analyses of amino acids in carbonaceous chondrites, identifying large L-enantiomeric excesses in the Tagish Lake meteorite that may point towards abiotic processes that could lead to homochirality. We made the first detection of amino acids in CH and CB chondrites, and used compound-specific isotopic analysis to understand formation mechanisms for amino acids in CM and CR chondrites. We hosted two graduate students, welcomed a new NAI NPP postdoctoral researcher to our laboratory, and participated in numerous public outreach and education events, including providing a lecturer to the annual NAI Santander Summer School. We continued our participation in the OSIRIS-REx asteroid sample return mission and provided support for the Sample Analysis at Mars instrument of NASA’s Mars rover Curiosity.

    ROADMAP OBJECTIVES: 3.1 3.2 7.1
  • Project 4B: Detection of Biosignatures in Extreme Environments, Analogs for Mars

    The chemical species sulfate, comprised of sulfur and oxygen atoms, is a constituent of minerals on Earth and on Mars. The small variations in the proportions of the isotopes of oxygen found in sulfate have been used to identify whether and inorganic process or microbiological oxidation of sulfide was responsible for sulfate formation. An intermediate product during the oxidation of sulfide to sulfate is sulfite, which also contains sulfur and oxygen. The work described here shows for the first time the relationship between the oxygen isotope compositions of sulfite and water, which is seen to be a significant control of the oxygen isotope composition of sulfate.

  • Project 4C: New Ways for Exploring Mars for Environmental History and Biosignatures

    In situ analyses on Mars may take many different forms. We have focused on developing an instrument mounted on a Rover that can make wet chemical analysis of Martian soils. Samples are taken by the Rover’s arm into a scoop which delivers them to a hopper. They are fed from there to one of a number of “test tubes” containing water where they are mixed to extract chemicals for analysis. The analytical process uses a probe, with a number of analysis electrodes attached to it, which dips into the tube. We tested the instrument on a Rover in the JPL Mars Yard, the in-house test field, and were able to demonstrate a successful, complete operational sequence using synthetic soil as the test material.

  • Unicellular Protists of the Neoproterozoic

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

    ROADMAP OBJECTIVES: 4.1 4.2 5.1 6.1 7.1
  • Project 4D: Understanding Conditions of Formation of Mars Evaporite Materials by Quantitative Interpretation of Isotope Compositions of Salts

    The variation in the ratios of the naturally occurring (non-radioactive) isotopes of salts dissolved in evaporating water and of the water itself give unparalleled, detailed information on the climate and environment. The existence of hydrated sulfate minerals on Mars and in Terrestrial Martian analog sites indicates that some ancient Martian surface deposits not only precipitated from evaporating surface water but may retain some of that water as part of the crystal structure of the minerals. However, we cannot just analyze the water and use the information because the isotope values are shifted to a small but systematic amount when the water is incorporated in the mineral. We have performed careful laboratory experiments to measure the amount by which the isotope values are shifted for two important mineral types, magnesium sulfate and iron sulfate at a large range of relevant temperatures. In another investigation we have developed a new analytical technique to measure the isotopic compositions of the trace element bromine, similar to the much more common chlorine, present in common salt, sodium chloride. Although these isotopic elements hold a wealth of information progress in using them has been very slow because of the very arduous and lengthily analytical procedures necessary. Our new method allows analysis of samples very much smaller than before and in only a small fraction of the time. These are essential steps in unraveling the climatic and environmental history of Mars.

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

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

    ROADMAP OBJECTIVES: 2.1 4.1 7.1 7.2
  • Project 5B: A Rover-Based Miniature Mass-Spectrometer – Breakthroughs in Laser Ablation Analysis and Geochronology

    We have made great progress towards a technique to measure absolute ages of rocks using laser sampling methods and mass spectrometry. A laser is used to release potassium and argon from rocks containing feldspar minerals, and after measuring the amount of potassium and argon released we can calculate how old the rock is. Last year, we demonstrated that the potassium and argon are released from the rock using lasers. This year, we modified our instrument so that both the potassium and argon measurements can be made during the same experiment.