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2013 Annual Science Report

Astrobiology Roadmap Objective 7.2 Reports Reporting  |  SEP 2012 – AUG 2013

Project Reports

  • Life Underground

    Our multidisciplinary team from USC, Caltech, JPL, DRI, and RPI is developing and employing field, laboratory, and modeling approaches aimed at detecting and characterizing microbial life in the subsurface—the intraterrestrials. We posit that if life exists, or ever existed, on Mars or other planetary body in our solar system, evidence thereof would most likely be found in the subsurface. This study takes advantage of unique opportunities to explore the subsurface ecosystems on Earth through boreholes, mine shafts, and deeply-sourced springs. Access to the subsurface, both continental and marine, and broad characterization of the rocks, fluids, and microbial inhabitants is central to this study. Our focused research themes require subsurface samples for laboratory and in situ experiments. Specifically, we seek to carry out in situ life detection and characterization experiments, employ numerous novel and traditional techniques to culture heretofore unknown intraterrestrial archaea and bacteria, and incorporate new and existing data into regional and global metabolic energy models.

    ROADMAP OBJECTIVES: 2.1 2.2 3.1 3.3 4.1 5.1 5.2 5.3 6.1 6.2 7.2
  • Biogenic Gases From Anoxygenic Photosynthesis in Microbial Mats

    This lab and field project aims to measure biogenic gas fluxes in engineered and natural microbial mats composed of anoxygenic phototrophs and anaerobic chemotrophs, such as may have existed on the early Earth prior to the advent of oxygenic photosynthesis. The goal is to characterize the biogeochemical cycling of S, H, and C in an effort to constrain the sources and sinks of gaseous biosignatures that may be relevant to the detection of life in anoxic biospheres on habitable exoplanets.

    ROADMAP OBJECTIVES: 4.1 5.2 5.3 6.1 6.2 7.2
  • Cosmic Distribution of Chemical Complexity

    This project explores the connections between chemistry in space and the origin of life. It is comprised of three tightly interwoven tasks. We track the formation and evolution of chemical complexity in space starting with simple carbon-rich molecules such as formaldehyde and acetylene. We then move on to more 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: 2.1 2.2 3.1 3.2 3.4 4.3 7.1 7.2
  • Biosignatures in Ancient Rocks – Kasting Group

    The work by Ramirez concerned updating the absorption coefficients in our 1-D climate model. Harman’s work consisted of developing a 1-D code for modeling hydrodynamic escape of hydrogen from rocky planets.

    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
  • Investigation 1: 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: 2.1 2.2 3.2 4.1 5.1 5.2 5.3 6.2 7.1 7.2
  • Habitability, Biosignatures, and Intelligence

    Understanding the nature and distribution of habitable environments in the Universe is one of the primary goals of astrobiology. Based on the only example of life we know, we have devel-oped various concepts to predict, detect, and investigate habitability, biosignatures and intelli-gence occurrence in the near-solar environment. In particular, we are searching for water vapor in atmospheres of extrasolar planets and protoplanets, developing techniques for remote detec-tion of photosynthetic organisms on other planets, have detected a possible bio-chemistry sig-nature in Martian clays contemporary with early life on Earth, developed a comprehensive methodology and an interactive website for calculating habitable zones in binary stellar systems, expanded on definitions of habitable zones in the Milky way Galaxy, and proposed a novel ap-proach for searching extraterrestrial intelligence.

    ROADMAP OBJECTIVES: 1.1 1.2 2.2 3.1 3.2 4.1 4.2 6.2 7.1 7.2
  • Project 1C: Compositional and Structural Variations in Dolomite and Ca-Bearing Magnesite From Modern and Ancient Carbonate Sediments

    Low-temperature Ca-Mg carbonates that have a wide range of chemical variation (from high-Mg calcite to Ca-bearing magnesite) may be used as a biosignature. Certain polysaccharides can inhibit aragonite precipitation and promote Ca-Mg-carbonate crystallization. Experiments indicate that ancient low-temperature, non-stoichiometry dolomite with the observed nano-precipitates of Ca-rich phases may be used as a biosignature.

  • Earth as an Extrasolar Planet

    Earth is our only example of a habitable planet, or a planet capable of maintaining liquid water on its surface. As a result, Earth serves as the archetypal habitable world in conceptual studies of future exoplanet characterization missions, or in studies of techniques for the remote characterization of potentially habitable exoplanets. We seek to accurately simulate the time-, phase-, and wavelength-dependent appearance of the Pale Blue Dot, and to use these models to understand how to best recognize and characterize potentially Earth-like exoplanets.

  • Exoplanet Detection and Characterization: Observations

    In this task, VPL researchers use astronomical instrumentation to detect and measure the properties of exoplanets. They also study terrestrial planets in our Solar System that can serve as practice targets for exoplanet observational techniques. These observations help us to develop and understand the techniques and measurements required to learn about planetary environments. Although many of these observations are now made on planets that are too large, or too close to their stars to be habitable, once proven, these techniques can then be adapted to help characterize the smaller, cooler planets that may be habitable.

    ROADMAP OBJECTIVES: 1.2 2.2 7.2
  • Astrobiology in Icy Extraterrestrial Environments

    Scientists in the Cosmic Ice Laboratory with the Goddard Center for Astrobiology (GCA) study the formation and stability of molecules under conditions found in outer space. In the past year, studies of amino-acid destruction were continued, a project on the formation of sulfate ions was completed (related to Europa), measurements of the infrared band strengths were published for application to the outer Solar System, and the formation and chemistry of a particularly-versatile interstellar molecule were investigated. All of this work is part of the Comic Ice Laboratory’s continuing contributions to understanding the chemistry of biologically-related molecules and chemical reactions in extra-terrestrial environments.

    ROADMAP OBJECTIVES: 2.1 2.2 3.1 7.1 7.2
  • Biosignatures in Extraterrestrial Settings

    We are working on finding potentially habitable extrasolar planets, using a variety of search techniques, and developing some of the technology necessary to find and characterize low mass extrasolar planets. We also work on modeling and numerical techniques relevant to the problem of identifying extrasolar sites for life, and on some aspects of the prospects for life in the Solar System outside the Earth. The ultimate goal is to find signatures of life on nearby extrasolar planets.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 4.1 4.3 6.2 7.1 7.2
  • Exoplanet Detection and Characterization: Techniques, Retrieval and Analysis

    In this task VPL team members use theoretical modeling and analysis to develop new techniques for detecting and characterizing extrasolar planets. These include developing new techniques for detecting exoplanets in transit data, especially those planets with unusual orbital properties. Team members also work to provide the underlying theory required to develop new remote-sensing techniques for probing planetary atmospheres. They also work on techniques and tests for the retrieval of information about planetary environments from exoplanet photometry and spectra.

  • Biosignatures in Relevant Microbial Ecosystems

    PSARC is investigating microbial life in some of Earth’s most mission-relevant modern ecosystems. These environments include the Dead Sea, the Chesapeake Bay impact structure, methane seeps, ice sheets, and redox-stratified Precambrian ocean analogs. 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.

    PSARC Ph.D. (now postdoctoral researcher at Caltech) Katherine Dawson published a new paper documenting the anaerobic biodegradation of organic biosignature compounds pristane and phytane. PSARC Ph.D. Daniel Jones (now postdoctoral researcher at U. Minnesota) published a new paper that uses metagenomic data to show how sulfur oxidation in the deep subsurface environments may contribute to the formation of caves and the maintenence of deep subsurface microbial ecosystems. PSARC Ph.D. student Khadouja Harouaka published a new paper that represents some of the first available information about possible Ca isotope biosignatures. Lastly, the Macalady group published a paper showing how ecological models based on available energy resources can be used to predict the distribution of microbial populations in space and time.

    ROADMAP OBJECTIVES: 4.1 4.3 5.1 5.2 5.3 6.1 7.1 7.2
  • Evolution of Protoplanetary Disks and Preparations for Future Observations of Habitable Worlds

    The evolution of protoplanetary disks tells the story of the birth of planets and the formation of habitable environments. Microscopic interstellar materials are built up into larger and larger bodies, eventually forming planetesimals that are the building blocks of terrestrial planets and their atmospheres. With the advent of ALMA, we are poised to break open the study of young exoplanetesimals, probing their organic content with detailed observations comparable to those obtained for Solar System bodies. Furthermore, studies of planetesimal debris around nearby mature stars are paving the way for future NASA missions to directly observe potentially habitable exoplanets.

    ROADMAP OBJECTIVES: 1.1 1.2 3.1 4.3 7.2
  • Exploring the Chemical Composition of Hot Exoplanets With the Hubble Space Telescope

    We have used the new Wide Field Camera 3 (WFC3) instrument on the Hubble Space Telescope (HST) to observe exoplanet transit and eclipse measurements for a number of highly irradiated, Jupiter-mass planets, with a focus on confirming which planets exhibit water absorption in transit and/or eclipse and measuring the characteristic brightness temperature at these wavelengths. Measurements of molecular absorption in the atmospheres of these planets offer the chance to explore several outstanding questions regarding the atmospheric structure and composition of hot Jupiters, including the possibility of bulk compositional variations between planets and the presence or absence of a stratospheric temperature inversion.

    ROADMAP OBJECTIVES: 1.1 1.2 7.2
  • Astrophysical Controls on the Elements of Life, Task 7: Update Catalog of Elemental Ratios in Nearby Stars

    Abundances of both common and trace elements can have substantial effects on the habitability of stellar systems. Elemental ratios can change the stellar evolution and mineralogy, geophysics, and surface processes of planets. We study the abundances of large samples of nearby stars and individual systems and the extent of their variation. We examine ratios of elements that have substantial effects on the mineralogy and interiors of planets. The relative abundances of common elements vary substantially among nearby stars. Extremely non-solar abundance ratios at the level that can produce substantial changes in planetary and stellar properties are present in interesting numbers.

  • Project 2A: Magnesium Isotope Fractionation Between Brucite [Mg(OH)2] and Mg Aqueous Species

    Recognition of clay minerals on Noachian martian terranes provides important information on the habitability of early Mars. Magnesium isotopic studies can aid in constraining the paleoenvironmental conditions of these clay deposits. Our goal is to conduct Mg isotope exchange experiments between clay minerals and aqueous Mg solutions to better understand how the formation of clay minerals can produce Mg isotope variability. In Mg-bearing phyllosilicates, octahedrally coordinated Mg2+ cations occur in a sheeted structure that is the same as brucite. Determination of Mg isotope fractionation between brucite and aqueous solution, therefore, may provide insight into the origin of Mg isotope variations during weathering and alteration of silicate rocks. Our results document the distinct Mg isotope signals produced by weathering in the presence of organic ligands, raising the possibility that abiotic weathering may be distinguished from biologically-catalyzed weathering using stable Mg isotopes.

    ROADMAP OBJECTIVES: 1.1 2.1 7.1 7.2
  • Project 2C: Calibrating the 13C-18O (“clumped”) Isotope Temperature Scale

    Determining paleotemperatures in ancient fluid-mineral systems is key to determining ancient habitability. Stable oxygen isotope studies of carbonates have long used changes in 18O/16O ratios to infer the temperature from which carbonate precipitated, using a laboratory-calibrated temperature conversion, but this requires knowledge of the 18O/16O ratios of the fluid. This is often not known. A relatively new approach is to use the non-random variations in rare C and O isotopes, specifically the preferential enhancement of 13C-18O bonds, which has been shown to be related to temperature and independent of the fluid isotopic composition. Experimental calibrations, however, have been inconsistent, and goal of this project is to reconcile these discrepancies.

    ROADMAP OBJECTIVES: 2.1 4.1 7.1 7.2
  • Project 2D: Catalytic Roles of Microbes in Dolomite Crystallization in a Modern Hypersaline Lake

    A key question is if the presence of Mg-bearing carbonates, such as dolomite or proto-dolomite, by itself, represents a biosignature. This proposal is based on the observation that inorganic precipitation of Mg-bearing carbonates is difficult in laboratory settings, possibly reflecting the high Mg dehydration energies in aqueous solutions. New work shows that microbial extracellular polymeric substances substance (EPS) from halophylic archaea from a hypersaline lake can catalyze disordered dolomite precipitation at low-temperature. Mg-rich dolomite can form at 40 degree C. No dolomite precipitates from solutions without the biomass. Low-temperature dolomite with wide range of compositions may therefore be used as a biosignature.

    ROADMAP OBJECTIVES: 6.1 7.1 7.2
  • The Long Wavelength Limit of Oxygenic Photosynthesis

    Oxygenic photosynthesis (OP) produces the strongest biosignatures at the planetary scale on Earth: atmospheric oxygen and the spectral reflectance of vegetation. Both are controlled by the properties of Chlorophyll a, its ability to perform the water-splitting to produce oxygen, and its spectral absorbance that is limited to red and shorter wavelength photons. We seek to answer what is the long wavelength limit at which OP might remain viable, and how. This would clarify whether and how to look for OP adapted to the light from red dwarfs or M stars, which emit little visible light but abundant far-red and near-infrared. Very recently discovered cyanobacteria have been found to harbor alternative chlorophylls adapted to spectral light environments very much like that of M stars. This projects uses field, lab, and modeling studies to study these far-red adapted cyanobacteria as analogues for extrasolar oxygenic photosynthesis pushing the long wavelength limit.

    ROADMAP OBJECTIVES: 3.2 4.2 5.1 5.3 6.2 7.2
  • The Nature and Detectability of Astronomical Biosignatures

    In this project VPL team members explore the nature and detectability of biosignatures, global signs of life in the atmosphere or on the surface of a planet. This year we completed comprehensive modeling work that explores the potential for non-biological generation of oxygen and ozone in early Earth-like atmospheres, which could result in a “false positives” for photosynthetic life. We also explored the detectability of molecular dimers, especially O2-O2 as potentially easier to detect biosignature gases for transit transmission observations.

    We also calculated maximum methane fluxes from the geological process of serpentinization, as a potential false positive for life, and looked at the nature and detectability of non-photosynthetic pigments as potential biosignatures for life on exoplanets. We also started work to develop new, more generalized biosignatures via measurement of thermodyamic and kinetic anomalies in planetary atmospheric compositions that are associated with life. We complemented this theoretical work with field work in caves dominated by sulfur-bacteria, to understand isotopic processing of sulfur by life, as a potential biosignature for life on Mars, or for planets with sulfur-domianted biospheres.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 7.2
  • Project 3A: Banded Iron Formation Deposition Across the Archean-Proterozoic Boundary

    Prior to widespread oxygenic photosynthesis, reduced iron, Fe(II), was the dominant form of soluble iron in surface environments on the early Earth, and likely Mars. On Earth, extensive iron deposits, Banded Iron Formations (BIFs), which currently supply the majority of the iron used in our society, largely formed prior to the Great Oxidation Event of ~2.4 Ga age, and yet contain substantial quantities of oxidized iron, Fe(III). The pathways by which these different oxidation states arose remains unclear. In addition, the chemical and isotopic compositions of BIFs have been used as proxies for ancient seawater or paleoenvironments. In competition with this proposal, however, has been use of BIFs as a tracer of microbial iron cycling. To test the use of BIFs as ambient paleoenvironmental proxies or proxies of microbial process, BIFs from South Africa and Australia were examined from the micron scale to the 100’s of meter scales. We find that BIFs tend to record specific pathways of oxidation of Fe(II), as well as reduction of Fe(III), and extensive post-depositional changes, and it may be quite difficult to infer ambient paleoenvironmental conditions form such deposits.

    ROADMAP OBJECTIVES: 2.1 4.1 5.2 6.1 7.1 7.2
  • Project 3B: Carbon Isotope Analysis of Archean Microfossils

    We have completed a study of petrography, Raman microspectroscopy, and in situ analyses of carbon isotope and H/C ratios using secondary ion mass spectrometry (SIMS) of diverse organic microstructures, including possible microfossils. This work has focussed on two localities of the 3.4-billion-year-old Strelley Pool Formation (Western Australia). For the first time, we show that the wide range of carbon isotope ratios recorded at the micrometer scale correlates with specific types of texture for organic matter (OM), arguing against abiotic processes to produce the textural and isotopic relations. These results support the biogenicity of OM in the Strelley Pool Formation.

    ROADMAP OBJECTIVES: 1.1 2.1 4.1 4.2 5.2 6.2 7.2
  • Task 3.5.1: Titan as a Prebiotic Chemical System

    Six years ago, NASA sponsored a National Academies report that asked whether life might exist in environments outside of the traditional habitable zone, where “weird” genetic molecules, metabolic processes, and bio‐structures might avoid the water‐based biochemistry that is found across the terran biosphere. In pursuit of this “big picture” question, we turned to Titan, which has exotic solvents both on its surface (methane‐hydrocarbon) and sub‐surface (perhaps super‐cooled ammonia‐rich water). This work sought genetic molecules that might support Darwinian evolution in both environments, including non‐ionic polyether molecules in the first and biopolymers linked by exotic oxyanions (such as phosphite, arsenate, arsenite, germanate) in the second. Further, we asked about the possibility that Titan might inform our understanding of prebiotic chemical processes, including those on “warm Titans”. Our experimental activities found few possibilities for non‐phosphate-based genetics in subsurface aqueous environments, even if they are rich in ammonia at very low temperatures. Further, we showed that polyethers are insufficiently soluble in hydrocarbons at very low temperatures, such as the 90‐100 K found on Titan’s surface. However, we did show that “warm Titans” could exploit propane as a biosolvent for certain of these “weird” alternative genetic biopolymers; propane has a huge liquid range (far larger than water). Further, we integrated this work with other work that allows reduced molecules to appear as precursors for more standard genetic biomolecules, especially through interaction with various mineral species.

    ROADMAP OBJECTIVES: 1.1 1.2 2.2 3.1 3.2 4.1 4.2 5.3 6.2 7.1 7.2
  • Project 3C: Carbon Isotope Analysis of Proterozoic Microfossils

    We have developed procedures for accurate in situ analysis of carbon isotope ratios by SIMS for individual Precambrian microfossils of unquestioned biogenicity. Data for three Proterozoic localities show a consistent fractionation of 19 per mil between organic matter and coexisting carbonates, in spite of over 6 per mil variability from rock to rock, consistent with fractionations seen for modern cyanobacteria. In one sample, a phytoplanktonic protistan acritarch, found within the same mm-scale domains, are 6 per mil more fractionated, consistent with photosynthetic eukaryotes. These findings show for the first time the possibility of using in situ isotopic microanalysis of fossil microbial mats and ancient sediments in order to distinguish metabolic fingerprints within complex microbial ecosystems and consortia.

    ROADMAP OBJECTIVES: 2.1 4.1 4.2 5.2 7.2
  • 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’s history the oceans were dominated by unicellular, bacteria-like organisms (prokaryotes) causing a substantially altered biogeochemistry. In this task, we experiment with the marine cyano-bacterium Synechococcus sp. as a model organism and test its aggregation and sinking speed as a function of nutrient (nitrogen, phosphorus, iron) limitation. So far, we have found that these minute cyanobacteria form aggregates in conditions that mimic the open ocean and can sink gravitationally in the water column. Experiments with added clay minerals (bentonite and kaolinite) that might have been present in the Proterozoic ocean show, that these can accelerate aggregate sinking.

    ROADMAP OBJECTIVES: 4.1 4.2 5.2 6.1 7.2
  • Project 3D: Microfossil Insights Into Proterozoic Microbial Ecology

    In a study of the chert-permineralized 1.8 Ga Duck Creek Dolomite, and underlying units, Western Australia, Schopf found that in sequences of 2.3 to 1.8 Ga age that indicate little environmental change, there has been no evolution of the form, function, or metabolic requirements of its biotic components. In a second study of sulfur-cycling bacteria from the 775 Ma chert-permineralized Bambui Group of Brazil, Schopf showed that pyritized microbes of this age were anaerobic sulfur-cyclers. This work, in addition to previous studies, forms the basis for ongoing studies of the biotic response to the Great Oxidation Event.

    ROADMAP OBJECTIVES: 4.1 5.1 5.2 6.1 7.2
  • Stoichiometry of Life, Task 2a: Field Studies – Yellowstone National Park

    Yellowstone National Park harbors an array of hydrothermal ecosystems with widely varying geochemical characteristics and microbial communities. Our research aims to understand how the geochemistry of these hot springs shapes their constituent microbial communities including their composition and function. To accomplish this aim, we measure (1) physical and geochemical properties of hot spring fluids and sediments, (2) the rates of biogeochemical processes (i.e., methane oxidation, nitrogen fixation, microbial Fe cycling, photosynthesis, de-nitrification, etc.), and (3) markers for microbial community diversity (i.e., SSU rRNA, metabolic genes, lipids, proteins).

    ROADMAP OBJECTIVES: 5.1 5.2 5.3 6.1 6.2 7.2
  • Project 4A: Better, Faster, Smaller Fe Isotope Analysis on Iron Oxides and Sulfides by Femtosecond Laser Ablation: Aerosol Characterization and the Influence of Ablation Cells

    New methods are being developed for in situ stable isotope analysis that increase the precision and/or decrease the volume sampled during the analysis. These improvements allow one to identify isotopic anomalies with increasing spatial resolution. We have focused on improving the ablation cell and mass spectrometer electronics to increase the spatial resolution of Fe isotope studies on iron oxides and sulfides whilst maintaining an external precision of +0.2 ‰ in 56Fe/54Fe using femtosecond Laser Ablation (fs-LA) with isotopic analysis by MC-ICP-MS (Micromass “IsoProbe”). These improvements have allowed us to decrease the volume needed for an Fe isotope analysis to ~600μm3 with an external precision of 0.2 ‰ in 56Fe/54Fe (for a typical analysis the laser beam is rastered over an area of 20 by 15 μm). Compared to previous LA Fe isotope studies the volume used for an analysis in an order of magnitude smaller and is similar to Fe isotope studies that have been done by ion microprobe.

    ROADMAP OBJECTIVES: 1.1 2.1 7.1 7.2
  • The Astrobiology Walk

    The Goddard Center for Astrobiology (GCA) has completed the development and installation of a permanent outdoor exhibit at the Goddard Space Flight Center (GSFC) Visitor Center as a major public outreach effort. The “Astrobiology Walk” is designed to showcase the latest scientific discoveries from the GCA research theme “Search for the Origin and Evolution of Organics” in the context of a timeline for the evolution of the Universe and the Solar System. The exhibit consists of ten outdoor stations situated on the circular pathway around the Visi-tor Center’s “Rocket Garden”, each with a memorable iconic 3D object to convey the main scientific message. QR codes link each placard to web sites relevant to that topic.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 3.2 4.1 4.3 7.1 7.2