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Project Reports

• 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

• 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

• 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

• Project 5A: Astrobiology Studies at the Utah Mars Desert Research Station in Support of Current and Future Mars Missions

  Pascale Ehrenfreund participated to Crew #77 at the Mars Desert Research Station (MDRS) in Utah in February 2009. The MDRS project was initiated by the Mars Society in 2000 and consists of a habitat complex optimized for a 6-person crew and includes a greenhouse and astronomical observatory. The goal of this field campaign sponsored by ESA, NASA and the international lunar exploration working group (ILEWG) was to demonstrate instrument capabilities in support of current and future planetary missions, to validate a procedure for Martian surface in-situ and return science, and to study human performance aspects. Special emphasis was given to sample collection in the geologically rich vicinity of MDRS and subsequent analysis of organic molecules and microorganisms in the soil to simulate the search for life with field instrumentation.

  ROADMAP OBJECTIVES: 2.1 5.1

• 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 1A: Stability of Polycyclic Aromatic Hydrocarbons and Fullerenes in Space Environment

  EXPOSE-R is a multi-user facility attached to an external platform at the outer hull of the Service Module of the International Space Station (ISS). The external platform, called URM-D is part of the Russian Segment. EXPOSE-R accommodates 10 biological and biochemical experiments, which are mounted in three removable containers, called trays. The Organics experiment on EXPOSE-R consists of thin films of polycyclic aromatic hydrocarbons (PAHs) and fullerenes that are exposed ~18-24 months to solar UV under vacuum or controlled atmosphere. The samples of the Organics experiment were analyzed before exposure to space environment with UV, visible and infrared spectroscopy and the ground control samples are measured regularly in the laboratory. EXPOSE-R experiments were activated by Extra Vehicular Activity (EVA) in March 2009 and are currently in orbit. The trays will be recovered by EVA again, brought into the RS-ISS and returned to Earth by the manned SOYUZ return capsule in early spring 2011.

  ROADMAP OBJECTIVES: 3.1

• Project 3A: Quantifying the Amount of Free Oxygen in the Neoarchean Photic Zone Through Combined Fe and Mo Isotopes

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

  ROADMAP OBJECTIVES: 4.1 5.2 6.1 7.1

• Project 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 4B: Development of Laser Ablation-Miniature Mass Spectrometer (LA-MMS) for Geochronology and Geochemistry of Martian Rocks

  Our goal is to develop a breadboard instrument for isotopic analysis of solids and age dating of different rocks based on Rb-Sr radiometric technique. This is based on the methodology of laser ablation-miniature mass spectrometer (LA-MMS). It performs the mass spectral and isotopic measurements of the laser ablated vapors from solids using the miniature mass spectrometer (MMS) and the modified CCD based array detector for the direct and simultaneous measurement of different mass ions. The approach has been demonstrated at the Jet Propulsion Laboratory by the chemical and isotopic analysis of gas and solid samples. The breadboard version of the above instrument can be miniaturized to meet the requirements of a rover based spacecraft instrument for applications to various NASA missions.

  ROADMAP OBJECTIVES: 2.1 7.2

• 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 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

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

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

  ROADMAP OBJECTIVES: 1.1 4.1 4.2 7.1

• Project 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

• Project 1B: Proto-Cell Membrane Evolution May Have Been Directed by Mineral Surface Properties

  In the present project, we used both experimental and classical modeling approaches to examine the novel hypothesis that the surface chemistry of minerals in contact with self-assembling lipid vesicles (i.e., model protocells) controlled the stability of the vesicle membrane, causing membranolysis and preventing self-assembly in the case of minerals with certain surface properties, while other minerals were relatively inert. We also examined the role of solution chemistry and temperature cycling on lipid vesicle stability in contact with mineral surfaces. By understanding the role of natural geochemical parameters such as mineral surface chemistry, solution chemistry (pH, ionic strength, presence or absence of Ca2+), and temperature cycling on protocell membrane stability under variable conditions, we attempted to model potential aqueous environments where life may have originated such as lacustrine, tidal pool, and sub-aerial or submarine hydrothermal vents. Our project addresses NASA Astrobiology Institute’s (NAI) Roadmap goals of understanding the origins of cellularity and the evolution of mechanisms for survival at environmental limits, 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

• 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

• 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

• 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

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

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

  ROADMAP OBJECTIVES: 3.3 4.1