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2009 Annual Science Report

University of Wisconsin Reporting  |  JUL 2008 – AUG 2009

Executive Summary

Understanding the signatures and environments of life are the primary goals of the Wisconsin Astrobiology Research Consortium (WARC). In Year 2, WARC pursued 14 research projects and three Education and Public Outreach (EPO) projects, which involved 12 primary investigators, nine research scientists and staff, 10 post-docs, 10 graduate students, and 27 collaborators at other institutions. WARC members have collaborations with seven other NAI teams, including NASA-Ames, the two NASA-JPL teams, Carnegie, Montana State, NASA-Goddard, and Penn State. Research efforts in Year 2 may be broadly grouped into three components: 1) organic compounds, and their planetary inventories, preservation, and interactions with minerals; 2) chemical and isotopic biosignatures in modern and ancient environments; and 3) new frontiers in analytical methods, applied in situ on other planetary bodies or used for analysis of materials of the early Earth or those returned from missions. EPO activities involved a wide ... Continue reading.

Field Sites
20 Institutions
14 Project Reports
73 Publications
9 Field Sites
Roadmap
Objectives

Project Reports

  • Chemolithotrophic Microbial Oxidation of Insoluble Fe(II)-Bearing Minerals

    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). Thought to be one of the oldest forms of microbial metabolism on Earth, Fe(II) oxidation may also 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 initial 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. Preliminary experiments suggest that the culture is able to oxidize a significant portion 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.

    ROADMAP OBJECTIVES: 4.1 6.1 7.1
  • The Role of Dissolved Sulfide in Controlling Carbonate Mineral Compositions

    Role of microbes in dolomite formation is still under debate. It was proposed that sulfate-reducing bacteria (SRB) can results in dolomite precipitation. We investigated the role of dissolved sulfide (a product of SRB metabolism) in controlling carbonate mineral compositions and even dolomite crystallization at low temperatures. Our results show that very high-magnesium calcite (VHMC) and disordered dolomite can precipitate from aqueous sulfide-bearing solutions at low temperature.

    ROADMAP OBJECTIVES: 4.1 7.1 7.2
  • Co-Evolution of Microbial Metabolisms in the Neoarchean and Paleoproterozoic

    The interplay between the biosphere, lithosphere, hydrosphere, and atmosphere has produced a complex evolution of microbial metabolisms that significantly affect the geochemical and mineralogical compositions of surface environments. One approach to tracing the evolution of very ancient microbial metabolisms is through studies of the isotopic compositions of elements that are cycled by life and preserved in the rock record. The Neoarchean and Paleoproterozoic (~3.1 to 2.4 billion years ago) record very large changes in C, S, and Fe isotope compositions in marine sedimentary rocks that are interpreted to reflect an explosion in microbial diversity, including establishment of oxygenic and anaerobic photosynthesis, aerobic methanotrophy, methanogenesis, and dissimilatory sulfate and iron reduction. The ecosystems on Earth in the Neoarchean and Paleoproterozoic juxtaposed oxidized and reduced environments, reflecting unique conditions during the time leading up to the first significant increase in atmospheric oxygen at ~2.4 b.y. ago.

    ROADMAP OBJECTIVES: 4.1 5.1 6.1 7.1
  • Qualitative Analysis of Soils Samples Using Solid Phase Microextraction (SPME) and Gas Chromatography/mass Spectrometry (GC/MS)

    The investigation of the physical and chemical properties of Mars soil analogues collected in arid deserts provide limits to exobiological models, evidence on the effects of subsurface mineral matrices, support current and planned space missions, and address planetary protection issues. We have collected samples in the Atacama desert and applied Solid Phase Micro-Extraction (SPME) to optimize the extraction of Polycyclic Aromatic Hydrocarbons (PAHs). PAHs are among the most abundant molecules found in various space environments in the solar system and beyond. SPME is a solvent-free extraction method invented and applied in a variety of sampling-detection scenarios. The aim of this study is to use SPME for fast screening and determination of PAHs in soil samples. This method minimizes sample handling and preserves chemical integrity of the sample. When compared to traditional extraction methods SPME may provide better analyte recoveries, less opportunity for rearrangement and decomposition of analytes, and faster analysis. This study and further optimization of this extraction technique provides important data for the calibration and performance of future Mars instrumentation that specializes on the detection of organic molecules.

    ROADMAP OBJECTIVES: 2.1 3.1
  • Laser Ablation-Electron Impact Ionization-Miniature Mass Spectrometer (LA-EI-MMS) for In-Situ Geochronology and Hydrology of Martian Rocks

    Geochronologic investigations of Mars have focused exclusively on Martian meteorites and crater counting the Martian surface to infer relative ages of different Martian surfaces. Our goal is to develop geochronologic methods that can be applied using a miniature mass spectrometer capable of being deployed on a Mars rover to perform chemical and Rb-Sr isotope analysis on samples collected from the Martian surface. In parallel with instrument development we are conducting terrestrial studies of Martian analog materials and SNC meteorites to develop standards for the miniature mass spectrometer and methodologies for interpretation of data that may be collected using this miniature mass spectrometer.

    ROADMAP OBJECTIVES: 2.1
  • Development of Laser Ablation-Electron Impact Ionization-Miniature Mass Spectrometer (LA-EI-MMS) for In-Situ Chemical and Isotopic Measurements of Martian Rocks

    Our goal is to develop instrumentation capable of being deployed on a lander style space craft that can measure the chemical and isotopic composition of Martian samples. The instrumentation is based on the technologies of (i) laser ablation (LA) sampling of minerals, (ii) electron-impact ionization (EI) of ablated neutrals, and (iii) mass spectral measurement using JPL-developed miniature mass spectrometer (MMS) of focal plane geometry with modified-CCD array detector.

    ROADMAP OBJECTIVES: 2.1 7.2
  • 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. As such, 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
  • New Frontiers in Micro-Analysis of Isotopic Compositions of Natural Materials: Development of O, S, Si, and Li Isotopes

    The isotope ratios of oxygen and silicon are a sensitive monitor of sedimentary and hydrothermal processes for deposition of banded iron formation. Our focus on banded iron formations reflects the importance these unusual units have in biogeochemical cycling in the early Earth. In particular, we are examining the deposition of microlaminated sections of the Dales Gorge member of the Brockman Iron Formation from the Hamersley basin, which have alternatively been interpreted to represent annual varves in chemical precipitates from seawater, or variations in a sub-surface hydrothermal system. These conflicting models have relevance for interpreting the role of microbial life in precipitation of the Fe-oxides. In addition, δ18O and δ34S values from coexisting minerals can be used to estimate the temperature of the Archean ocean, or of the hydrothermal system. Values of δ7Li and δ18O in zircons allow these tests to be applied to magmas that may have assimilated sedimentary materials, and in the case of pre-4 Ga Jack Hills zircons from SW Australia, provide a record of the earliest Earth before the formation of all known rocks.

    ROADMAP OBJECTIVES: 4.1 7.1
  • Microbial Pyrite Oxidation in Nature and the Lab: Sulfate Mineral Biosignature Investigation

    Deposits of minerals containing the chemical species sulfate, a constituent of ocean water, have been identified on the surface of Mars. Although there might be other methods for its formation, the process we are investigating is one that occurs on Earth and is the result of the metabolic activity of microbes, which oxidize the iron sulfide mineral pyrite (Fool’s Gold) to form sulfate. We have made the oxygen in water in a bacterial culture medium traceable by addition of a non-radioactive isotopic tracer and can thus differentiate oxygen from the atmosphere, used by biological processes, from oxygen in water, used by the non-biological processes. Our new data and approaches defy conventional wisdom, and offer a novel way for investigating the origin of sulfates on Mars by in situ instruments.

    ROADMAP OBJECTIVES: 2.1 7.1
  • Alternative Formation Mechanisms for Banded Iron Formations

    Based on field observations during the 2008 BIF filed trip and laboratory investigation, we have proposed a new generation mechanism for the banded iron formations, very important rocks that recorded early earth conditions and environment. Our new model shows how BIFs could have formed when hydrothermal fluids from the interaction between seawater and komatiite (Al-depleted rock) that comes from hot and deep Earth’s mantle, mixed with surface seawater. This mixing triggered the dynamics of oscillation between iron- and silica-rich minerals, which were deposited in layers on the seafloor.

    ROADMAP OBJECTIVES: 4.1
  • Evolution of Organic Matter in Space: UV-vis Spectroscopy Investigation on Nanosatellites

    The “Organics” experiment (PI: P. Ehrenfreund) was integrated in March 2009 on the International Space Station ISS. This experiment exposes specific PAHs and fullerene compounds for one year on-board the ISS. Laboratory measurements of the samples after retrieval will greatly enhance our understanding of the evolution of large molecules in space. A new generation of free-fliers and small satellites is also poised to enable in situ monitoring of changes to organic materials induced by space conditions. To optimize the scientific pay-off from frequent low-cost missions, the development of robust and capable in situ measurement technology is essential. We have investigated a research and technology program that includes 1) ground-based monitoring of EXPOSE-R samples in a simulated space environment, 2) development of a laboratory prototype UV-Vis spectrometer for in situ measurements of organic material on future free-fliers and lunar surface exposure facilities, and 3) detailed characterization of the prototype’s performance via in situ spectral measurements of control EXPOSE-R samples versus time in a simulated space
    environment, in direct comparison with a reference laboratory spectrometer. The research program combines the expertise and facilities of two NAI teams (Wisconsin and ARC) and addresses the key objectives of the Astrobiology Small Payloads (ASP) program, as well as Astrobiology Roadmap Goal 3 on cosmic and planetary precursors.

    ROADMAP OBJECTIVES: 3.1 7.1
  • 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
  • Iron Isotope Biosignatures: Laboratory Studies and Modern Environments

    The isotopic fingerprints of biological carbon and sulfur cycling in modern and ancient marine environments is well established by research over several decades, but, until recently, potential iron isotope fingerprints of microbial iron cycling in the ancient Earth have not been pursued. Next to carbon, iron was probably the most important element cycled by early life, given the high abundance of iron in early Earth environments and the energy gains that may be obtained by microbes during iron redox changes. Our new laboratory studies moved away from simple systems to those more analogous to nature, and we demonstrated that iron isotope fractionations can be produced by biological cycling in complex systems. Moreover, in a field study, we isolated natural iron cycling microbes and demonstrated that the iron isotope fractionations produced by natural microbial ecosystems are the same as those produced by pure strains in the laboratory; these are key components to confidently applying Fe isotopes as a biosignature for ancient life.

    ROADMAP OBJECTIVES: 2.1 4.1 5.2 6.1 7.1 7.2
  • New Frontiers in Micro-Analysis of Isotopic Compositions of Natural Materials: Development of Fe Isotopes

    We are developing micro-analytical techniques to perform in situ Fe isotope analysis of Fe-bearing minerals by ion microprobe and laser ablation mass spectrometry. Iron isotope compositions are important signatures in tracking redox processes, chemical weathering, and dissimilatory iron reduction by bacteria. In situ micro analysis procedures will allow us to better apply the Fe isotope system by allowing one to determine Fe isotope compositions within a petrographic framework, minimize sample requirements, evaluate microscale heterogeneity, and inter-mineral isotopic equilibrium. Such in situ procedures are critical for analysis of samples that may be returned from future space missions or for analysis by instruments that can be deployed on space craft.

    ROADMAP OBJECTIVES: 2.1 4.1 7.1 7.2

Education & Public Outreach

Publications

  • Aubrey, A. D., Chalmers, J. H., Bada, J. L., Grunthaner, F. J., Amashukeli, X., Willis, P., … Yen, A. (2008). The Urey Instrument: An Advanced In Situ Organic and Oxidant Detector for Mars Exploration. Astrobiology, 8(3), 583–595. doi:10.1089/ast.2007.0169

  • Blank, J. G., Green, S. J., Blake, D., Valley, J. W., Kita, N. T., Treiman, A., & Dobson, P. F. (2009). An alkaline spring system within the Del Puerto Ophiolite (California, USA): A Mars analog site. Planetary and Space Science, 57(5-6), 533–540. doi:10.1016/j.pss.2008.11.018

  • Blothe, M., & Roden, E. E. (2009). Composition and Activity of an Autotrophic Fe(II)-Oxidizing, Nitrate-Reducing Enrichment Culture. Applied and Environmental Microbiology, 75(21), 6937–6940. doi:10.1128/aem.01742-09

  • Czaja, A. D., Johnson, C. M., Beard, B. L., Eigenbrode, J. L., Freeman, K. H., & Yamaguchi, K. E. (2010). Iron and carbon isotope evidence for ecosystem and environmental diversity in the ∼2.7 to 2.5Ga Hamersley Province, Western Australia. Earth and Planetary Science Letters, 292(1-2), 170–180. doi:10.1016/j.epsl.2010.01.032

  • Dattagupta, S., Schaperdoth, I., Montanari, A., Mariani, S., Kita, N., Valley, J. W., & MacAlady, J. L. (2009). A novel symbiosis between chemoautotrophic bacteria and a freshwater cave amphipod. ISME J, 3(8), 935–943. doi:10.1038/ismej.2009.34

  • Ehrenfreund, P., & Peter, N. (2009). Toward a paradigm shift in managing future global space exploration endeavors. Space Policy, 25(4), 244–256. doi:10.1016/j.spacepol.2009.09.004

  • Fehr, M. A., Andersson, P. S., Hålenius, U., & Mörth, C-M. (2008). Iron isotope variations in Holocene sediments of the Gotland Deep, Baltic Sea. Geochimica et Cosmochimica Acta, 72(3), 807–826. doi:10.1016/j.gca.2007.11.033

  • Heimann, A., Johnson, C. M., Beard, B. L., Valley, J. W., Roden, E. E., Spicuzza, M. J., & Beukes, N. J. (2010). Fe, C, and O isotope compositions of banded iron formation carbonates demonstrate a major role for dissimilatory iron reduction in ~2.5Ga marine environments. Earth and Planetary Science Letters, 294(1-2), 8–18. doi:10.1016/j.epsl.2010.02.015

  • Homoky, W. B., Severmann, S., Mills, R. A., Statham, P. J., & Fones, G. R. (2009). Pore-fluid Fe isotopes reflect the extent of benthic Fe redox recycling: Evidence from continental shelf and deep-sea sediments. Geology, 37(8), 751–754. doi:10.1130/g25731a.1

  • Huberty, J. M., Kita, N. T., Kozdon, R., Heck, P. R., Fournelle, J. H., Spicuzza, M. J., … Valley, J. W. (2010). Crystal orientation effects in δ18O for magnetite and hematite by SIMS. Chemical Geology, 276(3-4), 269–283. doi:10.1016/j.chemgeo.2010.06.012

  • Johnson, C. M., Beard, B. L., Klein, C., Beukes, N. J., & Roden, E. E. (2008). Iron isotopes constrain biologic and abiologic processes in banded iron formation genesis. Geochimica et Cosmochimica Acta, 72(1), 151–169. doi:10.1016/j.gca.2007.10.013

  • Kita, N. T., Ushikubo, T., Fu, B., & Valley, J. W. (2009). High precision SIMS oxygen isotope analysis and the effect of sample topography. Chemical Geology, 264(1-4), 43–57. doi:10.1016/j.chemgeo.2009.02.012

  • Knight, K. B., Kita, N. T., Mendybaev, R. A., Richter, F. M., Davis, A. M., & Valley, J. W. (2009). Silicon isotopic fractionation of CAI-like vacuum evaporation residues. Geochimica et Cosmochimica Acta, 73(20), 6390–6401. doi:10.1016/j.gca.2009.07.008

  • Kozdon, R., Kita, N. T., Huberty, J. M., Fournelle, J. H., Johnson, C. A., & Valley, J. W. (2010). In situ sulfur isotope analysis of sulfide minerals by SIMS: Precision and accuracy, with application to thermometry of ∼3.5Ga Pilbara cherts. Chemical Geology, 275(3-4), 243–253. doi:10.1016/j.chemgeo.2010.05.015

  • Küppers, M., Keller, H. U., Kührt, E., A’Hearn, M. F., Altwegg, K., Bertrand, R., … Zarnecki, J. C. (2008). Triple F—a comet nucleus sample return mission. Exp Astron, 23(3), 809–847. doi:10.1007/s10686-008-9115-8

  • Lammer, H., Bredehöft, J. H., Coustenis, A., Khodachenko, M. L., Kaltenegger, L., Grasset, O., … Rauer, H. (2009). What makes a planet habitable?. The Astronomy and Astrophysics Review, 17(2), 181–249. doi:10.1007/s00159-009-0019-z

  • Madzunkov, S. M., MacAskill, J. A., Chutjian, A., Ehrenfreund, P., Darrach, M. R., Vidali, G., & Shortt, B. J. (2009). FORMATION OF FORMALDEHYDE AND CARBON DIOXIDE ON AN ICY GRAIN ANALOG USING FAST HYDROGEN ATOMS. The Astrophysical Journal, 697(1), 801–806. doi:10.1088/0004-637x/697/1/801

  • Martins, Z., Botta, O., Fogel, M. L., Sephton, M. A., Glavin, D. P., Watson, J. S., … Ehrenfreund, P. (2008). Extraterrestrial nucleobases in the Murchison meteorite. Earth and Planetary Science Letters, 270(1-2), 130–136. doi:10.1016/j.epsl.2008.03.026

  • Osman, S., Peeters, Z., La Duc, M. T., Mancinelli, R., Ehrenfreund, P., & Venkateswaran, K. (2007). Effect of Shadowing on Survival of Bacteria under Conditions Simulating the Martian Atmosphere and UV Radiation. Applied and Environmental Microbiology, 74(4), 959–970. doi:10.1128/aem.01973-07

  • Richter, F. M., Watson, E. B., Mendybaev, R., Dauphas, N., Georg, B., Watkins, J., & Valley, J. (2009). Isotopic fractionation of the major elements of molten basalt by chemical and thermal diffusion. Geochimica et Cosmochimica Acta, 73(14), 4250–4263. doi:10.1016/j.gca.2009.04.011

  • Romanek, C. S., Jiménez-López, C., Navarro, A. R., Sánchez-Román, M., Sahai, N., & Coleman, M. (2009). Inorganic synthesis of Fe–Ca–Mg carbonates at low temperature. Geochimica et Cosmochimica Acta, 73(18), 5361–5376. doi:10.1016/j.gca.2009.05.065

  • Seiferlin, K., Ehrenfreund, P., Garry, J., Gunderson, K., Hütter, E., Kargl, G., … Merrison, J. P. (2008). Simulating Martian regolith in the laboratory. Planetary and Space Science, 56(15), 2009–2025. doi:10.1016/j.pss.2008.09.017

  • Srama, R., Stephan, T., Grün, E., Pailer, N., Kearsley, A., Graps, A., … Röser, H-P. (2008). Sample return of interstellar matter (SARIM). Exp Astron, 23(1), 303–328. doi:10.1007/s10686-008-9088-7

  • Tangalos, G. E., Beard, B. L., Johnson, C. M., Alpers, C. N., Shelobolina, E. S., Xu, H., … Roden, E. E. (2010). Microbial production of isotopically light iron(II) in a modern chemically precipitated sediment and implications for isotopic variations in ancient rocks. Geobiology, 8(3), 197–208. doi:10.1111/j.1472-4669.2010.00237.x

  • Teutsch, N., Schmid, M., Müller, B., Halliday, A. N., Bürgmann, H., & Wehrli, B. (2009). Large iron isotope fractionation at the oxic–anoxic boundary in Lake Nyos. Earth and Planetary Science Letters, 285(1-2), 52–60. doi:10.1016/j.epsl.2009.05.044

  • Wang, Y., Xu, H., Merino, E., & Konishi, H. (2009). Generation of banded iron formations by internal dynamics and leaching of oceanic crust. Nature Geosci, 2(11), 781–784. doi:10.1038/ngeo652

  • Worms, J-C., Lammer, H., Barucci, A., Beebe, R., Bibring, J-P., Blamont, J., … Zarnecki, J. (2009). ESSC-ESF Position Paper—Science-Driven Scenario for Space Exploration: Report from the European Space Sciences Committee (ESSC). Astrobiology, 9(1), 23–41. doi:10.1089/ast.2007.1226

  • Wu, L., Beard, B. L., Roden, E. E., & Johnson, C. M. (2009). Influence of pH and dissolved Si on Fe isotope fractionation during dissimilatory microbial reduction of hematite. Geochimica et Cosmochimica Acta, 73(19), 5584–5599. doi:10.1016/j.gca.2009.06.026

  • Xu, H. (2010). Synergistic Roles of Microorganisms in Mineral Precipitates Associated with Deep Sea Methane Seeps. Geomicrobiology: Molecular and Environmental Perspective, None, 325–346. doi:10.1007/978-90-481-9204-5_15

  • Xu, J., Stevens, M. J., Oleson, T. A., Last, J. A., & Sahai, N. (2009). Role of Oxide Surface Chemistry and Phospholipid Phase on Adsorption and Self-Assembly: Isotherms and Atomic Force Microscopy. The Journal of Physical Chemistry C, 113(6), 2187–2196. doi:10.1021/jp807680d

  • Zhang, F., Xu, H., Konishi, H., & Roden, E. E. (2010). A relationship between d104 value and composition in the calcite-disordered dolomite solid-solution series. American Mineralogist, 95(11-12), 1650–1656. doi:10.2138/am.2010.3414

  • Anbar, A.D. & Rouxel, O.  (2007).  Metal Stable Isotopes in Paleoceanography.  Annual Review of Earth and Planetary Sciences, 35: 717-746.
  • Anbar, A.D. & Rouxel, O.  (2007).  Metal stable isotopes in paleoceanography.  Annu Rev Earth Pl Sc, 35(1): 717-746.
  • Archer, C. & Vance, D.  (2006).  Coupled Fe and S isotope evidence for Archean microbial Fe(III) and sulfate reduction.  Geology, 34(3): 153-156.
  • Bada, J., Ehrenfreund, P. & Team, t.U.  (2008).  Urey: Mars Organic and Oxidant Detector.  Space Science Reviews journal, 135: 269-279.
  • Beard, B.L. & Johnson, C.M.  (1999).  High precision iron isotope measurements of terrestrial and lunar materials.  Geochim Cosmochim Acta, 63(11-12): 1653-1660.
  • Beard, B.L., Johnson, C.M., Skulan, J.L., Nealson, K.H., Cox, L. & Sun, H.  (2003).  Application of Fe isotopes to tracing the geochemical and biological cycling of Fe.  Chem Geol, 195(1-4): 87-117.
  • Bergquist, B.A. & Boyle, E.A.  (2006).  Iron isotopes in the Amazon River system: Weathering and transport signatures.  Earth Planet Sci Lett, 248(1-2): 54-68.
  • Botta, O., Martins, Z., Emmenegger, C., Dworkin, J.P., Glavin, D., Harvey, R.P., Zenobi, R., Bada, J.L. & Ehrenfreund, P.  (2008).  Polycyclic aromatic hydrocarbons and amino acids in meteorites and ice samples from La Paz ice field, Antarctica.  MAPS, 43: 1465-1480.
  • Brunner, B., Yu, J-., Mielke, R.E. & Coleman, M.  (2008).  Different chemical and isotopic signatures of pyrite oxidation by Acidithiobacillus ferrooxidans during lag and exponential growth phases.  Earth Planet. Sci. Let, 270: 63-72.
  • Crosby, H.A., Roden, E.E., Johnson, C.M. & Beard, B.L.  (2007).  The mechanisms of iron isotope fractionation produced during dissimilatory Fe(III) reduction by Shewanella putrefaciens and Geobacter sulfurreducens.  Geobiol, 5(2): 169-189.
  • Ehrenfreund, P. & Foing, B.H.  (2008).  Journey to the Moon: Recent results, science, future robotic and human exploration.  In: Oxford : Elsevier, 2. (Eds.).  Advances in Space Research.  Vol. 42.
  • Eigenbrode, J.L. & Freeman, K.H.  (2006).  Late Archean rise of aerobic microbial ecosystems.  Proc Natl Acad Sci U S A, 43: 15759-15764.
  • Farquhar, J. & Wing, B.A.  (2003).  Multiple sulfur isotopes and the evolution of the atmosphere.  Earth Planet Sci Lett, 213: 1-13.
  • Foing, B.H., Racca, G., Josset, J.L., Koschny, D., Frew, D., Almeida, M., Zender, J., Heather, D., Peters, S., Marini, A., Stagnaro, L., Beauvivre, S., Grande, M., Kellett, B., Huovelin, J., Nathues, A., Mall, U., Ehrenfreund, P. & McCannon, P.  (2008).  SMART-1 highlights and relevant studies on early bombardment and geological processes on rocky planets.  Physica Scripta, 130: 014026.
  • Huberty, J.M., Kita, N.T., Heck, P.R., Kozdon, R., Fournelle, J.H., Xu, H. & Valley, J.W.  (2009).  Crystal orientation effects on bias of δ18O in magnetite by SIMS. Goldschmidt Conference.  Geochim. Cosmochim. Acta, 73(13).
  • Jenkyns, H., Matthews, A., Tsikos, H. & Erel, Y.  (2007).  Nitrate reduction, sulfate reduction and sedimentary iron-isotope evolution during the Cenomanian-Turonian Anoxic Event.  Paleoceanography, 22(PA3208).
  • Jimenez-Lopez, C., Romanek, C.S. & Bazylinski, D.A.  (In Press).  Magnetite as a Prokaryotic Biomarker.  Journal of Geophysical Research-Biogeosciences.
  • Johnson, C.M., Beard, B.L. & Roden, E.E.  (2008).  The iron isotope fingerprints of redox and biogeochemical cycling in modern and ancient Earth.  Planetary Sciences, 36: 457-493.
  • Johnson, C.M., Beard, B.L. & Roden, E.E.  (2008).  The iron isotope fingerprints of redox and biogeochemical cycling in the modern and ancient Earth.  Ann Rev Earth Planet Sci, 36: 457-493.
  • Johnson, C.M., Roden, E.E., Welch, S.A. & Beard, B.L.  (2005).  Experimental constraints on Fe isotope fractionation during magnetite and Fe carbonate formation coupled to dissimilatory hydrous ferric oxide reduction.  Geochim Cosmochim Acta, 69(4): 963-993.
  • Kita, N., Huberty, J.M., Kozdon, R., Beard, B.L. & Valley, J.W.  (2010, In Press).  High precision SIMS oxygen, sulfur, and iron stable isotope analyses of geological materials: Accuracy, surface topography, and crystal orientation.  SIMS XVII Proceedings special issue Surface and Interface Analysis.
  • Kita, N.T., Huberty, J.M., Kozdon, R., Beard, B.L. & Valley, J.W.  (2009, In Review).  High precision SIMS oxygen, sulfur and iron stable isotope analyses of geological materials: Accuracy, surface topography and crystal orientation.  SIMS XVII Proceedings (Special Issue, Surface and Interface Analysis).
  • Klein, C.  (2005).  Some Precambrian banded iron-formations (BIFs) from around the world: Their age, geologic setting, mineralogy, metamorphism, geochemistry, and origin.  Am Mineral, 90(10): 1473-1499.
  • Lapen, T.J., Brandon, A.D., Beard, B.L., Peslier, A.H., Lee –T, A. & Dalton, H.A.  (2008).  Lu-Hf age of isotope systematics of the olivine-phyric shergottite RBT-04262 and implications for the sources of enriched shergotitites.  Lunar Planetary Sci.
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2009 Teams