Hostname: page-component-848d4c4894-4hhp2 Total loading time: 0 Render date: 2024-06-10T00:13:17.864Z Has data issue: false hasContentIssue false
  • English
  • Français

Evidence for biological activity in mineralization of secondary sulphate deposits in a basaltic environment: implications for the search for life in the Martian subsurface

Published online by Cambridge University Press:  24 July 2013

C. Doc Richardson ,
Nancy W. Hinman  and
Jill R. Scott
C. Doc Richardson
Affiliation:
Geosciences Department, University of Montana, Missoula, 32 Campus Drive #1296, Missoula, MT 59812, USA
Nancy W. Hinman
Affiliation:
Geosciences Department, University of Montana, Missoula, 32 Campus Drive #1296, Missoula, MT 59812, USA
Jill R. Scott
Affiliation:
Chemical and Radiation Measurement, Idaho National Laboratory, 1765 North Yellowstone Hwy, Idaho Falls, ID 83415-2208, USA e-mail: Jill.Scott@inl.gov
Get access Rights & Permissions [Opens in a new window]

Abstract

Evidence of microbial activity associated with mineralization of secondary Na-sulphate minerals (thenardite, mirabilite) in the basaltic subsurface of Craters of the Moon National Monument (COM), Idaho were examined by scanning electron microscopy, X-ray diffraction, laser desorption Fourier transform ion cyclotron resonance mass spectrometry (LD-FTICR-MS), Fourier transform infrared spectroscopy (FTIR) and isotope ratio mass spectrometry. Peaks suggestive of bio/organic compounds were observed in the secondary Na-sulphate deposits by LD-FTICR-MS. FTIR provided additional evidence for the presence of bio/organic compounds. Sulphur fractionation was explored to assist in determining if microbes may play a role in oxidizing sulphur. The presence of bio/organic compounds associated with Na-sulphate deposits, along with the necessity of oxidizing reduced sulphur to sulphate, suggests that biological activity may be involved in the formation of these secondary minerals. The secondary Na-sulphate minerals probably form from the overlying basalt through leached sodium ions and sulphate ions produced by bio-oxidation of Fe-sulphide minerals. Since the COM basalts are one of the most comparable terrestrial analogues for their Martian counterparts, the occurrence of biological activity in the formation of sulphate minerals at COM has direct implications for the search for life on Mars. In addition, the presence of caves on Mars suggests the importance of these environments as possible locations for growth and preservation of microbial activity. Therefore, understanding the physiochemical pathways of abiotic and biotic mineralization in the COM subsurface and similar basaltic settings has direct implications for the search for extinct or extant life on Mars.

Keywords

bio/organic compoundsCraters of the Moon National MonumentFTICR-MSFTIRMarsSEMsulphur isotopesThenarditeXRD
Type
Research Article
Information
International Journal of Astrobiology , Volume 12 , Issue 4 , October 2013 , pp. 357 - 368
Copyright
Copyright © Cambridge University Press 2013 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Badhwar, G. (2004). Martian radiation environment. Space Sci. Rev. 110, 131–142.CrossRefGoogle Scholar
Balci, N., Shanks, W.C. III, Mayer, B. & Mandernack, K.W. (2007). Oxygen and sulfur isotope systematics of sulfate produced by bacterial and abiotic oxidation of pyrite. Geochim. Cosmochim. Acta 71, 3796–3811.Google Scholar
Becker, L., Cornish, T., Antione, M., Cotter, R., Evans-Nugyen, T., Doroschenko, V., Goesmann, F., Raulin, F. & Ehrenfreund, P. (2009). MOMA-LDMS: instrument concept and results. Geochim. Cosmochim. Acta 73, A101.Google Scholar
Benner, S., Devine, K., Matveeva, L. & Powell, D. (2000). The missing organic molecules on Mars. Proc. Natl. Acad. Sci. USA 97, 2425–2430.CrossRefGoogle ScholarPubMed
Boston, P. (2010). Location, location, location. Lava caves on Mars for habitat, resources, and the search for life. J. Cosmol. 12, 3957–3979.Google Scholar
Boston, P. et al. (2001). Cave biosignatures suites: microbes, minerals, and Mars. Astrobiology 1, 25–55.Google Scholar
Bottcher, M., Thamdrup, B. & Vennemann, T. (2001). Oxygen and sulfur isotope fractionation during anaerobic bacterial disproportionation of elemental sulfur. Geochim. Cosmochim. Acta 65, 1601–1609.Google Scholar
Bottrell, S.H. & Newton, R.J. (2006). Reconstruction of changes in global sulfur cycling from marine sulfate isotopes. Earth-Sci. Rev. 75, 59–83.Google Scholar
Budimir, N., Blais, J.C., Fournier, T. & Tabet, J.C. (2007). Desorption/ionization on porous silicon mass spectrometry (DIOS) of model cationized fatty acids. J. Mass Spectrom. 42, 42–48.Google Scholar
Bullen, H.A., Oehrle, S.A., Bennett, A.F., Taylor, N.M. & Barton, H.A. (2008). Use of attenuated total reflectance Fourier transform infrared spectroscopy to identify microbial metabolic products on carbonate mineral surfaces. Appl. Environ. Microbiol. 74, 4553–4559.Google Scholar
Coates, J. (2000). Interpretation of infrared spectra, a practical approach. In Encyclopedia of Analytical Chemistry, ed. Meyers, R., pp. 10815–10837. John Wiley & Sons Ltd, Chichester, UK.Google Scholar
Cousins, C., Smellie, J., Jones, A. & Crawford, I. (2009). A comparative study of endolithic microborings in basaltic lavas from a transitional subglacial–marine environment. Int. J. Astrobiol. 8, 37–49.CrossRefGoogle Scholar
Cushing, G.E., Titus, T.N., Wynne, P.R. & Christensen, P.R. (2007). Themis observes possible cave skylights on Mars. Geophys. Res. Lett. 34, L17201.Google Scholar
Edwards, K.J., McCollom, T.M., Konishi, H. & Buseck, P.R. (2003). Seafloor bioalteration of sulfide minerals: results from in situ incubation studies. Geochim. Cosmochim. Acta 67, 2843–2856.Google Scholar
Evans-Nguyen, T., Becker, L., Doroschenko, V. & Cotter, R. (2008). Development of a low power, high mass range mass spectrometer for Mars surface analysis. Int. J. Mass Spectrom. 278, 170–177.Google Scholar
Fanale, F.P., Li, Y.-H., De Carlo, E., Farley, C., Sharma, S.K., Horton, K. & Granahan, J.C. (2001). An experimental estimate of Europa's “ocean” composition independent of Galileo orbital remote sensing. J. Geophys. Res. 106, 14595–14600.CrossRefGoogle Scholar
Finster, K. (2008). Microbiological disproportionation of inorganic sulfur compounds. J. Sulfur Chem. 29, 281–292.CrossRefGoogle Scholar
Forti, P. (2005). Genetic processes of cave minerals in volcanic environments: an overview. J. Cave Karst Stud. 67, 3–13.Google Scholar
Galeev, A.A., Vinokurov, V.M., Mouraviev, F.A. & Osin, Y.N. (2009). EPR and SEM study of organo-mineral associations in Lower Permian evaporite dolomites. Appl. Magn. Reson. 35, 473–479.CrossRefGoogle Scholar
Habicht, K., Canfield, D. & Rethmeier, J. (1998). Sulfur isotope fractionation during bacterial reduction and disproportionation of thiosulfate and sulfide. Geochim. Cosmochim. Acta 62, 2585–2595.Google Scholar
Hall, C. & Hamilton, A. (2008). The heptahydrate of sodium sulfate: does it have a role in terrestrial and planetary geochemistry? Icarus 198, 277–279.Google Scholar
Ham, J.E., Durham, B. & Scott, J.R. (2003). Comparison of laser desorption and matrix-assisted laser desorption/ionization for ruthenium and osmium trisbipyridine complexes using Fourier transform mass spectrometry. J. Am. Soc. Mass Spectrom. 14, 393–400.Google Scholar
Heidel, C. & Tichomirowa, M. (2011). The isotopic composition of sulfate from anaerobic and low oxygen pyrite oxidation experiments with ferric iron – new insights into oxidation mechanisms. Chem. Geol. 281, 305–316.Google Scholar
Hughes, S.S., Smith, R., Hackett, W. & Anderson, S. (1999). Mafic volcanism and environmental geology of the eastern Snake River Plain. In Guidebook to the Geology of Eastern Idaho, ed. Hughes, S.S. & Thackray, G., pp. 143–168. Idaho Museum of Natural History, Pocatello, Idaho.Google Scholar
Ignatova, V., Van Vaeck, L., Gijbels, R. & Adams, F. (2003). Molecular speciation of inorganic mixtures by Fourier transform laser microprobe mass spectrometry. Int. J. Mass Spectrom. 225, 213–224.Google Scholar
Izawa, M.R., Banerjee, N.R., Flemming, R.L., Bridge, N.J. & Schultz, C. (2010). Basaltic glass as a habitat for microbial life: implications for astrobiology and planetary exploration. Planet. Space Sci. 58, 583–591.Google Scholar
Kaplan, I. & Rittenberg, S. (1964). Microbial fractionation of sulfur isotopes. J. Gen. Microbiol. 34, 195–212.CrossRefGoogle Scholar
Karas, M. & Kruger, R. (2000). Ion formation in MALDI: the cluster ionization mechanism. Chem. Rev. 103, 427–439.CrossRefGoogle Scholar
Karas, M., Bachmann, D. & Hillenkamp, F. (1985). Influence of the wavelength in high-irradiance ultraviolet laser desorption mass spectrometry of organic molecules. Anal. Chem. 57, 2935–2939.Google Scholar
Kargel, J., Furfaro, R., Prieto-Ballesteros, O., Rodriguez, J., Montgomery, D., Gillespie, A., Marion, G. & Wood, S. (2007). Martian hydrogeology sustained by thermally insulating gas and salt hydrates. Geology 35, 975–978.Google Scholar
Kargel, J.S., Kaye, J.Z., Head, J.W.I., Marion, G.M., Sassen, R., Crowly, J.K., Ballesteros, O.P., Grant, S.A. & Hogenboom, D.L. (2000). Europa's crust and ocean: origin, composition, and the prospects for life. Icarus 148, 226–265.Google Scholar
Karlo, J.H., Jorgenson, D.B. & Shineldecker, C.L. (1980). Sulfate minerals in Snake River Plain volcanoes. Northwest Sci. 54, 178–182.Google Scholar
Keszthelyi, L., Jaeger, W., McEwen, A., Tornabene, L., Beyer, R., Dundas, C. & Milazzo, M. (2008). High resolution imaging science experiment (HIRISE) images of volcanic terrains from the first 6 months of the Mars Reconnaissance Orbiter primary science phase. J. Geophys. Res. 113, E04005.Google Scholar
Knochenmuss, R., Dubois, F., Dale, M.J. & Zenobi, R. (1996). The matrix suppression effect and ionization mechanisms in matrix-assisted laser desorption/ionization. Rapid Commun. Mass Spectrom. 10, 871–877.3.0.CO;2-R>CrossRefGoogle Scholar
Kolleck, C., Büttner, A., Ernst, M., Hülsenbusch, T., Lang, T., Marwah, R., Mebben, S., Priehs, M., Kracht, D. & Neumann, J. (2010). Development of a Pulsed UV Laser System for Laser-Desorption Mass Spectrometry on Mars, International Conference on Space Optics, Rhodes Island, Greece, 4–8 October. http://congrex.nl/icso/2012/papers/FP_ICSO-063.pdf (accessed June 24, 2013).Google Scholar
Kotler, J.M., Hinman, N.W., Yan, B., Stoner, D.L. & Scott, J.R. (2008). Glycine identification in natural jarosites using laser-desorption Fourier transform mass spectrometry: implications for the search for life on Mars. Astrobiology 8, 253–266.CrossRefGoogle ScholarPubMed
Kuntz, M., Champion, D., Spiker, E. & Lefebvre, R. (1986). Contrasting magma types and steady-state, volume-predictable volcanism along the great rift, Idaho. GSA Bull. 97, 579–594.2.0.CO;2>CrossRefGoogle Scholar
Kuntz, M., Covington, H. & Schorr, L. (1992). An overview of basaltic volcanism of the eastern Snake River Plain, Idaho. In Regional Geology of Eastern Idaho and Western Wyoming:Geological Society of America Memoir 179, eds. Link, P., Kuntz, M. & Platt, L., pp. 227–267. Geological Society of America, Boulder.CrossRefGoogle Scholar
Kuntz, M.A. (1989). In Field Trip Guidebooks, vol. T305, pp. 51–61. American Geophysical Union, Washington, DC.Google Scholar
Leeman, W., Vitaliano, C. & Prinz, M. (1976). Evolved lavas from the Snake River Plain: craters of the Moon National Monument, Idaho. Contrib. Mineral. Petrol. 56, 35–60.Google Scholar
Lefticariu, L., Pratt, L.M. & Ripley, E.M. (2006). Mineralogic and sulfur isotopic effects accompanying oxidation of pyrite in millimolar solutions of hydrogen peroxide at temperatures from 4 to 150 °C. Geochim. Cosmochim. Acta 70, 4889–4905.CrossRefGoogle Scholar
Léveillé, R. & Datta, S. (2010). Lava tubes and basaltic caves as astrobiological targets on Earth and Mars: a review. Planet. Space Sci. 58, 592–598.Google Scholar
Mangold, N., Gendrin, A., Gondet, B., LeMouelic, S., Quantin, C., Ansan, V., Bibring, J., Langevin, Y., Masson, P. & Neukum, G. (2008). Spectral and geological study of the sulfate-rich region of West Candor Chasma, Mars. Icarus 194, 519–543.Google Scholar
Marlow, J.J., Martins, Z. & Sephton, M.A. (2011). Organic host analogues and the search for life on Mars. Int. J. Astrobiol. 10, 31–44.Google Scholar
Martinez-Frias, J., Amaral, G. & Vazquez, L. (2006). Astrobiological significance of minerals on Mars surface environment. Rev. Environ. Sci. Biotechnol. 5, 219–231.Google Scholar
Materials Characterization Lab (2012). Pennsylvania State University. http://www.mri.psu.edu/facilities/mcl/techniques/FTIR/FTIR.asp (accessed 5 December 2012).Google Scholar
Mazumdar, A., Goldberg, T. & Strauss, H. (2008). Abiotic oxidation of pyrite by Fe(III) in acidic media and its implications for sulfur isotope measurements of lattice-bound sulfate in sediments. Chem. Geol. 253, 30–37.Google Scholar
McCord, T.B. et al. (1998). Salts on Europa's surface detected by Galileo's near infrared mapping spectrometer. Science 280, 1242–1245.CrossRefGoogle ScholarPubMed
McCord, T.B. et al. (1999). Hydrated salt minerals on Europa's surface from the Galileo near-infrared mapping spectrometer (NIMS) investigation. J. Geophys. Res. 104, 11827–11851.CrossRefGoogle Scholar
McGuire, M., Edwards, K., Banfield, J. & Hamers, R. (2001). Kinetics, surface chemistry, and structural evolution of microbially mediated sulfide mineral dissolution. Geochim. Cosmochim. Acta 65, 1243–1258.Google Scholar
McJunkin, T.R., Tremblay, P.L. & Scott, J.R. (2002). Automation and control of an imaging internal laser desorption Fourier transform mass spectrometer (I2LD-FTMS). J. Assoc. Lab. Autom. 7, 76–83.Google Scholar
McKinley, J.P., Stevens, T.O. & Westall, F. (2000). Microfossils and paleoenvironments in deep subsurface basalt samples. Geomicrobiol. J. 17, 43–54.Google Scholar
Métrich, N., Berry, A., O'Neill, H. & Susini, J. (2009). The oxidation state of sulfur in synthetic and natural glasses determined by X-ray absorption spectroscopy. Geochim. Cosmochim. Acta 73, 2382–2399.CrossRefGoogle Scholar
Moore, J.M., Bullock, M.A., Newsom, H. & Nelson, M. (2010). Laboratory simulations of Mars evaporite geochemistry. J. Geophys. Res-Planet. 115, E06009.CrossRefGoogle Scholar
Northup, D.E., Melim, L.A., Spilde, M.N., Hathaway, J.J.M., Garcia, M.G., Moya, M., Stone, F.D., Boston, P.J., Dapkevicius, M. & Riquelme, C. (2011). Lava cave microbial communities within mats and secondary mineral deposits: implications for life detection on other planets. Astrobiology 11, 601–618.Google Scholar
Parnell, J. et al. (2007). Searching for Life on Mars: selection of Molecular Targets for ESA's Aurora ExoMars Mission. Astrobiology 7, 578–604.Google Scholar
Parnell, J., Boyce, A.J., Osinski, G.R., Izawa, M.R.M., Banerjee, N., Flemming, R. & Lee, P. (2012). Evidence for life in the isotopic analysis of surface sulphates in the Haughton impact structure, and potential application on Mars. Int. J. Astrobiol. 11, 93–101.CrossRefGoogle Scholar
Peck, S.B. (1974). Unusual mineralogy of the Crystal Pit Spatter Cone, Craters of the Moon National Mounument, Idaho. NSS Bull. 36, 19–24.Google Scholar
Peters, M., Strauss, H. & Farquhar, J. (2009). Sulfur cycling at the Mid-Atlantic Ridge: a multiple sulfur isotope approach. Geochim. Cosmochim. Acta 73, A1017.Google Scholar
Peters, M., Strauss, H., Farquhar, J., Ockert, C., Eickmann, B. & Jost, C.L. (2010). Sulfur cycling at the Mid-Atlantic Ridge: a multiple sulfur isotope approach. Chem. Geol. 269, 180–196.CrossRefGoogle Scholar
Peterson, B.J. (1999). Stable isotopes as tracers of organic matter input and transfer in benthic food webs: a review. Acta Oecol.-Int. J. Ecol. 20, 479–487.CrossRefGoogle Scholar
Philippot, P., Van Zuilen, M., Lepot, K., Thomazo, C., Farquhar, J. & Van Kranendonk, M. (2007). Early Archean microorganisms preferred elemental sulfur, not sulfate. Science 317, 1534–1537.CrossRefGoogle Scholar
Pisapia, C., Chaussidon, M., Mustin, C. & Humbert, B. (2007). O and S isotopic composition of dissolved and attached oxidation products of pyrite by Acidithiobacillus ferrooxidans: comparison with abiotic oxidations. Geochim. Cosmochim. Acta 71, 2474–2490.Google Scholar
Poels, K., Van Vaeck, L. & Gijbels, R. (1998). Microprobe speciation analysis of inorganic solids by Fourier transform laser mass spectrometry. Anal. Chem. 70, 504–512.Google Scholar
Reid, M. (1995). Processes of mantle enrichment and magmatic differentiation in the eastern Snake River Plain: Th isotope evidence. Earth Planet. Sci. Lett. 131, 239–254.Google Scholar
Richardson, C., Hinman, N., McJunkin, T., Kotler, J. & Scott, J. (2008). Exploring biosignatures associated with thenardite by geomatrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (GALDI-FTICR-MS). Geomicrobiol. J. 25, 432–440.CrossRefGoogle Scholar
Richardson, C., Hinman, N. & Scott, J. (2009). Effect of thenardite on the direct detection of aromatic amino acids: implications for the search for life in the solar system. Int. J. Astrobiol. 8, 291–300.Google Scholar
Richardson, C.D. & Becker, L. (2010). Detection of organic compounds in the presence of perchlorate by the Mars organic molecular analyzer (MOMA). In Astrobiology Graduate Student Conference (AbGradCon), Tällberg, Sweden, 14–18 June.Google Scholar
Richardson, C.D., Hinman, N.W., McHenry, L.J., Kotler, J.M., Knipe, D.L. & Scott, J.R. (2012). Secondary sulfate mineralization and basaltic chemistry of craters of the Moon National Monument, Idaho: potential martian analog. Planet. Space Sci. 65, 93–103.CrossRefGoogle Scholar
Rye, R.O., Bethke, P.M. & Wasserman, M.D. (1992). The stable isotope geochemistry of acid sulfate alteration. Econ. Geol. 87, 225–262.Google Scholar
Sakimoto, S., Gregg, T., Hughes, S.S. & Chadwick, J. (2003). Re-assessing plains-style volcanism on Mars. In Sixth International Conference on Mars, Pasadena, CA, 20–25 July, 3197.Google Scholar
Sampson, M., Phillips, C. & Ball, A. (2000). Investigation of the attachment of Thiobacillus ferrooxidans to mineral sulfides using scanning electron microscopy analysis. Miner. Eng. 13, 643–656.Google Scholar
Scott, J.R. & Tremblay, P.L. (2002). Highly reproducible laser beam scanning device for an internal source laser desorption microprobe Fourier transform mass spectrometer. Rev. Sci. Instrum. 73, 1108–1116.Google Scholar
Scott, J.R., McJunkin, T.R. & Tremblay, P.L. (2003). Automated analysis of mass spectral data using fuzzy logic classification. J. Assoc. Lab. Autom. 8, 61–63.CrossRefGoogle Scholar
Scott, J.R., Beardsley, B., Groenewold, G.S., Lammert, S., Lee, E., McJunkin, T.R., Ritchie, G., Almirall, J.R. & Becker, L. (2012). Integrated portable, rugged optical and mass instrument suite (PROMIS) for geologic, biologic, and organic signature characterization for space exporation. In Concepts and Approaches for Mars Exploration, Houston, TX, 12–14 June, 4255.Google Scholar
Singer, P. & Stumm, W. (1970). Acidic mine drainage: the rate-determining step. Science 164, 1121–1123.Google Scholar
Smith, B. (1999). Infrared Spectral Interpretation: A Systematic Approach. CRC Press, Boca Raton, FL.Google Scholar
Smock, A., Bottcher, M. & Cypionka, H. (1998). Fractionation of sulfur isotopes during thiosulfate reduction by Desulfovibrio desulfuricans. Arch. Microbiol. 169, 460–463.CrossRefGoogle ScholarPubMed
Stearns, H.T. (1963). Geology of the Craters of the Moon, Idaho. Craters of the Moon Natural History Association, Caldwell, Idaho.Google Scholar
Stout, M.Z., Nicholls, J. & Kuntz, M.A. (1994). Petrological and mineralogical variations in 2500–2000 yr B.P. lava flows. Craters of the Moon lava field, Idaho. J. Petrol. 35, 1681–1715.Google Scholar
Takai, K. & Nakamura, K. (2011). Archaeal diversity and community development in deep-sea hydrothermal vents. Curr. Opin. Microbiol. 14, 282–291.Google Scholar
Toran, L. & Harris, R. (1989). Interpretation of sulfur and oxygen isotopes in biological adn abiological sulfide oxidation. Geochim. Cosmochin Acta. 53(9), 2341–2348.CrossRefGoogle Scholar
Taylor, B. & Wheeler, M. (1994). Sulfur and oxygen-isotope geochemistry of acid mine drainage in the western United States. In Environmental geochemistry of sulfide oxidation, ACS Symposium Series Vol. 550, ed. Alpers, C. & Blowes, D., pp. 481–514. American Chemical Society, Washington, DC.CrossRefGoogle Scholar
Thorseth, I., Furnes, H. & Tumyr, O. (1995). Textural and chemical effects of bacterial activity on basaltic glass: an experimental approach. Chem. Geol. 119, 139–160.Google Scholar
Thurston, R., Mandernack, K. & Shanks, W. III (2010). Laboratory chalcopyrite oxidation by Acidithiobacillus ferrooxidans: oxygen and sulfur isotope fractionation. Chem Geol. 269, 252–261.CrossRefGoogle Scholar
Van Vaeck, L., Adriaens, A. & Adams, F. (1998). Microscopical speciation analysis with laser microprobe mass spectrometry and static secondary ion mass spectrometry. Spectrochim. Acta B-Atom. Spectrosc. 53, 367–378.CrossRefGoogle Scholar
Wacey, D., Saunders, M., Brasier, M. & Kilburn, M. (2011). Earliest microbially mediated pyrite oxidation in ∼3.4 billion-year-old sediments. Earth Planet. Sci. Lett. 301, 393–402.CrossRefGoogle Scholar
Wyrick, D., Ferrill, D., Morris, A., Colton, S. & Sims, D. (2004). Distribution, morphology, and origins of martian pit crater chains. J. Geophys. Res. 109, E06005.Google Scholar
Yan, B., Stoner, D.L., Kotler, J.M., Hinman, N.W. & Scott, J.R. (2007a). Detection of biosignatures by geomatrix-assisted laser desorption/ionization (GALDI) mass spectrometry. Geomicrobiol. J. 24, 379–385.Google Scholar
Yan, B., Stoner, D.L. & Scott, J.R. (2007b). Direct LD-FTMS detection of mineral-associated PAHs and their influence on the detection of other organics. Talanta 72, 634–641.Google Scholar
Zerkle, A.L., Farquhar, J., Johnston, D.T., Cox, R.P. & Canfield, D.E. (2009). Fractionation of multiple sulfur isotopes during phototrophic oxidation of sulfide and elemental sulfur by a green sulfur bacterium. Geochim. Cosmochim. Acta 73, 291–306.Google Scholar
Zhu, M., Xie, H., Guan, H. & Smith, R. (2006). Mineral and lithologic mapping of martian low albedo regions using OMEGA data. Lunar Planet. Sci. XXXVII 2173.Google Scholar
Zolotov, M.Y. & Shock, E.L. (2001). Composition and stability of salts on the surface of Europa and their oceanic origin. J. Geophys. Res. 106, 32815–32827.CrossRefGoogle Scholar