The question of the type of elements and minerals comprising the surface of Mars is of extreme interest for the reconstruction of the geological evolution of the planet (Baker, 2006). The mineral composition of the Martian surface may provide clues to deciphering the question of possible life on Mars. The recent missions of the NASA's exploration rovers Spirit and Opportunity and ESA's Mars Express have produced a wealth of new data about its surface composition by using a variety of instruments, including different types of spectrometers (e.g., Christensen et al., 2004a, b; Bibring et al., 2005). The most exciting discovery of astrobiological interest is the mineralogical evidence for the (past) presence of water on the Mars surface, provided by hematite-rich grains and hydrated sulfate minerals (gypsum, jarosite, and kieserite) of a possible evaporite origin (Gendrin et al., 2005). From an astrobiological point of view, it is somewhat disappointing that carbonates have thus far only been detected in low abundance, with concentrations of approx. 1 weight% in several martian meteorites (Gooding, 1992) and 2 to 5 weight% in the martian dust (Bandfield et al., 2003). Based on our terrestrial experience, calcium carbonate is common biological byproduct and its paucity, combined with high sulfur content in surface rocks and soils, is explained by the presence of acidic waters, such as possible ancient martian oceans with acidic environments (Fairen et al., 2004). They may have prevented carbonate accumulation. Small carbonate concentrations, however, may also have other explanations, such as ultraviolet photodissociation and acid-fog weathering (Bandfield et al., 2003). Mars might also have had a thicker and denser CO2 atmosphere during the
Noachian era (about 4 billion years ago), which has been stored as carbonate accumulations (Kahn, 1995). Apart from basin-wide sedimentary processes, carbonate-bearing rocks might be present on Mars as the product of local processes, as in hydrothermal precipitation (Griffith and Shock, 1995), and perhaps might not have been detected remotely yet. Hydrothermal carbonates are plausible as geological products when considering the presence of effusive vulcanite on Mars that may have produced geyser and hot spring phenomena (Walter and Des Marais, 1993). In summary, although only small amounts of calcium carbonate have been detected in martian dust and meteorites, perhaps larger carbonate accumulations will be discovered by subsurface investigations.
Most published scientific research papers agree on the abiotic nature of the bacteriomorphs from the carbonate globules described in the famous martian meteorite ALH84001 (McKay et al., 1996), however, these globules deserve some interest since they could have precipitated as a consequence of early aqueous processes on Mars (Scott, 1999; Kargel, 2004). The zoned organization of the globules is indicative of compositional variations and resembles the zoning that characterize rhombs and spheroids described from Mg-rich, terrestrial cold seep carbonates (Cavalazzi and Barbieri, 2006), as a consequence of ambient chemistry changes. Since seep carbonates can entrap micrometer-scale fluid inclusions during precipitation, direct information on ambient fluids (including methane) and organic molecules, if any, might be gained through this type of rock (Parnell et al., 2002).
5.2. METHANE ON MARS (AND ELSEWHERE)
Most of the terrestrial methane has a biogenic origin that is derived from the activity of methanogenic archaea (Kvenvolden and Rogers, 2005). Marine and continental clathrates (also known as gas hydrates) stock the largest methane amounts ever detected, which probably originate through abiotic (thermal) and biotic (microbial) processes (Kvenvolden, 1993), in which the microbial decomposition of organic material by deep-earth methanogens leads to the production of methane gas. Methane release from clathrates in the atmosphere through time depends on their dissociation, which is driven by fluctuations in the sea level and bottom water temperature (Dickens, 1999, 2003) with environmental effects registered in the sedimentary record. On Mars, unlike on Earth, vast deposits of clathrates are believed to occur as carbon dioxide clathrates because of the abundance of atmospheric CO2 and H2O, both in the atmosphere and beneath the surface in the form of water ice (Hansen et al., 2005). CO2 clathrates would be present, therefore, especially at the south polar surface, in a way similar to the terrestrial clathrate-bearing permafrost (Kargel and Lunine, 1998; Kargel, 2004). The recent detection of methane in the martian atmosphere, obtained using Earth-based spectrometers and the spectrometer onboard the ESA's Mars Express spacecraft (Formisano et al., 2004; Krasnopolsky et al., 2004; Mumma et al., 2005), has redoubled the interest for possible methane-related biological activity on Mars and other bodies of the solar system, such as Europa and Titan. Although methane is a potential tracer of biological processes, on Mars it would also have been formed by other (abiotic) processes, including magmatic/hydrothermal out-gassing and cometary/meteorite impacts (Wong et al., 2003; Krasnopolsky et al., 2004). Recently, the near surface hydration of olivine and pyroxenes (serpentini-zation) has also been proposed as a possible way for the martian abiotic production of methane (Oze and Sharma, 2005). A similar process of methane formation has been described through the reaction between upper mantle rocks (serpentinized peridotites) and ocean waters in submarine hydrothermal fields (Kelley et al., 2001). Regardless of the source of martian methane, however, its supply is assumed to be continuous or very recent because of the limited residence time of methane in the atmosphere (evaluated at about 340 years) due to the photolytic breakdown by the UV radiation (Krasnopolsky et al., 2004). The detected methane and water vapor association in the atmosphere of Mars and the large variations of methane abundance that changes with the location are both potential indicators of possible releases from clathrate destabilization (Formisano et al., 2004; Max and Clifford, 2005), if any is present. Such a subsurface, possibly deep source of methane, is compatible with the hypotheses of autotrophic methanogenesis that was potentially developed by chemosynthetic ecosystems on Mars and Europa (Boston et al., 1992; McCollom, 1999). In ice-covered planetary bodies, such as Europa and Callisto, methanogenesis and the reduction of sulfur compounds has been hypothesized as a possible, although unlikely, energy source for life (Gaidos et al., 1999). The above scenarios necessarily require that ancient or still extant microbial life in the subsurface environments of Mars (and other bodies) have stored methane for later release. A possible origin of the martian methane from an ancient (extinct) biosphere is debated. The supporters of a martian subsurface biosphere - similar to the one established on Earth, for example, by methanogenic archaea in permafrost (Wagner et al., 2002) - speculate on the presence of methanogens in permafrost aquifers and of methane and carbon dioxide clathrates that would have stored fossil methane that was developed on early Mars (Pellenbarg et al., 2003; Max and Clifford, 2005). Other estimates, based on expected low biomass production by methanogenesis (Krasnopolsky et al., 2004), assume that methane on Mars cannot originate from an ancient biosphere. Whether it formed bioti-cally or abiotically, this does not inhibit the possibility of methane to be the fuel of biogeochemical processes that consume methane anaerobically as in the terrestrial cold seeps.
The present-day harsh conditions of the martian regolith, due to factors such as intense cosmic radiation, dryness, and daily temperature excursion, combined with geothermal gradient and surface gravity that is much lower than terrestrial ones, might potentially favor a deep biological activity at depths down to 10-12 km (Kargel, 2004). In the case that it derives from mechanisms that are related to seepage, such a deep biosphere can in fact reach surface (or near surface) locations, with detectable localized spots that are similar to the ones described on Earth. The interest in seep mechanisms, together with the obvious relationship with methane, relies on the variable methane concentrations detected from localized spots in the terrestrial methane seeps, which apply to methane as is detected on Mars. Moreover, low-temperature minerals of seep deposits can contain fluid inclusions in which methane might be preserved and (assuming with the adequate analytical techniques) detected.
The recent discovery of methane in the martian atmosphere, coupled with unequivocal evidences of the activity of liquid water on its surface, has revived interest in the possibility of life on Mars. Methane seep carbonates, that are known in the geological record since the Palezoic and precipitate in modern continental slopes, can be considered a prime astrobiological target because (i) they are chemically precipitated deposits with the advantage of preserving potential traces of life; (ii) they represent good repositories for microbiologically derived features; (iii) in terms of size they may develop different types of geological bodies that are often recognizable as anomalous deposits in the rock record; (iv) they have obvious and detectable relationships with methane. Well-developed microbial features include morphologies, biominerals, chemofossils, and stable isotope signatures. The genesis and patchy distribution of the terrestrial methane seep deposits agree with the distribution of methane as has been recently depicted on the surface of Mars. The paucity of carbonate-rich sediments found to date on the martian surface, as well as the lack of carbonate outcrops, do not appear to be major limiting factors for considering methane seep carbonates a target for astrobiology. For example, one would expect greater amounts of carbonates in older (and therefore buried) successions, for which only a drilling exploration would provide solid information. Also, a patchy distribution for martian carbonates cannot be excluded a priori at the present stage of knowledge, and it might imply limitations for a clear detection of these mineral components based on remote sensing instruments, with negative consequences for field recognition and sampling during future landing missions. Future issues in a thorough investigation of methane seep ecosystems and their geological products should therefore consider their potential as possible terrestrial analogues for methane-derived deposits on Mars. For this purpose, the integrated investigation of the microbiological-mineral interactions of methane-seep limestones associated with the assessment of their spectral and geochemical characteristics would set the base for the identification of martian outcrops. This approach can be best performed by investigating extant seeps where the influence of microbial processes on the precipitation can be directly established. In addition, similar comparative studies extended to the fossil counterparts can establish a link with unique, ancient textures containing microbial imprints.
The authors would like to thank Russel S. Shapiro and an anonymous reviewer for their careful review.
Aharon, P. (2000). Microbial processes and products fueled by hydrocarbons at submarine seeps. In: R.E. Riding and S.M. Awramik (eds.) Microbial Sediments. Springer, New York, pp. 270-281.
Aiello, I.W., Garrison, R.E., Moore, J.C., Kastner, M. and Stakes, D.S. (2001). Anatomy and origin of carbonate structures in a Miocene cold-seep field. Geology 29: 1111-1114.
Aloisi, V., Wallmann, K., Bollwerk, S.M., Derkachev, A., Bohrmann, G. and Suess, E. (2004). The effect dissolved barium on biogeochemical processes at cold seeps. Geochimica et Cosmochimica Acta 68: 1735-1748.
Altermann, W., Kazmierczak, J., Oren, A. and Wright, D. T. (2006). Cyanobacterial calcification and its rockbuilding potential during 3.5 billion years of Earth history. Geobiology 4: 147-166.
Baker, V.R. (2006). Water and the evolutionary geological history of Mars. Bollettino della Societa Geologica Italiana 125: 357-369.
Bandfield, J.L., Glotch, D. and Christensen, P.R. (2003). Spectroscopic identification of carbonate minerals in the Martian dust. Science 301: 1084-1087.
Barbieri, R. and Cavalazzi, B. (2005). Microbial fabrics from Neogene cold seep carbonates, Northern Apennine, Italy. Palaeogeography, Palaeoclimatology, Palaeoecology 227: 143-155.
Barbieri, R., Ori, G.G. and Taviani, M. (2001). Phanerozoic submarine cold vent biota and its exobio-logical potential. European Space Agency SP-496: 295-298.
Barbieri, R., Ori, G.G. and Cavalazzi, B. (2004). A Silurian cold-seep ecosystem from Middle Atlas, Morocco. PALAIOS 19: 527-542.
Bauld, J., D'Amelio, E. and Farmer, J.D. (1993). Modern microbial mats. In: J.W. Schopf and C. Klein (eds.) The Proterozoic Biosphere. A Multidisciplinary Study. Cambridge University Press, Cambridge, pp. 261-269.
Bibring, J.-P., Langevin, Y., Gendrin, A., Gondet, B., Poulet, F., Berthe, M., Soufflot, A., Arvidson, R., Mangold, N., Mustard, J., Drossart, P. and the OMEGA team (2005). Mars surface diversity as revealed by the OMEGA/Mars Express observations. Science 307: 1576-1581.
Boston, P.J., Ivanov, M.V. and McKay, C.P. (1992). On the possibility of chemosynthetic ecosystems in subsurface habitats on Mars. Icarus 95: 300-308.
Bottjer, D.J. (2005). Geobiology and the fossil record: eukayotes, microbes, and their interactions. Palaeogeography, Palaeoclimatology, Palaeoecology 219: 5-21.
Campbell, K.A. (2006). Hydrocarbon seep and hydrothermal vent paleoenvironments and paleontology: past developments and future research directions. Palaeogeography, Palaeoclimatology, Palaeoecology 232: 362-407.
Campbell, K.A. and Bottjer, D.J. (1995). Peregrinella: an Early Cretaceous cold-seep-restricted bra-chiopod. Paleobiology 21: 461-478.
Campbell, K.A., Farmer, J.D. and Des Marais, D. (2002). Ancient hydrocarbon seeps from the Mesozoic convergent margin of California: carbonate geochemistry, fluids and palaeoenviron-ments. Geofluids 2: 63-94.
Cavagna, S., Clari, P. and Martire, L. (1999). The role of bacteria in the formation of cold seep carbonates: geological evidence from Monferrato (Tertiary NW Italy). Sedimentary Geology 126: 253-270.
Cavalazzi, B. (2007). Chemotrophic filamentous microfossils from the Hollard Mound (Devonian, Morocco) as investigated by focused ion beam. Astrobiology 7: 402-415.
Cavalazzi, B. and Barbieri, R. (2006). Prokaryote-derived fossils from cold-seep carbonates. In: F. Briand (ed.) Fluid Seepages/Mud Volcanism in the Mediterranean and Adjacent Domains. CIESM Workshop Monographs 29, pp. 123-132.
Cavalazzi, B., Barbieri, R. and Ori, G.G. (2007). Chemosynthetic microbialites in Devonian carbonate mounds of the Hamar Laghdad (Anti-Atlas, Morocco). Sedimentary Geology 200: 73-88.
Chafetz, H.S., Rush, P.F. and Schoderbek, D. (1993). Occult aragonitic fabrics and structures within microbialites, Pennsylvanian Panther Seep Formation, San Andres Mountains, New Mexico, U.S.A. Carbonates and Evaporites 8: 123-134.
Chen, D.F., Feng, D., Su, Z., Song, Z.G., Chen, G.Q. and Cathles III, L.M. (2006). Pyrite crystallization in seep carbonates at gas vent and hydrate site. Materials Science and Engineering: C 26: 602-605.
Childress, J.J., Fischer, C.R., Brooks, J.M., Kennicutt, M.C., Bidigare, R. and Anderson, A.E. (1986). A methanotrophic marine molluscan (Bivalvia, Mytilidae) symbiosis: mussels fueled by gas. Science 233: 1306-1308.
Christensen, P.R., Ruff, S.W., Fergason, R.L., Knudson, A.T., Arvidson, R.E., Bandfield, J.L., Blaney, D.L., Budney, C., Calvin, W.M., Glotch, T.D., Golombek, M.P., Graff, T.G., Hamilton, V.E., Hayes, A., Johnson, J.R., McSween, H.Y., Mehall, G.L., Jr., Mehall, L.K., Moersch, J.E., Morris, R.V., Rogers, A.D., Smith, M.D., Squyres, S.W., Wolff, M.J. and Wyatt, M.B. (2004a). Initial results from the Miniature Thermal Emission Spectrometer experiment at the Spirit landing site at Gusev Crater. Science 305: 837-842.
Christensen, P.R., Wyatt, M.B., Glotch, T.D., Rogers, A.D., Anwar, S., Arvidson, R.E., Bandfield, J.L., Blaney, D.L., Budney, C., Calvin, W.M., Fallacaro, A., Fergason, R.L., Gorelick, N., Graff, T.G., Hamilton, V.E., Hayes, A.G., Johnson, J.R., Knudson, A.T., McSween, H.Y., Mehall, G.L., Jr., Mehall, L.K., Moersch, J.E., Morris, R.V., Smith, M.D., Squyres, S.W., Ruff, S.W. and Wolff, M.J. (2004b). Mineralogy at Meridiani Planum from the Mini-TES Experiment on the Opportunity Rover. Science 306: 1733-1739.
Dickens, G.R. (1999). The blast in the past. Nature 401: 752-755.
Dickens, G.R. (2003). Rethinking the global carbon cycle with a large, dynamic and microbially mediated gas hydrate capacitor. Earth and Planetary Science Letters 213: 169-183.
Domack, E., Ishman, S., Leventer, A., Sylva, S., Willmott, V. and Huber, H. (2005a). A chemotrophic ecosystem found beneath Antarctic Ice Shelf. Eos, Transactions of the American Geophysical Union 86: 271-272.
Domack, E., Duran, D., Leventer, A., Ishman, S., Doane, S., McCallum, S., Amblas, D., Ring, J., Gilbert, R. and Prentice, M. (2005b). Stability of the Larsen B ice shelf on the Antarctic Peninsula during the Holocene epoch. Nature 436: 681-685.
Durisch-Kaiser, E., Klauser, L., Wehrli, B. and Schubert, C. (2005). Evidence of intense archaeal and bacterial methanotrophic activity in the Black Sea water column. Applied and Environmental Microbiology 71: 8099-8106.
Ehrlich, H.L. (1998). Geomicrobiology: its significance for geology. Earth-Science Reviews 45: 45-60.
Fairén, A.G., Fernández-Remolar, D., Dohm, J.M., Baker, V.R. and Amils, R. (2004). Inhibition of carbonate synthesis in acidic oceans on early Mars. Nature 431: 423-426.
Fisher, C.R., MacDonald, I.R., Sasson, R., Young, C.M., Macko, S.A., Hourdez, S., Carney, R.S., Joye, S. and McMullin, E. (2000). Methane ice worms: Hesiocaeca methanolica colonizing fossil fuel reserves. Naturwissenschaften 87: 184-187.
Fisher, R.C. (1990). Chemoautotrophic and metanotrophic symbioses in marine invertebrates. Reviews in Aquatic Sciences 2: 399-436.
Formisano, V., Atreya, S., Encrenaz, T., Ignatiev, N. and Giuranna, M. (2004). Detection of methane in the atmosphere of Mars. Science 306: 1758-1761.
Fujikura, K., Kojima, S., Tamaki, K., Maki, Y., Hunt, J. and Okutani, T. (1999). The deepest chem-osynthesisbased community yet discovered from the hadal zone, 7326 m deep, in the Japan Trench. Marine Ecology Progress Series 190: 17-26.
Gaidos, E.J., Nealson, K.H. and Kirschvink, J.L. (1999). Life in ice-covered oceans. Science 284: 1631-1633.
Gendrin, A., Mangold, N., Bibring, J.-P., Langevin, Y., Gondet, B., Poulet, F., Bonello, G., Quantin, C., Mustard, J., Arvidson, R. and LeMouelic, S. (2005). Sulfates in Martian layered terrains: the OMEGA/Mars Express view. Science 307: 1587-1591.
Gooding, J.L. (1992). Soil mineralogy and chemistry on Mars: possible clues from salts and clays in SNC meteorites. Icarus 99: 28-41.
Greinert, J., Bohrmann, G. and Elvert, M. (2002). Stromatolitic fabric of authigenic carbonate crusts: result of anaerobic methane oxidation at cold seeps in 4,850 m water depth. International Journal of Earth Sciences 91: 698-711.
Griffith, L.L. and Shock, E.L. (1995). A geochemical model for the formation of hydrothermal carbonates on Mars. Nature 377: 406-408.
Hansen, G., Giuranna, M., Formisano, V., Fonti, S., Grassi, D., Hirsh, H., Ignatiev, N., Maturilli, A., Orleanski, P., Piccioni, G., Rataj, M., Saggin, B. and Zasova, L. (2005). PFS-MEX observation of ices in the residual south polar cap of Mars. Planetary and Space Science 53: 1089-1095.
Hickman, C.S. (2003). Mollusc-microbe mutualisms extend the potential for life in hypersaline systems. Astrobiology 3: 631-644.
Hinrichs, K.U., Hayes, J.M., Sylva, S.P., Brewer, P.G. and DeLong, E.F. (1999). Methane-consuming archaeobacteria in marine sediments. Nature 398: 802-805.
Inagaki, F., Nunoura, T., Nakagawa, S., Teske, A., Lever, M., Lauer, A., Suzuki, M., Takai, K., Delwiche, M., Colwell, F.S., Nealson, K.H., Horikoshi, K., D'Hondt, S. and Jorgensen, BB. (2006). Biogeographical distribution and diversity of microbes in methane hydrate-bearing deep marine sediments on the Pacific Ocean Margin. PNAS 103: 2815-2820.
Jannasch, H.W., Nelson, D.C. and Wirsen C.O. (1989). Massive natural occurrence of unusually large bacteria (Beggiatoa sp.) at a hydrothermal deep-sea vent site. Nature 342: 834-836.
Kahn, R. (1995). The evolution of CO2 on Mars. Icarus 62: 175-190.
Kargel, J.S. (2004). Mars - A Warmer, Wetter Planet. Springer-Praxis, Chichester.
Kargel, J.S. and Lunine, J.I. (1998). Clathrate hydrates on Earth and in the solar system. In: C. de Bergh, M. Festou and B. Schmitt (eds.) Solar System Ices. Kluwer, Dordrecht, pp. 97-117.
Kelley, D.S., Karson, J.A., Blackman, D.K., Fruh-Green, G., Gee, J., Butterfield, D.A., Lilley, M.D., Olson, E.J., Schrenk, M.O., Roe, K.R. and Shipboard Scientific Party (2001). An off-axis hydrothermal field discovered near the Mid-Atlantic Ridge at 30°N. Nature 412: 145-149.
Kelley, D.S., Karson, J.A., Fruh-Green, G.L., Yoerger, D.A., Butterfield, D.A., Hayes, J., Shank, T., Schrenk, M.O., Olson, E.J., Proskurowski, G., Jakuba, M., Bradleey, A., Larson, B., Ludwig, K., Glickson, D., Buckman, K., Bradley, A.S., Brazelton, W.J., Roe, K., Elend, M.J., Delacour, A., Bernasconi, S. M., Lilley, M.D., Baross, J.A., Summons, R.E. and Sylva, S.P. (2005). A serpenti-nite-hosted submarine ecosystem: the Lost City Hydrothermal Field. Science 307: 1428-1434.
Kelly, S.R.A., Ditchfield, P.W., Doubleday, P.A. and Marshall, J.D. (1995). An Upper Jurassic methane-seep limestone from the Fossil Bluff Group forearc basin of Alexander Island, Antarctica. Journal of Sedimentary Research 65: 274-282.
Kennett, J.P., Cannariato, K.G., Hendy, I.L. and Behl, R.J. (2003). Methane hydrates in quaternary climate change. The Clathrate Gun hypothesis. American Geophysical Union, Special Publication 54: 1-216.
Kiel, S. and Little, C.T.S. (2006). Cold seep mollusks are older than the general marine mollusk fauna. Science 313: 1429-1431.
Koski, R.A. and Hein, J.R. (2003). Stratiform barite deposits in the Roberts Mountains Allochthon, Nevada: a review of potential analogs in modern sea-floor environments. In: J.D. Bliss, P.R. Moyle, and K.R. Long (eds.) Contributions to Industrial-Minerals Research. U.S. Geological Survey Bulletin 2209-H, pp. 1-17.
Krasnopolsky, V.A., Maillard, J.P. and Owen, T.C. (2004). Detection of methane in the martian atmosphere: evidence for life? Icarus 172: 537-547.
Kvenvolden, K.A. (1993) A primer on gas hydrates. The future of energy gases. U.S. Geological Survey Professional Paper 1570: 279-291.
Kvenvolden, K.A. and Rogers, B.W. (2005). Gaia's breath - global methane exhalations. Marine and Petroleum Geology 22: 579-590.
Levin, L.A. (2005). Ecology of cold seep sediments: interactions of fauna with flow, chemistry and microbes. In: R.N. Gibson, R.J.A. Atkinson and J.D.M. Gordon (eds.) Oceanography and Marine Biology. An Annual Review 43, pp. 1-46.
Lichtschlag, A., Roey, H., Niemann, H., Boetius, A., Klages, M. and deBeer, D. (2006). Microbial turnover of sulfide in combination with iron precipitation at the HMosby Mud Volcano. Geophysical Research Abstracts 8: 07069.
Liljedahl, L. (1992). The Silurian Ilionia prisca, oldest known deep-burrowing suspension feeding bivalve. Journal of Paleontology 66: 206-210.
Little, C.T.S., Campbell, K.A. and Herrington, R.J. (2002). Why did ancient chemosynthetic seep and vent assemblages occur in shallower water than they do today? Comment. International Journal of Earth Sciences 91: 149-153.
Lowenstam, H.A. (1981). Minerals formed by organisms. Science 211: 1126-1131.
Max, M.D. and Clifford, S.M. (2005). Crustal sources of the atmospheric methane on Mars: the association with ground ice and the potential role of local thermal anomalies. Lunar and Planetary Science Conference XXXVI, Vol. Abstracts: #2303.
McCollom, T.M. (1999). Methanogenesis as a potential source of chemical energy for primary biomass production by autotrophic organisms in hydrothermal systems on Europa. Journal of Geophysical Research 104: 30729-30742.
McKay, D.S., Gibson, E.K., Jr., Thomas-Keprta, K.L., Vali, H., Romanek, C.S., Clemett, S.J., Chillier, X.D.F., Maechling, C.R. and Zare, R.N. (1996). Search for past life on Mars: possible relic biogenic activity in Martian meteorite ALH84001. Science 273: 924-930.
Meyerdierks, A., Kube, M., Lombardot, T., Knittel, K., Bauer, M., Glöckner, F.O., Reinhardt, R. and Amann, R. (2005). Insight into the genomes of archaea mediating the anaerobic oxidation of methane. Environmental Microbiology 7: 1937-1951.
Mumma, M.J., Novak, R.E., Hewagama, T., Villanueva, G.L., Bonev, B.P., Di Santi, M.A., Smith, M.D. and Dello Russo, N. (2005). Absolute abundance of methane and water on Mars. Bulletin of the American Astronomical Society 37: Abstract 27.04.
Olu-Le Roy, K., Sibuet, M., Fiala-Medioni, A., Gofas, S., Salas, C., Mariotti, A., Foucher, J.-P. and Woodside, J. (2004). Cold seep communities in the deep eastern Mediterranean Sea: composition, symbiosis and spatial distribution on mud volcanoes. Deep Sea Research I 51: 1915-1936.
Orphan, V.J., Hinrichs, K.U., Ussler III, W., Paull, C.K., Taylor, L.T., Sylva, S.P., Hayes, J.M. and DeLong, E.F. (2001). Comparative analysis of methane-Oxidizing archaea and sulfate-reducing bacteria in anoxic marine sediments. Applied and Environmental Microbiology 67: 1922-1934.
Oze, C. and Sharma, M. (2005). Have olivine, will gas: serpentinization and the abiogenic production of methane on Mars. Geophysical Research Letters 32: L10203.
Parnell, J., Mazzini, A. and Honghan, C. (2002). Fluid inclusion studies of chemosynthetic carbonates: strategy for seeking life on Mars. Astrobiology 2: 43-57.
Peckmann, J. and Thiel, V. (2004). Carbon cycling at ancient methane-seeps. Chemical Geology 205: 443-467.
Peckmann, J., Walliser, O.H., Riegel, W. and Reitner, J. (1999). Signatures of hydrocarbon venting in a Middle Devonian carbonate mound (Hollard Mound) at the Hamar Laghdad (Antiatlas Morocco). Facies 40: 281-296.
Peckmann, J., Reimer, A., Luth, U., Luth, C., Hansen, B.T., Heinicke, C., Hoefs, J. and Reitner, J. (2001). Methane-derived carbonates and authigenic pyrite from the northwestern Black Sea. Marine Geology 177: 129-150.
Peckmann, J., Thiel, V., Reitner, J., Taviani, M., Aharon, P. and Michaelis, W. (2004). A microbial mat of a large sulfur bacterium preserved in a Miocene methane-seep limestone. Geomicrobiology Journal 21: 247-255.
Pellenbarg, R.E., Max, M.D. and Clifford, S.M. (2003). Methane and carbon dioxide hydrates on Mars: potential origins, distribution, detection, and implications for future in situ resource utilization. Journal of Geophysical Research 108E4: 8042.
Prince, R.C., Stokley, K.E., Haith, C.E. and Jannasch, H.W. (1988). The cytochromes of a marine Beggiatoa. Archives of Microbiology 150: 193-196.
Reitner, J., Peckmann, J., Reimer, A., Schumann, G. and Thiel, V. (2005). Methane-derived carbonate build-ups and associated microbial communities at cold seeps on the lower Crimean shelf (Black Sea). Facies 51: 66-79.
Ritger, S., Carson, B. and Suess, E. (1987). Methane-derived authigenic carbonates formed by subduc-tioninduced pore-water expulsion along the Oregon/Washington margin. Geological Society of America Bulletin 98: 147-156.
Robinson, C.A., Bernhard, J.M., Levin, L.A., Mendoza, G.F. and Blanks, J.K. (2004). Surficial hydrocarbon seep infauna from the Blake Ridge (Atlantic Ocean, 2150 m) and the Gulf of Mexico (690-2240 m). P.S.Z.N. Marine Ecology 25: 313-336.
Sassen, R., Roberts, H.H., Aharon, P., Larkin, J., Chinn, E.W. and Carney, R. (1993). Chemosynthetic bacterial mats at cold hydrocarbon seeps, Gulf of Mexico continental slope. Organic Geochemistry 20: 77-89.
Sassen, R., Roberts, H.H., Carney, R., Milkov, A.V., DeFreitas, D.A., Lanoil, B. and Zhang, C. (2004). Free hydrocarbon gas, gas hydrate, and authigenic minerals in chemosynthetic communities of the northern Gulf of Mexico continental slope: relation to microbial processes. Chemical Geology 205: 195-217.
Savard, M.M., Beauchamp, B. and Veizer, J. (1996). Significance of aragonite cements around Cretaceous marine methane seeps. Journal of Sedimentary Research 66: 430-438.
Schoell, M. (1988). Multiple origins of methane in the earth. Chemical Geology 71: 1-10.
Schweimanns, M. and Felbeck, H. (1985). Significance of the occurrence of chemoautotrophic bacterial endosymbionts in lucinid clams from Bermuda. Marine Ecology Progress Series 24: 113-120.
Scott, E.R.D. (1999). Origin of carbonate-magnetite-sulfide assemblages in Martian meteorite ALH84001. Journal of Geophysical Research 104E: 3803-3814.
Shapiro, R.S. (2004). Recognition of fossil prokaryotes in Cretaceous methane seep carbonates: relevance to astrobiology. Astrobiology 4: 438-449.
Sibuet, M. and Olu, K. (1998). Biogeography, biodiversity and fluid dependence of deep-sea cold-seep communities at active and passive margins. Deep-Sea Research II 45: 517-567.
Sprachta, S., Camoin, G., Golubic, S. and Le Campion, T. (2001). Microbialites in a modern lagoonal environment: nature and distribution, Tikehau atoll (French Polynesia). Palaeogeography, Palaeoclimatology, Palaeoecology 175: 103-124.
Teichert, B.M.A., Bohrmann, G. and Suess, E. (2005). Chemoherms on Hydrate Ridge - unique microbially mediated carbonate build-ups growing into the water column. Palaeogeography, Palaeoclimatology, Palaeoecology 227: 67-85.
Terzi, C., Aharon, P., Ricci Lucchi, F. and Vai, G.B. (1994). Petrographic and stable isotopes aspects of coldvent activity imprinted on Miocene-age "calcari a Lucina" from Tuscan and Romagna Apennines, Italy. Geo-Marine Letters 14: 177-184.
Treude, T., Knittel, K., Blumenberg, M., Seifert, R. and Boetius, A. (2005). Subsurface microbial methanotrophic mats in the Black Sea. Applied and Environmental Microbiology 71: 63756378.
Tunnicliffe, V. (1992). The nature and origin of the modern hydrothermal vent fauna. PALAIOS 7:
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