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Characterization of a Subsurface Biosphere in a Massive Sulfide Deposit at Rio Tinto, Spain: Implications for Extant Life on Mars C.R. Stoker, T. Stevens, R. Amils, D. Fernandez-Remolar and the MARTE Team


Rio Tinto Rio Tinto originates in Iberian Pyrite deposit of sulfide minerals. River is an acidic extreme environment that hosts a microbial ecosystem.


Opportunity Site, Mars Layered sediments from ancient and modern river system include deposits of jarosite, hematite, geothite


Rio Tinto - Subsurface Biosphere Hypothesis Source springs point to subsurface chemolithotrophs using sulfide minerals as resources Source springs Springs are mineral and bacteria laden at their source. Some bacteria (L. Ferroxidans, At. Ferroxidans) found in the river system are capable of anaerobic metabolism of iron and sulfur minerals.


Tailings Gossan Grey Shale Purple shale Ash Host rock (acidic tuff) Pyrite stockwork With massive pyrite Pyroclasts volcanics Sampling Strategy


Drilling Rig ~ 90m Subsurface Aquifer Bore Hole 4 Drill Site September, 2003


Drilling fluid spiked with bromide as a contamination tracer Commercial coring drill uses drilling fluid


Core Processing Steps Cores brought to surface Cores in plastic liners, cut, labeled Bags filled with N2 Anaerobic chamber


Data Analysis Borehole Glovebox/Lab Aseptic Samples Samples 3m cores cut to 1 m lengths Drill rate Water Use Geological Observations Periodic Samples of drill fluid spiked with tracers Core photograph Aseptic samples Geologic description of core slice using microscope Core Remainder FISH LAL Culturing experiments Ion Chromotography Remote Sensing Panoramic image Microscopic image Vis-NIR spectra Hyperspectral imager


1929 1800 1427 2269 2342 860 864 Remote sensing data See poster by Battler and Stoker Study to identify mineral signatures associated with biological activity

chemolithotrophic enrichment cultures (aerobic and anaerobic): 

chemolithotrophic enrichment cultures (aerobic and anaerobic) DAPI staining and microscopic examination to visualize/ count cells


Sample Ground Water Fluids Multi-Level Diffusion Sampler inserted in completed wells Samples analyzed after several months to achieve equilibrium Dissolved ions measured with Ion Chromatograph Dissolved gases measured with Gas Chromatograph Same technique used to sample fluids from springs upgradient of pyrite Objective: Identify Resources for and Products of Microbial Growth


• At least three types of Microbes have been identified in contamination free cores both above and below the water table in BH4 and BH1 • Resources (as determined by anions leached from rock samples) are available to support anoxic chemolithotrophic metabolism • Microorganisms correlate with mineral alteration, and sulfate concentration • Hydrogen is produced when sulfide ore is exposed to water in sterile anaerobic conditions • Methanogens are present and producing considerable methane Results Summary


Implications for Subsurface Life on Mars MARTE project Co-I’s and I do not claim to have found new evidence for life on Mars (contrary to Feb. 16 report on by Brian Berger that was based on second hand information derived from a cocktail party conversation.) IF Rio Tinto really is a geochemical analog for Sinus Merdiani, ……………….and IF these minerals are derived from Pyrite ores.…… and IF pyrite ores are present in the subsurface of Mars….. and IF liquid water is also present Then: resources are available to support a subsurface biosphere analogous to that at Rio Tinto. Methane could be a product of such a biosphere.


Simulation of Mars Drilling Mission in Sept 2005 - Remotely Operated Drill, Core Inspection, Borehole Inspection, and Life Detection Instruments MARTE Future Plans Mars drill Subsurface instruments Core handling Core Remote sensing & life detection instruments For further info see: WANTED Remote Science team

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