OBJECTIVESTHE NUMEROUS OBSERVATIONS OF LARGE SULFATE DEPOSITS ON MARS HAVE RAISED OUR INTEREST IN TERRESTRIAL ANAEOROBIC SULFATE-REDUCING BACTERIA AS MODELS FOR POSSIBLE LIFE ON MARS. THEREFORE OUR OBJECTIVES ARE (1) TO DETERMINE THE PARAMETER SPACE FOR GROWTH AND SURVIVABILITY OF SULFATE REDUCING BACTERIA LOOKING FOR OVERLAP WITH MARTIAN SURFACE AND SUBSURFACE CONDITIONS WITH A SPECIAL EMPHASIZE ON THE EFFECTS OF SUB-ZERO TEMPERATURE LOW PRESSURE AND WATER ACTIVITY AS THEY ARE THOUGHT TO BE THE MAIN PARAMETERS AFFECTING GROWTH METABOLISM AND SURVIVAL OF ORGANISMS AND (2) TO CHARACTERIZE THE POSSIBLE BIOSIGNATURE COMPOUNDS THAT WOULD BE PRODUCED BY THESE ORGANISMS UNDER MARTIAN CONDITIONS.METHODSWE WILL CULTIVATE SULFATE-REDUCING BACTERIA IN OUR UNIQUE MARTIAN ENVIRONMENTAL SIMULATION CHAMBER. WE WILL START WITH OPTIMAL CONDITIONS USED AS CONTROL EXPERIMENTS AND WORK SYSTEMATICALLY TOWARDS CONDITIONS MORE AGGRESSIVE TO THE ORGANISMS AND MORE SIMILAR TO THOSE AT THE MARTIAN SURFACE BY VARYING THE PRESSURE TEMPERATURE AND WATER ACTIVITY. WE WILL DETERMINE THE BIOLOGICAL AND METABOLIC ADAPTATION OF THESE TERRESTRIAL ORGANISMS UNDER THESE EXTREME CONDITIONS. FINALLY USING A LARGE ARRAY OF ANALYTICAL METHODS RELEVANT TO PRESENT AND FUTURE SPACECRAFT MISSIONS WE WILL DETERMINE THE METABOLIC PRODUCTS OF THE ORGANISMS (GASES MINERALS AND ORGANIC MOLECULES) WITH REGARD TO THEIR POTENTIAL STABILITY AND CONCENTRATION UNDER MARTIAN SIMULATED CONDITIONS.RELEVANCEBY DETERMINING CONDITIONS OF GROWTH AND SURVIVAL OF SULFATE REDUCING BACTERIA WE WILL IDENTIFY THE OPTIMUM "SPECIAL" REGIONS ON MARS IN WHICH POTENTIAL CONTAMINATION MIGHT OCCUR AND HOW IT COULD BE IDENTIFIED / CHARACTERIZED BY PRESENT AND FUTURE INSTRUMENTS. WE WILL ADDRESS THE FIRST GOAL OF THE PPR SOLICITATION E.G. "CHARACTERIZE THE LIMITS OF LIFE IN LABORATORY SIMULATIONS OF PLANETARY ENVIRONMENTS OR IN APPROPRIATE EARTH ANALOGS. OF PARTICULAR INTEREST ARE STUDIES ON THE POTENTIAL AND DYNAMICS OF ORGANISM SURVIVAL AND REPRODUCTION IN CONDITIONS PRESENT ON THE SURFACE OR SUBSURFACE OF MARS (E.G. GULLIES AND ICE-RICH ENVIRONMENTS)".