A SURFACE FEATURE KNOWN AS BLOOD FALLS IS THE RELEASE POINT FOR A RECENTLY DETECTED SUBGLACIAL AQUIFER BELOW THE TAYLOR GLACIER IN ANTARCTICA S MCMURDO DRY VALLEYS. THE DISCHARGED LIQUID IS COLD SALTY FERROUS RICH IN SULFATE AND CONTAINS CHEMOSYNTHETIC MICROBES THAT USE IRON AND SULFUR BASED METABOLISMS. THUS BLOOD FALLS PROVIDES AN IMPORTANT TERRESTRIAL ANALOG FOR SUBSURFACE BRINES ON MARS AND SULFUR-RICH SUBICE OCEANS ON EUROPA. THE SUBGLACIAL AQUIFER SUPPLYING BLOOD FALLS APPEARS TO BE THE REMNANT OF A LARGE FJORD THAT ONCE OCCUPIED THIS DRY VALLEY BUT THEN FREEZE-CONCENTRATED BEFORE BECOMING COVERED BY TAYLOR GLACIER. THIS SYSTEM ALLOWS FOR THE STUDY OF HOW ECOSYSTEMS SURVIVE THROUGH DEEP TIME AFTER DRAMATIC ENVIRONMENTAL CHANGE (FROM ICE-FREE TO ICE-COVERED) AND THE SPECIFIC MICROBIAL ENERGETICS INVOLVED. COMPARABLE ICE-COVERED SULFUR-RICH OCEANS WITH IRON MINERAL ENERGY SOURCES MAY SUSTAIN CHEMOSYNTHETIC COMMUNITIES ON ICY MOONS. HERE WE PROPOSE AN INTERDISCIPLINARY STUDY THAT EXAMINES HOW ECOSYSTEMS ARE STRUCTURED BY THEIR LOCAL ENVIRONMENT THROUGH TIME BY INVESTIGATING BIOLOGICAL (ENVIRONMENTAL OMICS) AND GEOCHEMICAL (M SSBAUER ANALYSIS OF IRON DYNAMICS MASS SPECTROMETRY OF VOLATILE ORGANIC METABOLIC SUBSTRATES) CO-EVOLUTION IN AN ICE-COVERED OCEAN. WE PROPOSE FOUR INTEGRATED OVERLAPPING AIMS: 1) CHARACTERIZE CHANGES IN BLOOD FALLS IRON MINERALOGY. ALTHOUGH THE BRINE IS CLEAR WHEN FIRST RELEASED AT BLOOD FALLS INTERACTIONS WITH THE ATMOSPHERE CAUSE A RAPID COLOR CHANGE FOR WHICH THE EXACT MINERALOGICAL TRANSFORMATION IS UNKNOWN. USING SAMPLES OF BRINE COLLECTED AT THE RELEASE POINT AND AT VARYING DISTANCES FROM THE GLACIER SURFACE WE WILL ANALYZE THE MINERALOGY OF INCREASINGLY OXIDIZED BRINES USING XRD M SSBAUER VISIBLE-NEAR INFRARED (VNIR) MID- TO FAR-INFRARED (MIR-FIR) AND RAMAN SPECTROSCOPIES. 2) CHARACTERIZE THE BRINE METAGENOME AND METATRANSCRIPTOME TO DETERMINE GENETIC LINKS TO IRON AND SULFUR CYCLING IN SUBICE OCEANS. RESIDENT MICROBES USE REDUCED SULFUR COMPOUNDS TO RESPIRE SUBGLACIAL IRON MINERALS IN THE BRINE RESULTING IN LIBERATION OF IRON BELOW THE GLACIER AND RELEASE AT THE SURFACE. AN OMICS APPROACH WILL HELP IDENTIFY THE GENETIC POTENTIAL OF RESIDENT MICROBES TO LINK IRON AND SULFUR METABOLISM AND TARGET THE GENES AND ORGANISMS INVOLVED IN MINERAL TRANSFORMATIONS AND BIOMARKER PRODUCTION. 3) EXAMINE SUBGLACIAL VOLATILE METABOLIC BIOSIGNATURES. THE NATURE AND EXTENT OF VOLATILE ORGANIC METABOLITE PRODUCTION BY SUBGLACIAL CHEMOSYNTHETIC MICROBIAL COMMUNITIES ARE POORLY UNDERSTOOD. PTR-MS WILL BE USED TO PROFILE AND CHARACTERIZE THE VOLATILE COMPOUNDS PRODUCED BY THE ORGANISMS. 4) DEVELOP ICY WORLDS MICROCOSMS WITH ENVIRONMENTAL SAMPLES AND MICROBIAL ISOLATES AND CORRELATE GENE EXPRESSION WITH VOC PRODUCTION AND MINERALOGY CHANGES. PROPOSED MEASUREMENTS INCLUDE FUNCTIONAL GENE ABUNDANCES; M SSBAUER VISIBLE NEAR- MID- AND FAR-IR REFLECTANCE AND RAMAN SPECTROSCOPIES TO CHARACTERIZE MINERAL REACTANTS AND PRODUCTS; AND MONITORING OF MICROCOSM HEADSPACE FOR VOLATILE ORGANIC METABOLIC SIGNALS. THIS RESEARCH IS RELEVANT TO THE LARGE-SCALE ENVIRONMENTAL CHANGE AND MACRO-EVOLUTION AND THE BIOSIGNATURES AND LIFE ELSEWHERE EMPHASES OF THE NASA EXOBIOLOGY PROGRAM. FIRST THE PROPOSED OMICS AND HIGH RESOLUTION SPECTROSCOPY TO INVESTIGATE HOW ECOSYSTEMS RESPOND AND CHANGE IN STRUCTURE AND FUNCTION WHEN COVERED BY ICE RELATES TO ENVIRONMENTAL FACTORS SUCH AS PLANETARY PROCESSES ( SNOWBALL EARTH EVENTS RAPID CLIMATE CHANGE ETC.) ON THE LARGE-SCALE EVOLUTION OF LIFE ON EARTH. SECOND OUR PROPOSED LINKED GEOCHEMICAL MINERALOGICAL AND GENOMICS ANALYSES ON SUBGLACIAL BRINE SAMPLES WILL ADDRESS BASIC RESEARCH ON THE FORMATION AND RETENTION OF BIOSIGNATURES UNDER NON-EARTH CONDITIONS (E.G. MARS EUROPA) IN THAT THE BLOOD FALLS ECOSYSTEM HAS ANALOGOUS PROPERTIES TO PUTATIVE ANCIENT AND EXTANT HABITATS ON MARS (SUBSURFACE BRINE) AND EUROPA (SULFUR-RICH SUBICE OCEANS).