SERPENTINIZATION OR THE HYDRATION OF IRON AND MAGNESIUM-RICH IGNEOUS ROCKS YIELDS ABUNDANT ENERGY FOR MICROBIAL METABOLISM THROUGH THE PRODUCTION OF HYDROGEN AND THE CONCOMITANT ABIOTIC SYNTHESIS OF CARBON COMPOUNDS SUCH AS ORGANIC ACIDS METHANE AND HIGHER HYDROCARBONS. SEVERAL HYPOTHESES INVOKE SERPENTINIZATION PROCESSES AS A SUSTAINED SOURCE OF ENERGY FOR THE EMERGENCE OF LIFE ON EARTH AND POSSIBLY ON OTHER EXTRATERRESTRIAL BODIES (E.G. MARS AND ICY SATELLITES) WHERE THERE IS INCREASING EVIDENCE FOR ANCIENT OR ACTIVE SERPENTINIZATION. THUS THERE IS GREAT NEED TO DETERMINE ROBUST BIOSIGNATURES THAT COULD GREATLY AID OUR ABILITY TO IDENTIFY EXTINCT MICROBIAL PROCESSES FROM THESE ENVIRONMENTS. CELL MEMBRANE LIPIDS (LIPID BIOMARKERS) ARE OF PARTICULAR INTEREST DUE TO THE STRONG PRESERVATION OF THEIR LESS POLAR CORE SKELETONS (CORE LIPIDS) IN THE ROCK RECORD FOR UP TO BILLIONS OF YEARS. HOWEVER LITTLE WORK HAS BEEN DONE TO CHARACTERIZE THE INITIAL PRODUCTION OF INTACT POLAR LIPIDS (IPLS) IN ANALOG SYSTEMS OR THE PRESERVATION OF THEIR PARTIAL DEGRADATION PRODUCTS. THE PROPOSED RESEARCH SEEKS TO ADDRESS THIS GAP IN KNOWLEDGE BY COMPREHENSIVELY INVENTORYING IPLS AS WELL AS CORE LIPID SIGNATURES OF BACTERIAL AND ARCHAEAL COMMUNITIES HOSTED IN THE SUBSURFACE FLUIDS AND ROCK OF THE ACTIVELY SERPENTINIZING SAMAIL OPHIOLITE IN OMAN USING HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC)-QUADRUPOLE-ORBITRAP MASS SPECTROMETRY (MS) AND GAS CHROMATOGRAPHY (GC) MS. I WILL COUPLE LIPID ANALYSES WITH TAXONOMIC DATA OF MICROBIAL COMMUNITIES AND AQUEOUS GEOCHEMISTRY TO ENABLE BETTER CORRELATION OF LIPID SIGNATURES WITH SPECIFIC MICROBIAL LINEAGES AND PUTATIVE METABOLISMS. THROUGH COMPARISON OF IPLS DERIVED FROM THE ACTIVE BIOSPHERE TO CORE LIPIDS WHICH MORE CLOSELY REFLECT THE EXTINCT BIOSPHERE I CAN THEN ASSESS THE POTENTIAL TO PRESERVE SIGNATURES OF THE ACTIVE COMMUNITY IN THE ROCK RECORD. RESULTS FROM THIS WORK WILL SIGNIFICANTLY IMPROVE OUR UNDERSTANDING OF MOLECULAR FOSSIL RECORDS IN SERPENTINITE-HOSTED SYSTEMS SUCH AS THOSE POTENTIALLY LEFT ON EARLY EARTH MARS OR SIMILAR PLANETARY SYSTEMS WHICH WILL HELP GUIDE FUTURE EFFORTS TO DETECT SIGNATURES OF SUBSURFACE LIFE.