EVIDENCE FOR THE ORIGIN AND ACTIVITIES OF EARLY MICROBIAL LIFE ON EARTH REMAIN CONTROVERSIAL OBSCURING OUR UNDERSTANDING OF HOWLIFE EVOLVED ON OUR PLANET AND IMPEDING OUR ABILITY TO DETECT THE EXISTENCE OF EXTRATERRESTRIAL LIFE. CURRENTLY CHEMICALLY-PRECIPITATEDROCKS PRESERVE THE RICHEST INFORMATION RECORDING THE BIOGEOCHEMISTRY OF LIFE ON ANCIENT EARTH. IF WE CAN ESTABLISH A MECHANISTICUNDERSTANDING OF HOW THE PRESENCE ACTIVITIES AND METABOLIC CAPABILITIES OF LIFE LEAD TO THE CHEMICAL PRECIPITATION OF AUTHIGENICMINERALS THEN IT WILL BE POSSIBLE TO INTERPRET MINERALS AS PROXIES FOR LIFE IN THE GEOLOGIC RECORD OF EARTH AND OTHER PLANETARY BODIES.RECENT DISCOVERIES HAVE PLACED CLAY MINERALS AND IRON SILICATES IN PARTICULAR INTO A POSITION OF GREAT IMPORTANCE FOR BOTH DECIPHERINGEARLY LIFE ON EARTH AND IDENTIFYING LIFE ON OTHER PLANETS. A PROMINENT EXAMPLE OF CHEMICALLY-PRECIPITATED ROCKS ON EARTH ARE THEANCIENT BANDED IRON FORMATIONS (BIFS) IRON- AND SILICA-RICH ROCKS THAT ARE FOUND GLOBALLY FROM DEEP MARINE PRECAMBRIAN RECORDS.NANO-INCLUSIONS OF IRON(II)-RICH SILICATE MINERALS WERE RECENTLY DISCOVERED IN WELL-PRESERVED CHERTS FROM AUSTRALIAN AND SOUTH AFRICANBIFS AND ARE COMPELLING NEW EVIDENCE THAT IRON SILICATES WERE ACTUALLY A PRIMARY MINERAL PRECIPITATING IN THE EARLY OCEAN DEMANDINGFRESH STUDIES INTO THE FORMATION OF IRON-RICH CLAYS. WITH OUR EVOLVING VIEW OF THE ORIGINAL BIF MINERALS WE MAY BE MISSING SIGNALS OFLIFE IN THE GEOLOGIC RECORD FOR OVER TWO BILLION YEARS OF EARTHS HISTORY. INVESTIGATING THE FORMATION PATHWAYS OF IRON SILICATE MINERALSAND THE EFFECTS OF BIOLOGICAL MEDIATION WOULD ALSO HAVE MAJOR IMPLICATIONS FOR DETERMINING SIGNALS OF EXTRATERRESTRIAL LIFE. OTHERPLANETOID BODIES ARE THOUGHT TO CURRENTLY CONTAIN OR HAVE PREVIOUSLY HOSTED ENVIRONMENTS WHERE MAFIC AND ULTRAMAFIC ROCKS INTERACTWITH ANOXIC WATER YIELDING FERRUGINOUS AND SILICA-RICH FLUIDS. INDEED ABUNDANT IRON-RICH SILICATES HAVE BEEN REPORTED ON MARS FROMANCIENT NOACHIAN TERRAINS OVER 3.5 BILLION YEARS OLD. YET TO BE ABLE TO ACCURATELY PROBE FOR SIGNALS OF LIFES ACTIVITIES IN THESE POTENTIALEXTRATERRESTRIAL HABITATS WE NEED TO FULLY UNDERSTAND THE IMPACT OF BIOLOGY ON THE CHEMISTRY OF CLAY MINERALS.WE INTEND TO PERFORM LABORATORY STUDIES TO PROBE THE PATHWAYS AND PRODUCTS OF IRON SILICATE PRECIPITATION IN FERRUGINOUS SILICA-RICHSYSTEMS AND TEST THE EFFECTS OF THE MICROBIAL LIFE WHICH MAY INHABIT SUCH ENVIRONMENTS. WE WILL:1) SYNTHESIZE LOW-TEMPERATURE IRON SILICATE PRECIPITATES FROM FERROUS SILICA-RICH FLUIDS WITH AND WITHOUT FE(II)-OXIDIZING MICROBES(PHOTOFERROTROPHS AND MICROAEROPHILIC BACTERIA) AND DEAD BIOMASS2) SIMULATE EARLY DIAGENESIS OF THE INITIAL PHASES INCLUDING INCUBATIONS WITH FE(III)-REDUCING MICROBES3) CHARACTERIZE THE FULL SUITE OF INITIAL DIAGENETICALLY-ALTERED AND HYDROTHERMALLY-CRYSTALLIZED PRECIPITATES FOR ELEMENTAL CHEMISTRY MINERALOGY AND FE-REDOX STATEWE WILL DEVELOP A RIGOROUS UNDERSTANDING OF WHAT SPECIFIC IRON SILICATE CHEMISTRY STRUCTURE AND FE REDOX STATE SIGNIFIES FOR THEENVIRONMENTAL AND MICROBIOLOGICAL CONDITIONS OF FORMATION. IT IS CRITICAL TO DOCUMENT THE ROUTE OF FORMATION AND STABILIZATIONOF PRECIPITATES TO IDENTIFY WHETHER THESE PROCESSES ARE HAPPENING TODAY OR IN THE PAST ON EARTH OR OTHER PLANETARY BODIES. THISMECHANISTIC UNDERSTANDING WILL ENABLE US TO DECIPHER WHETHER CELLULAR SURFACES OR IRON METABOLISMS HAVE INFLUENCED IRON CLAYPRECIPITATION IN EXAMPLES LIKE IRON SILICATE INCLUSIONS IN ANCIENT BIFS ON EARTH AND IRON-RICH CLAYS ON MARS ADDRESSING THE EXOBIOLOGYPROGRAM GOALS: EARLY EVOLUTION OF LIFE AND THE BIOSPHERE AND BIOSIGNATURES AND LIFE ELSEWHERE.