THE NEXT DECADE WILL SEE THE CHARACTERIZATION OF POTENTIALLY HABITABLE PLANETS AROUND OTHER STARS AND THE SEARCH FOR BIOSIGNATURES WILL BEGIN IN EARNEST. MUCH OF THAT EFFORT WILL INVOLVE OBSERVATIONS BY JWST AND OTHER TELESCOPES TO DETECT GASES IN THE ATMOSPHERES OF EARTH- TO NEPTUNE-SIZE PLANETS INCLUDING PLANETS WITHIN THE COMPACT HABITABLE ZONES OF M DWARF STARS. IN ORDER TO ASSESS THE CHEMICAL AND (POTENTIALLY) BIOLOGICAL SIGNIFICANCE OF THESE OBSERVATIONS WE MUST UNDERSTAND THE FORMATION AND EVOLUTION OF THE ATMOSPHERES OF SMALL PLANETS THE PATHWAYS OF VOLATILE ELEMENTS THAT COMPRISE SUCH ATMOSPHERES FROM STAR-FORMING CLOUDS INTO PROTOPLANETARY DISKS AND PLANETS THE EXCHANGE OF SUCH VOLATILES WITH THE INTERIOR AND THEIR POSSIBLE LOSS TO SPACE. OUR UNDERSTANDING OF THESE ABIOTIC PROCESSES IS LARGELY BASED ON THE SOLAR SYSTEM BUT KNOWN EXOPLANETARY SYSTEMS COMPRISE VASTLY GREATER DIVERSITY WHICH CHALLENGES THIS FRAMEWORK AND OUR ABILITY TO INTERPRET ANY POTENTIAL BIOSIGNATURE AGAINST THE POSSIBILITY OF A FALSE POSITIVE . OUR INTERDISCIPLINARY TEAM PROPOSES A SYNERGISTIC PROGRAM OF OBSERVATIONS LABORATORY EXPERIMENTS AND MODELING TO UNDERSTAND THE JOURNEY OF PLANETARY VOLATILES PARTICULARLY BUT NOT LIMITED TO CARBON- AND OXYGEN-CONTAINING SPECIES AND THEIR MANIFESTATION IN ATMOSPHERES. WE WILL ADDRESS FOUR FUNDAMENTAL QUESTIONS: (1) WHAT IS THE INVENTORY OF VOLATILES IN THE PLANETARY BUILDING BLOCKS THAT MAKE UP PROTOPLANETARY AND DEBRIS DISKS? WE WILL USE MM- AND RADIO-WAVE INTERFEROMETERS AND OCCULTATION TECHNIQUES TO DETECT STRUCTURES IN DISKS THAT TRACE OR INFLUENCE THE MIGRATION OF THAT MATERIAL AND PROBE ITS SIZE AND COMPOSITION. WE COMPLEMENT THOSE OBSERVATIONS WITH MEASUREMENTS OF VOLATILES IN PRIMITIVE MATERIAL (METEORITES) IN THE SOLAR SYSTEM AND LABORATORY EXPERIMENTS THAT MEASURE HOW SUCH VOLATILES ARE RELEASED BY HEATING AND ACCRETION. (2) WHICH AND HOW MUCH VOLATILES ARE ACCRETED FROM THE DISK AS GAS OR SOLIDS AND ARE LOST TO SPACE AND HOW DOES THIS SHAPE THE OBSERVABLE POPULATION OF EXOPLANETS? WE WILL COMBINE MODELS AND OBSERVATIONS OF DISKS TO MAP THESE VOLATILES AND USE LABORATORY EXPERIMENTS TO STUDY HOW VOLATILES MAY BE INCORPORATED IN OR LOST FROM PLANETESIMALS. WE WILL USE DATA FROM SPACE MISSIONS TO MAP THE DISTRIBUTION OF GAS- AND VOLATILE-RICH SUB-NEPTUNE VS ROCKY PLANETS INFORMED BY OBSERVATIONS OF ONGOING ESCAPE OF PLANETARY ATMOSPHERES AND AN IMPROVED UNDERSTANDING OF THE STELLAR ACTIVITY THAT DRIVES IT. (3) HOW ARE VOLATILES EXCHANGED BETWEEN THE ATMOSPHERE SURFACE AND INTERIOR OF A PLANET? WE WILL USE HIGH-PRESSURE LABORATORY EXPERIMENTS AND MODELS OF ACCRETIONAL AND RADIOACTIVE HEATING TO STUDY THE PARTITIONING OF VOLATILES BETWEEN THE SURFACE AND INTERIOR DURING THE CRUCIAL EARLY PHASE OF DIFFERENTIATION OF A PLANET AND INVESTIGATE THE POSSIBILITY THAT PRIMORDIAL VOLATILES ARE STILL PRESENT IN EARTH AND OTHER PLANETARY BODIES. (4) HOW CAN OBSERVATIONS OF EXOPLANET ATMOSPHERES INFORM US ABOUT THE VOLATILE INVENTORIES AND CHEMISTRIES OF EXOPLANETS? WE WILL LAY THE FOUNDATIONS FOR THESE OBSERVATIONS BY TELESCOPES LIKE JWST BY MEASURING THE MASSES OF THE TESS-DETECTED PLANETS THAT ARE THE MOST SUITABLE TARGETS AND DEVELOP STRATEGIES FOR DETECTING AND ROBUSTLY QUANTIFYING VOLATILES IN OBJECTS FROM GIANT TO SMALL EVAPORATING PLANETS. FINALLY WE WILL DEVELOP A SYNTHESIS OF OUR WORK AND TRACE THE PATHWAYS OF VOLATILE ELEMENTS AND THEIR ISOTOPES WITH PARTICULAR ATTENTION TO C AND O AND THEIR RELATIVE ABUNDANCE AS A WIDESPREAD INDICATOR AND DETERMINANT OF THE CHEMISTRY LEADING TO ROCKY ATMOSPHERES. OUR TEAM WILL WORK SYNERGISTICALLY WITH OTHER MEMBERS OF THE NEXSS RESEARCH COORDINATION NETWORK AND OUR RESEARCH WILL SUPPORT THE DETECTION OF BIOSIGNATURES IN EXOPLANETS IN SUPPORT OF FUTURE NASA FLAGSHIP MISSIONS AND IS ONE OF THE PRINCIPAL GOALS OF THE NASA ASTROBIOLOGY STRATEGIC PLAN (2015) AND NASA S 30-YEAR ROADMAP FOR ASTROPHYSICS (2014).