Exoplanetary Ecosystems: Exploring Life's Detectability on Chemically Diverse Exoplanets

Exoplanetary Ecosystems: Exploring Life's Detectability on Chemically Diverse Exoplanets Exoplanetary Ecosystems: Exploring Life's detectability on chemically diverse exoplanets We will undertake the first systematic survey of exoplanet types and compositions that catalogs both abiotic and biotic rates of net O2 and CH4 production and synthesizes those data to assess the detectability of life. In our Planet Formation tasks, we will use observations and models to determine the range of exoplanet compositions. We will standardize methods for calculating elemental abundances from stellar spectra, and use these to resolve discrepancies in existing observations and to generate results for new observations. We will model the process of planet formation, constrained by astronomical observations and meteoritics, to show how chemical fractionations translate stellar abundances into planetary compositions. For each star, we will define the range of exoplanet refractory (e.g. Mg/Si) and volatile (e.g., H2 O) compositions and construct a Periodic Table of Planetsa catalog of exoplanet types, including Water Worlds, Desert Planets, and Weird Earths. In our Planetary Processes tasks, we will use models and experiments to explore the effects of exoplanet composition on geochemical cycles of O2 and CH4 . For a range of chemically diverse planets, we will use geodynamic and thermodynamic modeling, supported by high-pressure mineral physics and petrology experiments, to predict five aspects of exoplanet structure and geochemical cycles: rates of mantle overturning, surface rock types, outgassed volatiles, water-rock interactions, and ocean chemistry. We will work closely with VPL@UW to define atmospheric photochemical sources and sinks of O2 and CH4 and estimate the geological production of CH4 and other reduced gases that destroy O2 . We will populate our Periodic Table of Planets with planetary O2 and CH4 production/destruction rates. In our Life Processes tasks we will measure net biological O2 and CH4 production rates in analog field sites and use laboratory studies and models to estimate global rates on exoplanets. Our six field sites are analogs for Water Worlds, Desert Planets, and Weird Earths. We will measure ecosystem production rates at these field sites, and we will conduct nutrient limitation experiments, contextualized by molecular biology, to elucidate metabolic pathways and extrapolate to how these might function in the environments of chemically different exoplanets. The integration of ecosystem rates with community metabolism modelling will allow us to scale our measured rates up to planetary rates. We will populate our Periodic Table of Planets with planetary biological O2 and CH4 production rates. Our Integration tasks combine the results from Planet Formation, Planetary Processes and Life Processes to compare biological and geochemical rates and assess lifes detectability on individual exoplanets. Four star jockeys are designated as integrators, responsible for coordinating the two-way flow of information among broad interdisciplinary groups. We will populate our Periodic Table of Planets with rate comparisons and detectability index for various exoplanets, information to help prioritize exoplanets for future observations.