Special Physics Seminar

Atmosphere-Mantle feedbacks: importance of mantle oxidation state

Laura Schaefer

Arizona State University

Oxidation state can be thought of as a measure of the amount of oxygen relative to the other major (Mg, Si, Fe) elements found in a rocky planet. The oxidation state of a rocky planet's mantle has a strong influence on the composition of secondary atmospheres formed through outgassing. Understanding how mantle oxidation state depends on planetary bulk composition and how it changes with time due to planetary differentiation, atmospheric outgassing, and interactions with a planet's volatile envelope is crucial to accurately predicting atmospheric compositions of rocky exoplanets. Distinguishing biosignature gases from geosignatures (false positive biosignatures produced by natural geological processes) will depend on understanding the geological processes operating on planets of different size and composition compared to the Earth. In this talk, I discuss models that explore how bulk composition, atmospheric escape and planetary differentiation (metal-silicate separation) influence mantle oxidation state and the resulting outgassed atmosphere. These and future models can help select the best exoplanetary targets for detailed characterization by future telescopes like the James Webb Space Telescope (JWST) by identifying planets with lower chances for producing false positive biosignatures.