GEOASTRONOMY · Exploring the chemical foundations for rocky exoplanets around Sun-like stars

Billions of rocky worlds likely exist around Sun-like stars in our Galaxy. Yet, attempts to understand these exoplanets lack information on the elements that compose them, the geodynamic processes that drive them, and the atmospheres that cloak them. To meet these cross-disciplinary challenges, three PIs at three institutes have combined forces to break new ground in understanding fully-formed silicate+metal+fluid (i.e. ‘rocky’) exoplanets. By synergizing astronomical data analysis with planetary geochemistry and experimental petrology and atmospheric physics/chemistry, we deviate from a purely theoretical approach via forward modeling. Instead, we blend Bayesian inference applied to telescope data and laboratory experiments with theory. Our thesis is straightforward: An exoplanet’s geologic history can only be decoded indirectly through spectroscopic observations of its atmosphere. To take advantage of remote observations of such atmospheres by next-generation telescopes we must work to understand how and why exoplanets have the physical and chemical properties they do. We devote our closely aligned efforts towards three categories of worlds around Sun-like (FGK) stars well-studied by astronomers: sub-Neptunes (exoplanets smaller than Neptune), Super Earths (exoplanets slightly larger than Earth) and “ultra-short period” (USP) exoplanets that may harbour magma oceans and atmospheres. GEOASTRONOMY fuses principles of the Geosciences with Astrophysics. Our aim is to build the chemical foundations for the exoplanet community to understand secondary (outgassed), hybrid (commingled primary- and secondary-) and magma-ocean atmospheres of already assembled mature rocky exoplanets. The proposed work is urgent because new and emerging datasets, including those being collected by the James Webb Space Telescope, are already providing constraints on these three categories of atmospheres.