EEPS Colloquium: Brad Foley

The compositional diversity of rocky exoplanets: Consequences for evolution, tectonics, and habitability

Thousands of exoplanets have been discovered over the last 30 years covering a wide range of sizes, compositions, interior structures, and stellar radiation environments. Many of these planets are likely rocky based on their bulk density. The variation in rock forming elements seen in stars show, to first order, that rocky exoplanets could span a wide range of mantle mineralogies, from Earth-like olivine-pyroxene mixtures to nearly pure olivine or pure pyroxene mantles. Combinations of pyroxene and quartz or olivine and periclase are also possible. Such compositional variation could have profound consequences for the tectonics, evolution, and habitability of rocky exoplanets. I will discuss how rocky planet compositional variations can influence their long-term thermal evolution and ability to promote habitable surface environments through volcanism and weathering. I will further show how planet composition can influence whether planets operate in a stagnant-lid or plate-tectonic regime. Planets with sub-equal mixtures of two or more minerals can more readily generate the weak lithospheric shear zones required for plate tectonics by mineral phase mixing and grain size reduction. Finally, I will discuss how models of exoplanet geological evolution are critical for interpreting astronomical observations.  

Host: Phil Skemer

EEPS Colloquia are made possible by the William C. Ferguson Fund