Seminar – Prof. Joshua Krissansen-Totton

Speaker: Prof. Joshua Krissansen-Totton, Earth and Space Sciences, University of Washington

Title: Developing fully coupled models of terrestrial planet evolution to assess habitability and enable exoplanet life detection

Abstract: Rocky planet evolution is shaped by complex geophysical, geochemical, and astrophysical processes. Interpreting current and future observations of terrestrial exoplanets will require an improved understanding of how these competing influences interact on long timescales. In particular, the interpretation of potential biosignature gases is contingent upon understanding the probable geochemical evolution of lifeless worlds. Here, I will present a generalized model of rocky planet evolution that connects early magma ocean evolution to subsequent, temperate geochemical cycling. The thermal evolution of the interior, tectonic recycling of volatiles, surface climate, and atmospheric escape are explicitly coupled throughout this evolution. The model can reproduce the atmospheric evolution of a lifeless Earth. Moreover, the model also sheds light on the atmospheric evolution of Venus and Venus-like exoplanets; it can successfully recover modern Venus’s atmosphere composition and thermal state. We find there is a clear dichotomy in the evolutionary scenarios that recover modern Venus conditions, one in which Venus was never habitable and perpetually in runaway greenhouse since formation, and another where Venus experienced ~1-2 Gyr of surface habitability. James Webb Space Telescope observations of terrestrial exoplanets such as Trappist-1 b-h, GJ 1132 b, and LP 890-9 b-c will provide valuable opportunities to test and improve such generalized models. Preliminary predictions for these characterizable exoplanets will be presented. I will argue that an understanding of terrestrial planets—both within the solar system and beyond—as a unified class of objects will be necessary to enable exoplanet life detection.

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