“Planetary Self-Regulation and The Role of Interior Processes for Habitability”

Zoom Link for Colloquium 11/16/2021 3:00pm PST.

Please email astrobio@uw.edu for zoom presentation password

Presented By Johnny Seales, Rice University

Planetary habitability depends on two energy sources: solar and interior. How a planet taps its internal energy determines how it cools, which influences planetary volcanism. Volcanic and magmatic activity connects a planet’s interior to its surface environment. One would suspect that a planet with decaying heat sources would experience a decay in magmatic activity over its lifetime until it inevitably ceased. However, Earth data suggest that Earth’s magmatic potential leveled off over the most recent few billion years. Using data-constrained models, I will argue that this leveling off resulted from the Earth locking into a self-regulated mode of planetary evolution. The combined effect of the deep-water cycling and planetary cooling on mantle viscosity produced this self-regulating behavior. However, not all planets will experience self-regulating behavior. For example, data-constrained models for Mars suggest that it did not. Different magmatic histories can play a role in determining the onset of planetary scale habitability. To explore this potential, I will extend the modeling of magmatic evolution by coupling it to simple climate models. I will show that for a population of Earth-like planets, a planet could have entered the habitable zone over a window spanning billions of years. The extent of this window varies depending on the planet’s distance from its host star. Given that Earth provides our most data rich planet, this suggests that the binary yes or no of habitability may lead us astray. Approaching habitability from a probabilistic perspective results in more nuanced expectations in the search for life. The more nuanced view remains a testable one with forthcoming data.