Prospects for Habitability of Earth-Sized Stagnant Lid Planets
When: October 9, 2018 3PM PDT
Abstract: Plate tectonics has often been considered a requirement for long-term habitability of rocky planets. A major reason for this is that plate tectonics facilitates the cycling of volatiles between the surface and interior, and this cycling, in particular of CO2, helps to stabilize climate on Earth. However, for the carbon cycle to operate and stabilize climate, all that is necessary is 1) for weathering rates to be, in bulk, sensitive to climate, rather than being solely controlled by the supply of weatherable rock at the surface, and 2) sufficiently high rates of CO2 outgassing to prevent global glaciation of the planet. As I show in this talk, planets that lack plate tectonics, like Mars and Venus (stagnant lid planets), can meet the two above requirements and sustain habitable climates over geologic timescales under certain conditions. I show the factors, mainly mantle heat budget and planetary CO2 budget, that are critical for sustaining long-term habitable climates on stagnant lid planets. I also explore the stability of climates on these planets, by assessing whether snowball episodes could be recovered from. Here I find that exchange between the atmosphere and ocean is critical for allowing stagnant lid planets to recover from a snowball episode, should such a climate develop.