LPL Colloquium: Dr. Daniel Koll
Atmospheres and Climates of Rocky Exoplanets: What Earth Teaches Us About Them, and What They Can Teach Us About Earth
Dr. Daniel Koll
Massachusetts Institute of Technology
Our understanding of rocky exoplanets is still in its infancy. We know rocky exoplanets are extremely common in the galaxy, but we currently know little about most of them. This fact is about to change, as new telescopes like the James Webb Space Telescope (JWST) and ground-based facilities will be able to characterize these planets. What should we expect to find with these observations? In this talk I will show that theories originally developed for Earth's atmosphere can also help us understand rocky exoplanets and, conversely, that the study of exoplanets can help us better understand Earth. First, I will present a theory for the mean wind speeds of tidally locked rocky planets. This theory traces back to work on tropical hurricanes, and opens up new ways of understanding the atmospheric circulations of exoplanets. Second, I will discuss how moist convection can lead to extreme climate variability on tidally locked planets and could provide a new way of identifying Earth-like planets around other stars. Third, I will show how the runaway greenhouse of exotic planets sheds new light on our own planet's climate. I will present a simple model for the thermal emission of an atmospheric column with a condensible greenhouse gas, which explains a basic feature of our climate, namely why Earth's radiation balance is such a persistently linear function of surface temperature. Looking toward the near future, I will place these ideas in the context of JWST and discuss how they can open up new ways of studying rocky exoplanets over the coming decade.