Modeling and Observing Atmospheres of Terrestrial Exoplanets

The recent launch of the James Webb Space Telescope (JWST) allows us to observe more exoplanets and in greater detail. Now that we can characterize terrestrial planets and their atmospheres, this dissertation features several theoretical works that study atmospheric dynamics and infer observability. First, we explore the processes of non-collisional atmospheres to determine the tendency of exospheric volatile transport. We use a Monte Carlo simulation to infer water cold-trapping efficiency for different planetary configurations and find that there are optimal conditions for planetoids to accumulate water on the surface. Planetoids outside these conditions are either too small and thus lose water to thermal escape, or too large and lose water to photodissociation. Bodies similar in size to the moon are ideal for cold-trapping water, which gives great insight into the solar system and its history. Planetoids that build large reservoirs of water, or other volatiles, can evolve to form observable transient collisional atmospheres. While only relatively small planetoids are subjected to exospheric dynamics and therefore not ideal for observations outside the solar system, the dynamics of a half collisional, half non-collisional atmosphere are present in lava planets. Because of the relative ease in observing these planets, they are currently the best target for detecting a rocky exoplanet atmosphere. We modelled the flow of lava planet K2-141b’s silicate atmosphere and inferred atmospheric pressure, temperature, and wind speed. We found that SiO should be the dominant gas species and that winds reach supersonic speed, typical for lava planets. However, our analysis where we coupled radiative transfer to the hydrodynamics suggests that the large wind speed induced from a large negative lapse rate cools down the atmosphere much more than previously thought. Therefore, the simulated eclipse spectrum shows absorptive SiO spectral features, as opposed to emission features, that are prominent enough to be observed with JWST. However, the atmosphere is still too thin and the transit depth too small, making observing K2-141b’s atmosphere via transmission spectroscopy too difficult with the current technology.