Presentation #428.02 in the session “Extrasolar Planets: Future Prospects”.
A key objective of exoplanet science is to determine the chemical, dynamical, and radiative processes that govern planetary atmospheres. Countless orbits/hours of HST/Spitzer have been employed to determine transiting exoplanet atmospheric properties spanning the UV to mid-IR. These multiwavelength observations have provided us preliminary estimates on molecular abundances, thermal structures, and cloud properties. Each wavelength regime and geometry offers complementary information on these properties at different altitudes in a planetary atmosphere. In particular, the poorly understood region that connects the deep atmosphere to the exosphere (1 mbar - 1 nbar)—a critical region that ultimately dictates the composition of the escaping atmosphere—is uniquely probed with NUV-to-FUV transmission spectroscopy. Here we will discuss the physics that governs this atmospheric region and how these processes link the deep atmosphere to the exosphere. Specifically, we look at the effects of vertical mixing (near the homopause), photochemistry, and condensate formation as well as provide testable predictions for the expected NUV and FUV transmission spectral trends within the giant planet population. We will then discuss how a NASA Medium-Class Explorer Mission concept, the Ultraviolet Spectroscopic Characterization Of Planets and their Environments (UV-SCOPE), could provide the necessary measurements to test these population level atmospheric process predictions and how such measurements would complement up-coming near-to-mid-IR observations with the James Webb Space Telescope.