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201226 https://hdl.handle.net/2286/R.2.N.201226 http://rightsstatements.org/vocab/InC/1.0/ All Rights Reserved 2025 209 pages Doctoral Dissertation Academic theses en Wiser, Lindsey Line, Michael Shkolnik, Evgenya Patience, Jennifer Walker, Sara Bossert, Katrina Arizona State University Partial requirement for: Ph.D., Arizona State University, 2025 Field of study: Astrophysics Over the past three decades, exoplanet research has evolved from discovery to atmospheric characterization and population-wide trends. In this dissertation, I examine how improvements in observations and models refine an understanding of exoplanet atmospheres and their signatures of planet formation and climate processes. My dissertation is divided into five main chapters. In Chapter 1, I present my motivation for studying exoplanets, an introduction to exoplanet populations, and methods for observing and inferring their properties. In Chapter 2, I present a population-level analysis of hot gas giant exoplanets observed with the Hubble and Spitzer space telescopes. I summarize knowledge gained from these telescopes and show that while these groundbreaking observatories provided initial insights into exoplanet atmospheres, their use alone limits inferences about atmosphere compositions. In Chapter 3, I present observations of a warm gas giant, WASP-80 b, with the James Webb Space Telescope (JWST). WASP-80 b is a rare massive planet around a low-mass star. Because of the scarcity of this population, I consider whether WASP-80 b may have formed through different processes than more common gas giants around higher-mass stars. This analysis highlights how JWST observations can enable inferences beyond those from Hubble and Spitzer observations. In Chapter 4, I compare exoplanet atmosphere models assuming one-dimensional atmospheres, i.e., variation only with altitude, to three-dimensional models incorporating circulation and spatial variability. I discuss the types of planets for which 3D effects influence the observed spectrum significantly enough that 1D models cannot adequately explain observations with JWST. In Chapter 5, I introduce the Pandora SmallSat. The Pandora mission aims to characterize exoplanet host star variability and assess the impact of that variability on transiting exoplanet spectra. I present an outline of the science instrument commissioning plan and highlight the value of future missions for continuing to improve an understanding of exoplanet atmospheres. Finally, in the Appendix, I briefly summarize work I led throughout my PhD advocating for space and science policy. Science does not happen in a vacuum, and ensuring continued access to space for science and other uses requires acts of policy. Atmospheric sciences Astrophysics Planetology atmospheres Exoplanets Planet Formation Space telescopes Spectroscopy From Hubble to JWST and Beyond: Revealing Exoplanet Formation and Climate with Space Telescopes