Radiative Transfer Modeling of Jupiter’s Hot Spots and NH₃ Plumes with HST UVIS and Keck NIRSPEC

Hot spots are downwelling regions of the Jovian atmosphere that appear bright in the thermal infrared and dark at visible wavelengths, owing to a combination of low ammonia (NH₃) abundances and thin clouds. They open a window into Jupiter’s deeper atmospheric layers, which are normally obscured by overlying clouds, providing sensitivity to layers as deep as ~6 bar. Conversely, NH₃ plumes are upwelling regions with thick overlying clouds and high NH₃ abundances, which appear bright at visible wavelengths and dark in the thermal infrared. NH₃ is a tracer of atmospheric dynamics, so studying these NH₃ extremes is important for understanding the vertical transport of volatiles in Jupiter’s atmosphere. We present radiative transfer (RT) models of hot spots and NH₃ plumes found in Jupiter’s North Equatorial Belt (NEB). Our models use observations at visible (0.3-0.9 μm) and thermal infrared (4.5-5.5 μm) wavelengths from the HST WFC3/UVIS and Keck NIRSPEC instruments, respectively. These observations are part of a suite of Juno support observations, which include simultaneous observations with HST, Keck, Gemini, and the Very Large Array. HST observations are sensitive to atmospheric conditions between the tropopause at ~0.1 bar down to the uppermost opaque cloud tops, which range from ~0.7–4 bar depending on cloud opacities. Our NIRSPEC observations are sensitive to cloud opacities and volatile abundances between ~2–6 bar. We combine these two datasets to simultaneously model the structure and composition of Jupiter’s hot spots and NH₃ plumes from ~0.1–6 bar. We use our in-house RT modeling package, SUNBEAR, to derive the extent and thickness of tropospheric hazes, the location and structure of Jupiter’s clouds, and the abundances of volatiles such as NH₃.