DIX Planetary Science Seminar

Julie Inglis

The benchmark hot Jupiter, HD 189733b, remains one of the best studied exoplanets to date and is a cornerstone for models of hot giant planets. Early observations with HST (Swain et al. 2008, 2009, 2014) and Spitzer (Grillmair et al. 2007, 2008) in emission uncovered some of the first evidence for the presence of multiple molecules in its atmosphere, as well as signs of disequilibrium chemistry. It was also the first planet with a measured phase curve, revealing the presence of an equatorial super-rotating jet (Knutson et al. 2007). With the launch of JWST, we now have renewed access to mid-infrared wavelengths at unprecedented spectral precision; this provides us with a new opportunity to revisit this benchmark planet's mid-infrared emission spectrum. We will present new dayside emission observations of HD 189733b with MIRI LRS and place them in context of previous observations with HST and Spitzer. We will also discuss how the exceptional precision of JWST observations of this prototypical hot Jupiter can be used to advance our understanding of the thermal structure and atmospheric chemistry of hot gas giant exoplanets.

Ryleigh Davis

A weak absorption feature at 2.07 μm on Europa's trailing hemisphere has been suggested to arise from radiolytic processing of an endogenic salt, possibly sourced from the interior ocean. However, if the genesis of this feature requires endogenic material to be present, one would expect to find a correlation between its spatial distribution and the recently disrupted geologic units. We will present a new analysis using archived moderate spatial and spectral resolution data from VLT/SINFONI, and show that while the presence of the 2.07 μm feature is strongly correlated with the irradiation pattern on Europa's trailing hemisphere, there is no apparent correlation between the presence or depth of the absorption and Europa's large-scale chaos terrain. For locations at a given estimated irradiation flux, the average absorption depth is constant between chaos terrains and the background ridged plains. This suggests that the formation pathway of the 2.07 μm feature on Europa is independent of any endogenous salts within the recent geology. Instead, we propose that the source of this feature may simply be a product of the radiolytic sulfur cycle or arise from some unidentified parallel irradiation process.