0 Assigned ID: 4692 ----- Attempting Submission 1 (Wed May 24 21:54:32 GMT 2023) ----- On 7 June 2021, NASA's Juno spacecraft flew over Ganymede's leading and sub-Jovian hemispheres with a closest approach altitude of 1046 km. During the flyby period, Ganymede's auroral emissions and surface reflectance were observed by the Juno-UVS instrument, which detected an absorption feature in the high latitudes at wavelengths longward of 190 nm. Since only part of this feature fell within the 68 - 210 nm Juno-UVS bandpass it was difficult to confidently identify the material responsible for the absorption, but Molyneux et al. (2022) [doi:10.1029/2022GL099532] suggested it may be the beginning of a known ozone absorption centered at 260 nm. However, a quick look at archival STIS G230L observations of the same surface regions indicates that this interpretation is incorrect and the feature observed by Juno-UVS is instead the start of a previously unknown ~190 - 240 nm absorption. In this proposed Archival Research program, we request funding to map the >190 nm absorption across the entirety of Ganymede's surface using STIS G230L data from Programs 7317 (Cycle 7) and 15925 (Cycle 27). Our proposed program will constrain the identity of the absorber, aid with the planning and interpretation of future observations by ESA's JUICE mission, and inform searches for related materials both on Ganymede and on other icy moons. PI Pippa Molyneux has significant experience analyzing the UV reflectance of the Galilean satellites using HST STIS and COS and Juno-UVS. She has produced Hapke spectral reflectance models to constrain surface compositions, and produced spectral fits to UV absorption features based on lab data. Co-I Josh Kammer (Co-I 1) is experienced in spectral data analysis, including using HST data. He regularly uses SPICE tools for mapping data and will lead the task to map the STIS pixels to Ganymede's surface. Co-I Tracy Becker (Co-I 2) has extensive experience analyzing HST STIS data, including extracting reflectance spectra and mapping Europa's 280 nm sulfur dioxide absorption. She will apply this experience to extract the Ganymede UV reflectance spectra. Co-I Kurt Retherford (Co-I 3) has decades of experience analyzing observations of the Galilean moons from HST and other facilities, and is deputy PI of the JUICE-UVS instrument. He will assist with the interpretation of the UV maps, using his knowledge of the distribution of charged particles and neutral materials throughout the Jovian system. Co-I Ujjwal Raut (Co-I 4) is an expert in UV laboratory measurements of planetary materials including ices, and has performed experiments involving irradiated samples. He will advise on the likely irradiation products that could explain the UV absorption, and will assist with relevant literature reviews. Solar System Astronomy 0 Regular false false true false false false SUPPORTED