Identifying priority cryovolcanic targets on Ganymede for ESA’s JUICE mission

The characterization and identification of possible cryovolcanic activity on Ganymede is key to understanding the evolution and potential habitability of Jupiter’s largest moon. ESA’s JUpiter ICy moons Explorer (JUICE) mission, launched in 2023, will provide the first dedicated, high-resolution investigation of Ganymede’s surface and interior. Before JUICE reaches Jupiter’s system and obtains its first observations of Ganymede, it is essential to reassess previously proposed cryovolcanic regions using a consistent and comparative approach.Based on Voyager and Galileo spectro-imaging, 20 paterae and morphologically distinctive features have been suggested as candidate cryovolcanic regions, yet their geological context and compositional diversity have not been systematically evaluated. In this work, we present a reanalysis of all candidate regions, combining regional geomorphological assessment with comparative near-infrared spectra. Reprocessed Galileo Near-Infrared Mapping Spectrometer (NIMS) data are examined using a uniform linear spectral unmixing framework, with emphasis on relative spectral trends and temperature-dependent behaviour rather than absolute compositional determinations.This data reprocessing and spectral comparisons reveal distinct spectral categories among candidate regions, ranging from ice-dominated terrains to areas exhibiting enhanced non-ice components. When combined with morphological characteristics that are often similar to confirmed cryovolcanic features on other planetary bodies, these groupings suggest that multiple formation and modification processes may be represented, including end-member cases consistent with cryovolcanic resurfacing or brine-related processes.Rather than providing definitive interpretations, this work establishes a pre-JUICE framework for target prioritization and observation planning. We discuss implications for high-resolution imaging and spectroscopy by the JANUS and MAJIS instruments, and how forthcoming JUICE data can discriminate between plausible geological scenarios.