The Galilean moons of Jupiter are a primary focus of the planetary science community with missions under development by NASA and ESA that focus on Europa and Ganymede, respectively. Additionally, missions are currently being proposed for a focused study of Io. During its prime mission Juno obtained the first closeup observations of Io and Ganymede since the Galileo mission. Among the important results were the first map of the distribution of water ice across Ganymede’s northern latitudes, the detection and presence of salts, new insights on the magnetospheric coupling between the satellites and Jupiter’s ionosphere and aurora, and images plus spectra of Io that discovered new volcanic activity, constrained temperatures of volcanic thermal sources, identified new hot spots at the south polar region and detected variations potentially indicative of new lava flows. Juno’s extended mission began this summer and transforms the Jupiter focused mission to a full system explorer. The extended mission runs through 2025 and includes numerous close and distant flybys of Io, Europa and Ganymede along with the first exploration of Jupiter’s poorly understood ring system. The first Ganymede close flyby (mid-summer 2021) includes an array of observations to study of Ganymede’s magnetosphere and interaction with Jupiter, survey its near-surface ice crust and provide high-resolution maps of the surface geology and composition in search of changes since Voyager and Galileo. Juno’s polar orbit provides unique opportunities to study the polar regions of the Galilean satellites, search for topographical and compositional changes since Galileo, explore satellite-magnetosphere interactions, and provide detailed the first probe of the shallow ice structure of these icy, ocean and volcanic worlds. The close proximity of Juno’s orbit to Jupiter provides an opportunity for the in-situ characterization of ring dust charging and low-light high-resolution imaging to investigate ring structure and dynamics, as well as search for source bodies in both the main and halo components of the ring system. This session welcomes observations and models related to Juno’s observations of the Galilean satellites and rings obtained during the prime-to-early extended missions as well as look-forward studies related to the full Juno extended mission.

The suggested format for this Union session is a combination of invited and contributed oral presentations as well as a poster session. Ideally, we would need at least 6-7 invited presenters to cover overviews of results on Ganymede's ice shell, changes in Ganymede's composition and geology since the Voyager and Galileo missions, Ganymede's magnetosphere, Ganymede's ionosphere results from the first occultation experiment, the radiation environment near Ganymede, the interaction between Ganymede and Jupiter's magnetosphere, results of a Juno based search for plumes on Europa, and new measurements and images of Jupiter's main ring and halo. it is expected that many other contributed talks will be submitted related to models, specific instrument measurement results and earth based supporting observations. if the committee does not approve a Union session, please consider a joint session in Planetary Science and Magnetospheric Science.

• AAS: American Astronomical Society -
• AOGS: Asia Oceania Geosciences Society -
• EGU: European Geosciences Union -
• JpGU: Japan Geoscience Union -