Overview of Juno's Results from Europa and Ganymede

The evolution of Juno's elliptical polar orbit has brought it close enough to Jupiter at the inbound equatorial plane crossing to intersect the orbits of the Galilean moons.  A close pass by Ganymede occurred 7 June 2021, at an altitude of 1046 km.  The spacecraft came within 350 km of Europa's surface on 29 September 2022. 

            The Juno payload, designed to probe Jupiter's magnetosphere with a comprehensive complement of fields and particles instruments, was ideal for studying Ganymede's unique mini-magnetosphere.  The spacecraft approached Ganymede from the night side, went behind Ganymede as seen from the earth (achieving an earth occultation), passed through the moon's magnetosphere, and then departed on the sunlit ~sub-jovian side.  Juno's remote sensing instruments collected new data in the visible and near-infrared, and, for the first time, mapped the surface and subsurface with 6 microwave channels.  Remote sensing of Ganymede returned new results on geology, surface composition and thermal properties of the subsurface. 

            Europa, with its tenuous atmosphere, has a unique interaction with the jovian environment, also investigated with Juno's fields and particles instruments.  The production of water molecules from sputtering of the surface is compared to the processing and eventual loss of molecules from the atmosphere.  Juno's remote sensing instruments returned high resolution images and spectra that are being used to expand our understanding of the tectonic history of Europa's surface.  The Microwave Radiometer probe of the subsurface ice shows Europa to be very different than Ganymede.