Juno observations of Io

NASA’s Juno mission has been observing the Jovian aurorae since 2016 from a polar, highly elliptical orbit.
Although not in the main scientific objectives, Juno took images and spectra of the Galilean moons from a
very favourable position, using some of the cameras on board: JIRAM, JunoCam and SRU. In particular, The
Jovian Infrared Auroral Mapper (JIRAM) is a dual-band imager and spectrometer. The imager channel is a
single detector with 2D capability and with 2 different filters (L band, from 3.3 to 3.6 µm; M band, from 4.5
to 5 µm); the spectrometer is a 1-D detector with a spectral resolution of 9 nm in the range 2 - 5 µm. The
pixel angular resolution (0.01°) is fine enough for imaging the moons from the polar, highly elliptical orbit of
Juno; the spatial resolution at the surface of the moons varies along the s/c distance and is of the order of
100 km/pixel or even finer. Here we present JIRAM’s images and spectra of Io after
six years of Juno mission, together with JunoCam and SRU images of Io. On Io, these observations
characterize the location and possible morphology, and some temperatures, of the volcanic thermal
sources; the identification and distribution of SO 2 , the possible identification of CO 2 and other materials. 
Recent Juno flybys, at distance down to 50'000 km, allows unprecedented imaging of the moon with resolution of about 10 km.
This allows reconstructing the morphology of hot spots, and a better mapping of their distribution, in location and emitted power.