Results from JIRAM: The Jovian Infrared Auroral Mapper

Abstract:

NASA's mission Juno has been observing Jupiter since 2016. From its polar, highly elliptical orbit, it has set a milestone in the understanding of this planet. Among its scientific payload, the Jovian InfraRed Auroral Mapper (JIRAM) is a dual-band imager and spectrometer. Its main objectives are the study of the Jovian atmosphere, of the aurorae and, as targets of opportunity, of the Galilean moons. In the last four years, JIRAM obtained unprecedented measurements of Jupiter atmosphere composition and circulation, unique views of the auroral regions and close observations of the polar regions of the moons.

Jupiter’s atmosphere is complex and turbulent, and the polar regions were never observed before as Juno did. Images from the M-band filter of JIRAM, together with JunoCam, have revealed the presence of Earth-size cyclones densely clustered in different geometrical structures. Here we briefly discuss the evolution of these structures four years after their discovery, and recent findings on the atmospheric composition. JIRAM also observed the spatial, spectral and temporal distribution of the Jovian auroras.

Intense auroral emissions are observed in regions where little or no precipitating electron flux is detected, possibly indicating excitation from strong ionospheric electric currents. Juno also revealed a puzzling structure in the electromagnetic interactions between Jupiter and its moons, whose signature is highlighted in the shape of the auroral footprints.

Io, Europa, Ganymede and Callisto have been observed several times. Ganymede, in particular, has been observed from ~100'000 km during a flyby. JIRAM obtained high resolution images and spectra of the its North Pole region, an area that can't be covered from Earth-based instruments, confirming that Ganymede’s surface is strongly heterogeneous, likely due to the preferential paths of plasma bombardment