Presentation #521.06 in the session Dark Sea: Icy ocean worlds and astrobiology (iPosters).
The Juno spacecraft has been orbiting Jupiter for over six years, having arrived in the Jovian system in July 2016. Juno carries with it the Jovian Infrared Auroral Mapper (JIRAM), an Italian contribution to the payload, operated by the JIRAM team based out of the Istituto Nazionale di Astrofisca (INAF) in Rome, Italy. JIRAM is a dual imager and spectrometer. The spectrometer detects photons between 2 and 5 microns through a 1x336 pixel slit. The 256x432 pixel field of view of the imager is divided into sections: one of which detects near-infrared light in the L band (3320–3600 nm); the other of which records light in the M band (4537.5–5035 nm). As its name implies, JIRAM was primarily built to examine Jupiter’s aurorae and the dynamics of its atmosphere. The L-band portion of the imager tracks the Jovian aurorae through the observation of H3+ emission lines, while thermal emission from deeper in the Jovian atmosphere is recorded in the M band (Adriani et al., 2014). However, JIRAM has also been successful at obtaining data on many of the other targets in the Jovian system.
In this work, we will focus on our initial analysis of L-band and M-band images of Europa taken by JIRAM. The analysis of JIRAM spectra of Europa has been reported elsewhere by Filacchione et al. (2019). Between August 2017 and July 2020, Europa was targeted by the JIRAM imager over 580 times on 8 separate orbits. The images are of coarse spectral resolution, ranging between 50 and 200 km/pixel. These observations can be compared with Earth-based near-infrared observation campaigns of the Galilean moons, such as that of Tittemore and Sinton (1989). While radiation noise poses a challenge for the reduction of these observations, particularly for the observations attempted during orbits 27 and 28, these images allow us to look for broad spatial and temporal variations on the surface of Europa in the L and M bands. Of particular interest for this work would be placing the M-band variability reported by Tittemore and Sinton into appropriate context.