JIRAM observations of Io satellite from Juno perijoves 41-66

For several decades, Io—the most volcanically active body in the Solar System—has been the focus of extensive ground-based and remote sensing observations. In recent years, Io has been intensively investigated by NASA's Juno mission, particularly by the Jovian InfraRed Auroral Mapper (JIRAM) instrument. JIRAM is an imager equipped with two filters, L and M, centered at 3.3 µm and 4.8 µm respectively, and a slit spectrometer [1]. To date, JIRAM has acquired data nearly the entire surface of Io, achieving spatial resolutions up to 1 km/pixel, and revealing unprecedented surface details.In this study, we focus on JIRAM observations acquired during Juno perijoves 41-66, and characterized by spatial resolutions ranging between ~3 and 30 km/pixel. These images provide good coverage of the entire Io surface, including both polar regions. Data relative to previous Juno perijoves, characterized by coarser spatial resolution and larger radiance saturation level, have been excluded from this analysis.  Here, we focus on both JIRAM L and M-filter data. For each orbit, we selected hot spots giving priority to higher-resolution images in cases of data redundancy. This approach allowed to map the spatial distribution of total spectral radiance across Io and to assess the temporal variability of individual hot spots when observed during multiple Juno observations, as well as to calculate their temperature, when both L and M filters are available [2, 3]. Furthermore, the recent datasets reaching spatial resolutions of just a few kilometers per pixel, revealed previously unseen details of approximately ninety paterae. These data confirm the presence of numerous lava lakes [4] and show morphological details of a large number of features.JIRAM data offer a unique opportunity to investigate Io’s surface activity. The new dataset enhances our ability to resolve previously undetected hot spots, as well as to identify new, smaller, and fainter features. Furthermore, the global high-resolution coverage of both the hemispheres, enables more accurate distribution of hot spots across the overall Io surface. AcknowledgmentsThis work is supported by the Agenzia Spaziale Italiana (ASI). JIRAM is funded by the ASI–INAF Addendum n. 2016-23-H.3-2023 to grant 2016-23-H.0. Part of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.References[1] Adriani, A., et al. (2017). JIRAM, the Jovian infrared auroral mapper. SSR, 213(1–4), 393– 446.[2] Mura, A. et al. (2024). The temporal variability of Io's hotspots. Frontiers in Astronomy and Space Sciences.[3] Mura, A., et al. (2020). Infrared observations of Io from Juno. Icarus 341, 113607.[4] Mura A. et al. (2024). Hot rings on Io observed by Juno/JIRAM. Nature Communications Earth & Environment, in press.