The eyes on a comet: Rosetta-OSIRIS highlights on 67P/CG comet

Abstract: The European Space Agency Rosetta mission marked a turning point in cometary space exploration. Rosetta observed the comet 67P/Churyumov-Gerasimenko for about two years, from August 2014 to end of September 2016, delivering the lander Philae on the comet surface for the first time in the history of the space exploration. Among the suite of complex and diverse instruments onboard the mission, the OSIRIS imaging system represented the eyes of Rosetta. OSIRIS had two cameras, the Narrow and Wide Angle cameras (NAC and WAC), devoted to the nucleus and coma studies, respectively. More than 80,000 images of the comet have been acquired with OSIRIS with a spatial resolution ranging from several meters to a few centimeters per pixel. In particular, the high dynamics of the cameras detectors permitted to distinguish morphological structures on shadowed areas as well as frost layers, and to monitor at the same time the very dark surface, faint jets, and ices exposures, 10-15 times brighter than the average dark terrain of the nucleus. Six years after the end of the mission, the data exploitation is still ongoing with new interesting results, notably concerning the water ice spots size distribution, which is relevant for cometary models. I will present the main scientific results and the latest ones from OSIRIS observations on the structure, geomorphology, surface composition, cometary activity, and their evolution over time, as well as the implications on cometary models and solar system formation.