In 2033, after a 12-year trip across the Solar System, NASA’s Lucy mission will arrive at the Patroclus–Menoetius binary system, in Jupiter’s L5 cloud. On its way, Lucy will visit one asteroid and seven Jupiter Trojans, all of them primitive asteroids. Lucy’s foreseen discoveries about the surface geology, color, and composition of these Trojans, about their interior and bulk properties, and about the presence of satellites or rings, which have the potential of revolutionizing the knowledge of the Solar System and opening new insights into the origins of our Earth. In preparation for that moment, ground-based observations are fundamental to obtain important physical information on these targets, which is needed to plan the operations and the best observational strategy. Furthermore, they provide ground truth of the state-of-the-art analysis techniques used for the study of the whole population, which is essential to better understand the big picture.
In this work, we present surprising results from a set of 14 lightcurves of 11 mutual events of the Patroclus–Menoetius system obtained during the last season, in 2017–2018. Results based on the first set of seven light curves (corresponding to five different events) has been recently published (Pinilla-Alonso et al. 2020, PSJ, in press) reporting the imprint for a possible crater in the south pole of Menoetius, as deep as a fourth of its radius, and an improved orbit solution for the system. This new analysis, including seven inferior events and seven superior events, provides new details of the shape of both components and a new orbit solution, which is key for the planning of the flyby of the Patroclus and Menoetius system. Figure 1: Artistic representation of the Patroclus-Menoetius system showing a void in the southern limb of Menoetius. The profile of this void was extracted from the analysis of the light curve of an occultation obtained at the Gran Telescopio Canarias (GTC) on December 08, 2017.