(162173) Ryugu is a near-Earth C-type (i.e., carbonaceous) asteroid. It has been, after Itokawa, the second target for an asteroidal sample return, thanks to the JAXA Hayabusa2 mission (Watanabe et al. 2019). Most interestingly, Ryugu in situ observations in 2018–2019 have confirmed, as expected from its classification, the presence of significant amounts of organic molecules, together with hydrated minerals.Ryugu is a roundish, diamond-shaped body with an equatorial bulge. Such a shape, as previously observed during the Rosetta mission for asteroid (2867) Steins, may result from the re-accumulation of rubbles ejected by the catastrophic disruption of a larger aqueously altered parent body (Kitazako et al. 2019; Sugita et al. 2019). With a size and a mass, respectively, about 865 m and 4.5 × 1011 kg, its density is low (≈ 1200 kg m−3), as expected for a rubble-pile asteroid, while its rotation period is of 7.63 h