Resonant evolution of the asteroid 83982 Crantor (2002 GO₉). The relative deviation of its semi-major axis from that of Uranus, α, as a function of the relative mean longitude, λ_r, during the time intervals (−22, −10) kyr (black squares) and (2, 12) kyr (dots) is displayed. The first interval covers the close encounter observed in Fig. 4, panel A (see the text). The second interval lasts an entire cycle of the horseshoe orbit and includes a quasi-satellite half libration, i.e., λ_r goes beyond − 60°, passes 0° but does not reach 60°.