Damage curve and surface exposure age of Didymos. The top axis shows the corresponding surface exposure age at 1.64 AU, while the bottom axis shows the damage parameter d in 10¹⁸ displacements/cm², which is related to the top axis via Eq. (C.2). The black curve shows the relationship between the damage parameter d and C_S, as given by Eq. (C.1), and the black square indicates the measured C_S value of the Didymos surface, from which the surface exposure age is estimated.