Eurybates – the only asteroid family among Trojans?

We study the orbital and physical properties of Trojan asteroids of Jupiter. We try to discern all the families previously discussed in the literature, but we conclude that there is only one significant family among the Trojans, namely the cluster around the asteroid (3548) Eurybates. This is the only cluster that has all of the following characteristics: (i) it is clearly concentrated in the proper-element space; (ii) the size–frequency distribution is different from that of background asteroids; (iii) we have a reasonable collisional/dynamical model of the family. Henceforth, we can consider it as a real collisional family. We also report the discovery of a possible family around the asteroid (4709) Ennomos, composed mostly of small asteroids. The asteroid (4709) Ennomos is known to have a very high albedo pV≃ 0.15, which may be related to the hypothetical cratering event that exposed ice. The relation between the collisional family and the exposed surface of the parent body offers a unique means to study the physics of cratering events. However, more data are needed to confirm the existence of this family and its relationship with Ennomos.