On the density of EKOs and related objects

Recently published mass determinations of EKO binaries, combined with photometric size determinations, allow to derive a mean density of the distant minor planets of ≈ 0.2 g cm -3 . This agrees well with the nuclear density of 1P/Halley of 0.26 g cm -3 , determined in the Giotto mission, and it suggests that these low density objects are essentially undifferentiated planetesimals.