From Bill Robinson, Slough, Berkshire, UK
It is interesting that each observed Trans-Neptunian Object seems to have a moon of its own (18 March, p 19). You state that “these moons probably formed when a large rock collided with the parent body and the debris coalesced in orbit”. That is a plausible way to form a moon, but is it not as likely that, in the “crowded, chaotic past” you mention, these TNOs grabbed a passing body for a moon?
