Reunion, av John Gribbin och Marcus Chown.
Från Amazon-beskrivningen :
A sequel to "Double Planet". The moon has been colonized for more than 1000 years, but now the comets have stopped coming and the atmosphere is slipping away. Only one young girl holds the secret that can return the comets - but first she needs help, and Earth is the only place to find it.
Vidare tittar på kapitellistan, bok 2 inom detta heter "Ondray"