The poorest of poor went to live on Himalia. The rich went to Europa and the middle-class to Titan. Phobos remained inhabited, as no infected being had entered the artificial atmosphere. It is on Titan that our story lies.
Even though Titan is classified as a moon, it is larger than the planets Mercury and Pluto (eliminated as not being part of our solar system in 2006). It’s atmosphere is like that of a planet though, only slightly more dense then Earth was during the second and first dynasty. In 2004, information was published saying that Titan’s elements were most likely that of Earths before life brought oxygen into the atmosphere. It was also said that Titan’s hydrocarbon rich elements are the building blocks for amino acids necessary for the formation of life.