Earth, will most likely be detailed in Sunwards, and it is probably a postapocalyptic hell beyond reason (the thought gives me warm shivers as a GM :) ).
So as we of now don't know anything of what the book says, what would you think would be the most likely course to colonize our own mother Earth again, is it even plausible?
Nano Swarms, robotic terrors, viral clouds, nuclear wastelands (mutants perhaps, or mutant morphs...), acidic weather etc etc, is probably what would await us when we go down there.
But if we set aside the costs and dangers, how would one do it, what kind of military might would one need, and where would the most likely place be to start?
Some place that was not very habited to begin with maybe, one would think that the horrors of the war (if one would call near genocide that) would have been kindest there, so much that the dangers of T.I.T.A.N horrors may not even be there. And from there slowly branch out - but there must be a plan, something that wold not let it be a battle of attrition to take the planet back.
Could some kin of modified E.M.P blast take out the nano and robotic horrors, maybe they are shielded (do not remember the core book saying anything on that matter) against it.
Contrary to many science fiction games, visiting Earth, may be the most exciting place to go...
The Eternal Story Guide