I wonder if the hug differences with the earth still makes it viable though. No atmosphere, lower gravity, completely different lengths of days and months, it'll take a lot of adjusting for people to get used to that. In all of those aspects Mars is a lot better fit, just much further away.
Anyway, great read. Definitely following you! I plan on writing a post about how and why we would eventually will set base on Mars (big SpaceX fan).
Being underground and with artificial lighting would remove the worries about the day length, however the low gravity might be an issue, perhaps wheel shaped colonies rotating to create artificial gravity? The lack of atmosphere actually works in the favor of the colonists as long as you maintain the integrity of the shelter.