I actually found the potential of the Mars setting fascinating for a campaign. I came at the idea of Mars with three overarching research questions:
A) What would the politics of Mars look like across each of the eras?
B) Could the experiences of the isolation during the Occupation era lead to the rise of Mars nationalist organisations or sentiments (Mars First and/or Mars Independent)?
C) How would that nationalist sentiment sit in a broader political climate over time?
I still haven't quite finished it all yet, but I'll share some of the known facts (from core) and my own extrapolations up to about the Orion War era. Most of the questions I've got from each era are open questions which I refer to backwards and forwards throughout each explanation.
Occupation Era Known Facts:
* Mars was not occupied by aliens during the Occupation period.
This could give rise to a 'never conquered, never surrendered' rhetoric or mentality to any nationalist movement. It'd be applied retrospectively, probably as justification for some later part of the rhetoric and not expressed coherently during the Occupation period.
*Mars was isolated and left to its own devices to survive or fail during the Occupation period. Result: 40% mortality and terminal health problems, other health and maintenance issues (failing infrastructure) discovered after contact was re-established during the Expansion era (core 145).
1) What would be the cultural impact on the Mars colony of such a large mortality rate?
2) How would that isolation event shape concepts of Mars nationhood?
Expansion Era Known Facts and Questions:
3a) During the Expansion era, what effect would access to media about the PCEG trials on Earth have on Mars?
3b) How much of the PCEG anti-collaborator rhetoric would shape the Mars narrative?
3c) How much of the anti-collaborator rhetoric would be turned against Earth to explain the horrors of isolation?
The nationalist reasoning and rhetoric here is: Earth collaborated with aliens during the occupation (we know, we've seen the broadcasts). Earth left us alone to die (lived experience of the isolation). Earth caused this. Death to the collaborators! Never forgive, never forget, never again! Never conquered, never surrendered (from Occupation era). Welcome to hard-line Mars nationalism
* The privations of isolation were relieved with food and supply convoys from Earth during the Expansion.
4a) How would that relief effort play into the Mars national narrative?
4b) Too little, too late? Possible line of Mars nationalists (as an extension of reasoning from 3c)
4c) Earth as saviours?
Perhaps a polar opposite position from the nationalist line. Reasoning: Isolation happened (lived experience). Bad things happened (lived experience). Earth didn't forget us (to counter the nationalist rhetoric). Probably seen as a naive position by hard-line nationalists (but at least it establishes a possible spectrum of sentiment)
4d) Something in between?
There would have to be a moderate middle-ground position, I just can't think what that would look like enough to articulate into slogans.
* Mars becomes a space training hub for Earth and Mars. Prestige is attached to being Martian.
5a) Could that 'point of pride' in being Martian become arrogance or hubris?
5b) Would the Expansion era be the first point at which the nationalist pride sentiment is coherently voiced?
Orion War era: Things get interesting for Mars during and after the Orion War era.
* Increased trend of contact with aliens during this period
6a) How would that increased alien contact trend play against that initial 'never conquered, never surrendered' rhetoric from the Occupation era nationalist?
6b) Is 'contact with aliens' the same as 'collaborating with aliens' from a hard-line perspective? (see 3b and 3c)
* The Treaty of Parella and the Return (core 172)
7a) Could the Treaty of Parella be seen as another Earth betrayal of Mars (similar to the effect of the Treaty of Versailles and its impact on the rise of German nationalism during the inter-war period)?
7b) Could the Treaty of Parella be used as vindication by Mars against future alien collaboration?
That's all I've got so far. I think there's still more to do with the Orion era and definitely more stuff from Artifact era to go through (Unification Charter and Parella Station Defiant, particularly). I'll get back to it when my brain's not so fried.
Some of the specific questions:
1/2) The biggest changes are in order to prevent casualties from isolation from reoccurring in the future. After reestablishing contact, Mars's first priority is to set up the facilities it had been missing the first time it lost contact to fill in the gaps of their dependency on Earth. And every Martian learns the tools of survival, which on Mars means everyone is a mechanic.
I think the questions in points 3 and 4 would largely balance each other out, with a handful of people on either end of the spectrum causing problems one way or another.
5a) There's probably an element of that. As Humanity expands into the rest of the galaxy, the hubris could become evident when there proves to be little need for a Mars colony, as it's not exactly convenient to travel to for any of the more important locations (Earth, Ceres, Saturn), nor does Mars itself provide much in the way of helping Humans survive.
5b) It would have to be; the soonest the Martians would possibly know what happened on Earth wouldn't be until contact is reestablished during the Expansion Era.
6a/b) Would play out differently among different subcultures on Mars, and for sure some would see any amicable contact with aliens as a betrayal. That said, Mars never has an anti-alien movement anywhere near as strong as what Redland has, as a point of reference.
The biggest influence the Orion War has from Mars's perspective would be the influx of demand for the kinds of expertise (piloting, mechanics) that Mars excels at, so the war is quite a financial boon for the Martian economy.
7a) There's a lot of Humans everywhere, Mars included, not happy about the Treaty of Parella. This sentiment comes to a head during the Artifact Era, in particular the Backdoor Incursion incident (core 194).
7b) There'll be plenty of opportunity for both vindication and humiliation for anti-alien sentiments in the next sourcebook; that's one of the bigger historical themes of the following century. :)