Mars is the dusty, airless void of death and general unpleasantness it is today because it lost its magnetosphere millions of years ago. This was because Mars's dynamo in its core shut down. Because it lost its magnetosphere, the solar wind was able to strip away Mars's atmosphere, oceans, and any unfortunate aliens.
I'm working on a setting where Mars never became uninhabitable and is still nice and earth-like. I want to make sure it's scientifically accurate, though. I was thinking about giving Mars a moon (or more). My hope is that maybe the tidal forces the moon enacts on Mars could re-start the dynamo in Mars's core. I have no idea if this would work, though, and many more things might have to change that I don't know about in order to ensure Mars stays habitable. Would this work?