The part that I've been asking myself for years, is how do you create an atmosphere without (or almost without, can't remember) a magnetic field. Is it possible or we would have to generate one?
From ... https://www.reddit.com/r/SpaceX/wiki/faq/mars#wiki_what_will...
The most promising plan I've heard of is to create one using a satellite between Mars and the Sun.
https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmo...