There is a fundamental problem with terraforming Mars; it has no magnetic field to keep the solar “winds” from blowing away the atmosphere. Humans will not be able to live outside on the surface of Mars, no matter how long we try to generate atmospheric oxygen without a planetary magnetosphere to divert the high speed ions escaping from the sun. At one point in the planet Mars’ life time it had an atmosphere and liquid water on the surface but now nothing that counts. The surface of Mars now has an atmospheric pressure of 0.0060 atm!

Perhaps we could generate a Martian artificial planetary magnetosphere, but I don’t know how.

See [1] from NASA.

[1] https://science.nasa.gov/science-news/science-at-nasa/2001/a...