Just turn on the reactor and Mars will live.
The real problem with terra-forming Mars is that it has no magnetosphere. The Earth’s magnetosphere keeps the solar winds from blowing our atmosphere away.
Just turn on the reactor and Mars will live.
Those are two major problems that simply can’t be overcome. Either one by itself makes the proposition a non-starter. Both together? I think it would be cheaper to find that earth-like planet at another star and develop the technology to get to it.