To conclude “aliens aren’t real” is as uncalled for as to conclude they are real. We don’t know. From what I read it seems a majority of cosmologist favor the odds that sentient alien beings have evolved in the universe, and some have survived themselves is probable.
Your knowledge of the necessary actions to terraform mars are well taken. I suggest there is more benefit to terraform earth. We have a lot to work with here. If we continue to allow run away global warming, what reasonable chance is there we could terraform mars, and keep it livable?