The fundamental problem is if you need to live underground in self-sustaining terrarium environments there is plenty of land to do that on Earth. No need to ad

The fundamental problem is if you need to live underground in self-sustaining terrarium environments there is plenty of land to do that on Earth. No need to add an expensive and difficult spaceflight on top of your problems. Not to mention completely eliminating a huge safety factor you enjoy from doing this on Earth. Ultimately: what does Mars offer that you can't get on Earth or the Moon? Is it worth the extra trillions of dollars worth of expense and effort? Even if you're talking about surviving dinosaur-killing asteroid impacts the subterranian or subsea self contained colony offers many advantages over an offworld colony.