The revolutionary breakthrough will come with rockets that are fully and rapidly reusable. We will never conquer Mars unless we do that. It'll be too expensive. The American colonies would never have been pioneered if the ships that crossed the ocean hadn't been reusable.
You need to live in a dome initially, but over time you could terraform Mars to look like Earth and eventually walk around outside without anything on... So it's a fixer-upper of a planet.
You could warm Mars up, over time, with greenhouse gases.
My vision is for a fully reusable rocket transport system between Earth and Mars that is able to re-fuel on Mars - this is very important - so you don't have to carry the return fuel when you go there.
Mars is the only place in the solar system where it's possible for life to become multi-planetarian.
Land on Mars, a round-trip ticket - half a million dollars. It can be done.
It was obvious to me that we could never colonize Mars without reusability, any more than America would have been colonized if they had to burn the ships after every trip.