Is anyone really thinking we just need to reach Mars, then immediately set up a colony? No, reaching there is obviously only a first step, but once we can reach it, we can try things to see if we can live there. For myself, I’ve been saying we need to hurry up and reach Mars because we have like 100 years of work before we can establish a colony so let’s get started
We don’t know if a self-sustaining population is possible anywhere other than Earth. However we know lack of gravity is one issue we don’t have a workaround for. Mars is the only “large” gravity we can possibly reach with our current level of technology
I think the far-more realistic scenario is we create a colony of robots, first for experiments, then (if possible) to build out a colony that can eventually be inhabited by humans.
If we’re going to get anything useful out of mining (other than just building material), it’s going to be incredibly sparse. I think we need to start asap working on robotic mining vehicles to wander around collecting and refining useful stuff. By the time we send people, we ought to have spent years collecting tankfuls of oxygen and water, caches of refined ores, piles of bricks and pavers (maybe even sheds/garages), maybe even sheets of crude solar cells, miles of wire.
Navigation and communication will be crucial, so we need to lead with a constellation of gps/communications satellites so no matter where you are, you know your location, can reliably contact your base, and even all back to earth. We’ll want many automated weather and seismic stations that need to send a flood of data somewhere