There are some one-way missions that are reasonable. For example, if at some point, Mars missions resulted in a large, self-sustaining underground habitat, sufficiently advanced to have a purpose of slowly terraforming Mars, so that astronauts were effectively colonists, I see nothing wrong with their volunteering to do so.
Terraform what? The average temperature up there is about -30 celcius. That’s the average, who wants to live in that?
Until we can produce a magnetic field to encompass mars I think all habitability will be under cover on mars for at least a couple hundred years. Its certainly far more hospitable than the moon. Its not a hard vacuum like the moon and there is at least some protection from solar radiation. The nights aren’t two weeks long.
I’d like to put a dome over one of those arena sized craters and experiment with producing an atmosphere, growing plants etc.