He wrote a superb trilogy of hard science fiction about the first 100 settlers on Mars ('Red Mars','Green Mars','Blue Mars' Narrative is rather dry (a lot of science and philosophy) but I really enjoyed it.

As to Mars, I used to be a space nut and really wanted to go to Mars, but er...I've changed my mind on that one. Mars is, in reality, a cold, hard rock a long way from earth... a long way from any dentists, doctors and and coffee shops. No thanks

Humans ain't meant for space. It's our digital descendants (computers/robots) but are going to expand across the galaxy eventually I think. We can explore it all from the relative comfort of virtual reality.