I worked on some space shuttle experiments as a graduate student back in the early to mid 90’s. (I had about 10 years of active duty between undergrad and graduate school.) I had the pleasure of directly working for a few of the shuttle crews.
Amongst other fond memories, I got to spend a pleasant afternoon water skiing with Chris and his family just east of JSC where he lived. As the Canadian astronaut, he was a really personable guy.
As to going to Mars, he correctly points out that its going to be really tough given the challenges of keeping a life support system and all the other things required working long enough and well enough to get astronauts to Mars alive.
The two major problems with extended space travel are the effects of radiation and low gravity on the human body. This is what a current NASA employee, former air force colonel told me. That is also why astronauts do not stay on the International Space station for more than a year. They all come back shorter and near sited among other problems.
I do hope you waved at the Garriots as you skied past their home on Clear Lake.