Comment by rsynnott

It's also particularly awkward to land on, as it has just enough atmosphere to be annoying, but not enough to be particularly helpful. Most Mars landings have involved some sort of ridiculous Rube Goldberg machine or other (see https://en.wikipedia.org/wiki/Sky_crane_(landing_system) , https://en.wikipedia.org/wiki/Mars_Pathfinder#Entry,_descent... ) which would not be viable for humans (and were only arguably viable for the probes they were used for; the risk of failure was high).