Comment Magnetosphere too weak (Score 1) 473
Humans evolved on a planet with a robust atmosphere and a magnetosphere. Some estimate we actually have the atmosphere we have because of the magnetosphere that earth possesses. The Martian magnetosphere is just too weak to protect the planet, and anything crawling on it, from the many forms of radiation that humans cannot tolerate. Underground dwellings just may do it, but expect that to be of limited benefit in the end. First, create a robust magnetosphere, and then we'll see what happens.