Quick Answer: The hard part of settling Mars is the stay, not the trip. NASA’s Human Research Program ranks radiation effects, eye changes, behavioral health and food among its highest-priority risks, and its review quotes 300 to 450 mGy for a roughly 3-year Mars mission.1 The surface pressure is 6.36 mb, about 0.63% of Earth’s, in an atmosphere that is 95.1% carbon dioxide,2,3 and a…
