12. Should Not Have High Radiation Levels
One of the things that comes up time and time again is the issue of radiation on a new planet. We cannot know how much radiation a planet has without sending something there to either test the environment for it or bring something back for us to do it here.
This can be an issue, as high radiation levels will kill human life quickly while any radiation can be an issue to be exposed to long-term. We can thank the brilliant Marie Curie for our knowledge of radiation, the very thing that ended up resulting in her early passing. We’re smart enough to know not to go to a place that has tons of radiation as a result of her work.