Hello /sci/, curious but not scientifically literate anon here, what i wanted to ask of you is how are atmospheres formed? To my current knowledge it is like an envolopment of gasses that create a sort of protective layer around our planet, (if im incorrect please correct me) if this is the case what keeps it held there? I assume gravity but perhaps its something else? Is there a way to trigger this to happen on other uninhabitable planets to start terraforming them?