Watching the movie "The Martian" will give you an explanation but here is mine.We can get oxygen and use the other gases as something for the trees to use to produce oxygen.We can plant plants for a source of food since its a one way ticket by bringing some soil/dirt from earth in the rocket.Human habitation will roughly take about 20-50 years in my prediction because it is a whole new planet.Prosucing water is another problem,bring some water and use it as your source of drinks.For the plants however,you need to produce steam. You can see the recipe in the movie i mentioned.Since water can be a problem it can be physically impossible to make mars a place to stay in. So thats why i said it would take 20-50 years. Thats all I have for my explanation
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