In space, the moon is our closest neighbor. There is no water on the moon. If you want a drink, you must bring it with you. There is no atmosphere. You cannot breathe unless you bring your air with you. Nothing grows there. If you plant something, it won’t grow because it gets too hot in the sunshine and too cold in the shade. There is nothing to eat unless you bring it with you. There are no animals, not even insects. You cannot live there unless you bring everything you need with you. When everything you brought is used up, then you must go home. Such a place is a desert. The moon is a desert in space.
The nearby planet, Mars, also is a desert in space. Like the moon, if you want live there then you must take with you all the air, water and food that you will need. When everything you brought is 18 months before being used up, then you must go home. But now going home will take 18 months if you took with you enough air, water, food, and rocket power for the return trip. Mars is a desert in space, but much more remote than the moon and much more difficult to colonize. As difficult as the repair of planet, Earth, may be, it would be orders of magnitude easier than building a colony in space. Restore planet, Earth. There is no practical alternative.