“I don’t remember seeing a lake or oasis on Tatooine, and maybe I missed it but it seems like an awfully dry place for people to live and it wasn’t clear to me if they were growing crops,” says Andrew Johnston, a geoscience researcher at the National Air and Space Museum. “And where were the crops and how were they irrigating them?”

Johnston says moisture-farming situations are certainly possible; they’re used in the Atacama Desert in South America, for instance. But to sustain a population of Jawas, Tuskens, farm boys, and bounty hunters, the planet would need some bodies of water. Otherwise it would be harsh, unforgiving, and all but lifeless.

We even have an example of it in our solar system, albeit one that’s a little colder than Tatooine. “Mars is largely a desert world, but having an all desert world that has creatures that have grown up there and walk around is somewhat unusual,” Johnston says. (And anyone who has read The Martian knows Mars isn’t exactly an easy place to survive.)