In the science fiction novel and movie The Martian, a stranded astronaut survives more than 500 days on Mars by growing potatoes. A permanent human settlement on Mars would need to do much better. And according to a computer model created by planetary scientists, that’s actually an attainable goal. With the right food sources, we could grow a million-person population on Mars that doesn’t depend on food shipped from Earth in about a hundred years, a recent paper in the journal New Space reports.