Well, you haven't used the holy word and you have added some new ideas.
Consider developing the setting and graphics: maybe huge space centres and huge, enclosed colony cities?
Maybe a central space centre has some mega-defense laser beam that can destroy asteroids, and maybe even planets?
The objective could be to take control of the laser before invading aliens do, or politicians

But most of all, I agree to ditching the rivers and settling for craters-most players would find it too far fetched. Unless you have an intro about the setting being a long time in the future when mankind has created an atmosphere and water cycle on the moon?.
Maybe it could be another planet on the far side of the galaxy?