When you land on a planet, the next one is generated. So there is no limit. There are 6 different looks to them which will repeat.
But, to be honest, once you have made one successful landing you have pretty much experienced the game. I wanted to make the surface stuff more fun, there were going to be enemies which you had to avoid and they would sometimes drop rocket fuel. This is my first 3d game though and I ran out of time. I defiantly want to do more jams though.