How could I describe alien landscape?

Science Fiction people call this world building. What color sun or suns does your planet have? How strong is the gravity on your planet. How hot or cold is your planet? Then think of the alien plants and animals that may be on your planet. You might want to read Orson Scott Card's book called How to Write Science Fiction and Fantasy.

We landed on Corvis III, which has two red suns in the sky. We had to keep our suits on because there is not enough oxygen in the atmosphere. Thankfully there was some liquid water and we were able to get samples.