While I was watching Star Wars the other day, when they were on Tatooine, I got to thinking, would oxygen be able to exist in an abundance on such a planet?
From my understanding, Earth got its' oxygen through photosynthesis by plants and bacteria. So, would it be impossible for a planet like Tatooine, or Hoth, to form an oxygen atmosphere, to a level humans could breath?
On a similar note, the planet Bespin, the gas giant with Bespin, also seems to have a breathable atmosphere.