Final Mission

Star Trek is, of course, science fiction. As such it is fiction, but the science should be correct. The captain and Wesley land on a planet that apparently has an atmosphere that contains sufficient oxygen to support human life. Free oxygen cannot exist in an atmosphere unless it is continuously replenished some how. The only known way to put elemental oxygen into an atmosphere is by photosynthesis. The planet they land on looks like Mars, a dry desert with no apparent life. Oxygen is a highly reactive substance. It will react with almost anything it comes in contact with. If photosynthesis ceased all the oxygen in the earth's atmosphere would be gone in a very short period of time. In fact, before photosynthetic organisms evolved, there was no free oxygen in the atmosphere. In order to make this episode believable they should have put some living things there that could produce oxygen by some mechanism. I agree with the other reviewers. This was not a well done or well constructed episode.