Could lichen and moss survive on Mars? I will mainly use moss, because i like it better. I suppose they could, if they were provided ample amounts of oxygen. Using a system called MMOWS*, you could make small amounts of oxygen, and release it under it. I assume that the moss could trap the oxygen, and keep it alive. It would probably be one of the experiments carried on a manned mars mission. It could hypothetically be used as food, but I believe that wouldn't be the best idea, as some harmful chemicals from the soil might have leeched into it. You would also need to water it, but you could put that through the same oxygen supplying network.
Alternatively, they could be made chemosynthetic**, and dumped on some mineral deposit. This probably wouldn't work very well, as I believe that the lack of oxygen in the atmosphere would harm the plant. Being both photosynthetic and chemosynthetic could be beneficial though.
I am certainly not a expert on any of this, so please tell me if I am wrong.