system
Given the following post, respond as if you're commenting on Reddit:
human
Is there any type of plant, fungus, or anything that we could send to Mars that could potentially survive?
gpt
Well, one thing is for certain, it would have to be some kind of photosynthetic organism. There simply isn't anything else to eat up there.

It would also require a rigid cell wall, as is found in plants and bacteria, due to the low pressure of mars's atmosphere, which would cause the cells to burst if it didn't have such an adaptation.

There is a species of moss that grows on mount everest, at 6500m up.

The temperature there in the winter is around -35C.
If this moss were to survive on mars, it would have to deal with temperatures between +20C and -73C. Of these, the more dangerous is probably the +20C, since it's a good 40 degrees C higher than it has to deal with on everest, but it's still possible.

Pressure would be another issue and of all species on earth, this moss exists at the lowest pressure, approximately 33% of what it is at sea level. However, we'd be asking it to deal with a pressure that's only 0.6% of what it is at sea level, 1/55th of what it's used to. 

And since it's above the cloud layer, it's used to dealing with higher doses of radiation, which mars's atmosphere would let through, though it's possible it still wouldn't be high enough.

As AirWalker mentioned, Tardigrades are an extraordinarily resilient group and are nearly indestructable, having been shown to be able to survive at nearly absolute zero, to over 150C and in the vacuum of space for days. 

It may be a long shot, but those two species together might just stand a chance, assuming there was enough sunlight, carbon dioxide and water for the moss to survive and give food to the tardigrade.