How come there is oxygen on Terminus? (Foundation: Isaac Asimov / Apple TV Series)

Question

The planet is supposedly a frozen rock with little to no biosphere. There don't seem to be any trees or other plants capable of photosynthesis.

Answer 1

In the original novels it's made clear that Terminus' biosphere was life-bearing at the time of its discovery. The bulk of the atmospheric oxygen apparently comes from the oceans.

“Of course. Sayshell Planet was an oxygen world when the first settlers arrived, so it had to be life-bearing. And we have preserved some of the indigenous life, you may be sure. We have quite extensive natural parks in which both the flora and the fauna of Old Sayshell survive.”

Pelorat said sadly, “There you are in advance of us, S.Q. There was little land life on Terminus when human beings arrived and I’m afraid that for a long time no concerted effort was made to preserve the sea life, which had produced the oxygen that made Terminus habitable. Terminus has an ecology now that is purely Galactic in nature.”

_{^{Foundation's Edge}}

And

×When Terminus was first occupied by human beings in the days of the Encyclopedists, the highest form of plant life it produced was a moss-like growth on rocks; the highest forms of animal life were small coral-like growths in the ocean and insectlike flying organisms on land. We just about wiped them out and stocked sea and land with fish and rabbits and goats and grass and grain and trees and so on. We have nothing left of the indigenous life, except for what exists in zoos and aquaria.”

In the show we see that there is a fair bit of life when they arrive, including small bushes and grasses.