The Progenitors are an ancient race of almost infinite technological sophisitication, who mysteriously vanished millions of years ago for no good reason (I don't like TV Tropes, but you are welcome to google it).
In their myriad travels around the cosmos, they have taken a shine to creating new worlds. They are, of course, quite biased towards oxygen-having worlds suitable for human life. Photosynthesis works great, but supposing the progenitors wanted to seed a world with life that was dozens of AU from the sun (like Europa), shrouded in a hazy atmosphere (Venus), or both (Titan)?
What metabolic processes could the progenitors engineer into organisms in order to create an oxygen atmosphere and maintain it over time, where the energy source is not sunlight?
- This planet has an iron core, volcanic and tectonic activity, a rocky crust, and at least some oceans. None or all of these can be used to support your oxygen-making organisms.
- The focus is on the chemical reaction to produce oxygen, that will replace photosynthesis. Details of the creature itself (carbon based, silicon based, exotic, etc) are not so important.
- The creatures must stick around long enough to maintain the oxygen atmosphere for billions of years until humans come.
- 1 atm air pressure and 0.2 atm oxygen partial pressure are not required, but desired.