The future lifespan of Earth’s oxygenated atmosphere

Life on Earth already survived one transition from an anoxic environment to an oxygen-rich environment, I see no reason to expect that it could not make the transition back to an anoxic environment. Granted it may not look anything like the life we're accustomed to today, but I suspect life will exist on Earth in some way, shape, or form for a long time to come.

A planet spanning civilization on Mars is less likely. However, there are still ways it could be found, depending on how long ago it was. I list three ways below, and suspect there are more.

First, there is the possibility of a civilization dying and evidence being erased by tectonic plate recycling. Mars is approximately 4.6 billion years old. We know it has volcanic activity, and most consider it to have inactive tectonics now. Some scientists believe it could have had significant activity in the past, based on the 3 distinct regions of Mars. Earth's tectonic plates vary in their rates of recycling: the oldest non-oceanic tectonic plate is 3.6 billion years old, and shows no sign of recycling. Oceanic plates recycle on the average of every 180 million years though.

Second, there is the possibility of technology that didn't leave a visible trace. This is not supported by any evidence and is mere conjecture. If the society tore down non-organic structures and converted to using all biodegradable/organic materials then evidence of the society would be scarce, if existent at all, especially if bodies were cremated as many do today. Chemical analysis could detect this I suspect, or more importantly prove it wrong.

Last, if for some reason civilization evolved underground and stayed underground, then there wouldn't be any visible evidence above ground. This is also pure conjecture. Micro-robots that explore Mars' caves might find something, as might ground penetrating radar.

It would not surprise me if civilizations evolved in the same way life did on Earth.

Life evolved in the sea. At some point life evolved to leave the sea and go to land, whether the sea was no longer hospitable enough, or in search of better food. Life continued to evolve on Land, specializing into different groups and colonizing different lands.

Perhaps civilizations evolve on their planet, then at some point they leave their planet and go into space (when their planet is no longer hospitable or they need more/better food). Finally, while in space they evolve more, founding different colonies that evolve differently due to culture and environmental differences.

I find articles like this rich. We don't even know by what mechanism the medication I take every day works, yet people think they can confidently postulate on far distant and far future events with any kind of certainty.

> Earth will not host complex plants in 600 million years. So that’s also a problem - https://en.m.wikipedia.org/wiki/Timeline_of_the_far_future

If I'm reading that right, that's only C3 plants. C4 plants would keep going until 800–900 million years. And who knows if something else doesn't evolve or is engineered for the different conditions.