https://en.wikipedia.org/wiki/Hyperoxia
This was a screenshot I took months ago while watching a Geology Hub upload on YT. It was a lightbulb moment for my understanding of mass extinction events, (the largest was 250ma). I’ve referenced this multiple times, so thought I might share. Perhaps you find it as interesting as I do.
That also makes me wonder how we do our studies on other planets and if there is a category for “not habitable, but it could be”
Or similarly, “not habitable, but it could have been”. Subtle difference between the two.
We can just barely sometimes tell the difference between a small neptune, a large earth, an ocean planets, a coteless ocean planet, and a hycean planet. Trying to guage not just habitability but also terraformability is a ways off yet.
We can start with size and surface temperature though. We’re not going to survive on a gas giant, and anything with a four digit temperature is right out.