We already know there are some extreme environments with ancient life! The Movile cave [1] has been sealed off from the atmosphere for 5.5 million years, and i

We already know there are some extreme environments with ancient life! The Movile cave [1] has been sealed off from the atmosphere for 5.5 million years, and it's filled with very unique creatures. They survive off of chemosynthesis, rather than photosynthesis. It's an extremely low-oxygen environment! [1]https://en.wikipedia.org/wiki/Movile_Cave https://en.wikipedia.org/wiki/Movile_Cave