Organic creatures need a planetary surface environment on which life could emerge and evolve. But if post-humans make the transition to fully inorganic intelligence, they won’t need an atmosphere. They may even prefer zero-gravity, especially for constructing massive artifacts. It’s in deep space that non-biological brains may develop powers that humans can’t even imagine.
There are chemical and metabolic limits to the size and processing power of organic brains. Maybe we are close to these limits already. But no such limits apply to or constrain electronic computers (still less, perhaps, quantum computers). So, by any definition of “thinking,” the amount and intensity that can be achieved by organic human-type brains will be swamped by the cerebrations of AI.
We are perhaps near the end of Darwinian evolution, but technological evolution of intelligent beings is only just beginning. It may happen fastest away from Earth—we wouldn’t expect (and certainly wouldn’t wish for) such rapid changes in humanity here on the Earth, though our survival may depend on ensuring the AI on Earth remains “benevolent.”
It is entirely likely that whatever is visiting, is inorganic, and is a technology that evolved itself from organic beings.