>Rare Earth theory is the most sensible answer to the ET question
I disagree only to the extent that INTELLIGENT Life is probably astronomically improbable to the point of being functionally impossible. Out of the billions and trillions of planets in our galaxy I wouldn't be alarmed if there was less than 10 sapient civilization building species.
I don't expect this to be the case at all with non-people Eukaryotes: Microbes, Bacteria, Plants, even Animals. With how versatile, persistent, and adaptive organic life is on Earth I would not at all be surprised that once we actually achieve the ability to meaningfully "look for, observe, and document space moss" that we'd be finding extraterrestrial organisms left and right.
>I think it's crazy to think that there aren't bacteria or fungi on some other planet somewhere in the solar system.
Everybody wants to say Mars or Europa, but my big guess is Venus.
I'd put money on there being something resembling plankton, or perhaps even algae, in Venus' dense, warm, chemical rich, atmosphere.