Or life that doesn’t form on conditions like Earth. Earth life is best suited for the temperature and components of Earth, but organic molecules could form from other base elements under wildly different conditions. The plastics we make, for instance polymer chains, are similar in a lot of ways to organic chains. It’s been speculated that some kinds of life could form in temperatures way outside any conditions on Earth, or using chemicals completely toxic to Earth life, like ammonia. Imagine that! What if we finally meet another civilization, and we’re just outright toxic to each other. What if we couldn’t even be near each other?
I think popular science fiction is too conservative when it imagines alien life. It almost imagines alien life as being something like an undiscovered human race color. This is understandable because it’s within our experience. I mean, as humans, we have in the past explored strange new places and found new colors of other humans there. We almost expect to find the same thing outside our planet. Plus, it’s easier for us to empathize with human-like characters. We’ve never explored a strange new place and found a silicone based life that looks like nothing more than a rock and experiences itself in the orders of eons instead of years, or a life form made of ammonia that lives on the freezing surface of “cloud continents” on a gas giant. Or a creature that would die without radiation from its star that would be deadly to us.”