We don't know that, we have only one sure example of celestial bodies life, and an inhabitant of that world its reading this post. And yet another is typing it, wow! I don't mind speculation, in fact I love it, as long as we remember it IS speculation. Until we send a probe out to Europa, and dig around in that slush, we are not going to know anything.
A thing I don't like is rewriting or broadening the definition of word until it fits what you are trying to say. Picture this, a cat walks by, and your friend says "Hey look, a dog!" and you say "No, that is a cat." then your friend says "Well it is a dog, if we include in the definition of dog that some meow, and wag their tail when angry, and leave only one line of paw prints, then it's a dog!"

Yes, now it is a dog, at the expense of ruining the definition of dog.

__________________