What might be the impact, if any, on philosophical theory or practice is we found life elsewhere in the universe?

Funny you should ask this: The philosopher Tim Mulgan just published a nice article exploring this question, particularly its ethical and meta-ethical implications. Here's Mulgan's piece: https://aeon.co/essays/how-the-discovery-of-extraterrestrial-life-would-change-morality

Existence is filled with happiness and suffering, but the amount of happiness and suffering is not guaranteed. Non-existence, on the other hand, has no happiness or suffering. Non-existence isn't good or bad, yet existence is labeled either good or bad. Why is it that existence must be labeled good or bad (or fulfilled/not fulfilled) with no middle ground, yet non-existence must remain neutral?

Here's one reason to think that not existing is neither good nor bad (this reasoning is due, roughly, to Epicurus): Non-existence is not a state of us -- it's not a state that one can be in. Moreover, it's not a state a person can experience or undergo. And if everything is good or bad for us only because of our experiencing it, non-existence can't be good or bad for us. But not everyone thinks that 'non-existence' is neutral in this way. For one, many of us fear death, suggesting that we think it would be bad for us to be in a state of non-existence. Why that should be is somewhat mysterious -- indeed, Epicurus issued the argument above in order to persuade us we shouldn't fear death. Another route to questioning the neutrality of non-existence runs like this: Some people are harmed by being brought into existence. (Imagine a person born into the worst possible life circumstances you can think of -- persistent and painful medical condition, poverty, parental neglect, etc.) If so, then it follows...