What to look for? Where to look for? is the challenge for the knowledge seeker and same is the challenge for the one who is seeking alien life in the cosmic sea.
Life is like amino acids colliding for million years till the perfect combination happened though by an accident or by a careful sought pattern that recurred again and again till the right precision of life making amino acids was available.
So we get to the Philosophy defining either life is accidental or deliberate consideration of a creator or a mathematical outcome of existence out of many permutations and combinations.
Hence we have two ways to look at life, a pessimistic way that guarantees nothing more than a chance or an optimistic way that guarantees at least a working reason even if it is of a creator or of Mathematics. In the former case, life happened spontaneously while in the later case it was deliberations of the million years. In either case life is dear as when we win a lottery or a kudos for an achievement.
There is yet another way of looking at Philosophy as life having originated elsewhere in the universe and spread by an asteroid from planet to planet. This is the Philosophy that stays neutral as to the existence as could be seen in the religious preachings of various religions that deny accidental and deliberated reason to engender God as supreme being unlike humans and having origins elsewhere beyond the universe. The religion could never accept pessimist argument or optimistic argument though it engenders a creator as it believed life as existing on the earth is only temporary since the soul has place somewhere else in the universe or beyond the universe like the idea of limbo where souls are kept temporary. Hence religion equates the situation as life having originated through divine intervention from somewhere else.
So the next stage in the evolution of Philosophy is survival of the fittest. Thus Charles Darwin happens to hold his stance as opposing all the philosophical traditions and religions.