Hold up. Let's think this through. Tradition holds that Moses wrote the book of Genesis ca. 1600BC. Modern scholars hold that it was written between 1000BC and 500BC. Regardless of the date that these scholars attribute to the writing of the book, they agree that the oral tradition of the stories is much older and could very well be attributable to Moses in 1600BC.
Modern science as we know it, which starts to take shape in the 18th century, doesn't develop for at least 20 centuries after the writing of the story of creation and possibly over 30 centuries since the oral tradition began.
So, why are we trying to read the book of Genesis and the creation account as if it was an account of how things came to be according to modern scientific terms? Why do we equate scientific fact with truth, and everything else as fictional myth?
It's completely anachronistic to read the creation account with scientific eyes. That doesn't mean that it isn't true. But I digress.
What would it look like if we find life on Mars? It depends on the kind of life we find. What if we were to find intelligent life? It depends first on if we can communicate, and if we can, we have a lot of questions to ask. C.S. Lewis explores a lot of these ideas in his space trilogy, such as, if another intelligent race had never experienced a Fall, would they understand a lie?
We could say with some certainty, that if they hadn't experienced a fall, there would be no need for Baptism, as we know it. They would have no need for the forgiveness of original sin. If they didn't believe in God, surely we'd have the obligation of preaching our God, but how would the message change? There are so many hypotheticals to think about, which can be fun, that it is almost absurd to try.
The important thing to keep in mind is that life elsewhere does not discord with what we believe. If God's revelation is truth, and there is life elsewhere, all this means is that we know what 'truth' Genesis doesn't intend.