This has been a good week for those searching for life beyond the earth. The BBC Science and Nature web page links to three separate new articles pointing in this direction. Salt deposits from dried up lakes have been found on Mars, suggesting that once, billions of years ago, there were lakes of salty water which could have supported life, and that traces of this could be found in the salt. Beneath the icy surface of Saturn’s moon Titan, according to new evidence, very likely still today there are oceans of liquid water, which could well support life as organic molecules are also present. And for the first time these organic molecules have been found on a planet outside our solar system; although this particular planet is too hot for life, this finding, combined with the recent discovery of a planet of similar size and temperature to our earth orbiting a distant star, suggests that there may be billions of planets in our galaxy capable of supporting life.
It is highly unlikely that any life on Mars or on Titan will be anything like the intelligent aliens we know of from science fiction. Large organisms simply could not survive on Mars today; indeed it seems unlikely that any life could. Much more likely, both there and deep inside Titan, would be something like bacteria.
As for planets in other solar systems, from a scientific point of view anything is possible. But people have been listening for radio messages from aliens for 50 years and have so far not heard anything suggesting intelligent beings out there.
Would the discovery of life on other planets be a threat to the Christian faith? Certainly it should not be. If God can create life on earth, whether through natural processes (as I believe) or by direct creation (as other Christians prefer to understand it), he certainly can do so in other places, and we have no reason to think that he has not done so.
If there are non-human intelligent beings out there, one might speculate, or conceivably in future be able to study, whether they are also self-aware and spiritual beings, whether they too have sinned, and whether they too need to be saved by the sacrificial death and resurrection of the Son of God. CS Lewis memorably speculated in his novels Out of the Silent Planet and Voyage to Venus (also known as Perelandra) about intelligent inhabitants of Mars and Venus living in an unfallen Garden of Eden kind of environment. Of course we can’t know, until and unless we make actual contact. But the possibility of this should not be any kind of threat to our faith.