If we accept the Bible's account of creation, the discovery of alien life would be, for Christians, an extension of God's creation. There is no mention of extraterrestrial life in the Bible, but neither does the Bible rule out the possibility of life on other planets. There are a few problems that arise when we think of aliens being part of God's creation. Three of the main issues are the problem of redemption, the problem of God's image, and the problem of demonic activity.
Would proof that aliens exist impact the Christian faith?
First, there is the problem of redemption. To begin with, would an otherworldly, advanced sentient life form be sinful and in need of redemption as are humans? Assuming they, like humans, do need redemption, would Jesus still be their way of salvation? Some people link this question specifically to blood. Since Jesus' blood, shed for us on the cross, is the basis of human redemption, and human life is in the blood (Leviticus 17:11), would alien life forms be saved the same way? If Jesus Christ is the only way, truth, and life (John 14:6) and the aliens, for example, were silicon-based, or even had copper-based blood instead of iron-based blood like ours, would the redemption of Jesus still hold true for those species? It seems logical to assume that since God is all-powerful, He would be able to save aliens by some other means. This takes us to the very basic question: what is salvation? The gospel is "the power of God for salvation to everyone who believes" (Romans 1:16). Wouldn't this extend to other life-forms? Is salvation based in human physiology, or in God's power? When Jesus said that He was the way, the truth, and the life, was He referring only to His blood, or to the fact that He was able, because He is God, to take our sins on Himself and by His power, save us? If aliens were found to be imperfect, and sinful (whatever that might mean for their race), would they not be able to depend upon Christ's perfection and mercy, just as humans do?
Second, there is the problem of God's image. Humans are made "in the image of God" (Genesis 1:27). Since God has no physical form, this is taken to mean that we have spiritual characteristics like His—an understanding of morality, a need for relationships, a rational mind. What if aliens did not display these characteristics? Would they still be, in some sense, in God's image? And if they were not, what would that mean about their salvation? There's no way to know.
Finally, there is the problem of demonic activity. Reports of alien encounters bear many similarities to descriptions of demons from the Bible. They are often described as "extra-dimensional" and also as deceptive and evil. People who have these experiences almost exclusively report frightening rather than positive feelings. Furthermore, it is well-documented that these supposed alien encounters can be stopped by calling out to Jesus Christ for help.
All things taken into consideration, if true aliens (beings that God created to live on other planets) do exist, it will not have much bearing on Christianity. If God has created other beings like those of Earth, all relevant information about their salvation or their relationship with their Creator will either stay within their culture, undiscovered by humans, or it will be revealed to us on a need-to-know basis.
Are aliens and UFOs real?
What is the significance of the blood of Christ?
What are demons according to the Bible?
Did God create the universe?
Is creationism scientific?
Truth about Everything Else