It's a vexing question, mostly because it seems impossible to know the importance of the answer. Two years ago, Christian, Jewish and Muslim leaders told me the existence of extraterrestrials wouldn't contradict theological doctrine. Mormons and Seventh-day Adventists already believe aliens exist, though not the kind that tried to eat Sigourney Weaver. Scientology, on the other hand, is built upon scary space creatures.
From an article I wrote for The Sun (no longer available online):
The theological significance of extraterrestrial life has been debated for centuries. In the Middle Ages, as today, some argued that God could have created worlds better than ours; others maintained that Earth was the center of God's universe.
"Although it became heretical to deny that God could create other worlds, it was dangerous to claim he had,' Joseph L. Spradley, a physics and astronomy professor at Wheaton College in Wheaton, Ill., wrote in 1998 for a fellowship of Christian scientists.
The verdict from most Christians is still out. However, many theologians say, if God did create other worlds and other people, that would not contradict the biblical story of the sin of man being redeemed by the son of God.
"How God shares the story of creation and of love and of the ultimate hope for the restoration of all things in God's design, I think that can be worked out in many different ways,' said Philip A. Amerson, president of the Claremont School of Theology, a United Methodist seminary.
There could be different paths to God on different planets, Amerson said. Others accept a more traditional salvation model.
"Saint Paul would suggest to indicate, and it is just a hint, that if there is life on other planets, and these beings needed salvation or redemption, the death of Christ on planet Earth would be a sufficient price,' said the Rev. John Jefferson Davis, a Presbyterian and professor of theology at Gordon-Conwell Theological Seminary near Boston.
Another possibility is that extraterrestrials would not need atonement, Seventh-day Adventists believe. Because these beings would not have been borne of Adam and Eve, they would be perfectly moral beings incapable of sin.