The recent discovery of an Earth-like planet caused me to wonder: do any Christian denominations have official doctrine regarding humans on other planets? If so, what is the doctrine?
Related: Does the Bible make any allusions to life on other planets?
The Church of Jesus Christ of Latter-Day Saints mentions other worlds in their scripture.
Doctrine and Covenants 76:23-24
23 For we saw him [Jesus], even on the right hand of God; and we heard the voice bearing record that he is the Only Begotten of the Father—
24 That by him, and through him, and of him, the worlds are and were created, and the inhabitants thereof are begotten sons and daughters unto God.
31 And behold, the glory of the Lord was upon Moses, so that Moses stood in the presence of God, and talked with him face to face. And the Lord God said unto Moses: For mine own purpose have I made these things. Here is wisdom and it remaineth in me.
32 And by the word of my power, have I created them, which is mine Only Begotten Son, who is full of grace and truth.
33 And worlds without number have I created; and I also created them for mine own purpose; and by the Son I created them, which is mine Only Begotten.
34 And the first man of all men have I called Adam, which is many.
35 But only an account of this earth, and the inhabitants thereof, give I unto you. For behold, there are many worlds that have passed away by the word of my power. And there are many that now stand, and innumerable are they unto man; but all things are numbered unto me, for they are mine and I know them.
There is an interesting article at the Center for Science and Culture website pertaining to Christians and their belief in extra-terrestrials.
Notably, Seventh Day Adventists founder Ellen White believed in aliens. She taught that there are unfallen people living on other planets. She wrote about one vision she had of Jupiter:
"the inhabitants [of Jupiter] are a tall, majestic people, so unlike the inhabitants of earth. Sin has never entered here."
Also, in her Christian Experiences and Teachings of Ellen G. White she wrote
The Lord has given me a view of other worlds...The inhabitants of the place were of all sizes; they were noble, majestic, and lovely.
While not exactly official doctrine, Emanuel Swedenborg (1688-1772), whose Christian doctrines and Bible interpretations are accepted in the various "New Church" or "Swedenborgian" denominations, published a book about life on other planets in Latin, London, 1758:
Latin title: De Telluribus in Mundo Nostro Solari, Quae Vocantur Planetae, et de Telluribus in Coelo Astrifero, deque Illarum Incolis, Tum de Spiritibus et Angelis Ibi: Ex Auditis et Visis
English translation: Planets or Worlds in Our Solar System, and Worlds in the Starry Heavens, and Their Inhabitants, As Well as the Spirits and Angels There: Drawn from Things Heard and Seen
Traditional English short titles: Earths in the Universe, The Worlds in Space
In this book, Swedenborg extracts and edits from his earlier massive work Arcana Coelestia ("Secrets of Heaven") descriptions of human races living on all of the then-known planets in our solar system: Mercury, Venus, Mars, Jupiter, Saturn, and Earth's moon. He also describes human races living on five planets in other solar systems. (His original version in Arcana Coelestia describes six races from planets outside our solar system.)
This book is one of the more unusual ones in the corpus of Swedenborg's theological writings. For two centuries after it was published, Swedenborgians believed quite simply in Swedenborg's statement that:
Anyone who believes, as each one of us should, that the Deity's sole purpose in creating the universe was to bring into existence the human race, and from this to people heaven—the human race being the seed-bed of heaven—must inevitably believe that, where there is a world, there must be human beings. (The Worlds in Space #3)
In short, the members of the New Church (Swedenborgian) denominations generally believed that every planet in our solar system and in the universe was inhabited by human life of various races originating on those planets.
Of course, this belief was thrown into confusion when the United States sent astronauts to the moon in 1969, and found a barren, airless world incapable of supporting life.
Since then, various theories have been floated by Swedenborgians to account for the uninhabitability of the other planets in our solar system compared to Swedenborg's confident descriptions of human races living on those planets, complete with lush ecosystems containing their own variations of the plants and animals that live on earth.
Especially as a result of modern scientific findings about the uninhabitability of the other planets in our solar systems, the various Swedenborgian denominations generally do not take any official stance affirming that the particular planets Swedenborg identified as inhabited in our solar system actually are inhabited. Due to Swedenborg's own status as an accomplished scientist before he began his theological work later in life, and his statements that science and religion are in harmony rather than in conflict, Swedenborgians have a great respect for science, and have generally accepted the advances in scientific knowledge made over the centuries since Swedenborg's theological works were published.
However, due to the influence of Swedenborg's Earths in the Universe, the members of the various Swedenborgian denominations do commonly believe that there are many planets in the universe that are inhabited by human-like races, and that the people who inhabit these planets also have immortal souls that live eternally in heaven (or in hell) after their lives in the physical world are over.
For a two-part article by a Swedenborgian scholar updating Swedenborg's science and reconciling his views of life on other planets with more current scientific theories, see:
For my own assessment of Swedenborg's Earths in the Universe in light of modern scientific views of astronomy, cosmology, and planetary science, see: "Aliens vs. Advent: Swedenborg's 1758 Book on Extraterrestrial Life."
