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?
The Church of Jesus Christ of Latter-Day Saints mentions other worlds in their scripture.
There is an interesting article at the Center for Science and Culture website pertaining to Christians and their belief in extra-terrestrials.
Also, in her Christian Experiences and Teachings of Ellen G. White she wrote
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
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:
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."