In 1610, Galileo wrote in Sidereus Nuncius (The Starry Messenger) about the similarities between the Moon and Earth that he spied through his telescope, setting the stage for the possibility, and likelihood, of lunar life: “Thus, if anyone wanted to resuscitate the old opinion of the Pythagoreans that the Moon is, as it were, another Earth, its brighter part would represent the land surface while its darker part would more appropriately represent the water surface.”
As far back as ancient Greece, Democritus, a Greek philosopher who wrote extensively on the cosmos and contributed the word “atoms” to science, speculated that space was populated with habitable worlds.
It was likely H.G. Wells’s 1898 The War of the Worlds, a novel depicting a Martian invasion of Earth, that ignited our collective imagination—and fear—about alien life. But Wells wasn’t the first in the 19th century to chronicle a fictional alien encounter. That credit might go to a Belgian author Joseph Henri Honoré Boex (pen name J. H. Rosny Aîné—“aîné” means elder, he had a coauthor younger brother with the same pen name), who, in 1887 penned a novella, Les Xipéhuz, about a battle between neolithic nomadic tribes and a geometric, nonorganic alien life form.
Wells probably based his novel on then-popular speculation that Mars was lined with canals, a theory that grew from dark lines on the planet’s surface first spied by Italian astronomer Giovanni Schiaparelli in 1877. Percival Lowell, a British astronomer, proposed that the dark lines were actually canals possibly built by an intelligent civilization. Such speculation set in motion the outsized influence our solar system’s red planet has had on our wild and colorful theories about extraterrestrial life.
In 1926, Hugo Gernsback—after which the coveted Hugo Awards were named—launched America’s first science fiction magazine, Amazing Stories, which featured, among other topics, tales and images of such alien life. At the time, science fiction was not yet a thing. The budding genre, which blurred the lines between fiction and fact, was known as scientifiction.
In the 1960s, NASA launched a program devoted to the search for extraterrestrial intelligence—SETI. While the program was canceled in 1993, various alien-life research initiatives continue, including NASA’s own search for habitable worlds.
1906: War of the Worlds by H.G. Wells, originally published in 1898
Illustration by Henrique Alvim Correa for the French 1906 edition of H.G. Wells War of the Worlds. Martian Fighting Machine in the Thames Valley.
On the eve of Halloween, 1938, Orson Welles, broadcast a “news bulletin” based on H.G. Wells’s 1898 novel, The War of the Worlds. But he didn’t let on that his news bulletin, which described a Martian invasion of New Jersey, was fake, which rattled listeners and caused some hysteria.
1929: “The Moon is Made of Cinders”
In 1929, the 100-inch Hooker Telescope at Mount Wilson Observatory in California was the largest in the world, and the best way to glimpse distant worlds and galaxies. Photos of the lunar surface taken with the 100-inch Hooker Telescope were detailed enough to reveal topographical relief, such as the rims and valleys of craters, but not detailed enough to capture possible lifeforms, especially lunar crustaceans.
It’s no surprise that science writers and science fiction writers alike were able to credibly speculate about such lunar life. Popular Science contributing writer Thomas Elway made a compelling case in 1929 for the possibility of alien life on the moon in the form of lunar crabs, with hard outer shells to “prevent loss of bodily fluids into airless space” and “eyes which could turn sunlight into food.”
1930: “Do Beavers Rule On Mars?”
In a 1930 story that may have crossed the line between science and fiction, Popular Science contributing writer Thomas Elway (of lunar crab fame) makes the case for giant beavers as the dominant Martian lifeform: “Now, there is one creature on earth for the development of whose counterpart the supposed Martian conditions would be ideal. That animal is the beaver. It is either land-living or water-living. It has a fur coat to protect it from the 100 degrees below zero of the Martian night.”
To be fair, the best real-world images of Mars looked like blurry marbles as seen in these pictures taken by the 100-inch Hooker Telescope at the Mount Wilson Observatory in California. With only these images to work with, it left plenty of room for the imagination.
1934: “A Martian Odyssey” by Stanley G. Weinbaum
Originally published in Wonder Stories, Weinbaum’s short story, set in the early 21st century (roughly now), depicts Martians as bird-like creatures. Of course, canals figure prominently in Weinbaum’s Martian terrain.
1950s: Gray Aliens
Probably the most common alien form associated with human abductions, gray aliens are known for their lanky humanoid forms, bulbous eyes, and large craniums. Whether these visions arose from the 1947 Roswell UFO incident, or have other origins, they’re definitely not considered friendly. This particular variant of an alien persisted over decades of science fiction, more recently in such works as The X-Files, Stargate, and countless other television shows and films.
1968: Monoliths (Arthur C. Clarke, 2001: A Space Odyssey)
In Clarke’s science fiction classic, aliens are so much more advanced than humans that they control and manipulate energy at will. While they are not aliens, the iconic monoliths in Stanley Kubrick’s 2001: A Space Odyssey are machines the aliens use to manipulate human evolution.
1979: Xenomorphs (Alien)
Extraterrestrial life took a distinct turn toward horror with Ridley Scott’s (director) 1979 film Alien. Artist H. R. Giger created the terrifying species, known as Xenomorphs, a parasite who survives by preying on other species—like humans.
Whether we humans will survive as a civilization long enough to meet intelligent extraterrestrial life, these highlights taken from the earlier parts of last century showcase our delight in imagining what cosmic visitors might look like.