Alien Worlds is a Netflix Speculative Documentary aired on December 2, 2020. The miniseries describes life on four fictional alien planets, using the imagined creatures and ecosystems to describe concepts of ecology and evolution that also apply to life on Earth. The series consists of four episodes, which alternate between CGI segments depicting the alien lifeforms and live-action segments depicting terrestrial organisms and processes and interviews with a variety of experts in topics related to the episode's focus.
- "Atlas" describes the life of skyborne grazers on a high-gravity planet with a very dense atmosphere, and focuses on themes of sexual selection and generalization versus specialization.
- "Janus" describes a tidally locked planet home to five-legged alien animals, and focuses on themes of adaptability and life in extreme climates.
- "Eden" describes a lush but highly seasonal world whose twin stars and high atmospheric oxygen makes it ideal for life, and focuses on themes of predation and complex ecological relationships.
- "Terra" describes a hyper-advanced civilization fleeing its dying world, and focuses on themes of technological progress and contact between intelligent civilizations.
Not to be confused with Alien Planet, a film adaptation of Expedition, and with Extraterrestrial (2005), titled Alien Worlds in the UK, although both works focus on similar exobiological themes.
This series contains examples of the following tropes:
- Adaptive Ability: Downplayed. The pentapods breed by dispersing their eggs on the wind, and the version they grow into depends on what side of the planet they land on. Those that land on the sunlit side become well-adapted to the scorching desert, while those on the other side become adapted to the eternal night, allowing the species to dominate the planet Janus.
- Apocalypse How:
- A Class 4 — Planetary Scale, Biosphere Collapse — is implied to happen at the end of "Atlas" following a meteor impact compared to the end-Cretaceous mass extinction. The effects aren't shown, but the narration states that highly specialized animals like the skygrazers and their predators will be unable to cope with rapidly changing conditions and the loss of their food sources and will go extinct.
- A Class X 4 — Planetary Scale, Total Annihilation — is the approaching fate of Terra as its aging sun expands, dooming the planet to annihilation once it expands past its orbit.
- Binary Suns: Eden orbits two stars, a brighter yellow one and dimmer red one. This drastically increases the amount of sunlight it receives, fueling the planet's lush environments.
- Bizarre Alien Reproduction: The rabbit-like grazers on Eden are under too much danger from predators to be able to take the time to court, mate and give birth, so they instead release worm-like spawn that seek each other out, fuse into an embryo, and cover themselves in a tough cocoon. The cocoon then shoots out whip-like cords that attach themselves to trees and hoist it into the air, raising it beyond the reach of predators on the ground or in the tree branches and allowing the embryo to gestate in safety.
- Blob Monster: The surface of Atlas is home to boneless, blob-like scavengers that move by slowly rolling over the ground and feed by engulfing and dissolving organic matter.
- Brain in a Jar: The Terran aliens have developed past the point of needing physical bodies, instead existing as large networks of neural tissue within life-support tanks.
- Colony Drop: At the end of the Atlas segment, a large meteor compared to the Chicxulub bolide impacts the planet, and is implied to cause a mass extinction.
- Death from Above: The skygrazers' predators hunt by floating until they're above their prey and rapidly emptying their gas bladders, dropping like stones onto their unsuspecting targets.
- Descriptively-Named Species: Each of the aliens is only given a generic title that broadly describes what it is or what it does (resulting in two completely unrelated aliens being called "predators"). The skygrazers are aliens that graze... in the sky, the pentapods are aliens which have five feet, the spiny blob-like bottom-feeders are called scavengers, the grubs are grub-like aliens, and so on.
- Diverging Evolutionary Phases: The pentapods are aliens that live on a tidally-locked planet, with one side being perpetually cold and dark, the opposite side being hot and sunlit, and a thin band in-between of temperate perpetual twilight. The pentapods are able to change into forms suited to all three environments depending on where their drifting eggs land, allowing them to dominate the planet. Those on the dark side are woolly and stockily-built for conserving heat, those on the light side are spindly and have reflective skin for keeping cool, while the ones in the middle are colourful and have in-between proportions.
- Fantastic Fauna Counterpart: Eden's native animals closely resemble familiar Earth creatures whose niches they approximate — its skittish grazers are essentially rabbits with moth-like antennae instead of ears, while their arboreal predators resemble blue-furred, six-limbed tarsiers.
- Fantastic Flora:
- Atlas is home to large fields of plants resembling floating green balloons tethered to the ground by thin stalks.
- Eden is covered in forests of red-leaved trees, some of them simply recolored dragon's blood trees, interspersed with plants somewhat resembling large jellyfish on stalks.
- Festering Fungus: Eden is home to a species of fungi that have a complex parasitic and symbiotic relationship with the animals living there. The forest's primary grazers feed on the fungus, but during autumn this releases clouds of spores that infect the grazers and dull their fear responses. This allows their hunters to easily catch and eat them, but the spores still in the grazers' bodies quickly poison and kill them. After the predators die, the next crop of fungi grows from their bodies and the cycle begins again.
- Formula-Breaking Episode: The last episode doesn't feature an alien ecosystem like the other three, instead examining a highly advanced hive-mind race attempting to escape a dying world.
- Giant Flyer: The skygrazers are huge, whale-like organisms which graze on clouds of aeroplankton. Their existence is justified by the thicker atmosphere of Atlas being able to hold them up, but their size also means they can never land as adults, because they're too heavy to get airborne again.
- Heavyworlder: The first episode features a high-gravity world, known as Atlas, and the organisms which are adapted to its conditions. The higher gravity results in a denser atmosphere which can support a more complex aerial ecosystem than on Earth, but also draws in asteroids more easily...
- Hive Mind: The Terran aliens are distinct individuals, but remain in constant mental communication with one another in what the episode describes as a hive mind.
- Homeworld Evacuation: As Terra's sun comes closer and closer to swallowing it, its hyper-advanced natives terraform an outer-system planet and then move their habitation domes into orbit and onto vessels that move them to the new world. The narration states that the aging star will one day destroy the new world too, forcing the Terrans to evacuate again.
- Insectoid Aliens: The dominant species, Pentapods, of the Janus segment in particular are very arthropod-like, but the ballooning predators of Atlas and the prey grazers of Eden also have some arthropod-like features.
- Killer Space Monkey: The primary predators in the Eden segment are aggressive, tarsier-like creatures that prey on the smaller grazing animals.
- Living Gasbag: The skygrazers' predators raise themselves into the sky by using symbiotic microorganisms to inflate large sacs in their abdomens, allowing them to float like balloons until they're high enough to ambush skygrazers flying below them.
- Mix-and-Match Critters: Some of the aliens strongly resemble a mix of Earth animals.
- The skygrazers of Atlas resemble a cross between a manta ray and a whale shark but with pink skin. They even lay eggs identical to those of horned sharks.
- The desert grubs of Janus resemble a four-legged cross between pillbugs and ants, complete with venom and swarming habits.
- The predators of Eden resemble blue-furred primates, but with the elastic feeding arms of a cuttlefish. Their prey resemble a cross between a rabbit and a moth.
- Multi-Armed and Dangerous: The monkey-like predators on Eden possess a second pair of clawed arms they mostly keep folded against their chests, but which they can extend to increase their reach and snag elusive prey.
- Non-Indicative Name: The blob-like animals in "Atlas" are referred to as scavengers, but are never shown doing so — instead, their primary appearance shown them actively preying on living animals.
- Paradise Planet: Eden is a planet ideal for life, warmed by a pair of binary stars that foster the growth of lush forests that in turn fill the air with oxygen, allowing for the existence of extremely varied and energetic animal life. However, this also makes Eden a dangerous place, as this riotous growth of living beings means that its forests are also filled with deadly predators and parasites.
- The Place: Each episode is named after the planet it takes place on.
- Puppeteer Parasite: The prey species featured in "Eden" are the first-stage host of a fungus-like flora (clearly based strongly on Cordyceps) that after infecting them causes them to become Fearless Fools that are sitting ducks for their predators. The predators which eat the infected prey are themselves infected and killed by the fungus.
- Religious and Mythological Theme Naming: Each of the four alien planets is named after a being or place from real-life religion that reflects its nature and conditions. Atlas, a high-gravity super-Earth home to a complex airborne biota, is named after the titan who held up the vault of the sky; Janus, a tidally locked world divided between a scorched daylit side and a freezing night side, is named after the Roman two-faced god; Eden, a lush world filled with diverse life, is named after the garden where life began in the Abrahamic scriptures; and Terra, a world home to a highly advanced alien race used to model humanity's own future, is named after the Roman goddess of and word for the Earth itself.
- Speculative Biology: The series alternates between describing real-life processes and events in the natural world, such as sexual selection, hunting behaviors and mass extinctions, and attempts to use this knowledge to model imagined alien ecosystems and describing the ecologies and life cycles of alien organisms.
- Terraform: In order to escape their homeworld's imminent destruction, the Terrans decide to settle on a safer, outer-system world. However, their prospective planet is frozen over and has no atmosphere, a problem that they resolve by sending robots and automated systems to thaw out the ice, produce an atmosphere, and make the planet habitable before they move in.Rather than adapting to a different world, they have created a copy of their old world. Such are the benefits of an advanced civilization.
- The Theme Park Version: The alien worlds in question are used as tools to explain biological and ecological processes that occur on Earth (and would, theoretically, also occur for life across the universe), but broadly simplify the vast complexities that make up a real biosphere into something easily digestible and entertaining for general audiences, hence why each episode only focuses on two or three faunal species despite covering entire planets.
- Tidally Locked Planet: Janus closely orbits a red dwarf, and the star's gravity thus has a strong hold on the planet and keeps one side of it always facing the star. Janus's day side is thus a parched, torrid desert, and its night side a frozen wasteland. Between the two is a thin temperate strip scoured by endless winds blowing between the two extremes. The planet's native pentapods mostly live in the twilight area, where they use the canyons carved by meltwater rivers flowing from the night side to shelter from the high winds.
- Transhuman: The Terrans are transaliens, technically, but the themes are otherwise the same. They are an incredibly ancient, incredibly advanced civilization, and have developed to the point where each Terran is essentially a giant, diffuse brain in a life-support vat and connected to all other Terrans in a Hive Mind. They do not age and do not die, and possess the technology necessary to create strong AI, terraform other worlds and move their entire civilization from one planet to the next.
- Zerg Rush: The day side of Janus is home to small, insect-like creatures that can overwhelm the much larger and stronger pentapods by attacking them in large swarms, which can quickly overwhelm and cover the larger creatures.
