Extremophile Lifeforms

Archer: We've beamed a Tholian into decon. Modify the atmosphere in there.
Phlox: It may take a moment; Tholians have rather extreme life-support requirements. Increasing temperature to 480 Kelvin...

— Star Trek: Enterprise, "In a Mirror, Darkly"

When our present-day astronomers think about life on other planets, a term that gets thrown around a lot is the "Goldilocks Zone", the range of distances from the parent star where a planet could have liquid water. This is the only range of temperatures where life as we know it can exist. The only life-bearing planet we know of is in Sol's Goldilocks Zone, and all life on it requires water. However, even on our planet, life-forms are able to survive well below 0°C and well above 100°C (i.e. outside the liquid range of water at earth's standard atmospheric pressure) and in all manner of other extreme conditions, as per the "real life" section of this page.

Some alien life in fiction, however, does not roll that way. These lifeforms live in glowing-hot worlds with molten metal in their veins, or on icy ones with liquid helium metabolisms. They often have vastly different dietary needs, such as rock or metal. The planets they live on are generally Single Biome Planets by our standards, although they may be lush and varied to local eyes, and their inhabitants may seem like Elemental Embodiments. They're likely to be Starfish Aliens due to the radically different environment, though they can take more recognizable forms.

Compare to Silicon-Based Life, with which it often overlaps. Also compare to a Thermal Dissident, who wants it colder or hotter than normal but not necessarily needs it to be. Contrast Energy Beings, who can presumably survive anywhere, but whose environmental preferences tend to be simply ignored.

---

Examples:

Anime and Manga

• Neon Genesis Evangelion has the 8th angel, Sandalphon, which looks like an Anomalocaris. It was discovered in a volcano in embryonic form, and later ages rapidly to a subadult form, it was shown to be completely unaffected by lava both internally and externally, and was able to swim through it as if it were water.

Comic Books

• Planet Hulk: The spikes are a race resembling the symbiotes, who naturally float in the vacuum of space and feed off cosmic radiation. They're usually peaceful, but become starved and aggressive in terrestrial atmospheres and become parasite zombies.
• Batman: After a lab accident, Mr. Freeze became incapable of surviving at normal temperatures, and wears a special suit to keep himself constantly refrigerated, except for his eyes, which he must keep warm with special glasses.

Literature

• Alien in a Small Town: The Jan are silicon/carbon lifeforms native to a frigid planet with a very thin atmosphere, where they drink liquid oxygen the way we drink water. They find Earth's heat and air pressure painfully uncomfortable, and water is toxic to them. Given their preference when visiting Earth, they hang around in the polar regions. The tropics would kill them. Their life-support gear condenses Earth's atmospheric oxygen into a liquid for them.
• Animorphs: The Venber melt in above-zero temperatures. They nearly went extinct when it turned out the resulting liquid had many useful properties.
• Ben Bova:
  • Jupiter and Leviathans of Jupiter feature the Leviathans, immense Starfish Aliens living in a layer of liquid water deep within Jupiter. This layer is under intense pressure, far greater than even the deepest oceans of Earth, and is also extremely hot - just getting far down enough to see the Leviathans, let alone interact with them, requires an incredibly durable submersible.
  • Venus ends with the revelation that such a life form exists on Venus' blisteringly hot surface. It gathers food (such as metal deposits) from the surface with snakelike tendrils, while the bulk of the organism lies underground where it's even hotter. The alien has no need for water and consists primarily of a sulfur-based body under a silicone "skin".
• "Buy Jupiter", a short story by Isaac Asimov, describes a race of aliens that lives inside O-class stars. The Sun is too cold for them.
• Camelot 30K: The keracks live on a Pluto-like Kuiper Belt object with a surface temperature of 30 Kelvin and only a near-vacuum hydrogen atmosphere. They use oxygen difluoride as a solvent rather than water, and even then they have to use uranium to keep their bodies warm and pressurized.
• "Call Me Joe", a 1957 novellete by Poul Anderson, features a paraplegic who explores the frigid surface of Jupiter via a remote-controlled, centaur-like artificial body that's designed to drink methane and craft tools out of water ice. He encounters hostile wildlife which evolved there, and therefore is also adapted to such conditions.
• The Chronicles of Narnia: There's a deep subterranean land called Bism, which is very hot and features such wonders as fire salamanders and fresh gems full of delicious juice. When the characters encounter some of Bism's natives in a shallower layer of the underworld, these find it far too cold, its rocks too dead, and the endless abyss of the sky far too close for comfort.
• Terry Pratchett:
  • The Dark Side of the Sun: The Creapi's homeworld saw them evolve in molten phosphorous sulphides. When they spread into space, they simply redesigned themselves to fit the changing situations they encountered. Half a million years of forced evolution has created the middle-degree Creaps, who are happy at a mere 500 degrees C. The divergent High-Degree Creapii live on the outer surfaces of relatively cool stars. Wherever a star pushes the ambient temperature to beyond the melting point of tin, there you will find Creapii. In fact, they bartered with the human race, who were happy to sign over squatters' rights to the planet Mercury in exchange for Creap technology. To interact with humans they wear "spacesuits" that preserve life at habitable temperatures in what to them is a freezingly sub-zero hostile environment.
  • Discworld:
    • Trolls are living rocks whose brains are impure silicon, meaning they're slow and stupid under the snowline and extremely intelligent in the cold. However, they're still susceptible to freezing to death — their cold tolerance is much higher than a human's, but it still has its own limits.
    • Golems are made of clay, so they're resistant to a lot of things like lightning (allowing them to be atheists when Discworld gods are trigger-happy with the Bolt of Divine Retribution), heat (they can walk through fire and hold liquid metal), cold, and extreme pressure (one was buried on the ocean floor for centuries). As we find out in Going Postal, they can't take extreme heat and cold at the same time.
• Downward to the Earth: Some of Belzagor's native life is adapted for life in boiling hot pools. They would freeze to death in regular water, and tends to mutate and evolve quickly due to the strain placed by their home conditions on the DNA molecules in their bodies.
• Dragon's Egg: The Cheela live on a neutron star. The gravitational pull on its surface is 67 billion times that of Earth, and the temperature is hotter than the Sun.
• The rocktopi from Scott Sigler's EarthCore require oxygen and water just like terrestrial animals, but they do best in temperatures of around 200 degrees Fahrenheit. Thus, the only place on Earth they can live is deep underground, at a depth of about three miles. They can survive on the surface if necessary, but they can't live there full-time.
• Honor Harrington: The population of Grayson developed resistance to heavy metals poisoning, enabling them to survive on this planet, although with shortened lifespans.
• Iceworld by Hal Clement: Ken's species come from a planet even hotter than Mercury, where the air is gaseous sulfur and the oceans are molten zinc, and they have to make a crater into a giant parabolic mirror in order to keep their base warm on Mercury. Their researchers are amazed to discover life on a newly-discovered system's third planet, which is so cold the liquid medium is hydrogen oxide.
• Janitors of the Post-Apocalypse: The Nusurans are based around tardigrades. They take naked spacewalks for fun, and are the only species in the setting harder to kill than cured humans.
• Kir Bulychev:
  • Alice, Girl from the Future: An airless chasm on an asteroid converted into a Generation Ship is inhabited by "ice dragons" — octopus like creature possibly inspired by the Lucky Starr example. There are also sapient species fitting it — for example, a hotel on one planet was described as too hot to touch despite a thousand layers of insulation.
  • Bulychev also has a short story about a man who fell in love with a female alien — she looks like a human female, and a beautiful one, but her biochemistry is based on ammonia rather than water.
• Outsiders from Known Space are vacuum breathers with a metabolism based on liquid helium, and the series also occasionally features amoeboids with superfluid helium liquid media.
• The Laundry Files speaks of the Chthonians, codenamed DEEP SEVEN, who live in the upper regions of Earth's mantle.
• Lensman: The Palainians aren't comfortable any closer to Sol than Pluto, and their biology extends into the fourth dimension to accommodate this extreme. There are several other species like this, collectively called "frigid-blooded poison-breathers" - it's never stated exactly what gas they breathe or what liquid they use as blood.
• Lucky Starr: Creatures are discovered on Mercury that look like octopi made of rock that drain heat from any source they find.
• Mostly Harmless: Played with. The narration notes that life can exist in all sorts of hostile environments, such as the intoxicating seas of Santraginus V, the fire storms of Frastra, and even New York.
• In Project Hail Mary, the Eridians are ammonia-breathing Heavyworlders whose home planet has twice Earth's gravity and an atmosphere twenty-nine times thicker than ours, so thick that no light reaches the surface at all. The Eridians never evolved eyes, and "see" primarily using echolocation.
  • The Astrophage are an alien microbe species that lives on the surface of stars, absorbing their thermal energy. They “cheat” by using direct mass-energy conversion to maintain a constant internal temperature even in a star’s heat, but that temperature is 96 degrees Celsius - far too hot for almost any Earthly cell to tolerate.
• "Proof", a short story by Hal Clement, is about creatures who live in star cores and have difficulty believing in conditions under which regular elements become solid.
• The Saga of Seven Suns has the hydrogues, bizarre elemental aliens that live deep in the high-pressure cores of gas giants. They appear to be made of liquid metallic hydrogen and will die by Explosive Decompression in normal atmospheric pressure. When hydrogues need to appear in person on a planetary surface, they seal themselves in pressurized diamond spheres, which they can decompress as powerful suicide bombs.
• Sector General: There's a species of sapient crystals of frozen methane that can only survive close to absolute zero, another who is only comfortable at molten-rock temperature (these two require very heavily-insulated encounter suits to interact with other sentient species), and a culture of Hive Minded radiation-eaters who live inside the space station's main reactor pile.
• Spacehounds of IPC by E. E. "Doc" Smith features inhabitants of Titan, who as the moon cooled and they evolved had to terraform the place with a fluorine atmosphere just to have something reactive enough to metabolize with in the cold, and have kiln-suited foundry workers making stuff out of water. They're very glad when they first encounter humans, since their power station on Saturn was out of order, and the environment there would be only annoyingly warm for a human but a deadly inferno for them.
• Star Carrier: This is actually the norm in the series. The Sh'daar Masters state in the third book that out of around 50 million sapient species they've encountered, humans are only the twenty-thousandth or so with a carbon/nitrogen/oxygen/water metabolism. The first book alone shows species both intelligent and not that evolved on planets more like Venus than Earth, and the third mentions intelligent but non-technological life forms in the depths of Europa's ocean.
  • The Turusch, the first sentient aliens seen, evolved in a high-pressure atmosphere consisting mostly of carbon dioxide, with various sulfur compounds making up the rest. They live at temperatures of around 100 degrees Celsius, hot enough that sulfur particles in their air alternate between solid and liquid, and their environment is seething with ultraviolet radiation. Remarkably, this is their planet's equivalent to cold mountaintops, and they can live in even hotter and more pressurized places if needed.
  • The Glothr live in the frigid sea of ammonia-rich water beneath a rogue planet's crust. Their entire metabolism functions at just a hair above freezing, so they think and act very slowly, and even approaching a human could burn them to death. They breathe hydrogen instead of oxygen, since that respiratory pathway functions much better in such cold.
  • Subverted with the Denebans in the eighth book. Originally, Gray and his crew believe they are extremophiles since their ship has an internal temperature of 900 degrees Celsius, but it turns out they are an AI race with no need for physical environments at all.
• In The Star Diaries, Ijon Tichy is viewing a video filmed by a probe on a half melted planet. A local professor complains about the cold of 860° Celsius, and dismisses the idea of creatures living on planets as cold as Earth. Another part has a catholic priest complaining about the difficulties of preaching on a certain planet — its inhabitants are freezing at 600° Celsius, so of course they are more interested in Hell than Heaven.
• "Uncommon Sense" by Hal Clement takes place on a small airless planet orbiting the giant blue star Deneb. Due to the great heat, the life there is metal-based and uses a solution of liquid lead, tin, and bismuth as a chemical solvent. Given the total lack of air, they don't breathe, and they navigate using a sense best described as a hybrid of smell and sight.
• Uplift: Sundiver features creatures that live in the photosphere of the sun, and and are defined more by magnetic fields than chemicals. Some of them are even intelligent, although the "communications" from them during the story events are a hoax.
• In Ian Stewart and Jack Cohen's Wheelers, the blimps live just below the clouds of Jupiter, in a hydrogen atmosphere just barely warm enough for liquid ammonia (and often quite a bit colder). They find the idea of life on Earth, a planet with free oxygen and molten ice, to be ridiculous, meaning that they have no problem preventing comet strikes by diverting them to Earth instead.

Live-Action TV

• Doctor Who:
  • Whatever it was that haunted the planet in "Midnight" is capable on surviving a planet bathed in the X-tonic radiation of its sun, a place where no known life is capable of existing.
  • The Pting from "The Tsuranga Conundrum" lives in space, is essentially impossible to destroy, and foregoes conventional food, subsisting instead on energy drained from technology.

Multiple Media

• Star Trek has several examples:
  • Star Trek: The Original Series:
    • The Tholians are silicon-based, arachnoid, crystalline aliens adapted to environments so hot that being subjected to anything lower than 380 Kelvin — about ten degrees above the boiling point of water — will crack their carapace and kill them.
    • The Excalbians come from a planet well outside of class-M standards. They can also exist in space, as demonstrated when one of them takes the form of Abraham Lincoln.
  • Star Trek: The Next Generation has at least two:
    • The huge jellyfish-like aliens seen in "Encounter at Farpoint", luminous and pliant, yet able to survive nicely in the vacuum of space.
    • The "Brancher" alien, also known as the Crystalline Entity, is an enormous tree-like crystal that absorbs the life energy of entire worlds. It is first encountered in the episode "Datalore", where everyone on Omicron Theta had been consumed by the entity, leaving only the deactivated android Lore intact. This brancher can also travel easily through the vacuum of space.
  • Star Trek: Voyager has the Silver Blood, a deuterium-based race encountered on a Class Y planet in "Demon". The episode takes its name from the fact that Class Y planets are sometimes termed "demon" worlds because they're basically Fire and Brimstone Hell (start with temperatures averaging 500 Kelvin and go downhill from there).
  • The Star Trek Online Foundry mission "Relics" has the extinct Ugcinians, yet another species from a Class Y planet. They went extinct hundreds of years ago because their sun went supernova and their starship technology wasn't up to duplicating a Class Y atmosphere.
• Star Wars: A number of otherwise regular species live in worlds whose atmospheres are far too toxic for any other species to inhabit, and need special equipment to be able to breathe and see properly on other worlds — they tend to find oxygen toxic, and to have trouble focusing on objects through alien gas mixtures.
  • The Kel Dor, such as the Jedi Plo Koon, live on a planet poor in oxygen and rich in Dorin gas and helium, and breathe the former like most aliens breathe oxygen. They have to wear special goggles and respirator masks in terrestrial environments.
  • The Skakoans' homeworld has a very dense methane-based atmosphere, and need to wear full-body environmental suits on other worlds — their atmospheres, besides being toxic, are at a much lower pressure than their internal fluids, which can have... explosive results for them.
  • Gand has an ammonia-based atmosphere, and its eponymous native species is divided between ammonia-breathers who need specialized gear to live offworld and an entirely lungless subspecies who has no need to breathe anything.

Mythology and Religion

• In the realm of mythology and folklore, medieval and earlier thinkers such as the alchemists believed there were fire-lizards, salamanders, that thrived in extremely hot environments such as the inside of volcanoes and deep underground and could withstand heat and pressure that would kill most other life-forms.

Tabletop Games

• The Dawnline has a planet blasted by intolerable sunlight for half its surface and frozen solid for the other. The planet is inhabited, but only on a tiny strip of twilight between the two extremes, and they must constantly keep moving as the planet rotates. The things that live outside the twilight are extremely alien and extremely unpleasant.
• Eclipse Phase features many Transhuman morphs adapted to extreme environments. Ranging from the "mundane" Rusters adapted to the half-terraformed environment of Mars to Hulders that barely qualify as "biomorphs" and wander the surface of Titan herding similarly modified caribou, and Suryas, Space Whales that live in the corona of the Sun.
• Pathfinder: Targothas are fishlike alien organisms that evolved on a planet largely covered by hydrocarbon seas. A small population was carried to Golarion by a crashed starship, and despite the overall hostility of Golarion's dry, water-rich alien climate managed to settle a large system tar pits.

Video Games

• Final Fantasy XIV: the Burn is a desert badland created through repeated summonings of primals in what was once a fertile land. The area is now a stark-white desert that is completely drained of aether, with no plant life of any kind, and the only animals being those that evolved to survive in so lifeless a wasteland.
• FTL: Faster Than Light: The Lanius are metallic beings who have no trouble living in vacuum. They don't have trouble living in pressurized environment either; they just suck out any surrounding air.
• Halo: Lekgolo are eel-like aliens that thrive in the ring system of a gas giant by consuming metals, can survive in a vacuum and the Flood find them difficult to infect because they can only infect one worm at a time, a trait that the Forerunners tried to exploit in their fight against the Flood. Thanolekgolo, a type of Lekgolo gestalt group, take this even further by surviving the thermonuclear detonation of a starship's fusion engines that destroyed a Halo ring, being able to consume just about anything, and ending up being the only living thing on a fragment of the ring.
• Kirby:
  • Kirby's Return to Dream Land: A recurring Invincible Minor Minion in the game is Barbar, a gigantic eel that tries to swallow Kirby whole. While these enemies are normally native to Onion Ocean and the sewers of Egg Engines, the final area of the game introduces the Iron Barbar, a much scarier variant that surfaces out of nowhere from molten lava and looks like it's covered in igneous armor.
  • Kirby: Triple Deluxe: Pyribbit, the boss of Endless Explosions, is a huge frog-like creature described as living near the volcanoes and thriving off lava and hot rocks.
• Mass Effect: The volus originated on a planet with an ammonia atmosphere, with atmospheric pressure so much higher than most other races' homeworlds that they'll burst unless they wear heavy metal pressure suits.
• Star Control:
  • In order to procreate and spread their colonies, the Mycon terraform Earthlike planets into lava hell holes. They were designed to stabilize Earthlike planets and reproduce in lava hell holes, but over the millennia got their orders mixed up.
  • The Slylandro are a race of intelligent gasbags who live on a gas giant.
  • The Measure are sessile organisms living at the bottom of the sea under intense pressure. Their psychology is surprisingly easy to understand.
  • The Greegrox live in the vacuum of space in a symbiotic relationship with a sapient planet.
  • The Xraki live in possibly the most extreme environment possible: absolute void. They did not, however, evolve there.
• Stellaris: Some species can live on Tomb worlds, created from nuclear wars.
• XCOM 2: The Andromedons, while alive, are completely encased in bulky pressure suits filled with green gas, and can use acid weapons to attack.

Web Original

• Bosun's Return:
  • The goobellies are multicellular archaeans^note bacteria-like prokaryotes that, in real life, are exclusively unicelleluar adapted for life on the barren surface of the Sun-scorched Earth. As the Sun has become a red giant by the setting's time, the planet's outer surface became uninhabitable for everything but hyperthermophile archaeans, which in time evolved into animal-like forms thanks to being entirely isolated from existing macroscopic life. The goobellies are adapted for life in temperatures hot enough to flash-broil a human, to the point that they will drop into an immobile torpor if exposed to temperatures lower than 90 degrees Celsius.
  • Nightmasks are sessile fish descendants that evolved to inhabit the cooling towers that keep the Earth somewhat habitable, and spend their adult lives filter-feeding in literally boiling hot water.
• Captain Tardigrade is a miniseries about a half-man, half-tardigrade who is virtually indestructible, but his selfishness and incompetence does harm to everyone around him.
• Hamster's Paradise: The cragspringer is a small, theropod-like mammal that inhabits the peaks of a large mountain range comparable to Everest, where they have to deal with freezing temperatures, high levels of UV radiation, low amounts of food and oxygen as well as sheer drops and have developed a number of traits to deal with these issues. They use thick reflective fur to handle the cold and ultraviolet rays, an omnivorous diet and the ability to enter torpor to cope with lack of sustenance, large highly efficient lungs to extract as much oxygen as possible and a gliding patagium and shock absorbing tendons in their legs to handle falls. These same traits allow one branch of their species to become the bird-like pterodents, who are much better flyers than the previous flying animals living on the planet.
• Orion's Arm:
  • Many human tweaks are designed for life in extreme environments, such as unterraformed Venus or even outer space.
  • The actual aliens are usually adapted to environments very different from Old Terra. The first alien race encountered by Terragen life, and one of the most psychologically similar to humanity, the To'ul'hs, originated on a planet that can be compared to either a cool and wet "Cytherean" world or a very hot and high-pressure Gaian world (i.e., it's somewhere between Venus and Earth). Unmodified humans would quickly die of pressure, toxin or temperature overload on To'ul'h Prime's surface and the aliens wouldn't fare much better on Earth, although they've developed their own tweaks, some of whom are adapted to Gaian environments.

Western Animation

• Ben 10:
  • In the original Ben 10, Heatblast's species lives on the surface of a sun.
  • Ben 10: Alien Force features a planet that is sun-blasted on one side and ludicrously cold on the other, leaving a small barely-habitable band in the center. Ben asks who would want to live there; the answer is the Necrofridgians, or the mothlike Big Chill species.
  • Ben 10: Omniverse features tungsten-based lifeforms called the Kraaho who need life to be extremely hot to live. Since they decide to make a settlement on Earth, which is far too cold for them, they attempt to cause a lava flow on the surface to make it more habitable.

Real Life

• Of course real life features extremophiles, with many of the hardiest being microscopic life. Microbes have been found living on the rims of active volcanoes, in lakes with lower pH than battery acid, within the Antarctic ice sheets, in active nuclear reactor cores, and (maybe) on part of a probe retrieved from the moon by one of the Apollo missions.
• Deep sea hydrothermal vents are home to some of the more widely known examples of macroscopic extremophile lifeforms. Around these outflows of water that would boil several times over if it wasn't at the crushing pressure of the deep ocean, saturated with chemicals that would make Toxic, Inc. blush, entire ecosystems of strange creatures like giant tube worms, yeti crabs, and scaly-foot snails thrive in food chains with little to no reliance on energy from sunlight.
• The Death Valley Pupfish is noteworthy for being a fish native to one of the driest places on Earth, surviving in a few small patches of water salty enough to kill most ocean fish at temperatures ranging from freezing to above 110*F/43*C.
• The Tardigrade, or water bear, is a microscopic multicellular animal often cited as the most all-around durable organism - when conditions exceed the extremely broad range they consider tolerable, they are capable of entering a dormant state that renders them able to survive pretty much anything that does not destroy them on a chemical level, and resistant to most things that would.
• Humans have developed a range of ways to disinfect medical equipment food and stuff like it. The problem usually is to find a method that does not destroy the equipment or render the food toxic while still killing the microbes dead enough. The main methods used other than chemicals like ethanol are the autoclave which basically "steam boils" the sample^note The "steam" part is very important, given that loads of microbes are very good at surviving dry heat but do not have efficient mechanisms to survive the same temperature in a high moisture environment - this is likely due to most (but by no means all) environments on earth that would even approach those temperatures being bone-dry and blasting it with ionizing radiation. However, there are micro-organisms which would consider an autoclave a kind of sauna and Deinococcus Radiodurans is able to basically shrug off a thousand times the human lethal dose of ionizing radiation as if it were nothing. While most procedures are fine operating with only "mostly" sterile equipment, NASA and Co. are wrecking their brains over what they call "Planetary Protection" due to the fact that ensuring an unmanned probe is not bringing some life-forms as unintended "blind passengers" is pretty difficult.
• On the most basic level of metabolism there is "aerobic" (i.e. requires molecular oxygen to survive) and "anaerobic" (i.e. everything else). However, this is already an oversimplification explained partially by virtually all multicellular life being aerobic. In reality, there is "aerotolerant" (doesn't need oxygen, but can survive in an environment that contains it), "facultatively anaerobic" (can live without oxygen, but has a - usually more efficient - metabolic pathway that uses oxygen. Yeasts are a prominent example) "Obligately anaerobic" (cannot derive energy from a metabolic pathway using molecular oxygen and usually does not tolerate high amounts of oxygen). While most macroscopic life is indeed aerobic, for most of the history of life on earth, microbial life was all anaerobic. As a matter of fact, the gut microbiome of many animals (including humans) contains many organisms to which an excess of oxygen is toxic. Given that oxygen was introduced into the atmosphere as a "waste product" of photosynthesizing algae^note there are pathways of photosynthesis that do not produce oxygen, but the oxygen-producing one is more efficient and is one of the most chemically active and aggressive gases, from the point of view of anaerobic organisms we basically breathe chlorine.

---