Giant, vacuum-adapted human-derived clade

Image from Steve Bowers
Many Jotunn live in the resource-rich rings of gas giants

These very large vac-adapted microgravity humans name themselves for mythical ice giants, as they prefer to dwell among cold planetary rings.

The Jötunn are among the largest human-derived clades, larger than even Megapteras and Nephilim with adults reaching 30 meters from head to toes with masses around 1,000 metric tons. They appear quite 'alien', consisting of a bloated, almost spherical torso that sprouts four spindly, double-jointed arms. A hairless head sprouts from a bulbous neck on the front of the torso and is dominated by a broad, frog-like mouth and two large eyes. The face is noseless and lacks external ears, but retains middle and inner ear structures protected under a thick, frog-like tympanum. Their thick skin is usually smooth and unbroken except at limb joints where it shows accordion-like wrinkles, a concession to internal body pressure. Skin coloration depends on the local star because they have symbiotic photosynthetic bacteria in the skin, which is invariably optimized for local sunlight. Green and black are common, often mottled, thus further contributing to an obese frog-like appearance. Skin on the hands and belly takes a more scale-like appearance where the Jötunn need protection from extremely hot or cold surfaces.

Jötunn descend from vacuum-adapted humans who wanted to live in space with minimal technological aid, though most modern Jötunn frequently seek technological augmentation ranging from external tools to biological and cybernetic implants. The goal of minimal technological aid dictated several elements of Jötunnian habitats and biology. The biology takes a surprisingly minimalist approach to modifying the human genome by providing a sheltered interior condition where organs function without enduring the temperature extremes and vacuum of space. This dictated the round, pressure-resistant form and blubber insulation and, despite appearances, drew on terrestrial marine mammals rather than amphibians. Some significant metabolic changes were offloaded to symbiotic bacteria.

This clade was developed in the Zoeific Biopolity around 7500AT, but have settled in a number of systems beyond the Biopolity with large Orwood forests. Their human-like reproductive cycle has led to a rapid population growth where Dyson trees are common.

Structures, Organs, and Vacuum Adaptation

The gut and lungs fill a relatively small part of the body, following the curved spine along the dorsal surface from shoulders to pelvic girdle. Even so, these organ systems are oversized for the metabolic needs of most Jötunn, who expend very little energy in their weightless, vacuum environment. When not eating, most metabolic energy supports the large brain (which is large because it coordinates a vast body; the Su-level intelligence doesn't require such bulk) and a 37C body temperature (maintenance of which is considerably aided by thick blubber and a vacuum environment.) Instead, the large lungs and digestive system reflect the living style of Jötunn: they are burst feeders who gorge at their farms, where energy, water, and pre-processed oxygen is abundant.

This bounty of food and oxygen is rapidly processed by the large lungs and gut into the 'storage organs,' slightly-muscular sacks that fill much of the bulbous torso. Some hold reserves of water, undigested food, gases, and solid waste, but most are nothing more than capillary-laced soft tissues rich in (depending on the sack's specialty) myoglobin, glycogen, and fats. As storage organs are depleted of oxygen and nutrients, they are refilled with waste products like urea and carbon dioxide. From such huge reserves a drifting Jötunn can spend up to 10 days before risking suffocation, and months may pass before dehydration and starvation is an issue. (Of course, technological systems like respirocytes may greatly increase this endurance.)

Another reason for the storage organs is the Jötunn's symbiotic photosynthetic algae under their transparent epidermis. In addition to providing UV protection, these engineered algae use high-efficiency photosynthetic pathways to reprocess wastes in storage organs back into useful forms. The low surface-to-volume ratio of Jötunn means that they cannot support fully closed metabolism like a Faster, not without technological aid, but well-lit Jötunn may double their time between feeding and breathing.

Waste storage in the storage organs includes reinforced gas bags that hold stews of carbon dioxide, water vapor, oxygen, methane, and other metabolic products. These are drawn from both the gut and lungs and muscularly pressurized in the storage organs. They supply the Jotunns' very limited reaction propulsion system.

Regarding feeding, Jötunn expect to eat prodigiously in a vacuum. To maintain internal air pressure, their mouth and throat act like an airlock. The mouth and tongue may tolerate vacuum and temperatures of very hot or very cold food. The cheeks and roof of the mouth are simply "armored" like the hands, but the tongue has sacrificial, fast-regenerating surfaces that allow it to help seal the throat with a flexible, wet surface. After taking a large bite of food and chewing as necessary, the tongue pushes against the roof of the mouth in a wave to force the food mass into the throat as a compact mass. The throat, which closes tightly all along its length, peristaltically moves the food lump into the stomach. This avoids ever creating a direct opening between the stomach and mouth. As a second line of pressure control, the lips muscularly seal while chewing. A similar peristaltic system in the extended bowels prevents depressurization of the intestinal tract.

Jötunn endure solar illumination up to 2500 Watts per square meter (Venusian levels) by using two cooling mechanisms. First, they do sweat, and evaporation is a potent cooling method in a vacuum. However, Jötunn dislike environments warmer than 400 Watts per square meter (similar to Martian orbit) because it dehydrates them, and they have a space dweller's aversion to wasting volatiles. At the limit of their light tolerance, they may suffer fatal dehydration faster than suffocation. Second, they may "pant" as they call it, which involves opening the mouth and allowing saliva to evaporate from the tongue. This is particularly effective in cooling the brain, which cannot tolerate the same overheating as the rest of the body. (Metabolic activities, particularly in bacteria-rich sections of the gut, may see temperatures in excess of 42° C, but the brain is maintained at 37° C.) However, Jötunn dislike the "boiling tongue" sensation and sticky residues of evaporating saliva, so they rarely use "panting" for long. They most often pant while feeding, which is a time of elevated metabolic activity and they have plenty of food and drink to keep their tongues clean.

The pressure and temperature-resistant skin and blubber have several additional functions to protect a Jötunn from injury in a vacuum. The photosynthetic bacteria make excellent use of UV light and halt it from endangering inner layers of tissue. The thick blubber is able to halt most alpha- and beta-particle radiation as may be found in radiation belts, and the cells have extensive soft rad hardening not present in inner tissues due to the metabolic burden imposed by the hardening techniques. (The bulbous head is also swathed in blubber, leaving the large eyes poking out from under "beetle brows.")

Both skin and blubber have muscular responses to punctures to try to close wounds and the blubber has respectable tensile strength for fatty tissue, which helps prevent prolapse of organs through open wounds due to internal pressure. Compounds in the skin and blubber react to injury to quickly produce a drying, foaming scab-like plug that help bind the edges of the wound. (Modern Jötunn also typically wear harnesses or clothing akin to thin or thick suits, which can deploy over injuries.)

The skin and blubber do not, however, offer much protection against hypervelocity debris, no more than any thick, biological soft tissues. This may be surprising, but suitable Whipple shields and other armor architectures were not compatible with the intended form of Jötunn. Further, because Jötunn usually live in Dyson forests and planetary rings, most debris they might encounter will have a low relative velocity - the orbital bands will be moving in the same direction and local objects (like trees and ring material) will provide shielding.

The four limbs of Jötunn are still located in positions corresponding to baseline limbs. The hind limbs have been modified into arms, typical of zero-gravity adapted tweaks. The double-jointed limbs are able to reach most points on the body, though the dorsal and ventral 'poles' of the torso are usually out of reach unless a Jötunn has depleted its storage organs.


The outstanding sense of unaugmented Jötunn is vision. As suits their large heads and bodies, they have large eyes (typically approximately 30 centimeters) with long, adjustable focal lengths and large arrays of rod and cone cells. Hexachromacy covering near infrared, near ultraviolet, and four visible light bands gives them outstanding color vision. Similarly, they have large light gathering areas for vision by starlight. Distance vision beggars that of any terrestrial animal, but they can focus at arm length sufficiently for fine manual tasks. The visual field is not particularly wider than that of an unaugmented baseline. Jötunn expand this field of vision with a flexible neck. A large optical center in the brain makes good use of this flood of optical information, providing excellent vacuum-adjusted depth perception, motion tracking of numerous objects, better three-dimensional visualization than that of a ground-oriented baseline, and interpretation of light polarization data. The large eyeballs include lenses resistant to UV damage while the deep vitreous humor provides radiation shielding and UV protection to the retina (in higher UV bands so as not to block UV sensitivity). Permanently-deployed, glassy nictating membranes, under which the tear-lubricated eyes move normally, provide pressure resistance and include some protein crystals that serve as polarizing filters and others that respond to strong flashes with rapid darkening, enough to protect starlight-adapted Jötunn eyes from sudden solar glare or even nuclear glare. (Pupils and eyelids, of course, provide additional protection against strong light.) The outer eyelids are thick, blubber-and-blood rich shields used to clean the nictating membranes of dust, block intense light, and help warm eyes in particularly cold environments.

Touch is surprisingly good in two fashions: First, Jötunn are able to resolve tactile sensations as finely as unaugmented baselines, i.e., as a much smaller creature. For their size, they are thus minutely aware of their skins. Second, they are able to sense internal metabolic activities quite precisely, a result of requiring conscious control of their storage organs during recycling operations. Hearing is, of course, frequently useless, but it is retained because Jötunn do enter pressurized environments and it is convenient for "contact speaking". Their lack of external ears and protective tympanums reduce sensitivity to higher pitched sounds somewhat, but the underlying auditory system has the same frequency range as baselines. Taste is approximately as sensitive as baselines and this leads to Jötunn enjoying a diverse diet from their freefall farms, but some subclades are tolerant of consuming raw carbonaceous or cometary material. Even smell is present, though the lack of a nose moves the necessary chemical receptors to the mouth. Jötunn are not particularly sensitive to smell, but they do use that chemical sense to analyze atmospheric hazards in pressurized environments. (Since they are able to hold their breath an extremely long time, they may enter non-breathable atmospheres that require evaluation. Smell is also convenient for assessing internal digestive processes during eructation.)

They have some additional senses, depending on the subclade. A good but non-imaging magnetic sense helps orient them around their favored gas giant environments and estimate magnetic field strength and direction, which gives inferences about local radiation risks. Specialized tactile nerves throughout their body are responsive to ionizing radiation (usually perceived as a particular burning sensation), enabling them to more directly estimate current exposure than their magnetic sense.

Of course, many Jötunn have implants or carry equipment that greatly expand their senses to include such things as radar, assorted radiation and magnetic field sensors far more capable than the Jötunn' innate senses, chemical analyzers, hyperspectral telescopes and spectrometers, and any other sensor of use to modern spacecraft.


Jötunnian reproduction follows a fairly typical mammalian process, particularly those of terrestrial whales. Male organs are generally kept retracted in a blubber-shielded pouch until required. While some modosophonts have derogatory descriptions of the mating process ("amorous beach balls" being an infamous quote), the process is effective and most subclades of Jötunn are able to breed true without technological assistance. Gestation periods are about 18 months and produce an infant about as large as a baseline human, a size that is relatively easy for females to birth unassisted.

Children are typically raised in low-radiation, sheltered areas, like pressurized Dyson tree interiors or rings outside a planet's radiation belts, due to their lack of radiation-shielding bulk. They grow rapidly in the fashion of large marine mammals, reaching adult size by age 15 to 20. Nursing typically lasts 1 to 3 years, depending on the preferences of the parent.

Like aquatic mammals, the mammary glands (typically four to eight) are not obvious. They do offer additional functions beyond lactation, though. The glands include a placental-like function in which infants (and certain minute Jötunnian subclades) may respire via blood exchange. An adult female is so large that infants, Sylphs, and Jonahs are scarcely a burden to their metabolism and storage organs.


Despite the desires of the clade's founders for "natural" communication, communication is almost universally achieved by DNI implants. Indeed, the lack of stimulation and low physical activity of most Jötunn mean they seek stimulus in rich virch and augmented reality worlds. However, all Jötunn learn the four-limbed Anglic sign language of their founding members, which is adequate for communication over tens of kilometers with Jötunn' vision. A tertiary system is the archaic "contact speech," where two to four Jötunn bump their heads together and internally vocalize. This can deliver greater information than sign language, but is most favored by parents with young children. In pressurized environments, Jötunn are able to speak normally, albeit in very bass registers.


Jötunn have very limited innate propulsive abilities beyond those of any human in freefall, so they must push off something or utilize technological propulsion systems. Unlike aquatic whales, Jötunn are not muscularly powerful beings. They are truly creatures of freefall and cannot move their limbs with great speed. This is both a concession to their slow metabolism and material strength of the bone, muscle, and connective tissues of their long arms. They can generate tons of force but, proportionally, are weak for their size. This means they are extremely wary of any object with more than 3 m/s escape velocity, i.e., a comet or stony asteroid over two kilometers in average diameter. They are unable to generate leaps or pushes faster than that without assistance.

The prodigious production of carbon dioxide and methane of their metabolism is harnessed by a network of gas tubules and sphincters around the body, tapping the gaseous storage organs. The low mass and pressure of stored gas means this "biological warm gas propulsion"; does not offer high performance, but a well-fed Jötunn may store enough gas for about 5m/s. Acceleration, translational and rotational, is quite low, too, so they tend to use this capability sparingly for orientation and fine tuning courses while moving among planetary ring material. It also offers an emergency "get home" if they miss a jump or limbs in a Dyson tree.

They can endure up to 0.1G if on a hard surface, but are uncomfortable above 0.025G. When suspended in a liquid, they can tolerate up to 0.5G, after which they risk damage to their minimally-supported internal organs.

Chemical or conversion "jet packs" are almost ubiquitous among Jötunn, and some will use full-scale spacecraft for long-distance flights.


Because Jötunn metabolisms do not achieve true "closed" operation like Fasters and Sailors of the Ebon Sea, and because of their lack of integral space propulsion, they tend to live in planetary rings and Orwood forests. Such environments provide lots of mass and surfaces to move along, some debris shielding, and abundant material suitable for life support, like hydrates and carbonaceous materials.

Icy planetary rings are particularly favored as they are well-suited for growing Dyson trees and other vacuum-adapted plants. Jötunn cultivate these into farms, which address shortcomings in their internal recycling: let vast fields of plants turn rocks and solar energy into food and oxygen. Recycling is important, so Jötunn culture holds that it is courteous for visiting Jötunn to contribute their wastes to a farm's composting centers.

The Dyson trees cultivated by Jötunn generally have oxygen-filled passages and "oxygen nipples" from which they can respire for hours to refill their storage organs. Other farms maintain Greenbubbles and Freespheres in which Jötunn can relax, bathe, respire, and socialize in an open, air-filled environment. (Jötunn tend to be claustrophobic in Dyson internal tree passages.)

Jötunn are most in their element when they are tending to Orwood forests, grazing on foliage and other astragens growing on the trees, and drifting among the kilometers-long branches. Most have a widely varied diet of astragen plants, including vacuum-adapted meatshrooms, deliplants, OxyFruit, and numerous fruits. Energy-dense fatty or sugary cultivars are favored - the Su-level intellects of Jötunn are prone to boredom if they only eat low-energy leaves and bark of Dyson trees, or - for some subclades - just the raw material of planetary rings.

The Jötunn locate their industry and advanced technological services in a community (usually a concentration of farms). While some few try to live in a deliberately lowtech or Hider fashion, this is usually a passing interest. Most favor high and ultratech lifestyles and maintain the necessary forges, Known Net connections, and transportation links to the rest of Terragen space.


Greater Jötunn: Visually distinctive for their large, bat-like membranes strung between limbs, this offshoot of the Jötunn are S1 transapients. The membranes provide additional light collection and radiation area to handle their more energy-hungry brains.

Faster Jötunn: This branch eschew farms for more complete internal ecosystems and a Faster Lifestyle, requiring implanted conversion power plants or large solar arrays. They also tend to have significantly different interiors to their mouths than normal Jötunn because the Fasters will make up losses in their internal recycling with raw ices and carbonaceous material - eating the rocky, super-cold materials requires different dentition and protecting mouth tissues from temperature extremes. Faster Jötunn also often add propulsion systems ranging from solar sails to conversion rockets, becoming bioships.

Rocket Jötunn: Baseline Jötunn include very limited innate propulsion, and wear or implant propulsion systems for free space flight. Rocket Jötunn have specifically developed some biological chemical rockets to give them innate space maneuvering capabilities far beyond the Jötunn norm. That performance - rarely over 200 meters per second delta-V at less than 0.05G acceleration - is relatively low even compared to artificial chemical rockets for several reasons. The first issue is energy: it takes a long time for a natural Jötunnian metabolism to build up large quantities of oxidizer and fuel, though they can literally refuel rapidly at a farm. Secondly, propellant selection poses numerous challenges to the underlying biological production mechanisms and storage in the warm body of a Jötunn. It is easy enough to biologically produce oxygen and methane or hydrogen, but storage is necessarily gaseous and thus only a low mass can be carried relative to the Jötunn's bulk (limiting delta-V to under 20m/s). Liquid propellants are much denser and it is not difficult biologically to synthesize liquid fuels like alcohols, certain fats, or even straight hydrocarbons, but suitable liquid oxidizers are more difficult. Hydrogen peroxide, nitric acid, or nitrous oxides are possible, but hazardous to store in biological containers and require advanced synthesis pathways. Cybernetic implants make it quite easy to produce liquid oxidizers, but defeat the goals of Rocket Jötunn to be biological rockets. The most common solution is hydrocarbon-nitrous oxide propellants developed in organ systems almost entirely isolated from the remainder of the Jötunn to avoid the risk of mixed nitrous oxide poisoning.

Sylphs: The human-scale offshoots of Jötunn are also much more human-like in appearance, appearing very like dark-skinned, hairless humans with hybrid hands-feet typical of microgravity tweaks who expect to walk in low gravity. They are actually quite closely related to Jötunn despite the radically different size and appearance, and represent an offshoot interested in living in low gravity extra-terrestrial environments such as Galilean-type, Jötunnian-type, or smaller lithic-geledian moons. Sylphs were originally created by Jötunn as a sort of "handtech" that would support their lifestyle with bases on gas giant moons where gravity was too high for the larger beings. The Sylphs differ from methanoids in they retain Jötunnian warm metabolisms and photosynthetic partial recycling.

Though Sylphs are not in any way beholden or indentured to Jötunn, a common upbringing and enjoyment of the micro-G lifestyle means it is normal for a group of the smaller being to live on a given Jötunn or among a flock of Jötunn, nursing for nourishment and oxygen until independent action is required.

Jonahs: A bizarre variant of Sylphs found among some Faster Jötunn, Jonahs are adapted to live within the guts of Faster Jötunn. The Faster Jötunn serve as bioships to the Jonahs while the Jonahs tend complicated, specialized chambers in the guts, where fungi, algal, and bacterial cultures perform different functions of a mostly-closed metabolism. This necessarily involves tolerance of CO2-and methane-rich atmospheres, not to mention the digestive functions of the Faster Jötunn. Faster Jötunn with such symbiotic sophonts generally create some gut or lung gas cell chambers with much milder environments, so-called "passenger quarters" where infants may be raised and Jonahs rest in quiet. Jonahs also function as exterior helpers, retaining Sylph-like vacuum tolerance. Leaving or entering a Faster Jötunn entails passage through one of the digestive tract orifices, which disturbs many humans who are already askance at their distinctly septic habitats. (Wuppists, meanwhile, applaud Jonahs for their "ironic juxtaposition of wup and wuppist, a delightful introversion of traditional elements.") DNI is critical for good communication between the Jötunn and its symbiotic Jonahs.

Dweorg: The immediate ancestors to the Jötunn but not their creators, the Dweorg ("dwarfs") are vacuum-adapted humans that served as a centuries-long test case for many of the Jötunn's novel genetic enhancements. The Sylphs and Jonahs are also direct derivatives of Dweorgs, but shorter and slimmer. The Dweorg, though, are distinctive and have traits almost considered "throwbacks" among all vacuum-adapted, microgravity clades. They appear much like a baseline human in form with dark photosynthetic skin and glassy eyes (like Jonahs and Sylphs), but have legs and feet suited for walking under significant gravity. Indeed, they have some features for enduring high gravity for a lifetime, though not to the extent of Anakim or Kobolds. By baseline standards they are large, about 2.5m, and lean and robust in the fashion of a Goliath or Morrigan. They have many of the space adaptations of Jötunn, but (like Jonahs and Sylphs) their storage organ capacity is quite limited, representing most of the modified, thin layer of body fat that covers them. They lack an integral propulsion system. Their lack of blubber is usually addressed by light clothing and radiation protection is provided by more extensive "soft" modifications than found in most of a Jötunn's body. They retain hair on their head (typically a UV-bleached blond or white) and external ears. The Dweorg are, essentially, generalists in living in hostile environments: they can survive in anything from Earth-like conditions to Martian, vacuum, freefall, and high gravity, while Jötunn, Sylphs, and Jonahs are more tailored to low gravity vacuum environments. The creators of the Jötunn clade have slipped into obscurity so their full intent for the Dweorg is not known, but they have found productive lives as hostile environment workers and even protectors in lower technology environments. Their own communities tend to be frosthives and micro-G asteroid warrens, rarely near Jötunn farms, or conventional cities on superterrestrial worlds. Their name appears to derive from a clade-wide joke regarding their comparatively heavy musculature and small stature: short, odd-looking versions of the graceful Jötunn.

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Development Notes
Text by Michael Miller
Initially published on 29 June 2016.