Titan is the largest satellite of Saturn and the second largest moon in the Solar System (after Jupiter’s moon Ganymede). It has attracted interest over the years both for its unusual size and because of a property that caught the attention of the first astronomers to turn telescopes in its direction. Unlike every other moon in the Solar System, Titan’s disk shows a fuzzy edge in observations. In other words, Titan boasts an atmosphere. Indeed its atmosphere is thicker than that of Mercury or Mars… and even Earth. It is now known to be comprised mostly of nitrogen and methane, while the surface boasts abundant hydrocarbon compounds - the building blocks of larger molecules that form DNA and ultimately life. The landing of the Huygens probe on an water-ice-grain sandy surface in 2005 produced our clearest view of the moon and built on previous theories. Later surveys from its parent orbiter Cassini confirmed that, while distant from the Sun (and hence too cold for liquid water), Titan is believed to have frigid hydrocarbon lakes on its surface, possibly overlying ice-capped oceans.

 

Unsurprisingly, these unusual features have caught the attention of science fiction writers as well as scientists. Titan has been a popular solar system target in stories dating back to the first identification of methane in its atmosphere by Kuiper in 1944, and even before when its size and potential atmosphere were already recognised. Indeed, stories set on or about Titan have been plentiful enough that they were used to represent parent planet Saturn by both Isaac Asimov in his Science Fictional Solar System anthology (1979, selecting Saturn Rising by Arthur C Clarke) and by Mike Ashley in his anthology Born of the Sun (2020, as part of the British Library Science Fiction Classics series, selecting How Beautiful with Banners by James Blish) [1].

 

An unusual moon.

 

The interesting surface properties of Titan (as understood by astronomers and planetary scientists) have come to the fore in hard (or technically-oriented) science fiction. In Robert L Forward’s Rocheworld (novel, 1984), for example, the thick and opaque atmosphere of the moon was used as a convenient nearby location for training explorers in the use of their surface landing and ascent module and the Dragonfly - a survey aircraft designed for use in the atmosphere of the titular binary-planet. Here the scenes on Titan are brief but make good use of Titan’s unusual conditions as a proving ground for technology to be used off-Earth.

 

A more prominent role is played by Titan’s unusual conditions in The Dust of Death, a short story by Isaac Asimov (Venture SF, 1957). This is a murder mystery taking place in an Earth laboratory tasked with analysis of samples from out of this world. Amongst its equipment is a chamber to simulate the varied atmospheric conditions found in the Solar System. One of the characters has just returned from six months experimentation on Titan, the advantages of which over the giant plants is explained:

“Titan, however, was Mars-size, small enough to operate upon and large enough and cold enough to retain a medium-thin hydrogen-methane atmosphere. Large-scale reactions could proceed there easily in the hydrogen atmosphere, where on Earth those same reactions were kinetically troublesome.”

 

Key to determining the means, and hence the perpetrator, of the murder in question is a set of chemical reactions between platinum and hydrogen that will only occur in a Titan (rather than Earth) atmosphere. It thus represents a good example of Asimov making use of the latest observational evidence (as well as a reasonable amount of extrapolation) in shaping the plot of his story.

 

The atmosphere of Titan also has dramatic potential in its composition. In Clarke’s Saturn Rising (Arthur C Clarke, F&SF, March 1961), the methane-rich moon, for example, becomes a key refueling point for early journeys to the outer Solar System - based on the then-current belief that the atmosphere was methane-dominated rather than a 95%:5% spilt in favour of nitrogen. The hypothesised methane atmosphere also features in the television series Doctor Who, which visited Titan in the 1977 serial “The Invisible Enemy”. This story sees Tom Baker’s Fourth Doctor and others infected with a parasitic alien, the Swarm, which is personified by a “nucleus” inside the Doctor. Clones of the Doctor, his companion Leela and K9 (introduced in this series) are miniaturised and injected into the Doctor in an attempt to save his life [2]. When the infectious nucleus, as a result of various unlikely shenanigans, grows to monstrous size, the Doctor lures it to a now-abandoned, enclosed human base on Titan. Eventually blaster fire ignites Titan’s methane-heavy atmosphere as it mixes with flammable oxygen released through a breach, sterilising both the base and the infection with a vast conflagration.

Humans on Titan

 

For many stories, as in the film Gattaca (1997. dir. Niccol) and the short story Orbit XXIII-H by Robert Willey (Astounding, Sept 1938 [3]) simply reaching the moon is a challenging goal. In the former, genetic purity is the deciding factor in selection for a mission to Titan which forms the protagonists’ goal. In the latter, a industrialist must be rescued by a space guard who lack powerful enough ships to follow his abductors. Another such story is Stephen Baxter’s novel Titan (1997), in which the full resources of a dying NASA (including literal museum pieces!) are mobilised in a last ditch attempt at a spectacular one way trip [4], which doesn’t reach the moon until about 80% of the way through the story.

 

However once the hurdle of the (far-from-trivial) journey is overcome, the surface pressure of Titan, its rich chemical environment and its non-zero gravity (it has about a seventh of Earth’s) have made it a promising candidate for human settlement in the minds of a number of science fiction authors.

 

Inevitably, some authors treat this moon as having a breathable atmosphere, effectively just another surface in the Solar System which will ultimately be occupied by humanity with little or no requirement for artificial life support or conditions which might be extreme but remain survivable. Titan was visited in fiction, for instance, by Stanley Weinbaum - best known for his highly influential A Martian Odyssey (1934) - in a similarly themed novella: Flight on Titan (first appearing in Astounding, January 1935, before the detection of Titan’s methane). This describes a young couple of prospectors struggling to reach the one substantial settlement on the moon, after their own shack is destroyed. Here Titan is habitable but hostile: “Outside was the unbelievable Titanian night with its usual hundred-mile gale screaming against the curved walls, and the glitter of ice mountains showing green under the glare of Saturn.” It also boasts complex native life, several types of which are described in the story. As harsh as the conditions are - “surely no one could survive a cross-country journey here through nights that were generally eighty below zero, or even days that sometimes attained the balmy warmth of just above freezing” - it is ultimately survivable, given a few chance-found heat sources and a lot of luck.

 

Often the purpose of Titanian settlement in such stories is to mine the moon’s resources. This seen, for example, Imperial Earth by Arthur C Clarke (novel, 1975). Here colonisation on Titan owes its success and commercial power to the reliance of interplanetary transport on abundant hydrogen supplies. Titan’s upper atmosphere is describes as being largely made of hydrogen compounds (with more complex hydrocarbons concentrated in red clouds near the surface) rather than the nitrogen we now know dominates. The population lives underground, while ships scoop hydrogen from Titan’s shallow gravity well and despatch it sunwards. Resource exploitation is also the driving force in Trouble on Titan, a 1954 young adult novel by Alan Nourse in which Titan’s only settlement is a former penal colony, now mining ruthenium for use in solar energy converters on which the Solar System is dependent. In this example, the settlers live under a domed settlement, the explosive mixture of methane and oxygen atmospheres again features, and the cold surface temperatures of the moon (quoted here as 250 degrees below freezing) are also commented upon. An interesting aside is that both these examples (as well as The Dust of Death, above) comment explicitly on the use of oxygen jets used as fuel supply in the hydrocarbon-rich Titanian atmosphere, as contrasting with the flow of hydrocarbon fuel into our own oxygen-rich atmosphere required by Earth technologies.

 

In other cases the details of Titan’s surface conditions are simply not be discussed, whether these are directly habitable, terraformed or simply circumvented by enclosed settlements. In The Sirens of Titan by Kurt Vonnegut (novel, 1959), for instance, the surface is shown without comment as straightforwardly Earth-like, while in If You’re Smart - by Colin Keith (short story, Astounding, April 1942) Titan is fully settled and industrialised with no apparent restrictions. In other stories, as we saw in Trouble on Titan and Doctor Who, the entire action takes place within domed, sealed or underground cities (as, for example in Dan Dare’s Operation Saturn, comic story, 1953). A recent example of this kind, where issues of terraforming are side-stepped by enclosed habitats, can be found in the television series Star Trek: Discovery (episode “People of Earth”, TV, 2020). In the distant 32nd Century, after a breakdown in interstellar travel, any ship approaching Earth is attacked by raiders who steal the resources aboard. To the shock of those in charge of the newly-insular and suspicious planet, the raiders are revealed to be as human as themselves - in fact these are the desperate descendants of independent colonists on Titan whose infrastructures have broken down. While we never see conditions on Titan in this epoch, the settlers are clearly numerous enough to be named in a new “United Earth and Titan” which appears in later episodes.

 

Titanic Adaptations

 

A more explicit narrative of terraforming Titan can be found in the novella The Big Pill, by Raymond Z Gallun (appearing in Planet Stories, September 1952). In this story a group of settlers on a desert-arid Titan, living in domed bases with controlled environments, are being fleeced by corporate concerns from affluent Earth (a familiar theme in solar system settlement narratives). A local scientist has devised a method to trigger a monumental terraforming event on the moon’s surface, using an atomic device, but this is opposed by Earth-appointed authorities and - in truth - does carry substantial risks, causing considerable conflict between those who wish to trigger it and those opposed. When the device is finally triggered, the results were dramatic:

 

“The gases of the wind that howled around them, had been in part released from chemical compounds, but more had been transmuted from other elements of the rock and dust in the crust of Titan, in that atomic vortex where the Big Pill had struck. Those gases were so new that they were tainted with the fires of their birth—saturated with radioactivity.”

 

Fortunately, the scientist succeeded in making this radioactivity self-cancelling, and to create a fusion-based mini-sun from the remnants of the ‘Big Pill’, so that soon the atmosphere begins to produced a habitable environment:

 

“Plenty of nitrogen. Some helium. Plenty of hydrogen. A lot more oxygen. So that, as all of the hydrogen burns—combines with it to form water-vapour—there still will be lots of oxygen left over, floating free.”

 

This terraforming event is clearly shown as being a positive result, but then this was a Titan clearly devoid of life and potential (in the absence of human intervention), although: “Once, eons ago, when monster Saturn had been hot enough to supplement the far-off sun's heat with radiation of its own, those hills had been, for a few brief ages, verdant with primitive, mossy growths.”

 

An interesting alternative to such terraforming narratives are those in which humans must adapt to Titan instead. The Journey and the Goal by Chan Davis (short story, Astounding, March 1947) is interesting in that it envisages Titan as a barren, airless world (very different to the 1.5 atmospheres we now know about!) occupied by miners but producing products with very little demand. As the protagonists - a second-generation Titanian settler boy and girl - discover, returning to Earth is not an option for them: they are not only head and shoulders above Earth people, they have brittle bones under Earth gravity, suffer nitrogen narcosis in Earth atmosphere, are immune-deficient and have irises unable to contract sufficiently in response to Earth-orbit sunlight. These adaptations would, of course, be common to anyone raised in the outer solar system, but demonstrate how the massive Saturnian moon tempted writers imagining the long term consequences of human expansion.

 

A more recent example of Titan-forming humanity can be found in the 2018 film The Titan (dir. Ruff). This follows the experiences of Rick Janssen, an air force pilot who is selected for an unethical secret training programme explicitly aiming to adapt humans for a future settlement on Titan. This involves both surgical and DNA modifications, as well as physical training. Unfortunately the other test subjects in the programme are killed or driven insane by the process. Rick himself undergoes substantial physical and mental changes, shedding his hair, developing a tough outer skin, developing webbing membranes and losing the ability to communicate since his ears and voice are now adapted for the much thicker atmosphere of Titan. By the time the unethical nature of the experiments are laid bare, Rick is so Titan-adapted that he is dying in Earth conditions. At the end of the film he is left alone on Titan.

 

As many commentators have pointed out, it’s not entirely clear how the adaptations and training in this film (which seems to focus on swimming and holding one’s breath) actually address what we know of Titan’s conditions, even if that extent of transformation of an adult were (or becomes) possible. Setting aside the dubious science, though, the film asks a wider question about artificial human adaptation to extreme environments: at what point might an adapted humanity’s priorities, mindset and experience of reality - as well as appearance - so diverge from that of Homo sapiens that it is no longer recognisable as human?

Titanian Life

 

Of course, humans and their own interests are not necessarily everything. Perhaps the biggest lure of Titan in popular imaginations is the idea that its thick atmosphere and liquid surface - closer to Earth than anything else in the Solar System, even if at a very different temperature - might be able to support life of its own. Early fiction of this kind, such as Weinbaum’s Flight on Titan populated the new world with exotic life that could exist at frigid temperatures but not necessarily those below human tolerances. As observations became more detailed, authors had to adapt to the idea that any such life would have to be substantially different to that on Earth. Nourse’s Trouble on Titan, for example, imagines a silicon-based life form (the clordelkus) that processes oxygen from rocks and so presents a threat to the integrity of pressurised sub-surface channels. However as the truly appallingly low temperatures actually extant on Titan have been recognised, images of Titanian life has had to become more complex.

 

While Stephen Baxter’s Titan concentrated on the journey and its impact on the characters, the mission it describes was driven by the idea that a probe mission (in this case the then-forthcoming Huygens) might detect signs of non-equilibrium chemistry - in other words life. Baxter (following earlier researchers) hypothesised a form of low temperature life in which liquid ammonia (H3N) was used as a solvent rather than liquid water (H2O) as on Earth. Indeed there are close analogues to most compounds required by life that could use this solvent. In the final sequences of the novel Titan, we learn both that the traces detected were fossils from the earliest stages of the hot young solar system, and that the during the end stages - when the Sun expands into a red giant and Titan experiences its second warm ‘summer’ - such life may evolve again into a full and rich ecosystem.

 

Contemporary with Baxter’s writing is Down in the Dark, a short story by William Baron which appeared in the December 1998 issue of Asimov’s SF. It shares interesting parallels with Titan. In both contact is lost with Earth after an asteroid strike, and a very few survivors struggle with Titan’s conditions. However here there is an established settlement of several tens of people, and the story focuses on a technician visiting a scientist in a remote outpost. There he finds her studying strange brightly coloured streaks on the ground which seem to move. As she tells him “They’re a kind of… a complex waxy polymer construct. They form at the interface between the Waxsea and Terra Noursae, apparently.” or, put more simply, they’re “Wandering goo”. However it becomes clear that these bright waxy objects are not just a form of Titanian life, they’re intelligent and aware of the predicament in which the Earth-people find themselves.

 

Similarly bizarre and alien life forms are the “flying cloaks” described by James Blish in How Beautiful with Banners (short story, 1966). These are lifted in Titan’s thick (but cold, -316oF) atmosphere, which is being studied by a human being enswathed in a space-suit membrane formed by a living virus brought from Earth. The lyrical story studies both the aesthetics of these alien creatures and the way in which interactions between Titanian and Earth life might have unpredictable results.

 

Michael Swanwick explored a different kind of life again in his short story Slow Life (first appearing in Analog SF, December 2002). This centred on a scientific mission to Titan, correctly describing the nitrogen/methane atmosphere, low surface temperatures and the rain of complex hydrocarbons known as tholins. Baxter’s Titan also addressed this constant tholin rain and the sticky slush on the ground, which the astronauts in that novel described as “gumbo”. Swanwick instead describes it as “like wading ankle-deep in molasses”. His scientists take samples and send out probes, including one designed as a fish to sample the oceans. However one scientists begins to experience dreams whilst in the midst of a crisis, and realises that she has made mental contact with an intelligent life form below Titan’s oceans - and destroyed its worldview and sense of self at the same time. This is described as a complex organic structure surrounding a volcanic vent, deep in a sub-surface ocean, although it’s unclear whether magma volcanism or cryovolcanism (at temperatures in which water-ice acts like granite) is being discussed here.

 

Such stories, looking at how humanity might interact (or even recognise) alien life on Titan, as well as considering issues of planetary protection, continue to be written, and continue to be shaped by our improving understanding of Titan’s conditions. Two very recent examples can be found in the anthology Life Beyond Us (eds. Novakova, Law & Forest, published by the European Astrobiology Institute, 2023) which features short stories accompanied by essays by scientists.

 

The Lament of Kivu Lacus (short story, B Zelkovich) describes a married couple of researchers in an output half-submerged beneath the surface of a Titanian sea. They become aware of musical sounds produced by a large aquatic lifeform which inhabits the liquid methane sea, and which they dub a “whale”. At first they only hear the sound from a female. As the creature approaches and they begin to catch glimpses, it is eventually joined by a male and the two couples become aware of and connect with one another… but at the same time the narrator’s wife is dying of a terminal illness. The accompanying essay (by Ania Losak) explores the benefits to sending human explorers and scientists across the solar system in place of robots, despite the relative frailty of humans and the great expense of keeping them alive.

 

By contrast, Titan of Chaos (short story, G. David Nordley) is a more active story, in which the protagonist must rescue a small group of humans whose submersible vehicle has become lodged in the throat of a giant Kraken Sea worm on Titan:

 

“I tried to get my mind around the immensity of the animal. About sixty meters around and kilometers deep, its walls about half a meter thick, and an annual area something like thirty square meters, so about 30 tonnes per meter of length - more massive than a space station.

 

“It’s metabolism is glacial,” Watson said, “but it can store energy and its head can accordion out with surprising speed. They go deep enough to tap the temperature difference between the crust and the surface as well as interior chemistry.””

 

Despite the spectacular nature of this life, it’s put to a practical purpose, used by settlers to extract minerals from a body of water heated to a balmy 250K (well above the ambient Titan temperature) by cryo-volcanism. This is a Solar System at a more advanced stage of settlement than many of the other examples discussed here, with the narrator representing the Cislunar Republic (CLR)’s Saturn System constabulary, and responsibility for Titan divided between a Chief of Submarine Operations and a division of Blimp Operations overseeing liquid hydrocarbon seas and dense, nitrogen/methane atmosphere respectively. The narrative here is of typical human rivalries and commercial self-interest, carried with the race to the frigid oceans of Titan. The associated essay (by Fabian Klenner) discusses possible hydrocarbon-based biologies on Titan given known conditions there, including the potential for tapping thermal gradients, and also the upcoming Dragonfly probe mission to the moon.

 

Open for Exploration

 

Titan is a world about which we now know a lot, but still have much to learn. The Huygens lander of 2005 was expected to land on a liquid or slush surface, and instead came down on a dry lakebed surface coated with sand-like grains of ice. It nonetheless provided abundant information on the surface and atmosphere conditions. Its parent probe, Cassini, stayed in the Saturn system for thirteen years, and used Titan’s gravity as a navigation tool during repeated visits. As a result, it surveyed Titan extensively and confirmed the presence of liquid bodies on the surface, as well as the hydrocarbon composition.

 

The next (and currently only) planned robot probe to visit Titan will not arrive until the middle 2030s. This probe, Dragonfly, will be a rotor-copter drone capable of vertical take off and landing, and will be equipped for survey and chemical analysis - with a focus on conditions for organic or preorganic microbial life. While several earlier stories of Titan mentioned above (such as Flight on Titan) described violent storms, the dense atmosphere and low surface gravity of the moon actually make its weather relatively benign for drone flight.

 

However human spaceflight to Saturn’s moons remains firmly in the realm of science fiction at present. We currently lack launch capabilities (e.g. rockets) capable of providing enough change of velocity (delta-v) to propel large spacecraft to the Saturn system. A large craft would be required to carry humans together with all their life-support requirements and supplies, and still more would be required to make the return journey. As the hardest (i.e. most technologically-focussed) of the science fiction narratives I’ve discussed, Titan by Stephen Baxter, described, even if such a launch capacity were cobbled together from many existing and planned heavy-lift capabilities (including those aimed to reach Mars), at great cost, the astronauts would be subject to many years of space travel with the associated hazards: radiation exposure, muscle-loss, circulation problems and perhaps neurological problems in microgravity, unbalanced closed-cycle life support systems, interpersonal conflict, isolation, claustrophobia and other mental health difficulties. If any survived to arrive on Titan, current space suits would be unequal to the constant cold there - unlikely to be viable, let alone as (relatively) comfortable as those described in Down in the Dark or Slow Life, let alone the organic suit in How Beautiful with Banners. As Baxter also noted, it would likely be a one-way trip. Returning from Titan would require an equally ludicrous delta-v - and one not backed by the industrial infrastructure of Earth. Short of a breakthrough in space technology, of the types described in Imperial Earth or Trouble on Titan, such a mission would require a major cultural shift and rebalancing of scientific priorities versus value placed on human life.

 

The prospect of Dragonfly, and perhaps future probe missions, nonetheless provides abundant food for thought - both scientifically and in science fiction. Titan, as a cold world, and as a moon orbiting a gas giant, provides an interesting local example to compare with the many exoworlds now being discovered by astronomers around other stars. It also remains perhaps the most promising abode of potential life in our own solar system. Inevitably, changes in our understanding - whether life is discovered or not - will continue to inspire fiction over the coming years.

 

“Saturn’s Titan”, Elizabeth Stanway, Cosmic Stories blog. December 2024.

 

[1] While I’ll mention some of the well-known classics, such as these well-anthologised stories, I’m also going to try and explore a few less well-known examples here. [Return to text]

 

[2] Miniaturisation for medical operations is a familiar trope also seen in the films Fantastic Voyage (1966, dir. Fleischer) and InnerSpace (1987, dir. Dante) and the more recent Doctor Who story “Into the Dalek” (2024) amongst others. The scientific issues with this scenario are too big to discuss here but see my earlier blog on human miniaturisation. [Return to text]

 

[3] Robert Willey was, in fact, a pen name of science writer Willy Ley who wrote factual articles for Astounding Science Fiction for many years. Writing before Kuiper’s observations in 1944 his narrative confidently predicts that conditions on Titan may be Mars-like - far more benign than they really are. [Return to text]

 

[4] Baxter’s Titan is a book that gets successively more depressing as it goes on. It is also remarkably accurate in its extrapolation from the then-present of 1998, with the ageing shuttle Columbia destroyed during attempted reentry, the rise of popularism and Christian fundamentalism, increasing tensions with China over space and the south china sea, social media and online influences causing increasing disconnect between generations. We must hope the more cataclysmic aspects of Baxter’s predicted future prove exaggerated. [Return to text]

All views and opinions expressed are those of the author, and do not necessarily reflect those of the University of Warwick. All images are sourced online and are used here for academic commentary and criticism.