Cerberus: the ultimate desert coast under a white-dwarf sun. I’ve worldbuilt for it once or twice on this website, but although alien, I haven’t explored just how alien Sirius B’s planet in my fictional universe would be until recently. There are also new aspects to the planet that I’m adding in because of dramatic considerations, which also fit in to the quite un-Earth-like nature of this world.
To start off with, in my science-fiction universe, Sirius B hosts a planet, named Cerberus, which has an atmosphere of almost pure oxygen at 0.1 bars worth of pressure; a tenth as thick as Earth. Which sounds like it’d be much too thin to breathe, but as many a scuba diver knows it’s the partial pressure of oxygen (i.e. the absolute amount of oxygen) that matters, and 0.1 bar of oxygen is about half of Earth’s sea-level concentration, similar to the levels found in the high Andes or Tibet. To wit, equivalent to 18,000 feet altitude; breathable with adaptation.
But the very thinness of the air, even though it’s breathable, leads to interesting effects. By default the color of the sky will be blue, just like it is on Earth, but there’s only a tenth as much gas present, so at the horizon at midday the sky will appear a deep almost violet blue, and the zenith will appear almost black. Even at midday. This is a somewhat familiar phenomenon, in as much as the views from airplane windows at normal flight altitudes approximate this, only on this world you see it from the ground. Very spacey, and very classic sci-fi.
More classic old-timey sci-fi vibes come courtesy of how at lower pressures the wind can blow much faster for a given amount of energy. Gale-force winds? Nearly a constant. Hurricane-force? Routine. But you wouldn’t feel it shove you around because there’s only a tenth as much air blowing around. The net effect is you can stand easily but there’s an ebbing and flowing high-pitched hiss or shrieking sound. Again, very sci-fi.
Even more classic sci-fi vibes come courtesy of how I envision Cerberus as being hyper-arid in climate; there’s virtually no precipitation. The planet is mostly ocean, but the ocean water is so salty that it easily stays liquid at temperatures of 0 Fahrenheit or lower, and indeed the water temperatures might average around 0. This means little evaporation and hence little precipitation or humidity globally. Which too has interesting effects.
The continents I envision as being dominated by 60,000 foot tall or so columns of volcanic origin similar to Devil’s Tower in shape, only far more imposing. At the tops of these towers, the high plateaus, the air pressure is actually rather similar to Martian global averages, certainly well under the Armstrong limit (when pressure drops enough that the boiling point of water, which lowers with lower pressure, slips below the human body temperature, meaning you suffer ebullism). But there’s still enough air up there that at night when it cools off — and cool off it will, rapidly, because the thin air holds very little heat, leaving to daily ranges of 60 degrees Fahrenheit even at the beach, with ranges widening to 150 degrees or so in the deep interiors — that katabatic winds will scream down those cliffs, much like we see in Antarctica and Greenland today on Earth.
These katabatic winds on Earth already can reach 200 miles per hour, but with the pressure being so low here, speeds can build up even more; supersonic flow would easily be reached, with extreme wind gusts in ideal topographies perhaps even reaching 2000 miles per hour.
The exotic aspect here is that even a moderately supersonic wind would still not impart enough kinetic force to knock a human being off their feet, but any debris blown around would impact with just as much force as the speed of the wind suggests — it’s simple physics. And this is a hyper-arid world where the ground is dominated not by soil, but by regolith made of shards of volcanic glass. So it’s rough, it’s sharp, and it’s everywhere…and in the worst areas it hits your body at 1000 miles per hour.
The net effect? You could stand unaided in that supersonic wind, but when it blows up the dust would literally ablate your skin off in a matter of seconds. Certainly more toward the horror end of the sci-fi spectrum, but since you could easily stand up against the kinetic force, if you had a protective suit on to absorb the impacts you’d be just fine. The design of such a suit would be thick, no doubt with a protective helmet you could see out of, sort of like if you wore an outfit made out of kevlar and bulletproof glass. Again, very classic sci-fi.
Even more classic vibes come in from the structures that would prevail on such a world; against weather such as this, buildings wouldn’t have a hard time standing against the wind — indeed, especially considering gravity is lower as well, skyscraper construction and maintenance would conceptually be much easier than on Earth — but they would need to have a streamlined shape to deflect the high-speed dust and debris impacts, as well as windows and awnings to protect against nightly winds and gust fronts. Get the geometry right and you could even leave a crack open in complete safety to get fresh outside air.
And yes, people would want to get fresh air. All the time, on such a world. Because although the temperature ranges might seem extreme and cold, they are actually about optimal for human comfort. Already in our world it’s reported that at high altitudes near the equator, the air is so thin and the sun is so strong that even 60 degrees Fahrenheit can feel hot in the sun, though the shade feels chilly and nights can feel very cold indeed. Thin, dry air just doesn’t conduct or convect much heat (either toward or away from the body), so radiative effects dominate: to wit, in the sun, with all the heating its light provides, even very modest temperatures are more than enough to feel comfortable, as sweat wicks off the body more efficiently than any environment our ancestors were in.
Thermal management is simply easier in low-pressure environments with plenty of sunlight and little humidity, both for humans and for our industrial operations. Hence why high-altitude deserts are as popular as they are, and only growing more so; Cerberus just takes the same concept and turns the dials all the way up.
Yes, on a world like Cerberus, you would need to close those windows when the wind blew fast, because while the air wouldn’t be nearly thick enough to knock you down even at supersonic speeds, or even shake your building, the smallest piece of debris would impact like a gunshot against the building, and there would be an omnipresent ebbing and flowing high-pitched shrieking sound. Very alien, and very classic sci-fi.
All these strong winds would no doubt create vortices, even in the absence of much humidity or precipitation, which may well resemble the tornadoes familiar to us on Earth, only on Cerberus they’d scream at up to 2000 miles per hour. Even fancier is how Cerberus, while hyper-arid, is likely not entirely devoid of precipitation, let alone cloud cover. Where atmospheric rivers (in relative terms; there’s very little moisture available from that cold salty ocean, but no doubt it would concentrate in some areas…) interact with favorable topography, the default way precipitation forms on Cerberus may well be a rotating supercell of a thunderhead, given the vigor of the rotating winds.
Most of the time the clouds would tower in their rotating magnificence and that would be the end of it, bar the odd shaft of virga or two. Which considering how cold the upper levels of the atmosphere most likely are would no doubt take the form of snow…or hail. Consider that with abundant dust to nucleate and extreme winds, hailstones may well be the most common type of precipitation on this planet, in stark contrast to Earth.
Naturally at supersonic speeds, up to 2000 miles per hour, these hailstones would impact anything they touched with extreme force. So in areas with topography favorable to supercell thunderstorms, the rock faces would be pockmarked by craters not from meteors but from hail. Just brutal weather.
Aside from the hail, though, we can reasonably suppose that snow would be much more common than rain on Cerberus. Why? Because of evaporative cooling. Yes, during the coast daily highs rise to 60 Fahrenheit, and in the interiors could easily exceed 100 degrees, but there’s virtually no humidity in the air. I envision relative humidity during the day being perhaps 1% in many cases. And that means “wet-bulb temperatures” would most assuredly be below freezing most of the time. Sure, sometimes you’d see some raindrops fall at first out of these supercells, but once the temperature reached 50 degrees or so (!), it would change over to snow. And if heavy snow continued to fall, temperatures would quickly crash to around 0 Fahrenheit. Still with low humidity by Earth standards, but dank compared to usual.
With such strong winds, as the supercells dissipate, winds resembling terrestrial gust fronts would radiate out, creating drafts of air that smelled of ozone and minerals, crisp and fresh, much like the aftermath of an alpine thunderstorm on Earth, only far more pronounced.
No doubt a lot of dust would be carried out, both by these relatively rarer thunderstorms and the more ubiquitous katabatic winds and sea breezes. The sky is dark blue on Cerberus by default, but in areas of these dust hazes the sky will no doubt acquire a more Martian cast. Ordinarily this would turn the sky orange to red, much like what we see on Mars, but keep in mind Sirius B, this world’s sun, is a white dwarf, not a main-sequence star like our sun, and its spectrum is shifted toward the blues and the ultraviolets. Therefore the net effect is Cerberan dust haze leads to a yellow sky.
Notice the overlap with classic sci-fi, from the pulps right on through “Star Trek: The Original Series”. And there’s a simple reason for that: a body such as Cerberus is frankly intermediate between Earth and Mars, and such bodies were presumed to be the most common habitable environment for humans and Earth-like life in the universe. Consider that even in our own solar system we see larger numbers of smaller bodies, so planets smaller than Earth should be more common in the universe than Earth-sized worlds are. The modal world you can walk on therefore was expected to be intermediate between Earth and Mars: thin air with wide ranges in temperature between day and night, and likely dry and dusty as well, with winds screaming at high speed and high pitch but with little force. Perhaps hot, perhaps cold, but once you see the theme it’s hard to un-see it.
Even much of the physics was gotten completely right. In “Mudd’s Women”, an episode of “Star Trek”, one of the women suggests to her new miner husband to just put the pots and pans outside and let the sand blast them clean (much easier in a thin atmosphere where sand is blown at high speeds but the air just isn’t massive enough to blow anything away!). And in many a planet it’s reddish desert, much like Mars, often with a reddish sky (again, like Mars), with high-pitched winds. Comfort? Barely even a consideration, unless you’re outside at night (like the poor away team in “The Enemy Within”). Consider that even Vulcan answers to this general description: hot, yes, but described as having notably thin air; so the human away team is depicted (realistically) as being able to function outside with not much problem, with the only issue being Captain Kirk tiring easily exerting himself in a fight (classic high-altitude-style symptom: low oxygen). Lush Earth analogues do appear in “Star Trek”, yes, but they’re not as common. The modal Federation world is depicted as being rather more Martian in character, though still thick and lush enough to be habitable.
And you see this in so much science fiction of the period, before the idea took hold that life (humans included) was fragile and needed thick atmospheres to protect against radiation and buffer extremes in temperature, hence why we see in later science fiction Earth analogues take over (often with thicker air than on Earth).
But would people even prefer these lush worlds over their more Martian counterparts? Consider that thin dry air is just very forgiving. I have the metabolism of a Neanderthal yet a sunny 90 degree day here in California permits me to be outside as long as I’m in the shade; and of course mountaineers report that in full sun even temperatures not far above freezing can feel perfectly comfortable. Humidity conducts heat away from the body very effectively, and rainfall is even less forgiving. Logically the range at which humans can thermally manage themselves well enough to be comfortable will just be far narrower on high-pressure, thick, humid, rainy worlds than it’s going to be on low-pressure, thin, dry worlds.
Ergo, most of these wet, lush, thick-aired worlds are just not going to feel very good to be outside in; the modal space colony planetside in the future may well resemble the more Martian vistas of “Star Trek” and the old-timey stories…
“Star Trek” even gets another aspect of the physics right: caves show up a lot in the franchise, even in the original series, and it often gets ridiculed for that, but a cold, dry, thin-aired world like Cerberus would present an extremely forgiving environment for deep cave systems.
Consider that in Cerberus’s case my concept was that it formed in an outer-solar-system-style environment to begin with and then lost most of its water ice, leading to global oceans being retained but with only a wisp of an atmosphere, but where there was ice there now is just voids in the rock, leading to extensive cave systems: very large chambers (helped along by low gravity; the Moon, for instance, is thought to have cave chambers a mile wide, and that world doesn’t even have swiss-cheese geology!), extending very deep down.
On Earth the baseline at sea level is already thick, warm, and humid, so even shallow caves tend to be a clammy 60 degrees or so, with pressure around 1 bar. Go deeper and it gets suffocating: temperatures and humidities at sauna levels, with pressures rising to the point it’s hard to even breathe.
On Cerberus, by contrast? The surface temperature averages maybe 0 Fahrenheit, with pressure at 0.1 bar, all oxygen, humidity minimal. The inside of a cave would have what we’d consider impossibly crisp alpine-style air. And that extends extremely deep down. On Cerberus, due to it being smaller and geologically quieter than Earth, the geothermal gradient is gentler to begin with, but even without that factor, you have big airy cave chambers that even 10 miles down would be at maybe 0.2 bar worth of oxygen, with dry air at maybe 50 degrees. You’d only approach 0.3 bars (so much oxygen it becomes a bit harder to breathe) and temperatures approaching the boiling point at 20 miles down or so.
You could go almost arbitrarily far down, as far as the cave systems take you, and be perfectly comfortable, perhaps even more so than on Earth (!). Consider that the winds on the surface blow so strongly that air movement in the caves, even very deep down, would be fairly rapid. The large sizes of the cave chambers, the no doubt generous openings to the surface, and the extremely fast winds would ensure ventilation even miles underground. Consider also that with so many of these caves being interconnected, there are strong pressure gradients throughout the system, so these caves, unlike Earths, might be very windy. Not to the extent the surface is, but if you had a scenario of a sheer drop extending a mile or so down into another chamber, with the interface squeezed into a narrow volume, you could see winds screaming in and out in a daily rhythm up to 200 miles per hour or so.
This is a real phenomenon on Earth, by the way, this diurnal cycle: it’s called “cave breathing”. But our air is so thick and our winds so quiet that it’s a very subtle flow. On Cerberus? Nothing subtle about it at all. You hear that same high-pitched shriek on a regular basis in the caves too, which no doubt with all the echoes rebounding throughout the chambers might have a uniquely alien quality.
Also alien is how these caves are deep in a layer of permafrost, which extends very deep down. Ice will tend to accumulate in all these caves, and while dry, they’re still more humid than at the surface, so you end up with an underground landscape that’s dominated by snow and ice. And with these chambers extending for a mile in each direction easily, it would have the feel of a skiable, snowboardable hollow Earth.
Now, so much of this I’ve worldbuilt is because a character I have in mind to send on the expedition is supposed to be avid skier and snowboarder, and sending her into a dust bowl would just be too sad. Though most likely the ice would be in the form of…well, ice, one could posit the existence of microbes that thrive in these caves and break down the ice into something resembling fluffy powdery snow. This also has the fun side effect of making the snow much more transportable, and with those winds screaming through, each breath of the cave breathing means ground blizzards. In caves. How spectacularly alien is that?
Indeed one can envision these caves, with abundant water and dynamic changes, yet sheltered from the harshest surface conditions, as the primary habitat for land-based life on Cerberus, which adds a whole new dimension to the world I’ve built that’s creative, alien, and yet physically plausible at once.
And more reflected in classic sci-fi than we might think: consider that if the modal planet visited in “Star Trek” has thin but breathable air along with cold temperatures, i.e. Mars Lite, then caves would tend to be very hospitable indeed. I’m thinking of Janus VI in “The Devil in the Dark”: a treasure trove of minerals, and yet notice the entire Federation mining colony there is deep underground in a cave system, apparently without any challenge to human comfort whatsoever. Most likely Janus VI has a thin oxygen atmosphere and cold temperatures up top, perhaps not even quite thick enough to breathe unaided, but some miles down you encounter crisp alpine air.
Makes you think, doesn’t it?
I’ve also done some pondering as to the origin of Cerberus, and I like the idea of it being a lost moon of one of Sirius A’s gas giants that was captured later by Sirius B. Which suggests that it might have a singular origin, calling into question the idea of any more planets orbiting Sirius B. Yes, the idea I had with an orbital resonance with an inner planet that causes eclipses is cool, but it feels a bit too extra and too complicated, especially for the purposes of telling a story. Perhaps it’s better to let Cerberus be a singular planet, and absorb all the focus. There’s enough going on without spicing it up with fancy orbital configurations.
Consider also that planetary formation around white-dwarf suns is likely less common as well, so having only one planet, and even that captured from a companion star, makes sense. Though recent research has revealed that planetary formation around white dwarf stars probably isn’t that rare. And, more importantly, that white-dwarf suns might be much more hospitable to Earth-like life than previously assumed. And another hallmark of classic sci-fi was the willingness to contemplate other worlds around stars with exotic spectra: perhaps this is even reflected in the real-life distribution of habitable worlds for man; sure, perhaps the usual “FGK” parts of the Hertzsprung-Russell diagram have the most Earth analogues orbiting them, but consider that even A-type stars last for a billion years or so on the main sequence, which could easily be enough time for complex life to emerge (sure, on Earth it took longer than that, but not tremendously longer). White dwarf suns even have some advantage over our sun; they tend to be more stable in their output and only cool slowly, being devoid of flares and various extreme events that could be challenging to life.
The wrinkle is that their spectrum is shifted toward the blue and the ultraviolet, so a world like Cerberus would experience much higher UV radiation levels than Earth does. The extra ultraviolet radiation from its sun actually stimulates production of ozone, but consider that with 0.1 bars of oxygen to work with it’s still going to be a weaker ozone layer than Earth possesses (even if it’s more comparable in thickness than one would expect at first), and the total amount of ultraviolet radiation coming in from the sun is just much greater. The net effect? The surface at midday at low latitudes is going to peak out with a UV index more like 40, not the 10 or 11 we’re familiar with from Earth. You’d be sunburned within a minute. But a UV index of 40 at the peak is still low enough that very early or late during the day or at high latitudes the UV exposure would be familiarly Earth-like.
In any case even a UV index of 40 is nothing sunscreen or protective clothing can’t handle; these levels of radiation were what we think would have happened by the 2040s in real life if CFCs were emitted unchecked, which would have heralded the collapse of the entire biosphere, but from a human comfort perspective it’s actually manageable…and on Cerberus the local life would obviously be adapted to handle the higher radiation levels.
Again, the net effect is very classic sci-fi, and taking into account the full sweep of the environment, life on Cerberus would feel both closer to and more exposed to outer space, and actually more forgiving than the mother planet.
Consider if a human born and raised on Cerberus ever visited Earth. Compared to what she was used to, the air on Earth would have twice as much oxygen, yes, but the air is literally ten times thicker. Every movement would feel like resisting some thick fluid, the wind hitting with great force with every gust, to the point she might even compare it to being underwater. Not helping matter is how the ocean on Cerberus is saltier than the Dead Sea on Earth, so with a suit to protect against the cold, floating would be a given, swimming very easy; Earth ocean water by contrast would feel like you were sinking like a rock unless you exerted great effort. The fact Earth has more surface gravity than Cerberus would only make the effect more pronounced.
Thicker air also conducts heat away from the body much more easily, and the atmosphere is very humid compared to what she’d be used to, making it hard to breathe and most temperatures during the day uncomfortable to be outside in. Even the sky would seem very murky compared to what she was accustomed to; blue from top to bottom, and very bright, with an omnipresent haze obscuring the stars and the planets. Somewhere like Badwater Basin would feel more familiar, as far as actually being able to see the sky clearly is concerned (not to mention the salt and the dust in the air column), but even that would be thick and murky compared to their childhood.
Earth, the paradise planet? More like an unforgiving jungle of a world! Much kinder to be in a world of low gravity, thin air, and clear skies. Perhaps those colonists in the likes of “Star Trek” were onto something after all…