I know I just revisited my fictional planet Cerberus…but why not revisit it again? It is my blog, after all. But seriously, I do have some more details I’ve settled in on as I continue to tune the environment to suit the vibe I have in mind. In particular, in my science-fiction universe it’s the nearest world to Earth that has a solid surface that is a shirt-sleeve environment, where you can stand outside without protection on terra firma and breathe the ambient air. That’d make an amazing target for bold explorers…
In short, Cerberus orbits Sirius B at a range of 0.02 AU, but since it’s a dim white dwarf this is enough to keep its temperatures basically Earth-like. Though with an atmosphere just a tenth as thick, greenhouse effects are noticeably lesser, leading to a much colder climate. Ordinarily this would lead the oceans to freeze and for Cerberus to be a Snowball Earth, but the oceans are about as salty as the Dead Sea on Earth, so they stay liquid not down to the mere 27 degrees Fahrenheit of Earth seawater, but rather all the way down to -50 or so. Alien enough for a human to float easily when swimming, hostile enough to mean instant death without a wetsuit, but domestic enough that a beach would look, feel, and sound very familiar, even if the waves are larger and move more slowly due to gravity only being half as strong as on Earth.
Investigating the salt content, in particular, I find that the kind of salt matters a lot for how freezing-resistant saltwater is. Our own Dead Sea and Great Salt Lake are mostly sodium chloride, as is the case in seawater, and a eutectic mixture of water and sodium chloride (i.e. plain ordinary table salt; heh) freezes at -6 degrees Fahrenheit. At the eutectic it’s at full saturation and is more like a gooey brine, so the more domestic Great Salt Lakes and Dead Seas of the world tend to freeze at temperatures above 0 Fahrenheit. Meanwhile, Don Juan Pond in Antarctica has only slightly greater salinity yet it stays liquid down to a studly -50 Fahrenheit or better. This is because Don Juan Pond’s salts are mostly calcium chloride, which in a eutectic mixture with water freeze only at -67 Fahrenheit. Thus Don Juan Pond, which is near saturation, virtually never freezes over, despite being located deep inside what ought to be an icy climate zone.
The oceans on Cerberus thus are primarily saltened by calcium chloride, not sodium chloride. How could this be? Turns out that Earth’s sodium chloride enrichment comes courtesy of the type of rock that makes up our continental crust; mostly granites. My world’s continental landmasses are dominated by volcanic glass and various forms of basalt (in Devils-Tower-like formations that rise 60,000 feet above the sea level, by the way), which tend to give salts that are much more enriched in calcium chloride. It’s also worth noting that evaporite processes, such as those from large-scale atmospheric and oceanic stripping, should be expected to lead to less sodium chloride and more calcium chloride being present. A different mechanism, yet with a result carrying an Antarctica-in-space cast to it.
Indeed the hyper-arid nature of the climate would give my world a rather Antarctic vibe, in general, which seems strangely under-used in science fiction, particularly in recent generations. I’ve been thinking since my last post: what if I pushed this motif further?
In particular I’ve been wondering about the configuration of the continents on Cerberus. Thalassa, my lush ocean world orbiting Proxima Centauri, has no land, just sea ice on the dark side of the planet, but Cerberus’s land-and-sea mixture is much more Earth-like. Do I scatter small continents all over, a la Earth, or do I concentrate them into a single supercontinent? Interestingly, despite being in a spin-orbit resonance, tidal forces would not lead to a tendency for land to concentrate in specific parts of the planet, because the tidal bulge is not static; with a 2:1 spin-orbit resonance instead of a 1:1 tidal lock, the tidal bulge moves smoothly across the planet. Alien in mechanism, yet rather Earth-like in result.
However, I’ve decided that I might just go with a supercontinent anyway, though a supercontinent of the more terrestrial variety, where the tectonics just happen to congregate most of the continents into one area. I pondered yesterday the idea of a tropical supercontinent, a mid-latitude supercontinent, or a polar supercontinent, and I think I just might go with a polar supercontinent. For bonus points make the supercontinent centered around the south pole, much like Antarctica, but since the vast majority of land here is contained in the south the default orientation for a world map would be south up, instead of north up, which would be a delightful change. Also a delightful change would be wind rotation patterns characteristic of the southern rather than northern hemisphere.
An effect here is that if I want my desert coastal climate to be 60 Fahrenheit by day and 0 Fahrenheit or so by night, with greater extremes in the continental interior, this suggests polar waters should be around 0 degrees Fahrenheit on average, meaning that mid-latitude and equatorial waters would be warmer.
This might be a bit of a problem, since at 0.1 bars of atmospheric pressure water boils at 115 Fahrenheit, which is very substantially lower than Earth. Amusingly enough the chemical composition of these oceans is forgiving: the liquid range ranges from -50 to +115 Fahrenheit, a range of 165 degrees, only modestly less than our familiar +28 to +212 (a range of 184 degrees). Human comfort is also shifted downward; as climbers on high mountains report, in direct sunlight and with thin dry air even temperatures modestly above freezing feel perfectly comfortable. You just don’t need as much atmospheric buffer on such a world to maintain habitability, or even human comfort!
But consider that Earth’s polar seas are let’s say 30 degrees Fahrenheit; tropical waters average 80 or so, pushing 90 at the extremes. That’s a range of 60 degrees. Giving Cerberus the same range by latitude means that if polar waters are around 0 degrees we’d expect equatorial waters to be 60. Though if the ocean is global bar the south polar supercontinent heat might be better distributed than we’d expect, so in reality equatorial waters might be more around 50 degrees Fahrenheit with 60 being the extreme high end. Deep polar waters might average as low as -20 at the extreme end, still liquid: this is a world without sea ice, despite the cold air.
In any case, 60 degrees is comfortably below the boiling point of 115, and evaporation would be fairly minimal. Consider that what little warm moist air is generated would be strongly attenuated by the time it reaches most of the continents up south, because like our Antarctica it’s likely the supercontinent would be encircled by a cold circumpolar current which would isolate its waters and keep it nice and chilly and dry, though with the convergence of warm and cold waters around it, as with Antarctica in our world, being host to a potentially extremely productive habitat for local life.
Siting the supercontinent near the pole also has other interesting effects. Cerberus’s ultraviolet radiation levels are higher than Earth’s; Sirius B puts out a more UV-rich spectrum than our own sun to begin with, and although the oxygen-rich atmosphere would generate a respectable ozone layer (perhaps three-quarters as thick as Earth’s), the UV index would be expected to be 40 or better at noon in the tropics. Easily enough to cause sunburn in less than a minute. But a polar site, assuming an Earth-like axial tilt, means the sun peaks at a lower angle, so the UV index in our southern supercontinent would be more domestic.
At a low axial tilt, the sun would never rise more than 30 degrees or so above the horizon in even the northerly reaches of our south polar supercontinent. UV indexes? Probably no more than 20 on a bad day. Worse than Earth but not drastically so. The harsh ultraviolet radiation as the sun mostly circles you in the sky instead of rising or setting vertically lends yet more Antarctic vibes, so I’m liking it.
Something more exotic, though, comes once you approach the poles themselves. With low axial tilt, the sun’s path in the sky becomes closer and closer to a circle. At our poles the sun corkscrews up to 23.5 degrees above the horizon at the summer solstice and 23.5 degrees below at the winter solstice. Not coincidentally our planet’s tilt is also about 23.5 degrees. Without any tilt, the sun at each pole would just circle around the horizon endlessly. Providing essentially endless sunlight!
Exactly this effect is seen on planets like Mercury and the Moon, which have much lower axial tilts, and there are certain peaks in the polar regions where the sun shines the vast majority of the time. Elevation helps, since the horizon is “depressed” downward due to the curvature of the planet, and my towers at 60,000 feet above sea level are tall enough to get this effect pretty significantly; something like 4 degrees worth. So near the poles there will be peaks where Sirius B circles just above the horizon but never sets. And the hyper-arid climate and relative lack of cloud cover means that there will indeed be sunlight virtually eternally. Wild stuff.
The only downside for human settlers is that that high up, with sea level already being just 0.1 bars, the pressure will be 0.01 bars, similar to the Martian lowlands, and not breathable even though those 0.01 bars are almost all oxygen (climbers would experience ebullism before they even made it up halfway). Pressure is still above water’s triple point, so water could still be liquid…under 45 degrees Fahrenheit; humans have the inconvenient feature of not being able to operate with such a low body temperature (an ectotherm such as a crocodile could do it, though).
But still, what a sight it would be, a true peak of eternal light. There would also be corresponding pits of eternal darkness; lower areas which are permanently shadowed. In Cerberus’s thin air these areas in the shade would never heat up much, even on summer days, though atmospheric diffusion of warmth might, unlike the Moon or Mercury, be enough to melt the top inch or so of permafrost on the warmest days. That’d be about it.
Consider also that Sirius B is not alone; Sirius A is also shining brightly in the sky, and it has a 50-year orbit. At furthest separation Sirius A only contributes 1% as much sunlight as Earth receives from the sun, which is significant but not decisive. But at opposition Sirius A puts out 30% or so as much illumination as Earth gets from its sun, which is significant to warm the climate pretty substantially and lead to a distinct second sun in an entirely different area of the sky. So unlike the Moon or Mercury the pits of eternal darkness might not be quite totally dark, but you do get the delightfully alien effect of double shadows on a 50-year cycle.
Shadows that would be very sharp and crisp, under light that seems harsh and bluish, owing to the thin air as well as how both Sirius B and Sirius A put out a bluer and more UV-rich spectrum than our own sun.
Aside from Antarctica, I’m thinking that Cerberus might evoke almost proto-Earth vibes, in as much as Sirius (both A and B) is on the order of 200 million years old. Earth’s sun is over 4 billion years old. One wouldn’t think this would be enough time for planets to have done much of anything except form and cool, but consider that Sirius puts out more ultraviolet radiation than our sort of sun does, and since radiation leads to mutation which is the driver of evolution, it’s entirely plausible that under such bright stars life itself could evolve as if the clock runs faster. Not too much faster, but at the 200 million year mark you could already see not only microbial cells but also photosynthesis having evolved, as well as aggregation into blatantly macroscopic structures.
Consider that while multicellular life might not be likely at this stage, life doesn’t have to be multicellular or strongly differentiated to be macroscopic; behold our very own lichens, which are single-cell life-forms but in colonies large enough to be easily observed by the human eye and be touched by our hands. Many lichens even have branching structures that are quite similar to plants! Meanwhile, underwater certain forms of algae can look impressive despite being compositionally simple.
This would be a fantastic angle to take for Cerberus, in my view, since at this stage in its evolution, if you assume an evolutionary clock fast enough for photosynthetic lichen to be growing all over the place but not anything truly multicellular yet, you could see lichen and algae, primary producers, have free reign over the whole planet. Without predation they’d just tend to grow wherever they can take root, with sunlight and nutrients, and become as large as they can without the wind or some such ripping them to shreds. Which means you could see branching tendrils of lichen everywhere; primitive under the microscope, perhaps lacking complexity even to a close inspection by the human eye, but it would visually register as “plants!”.
Even more alien vibes would come courtesy of the effects of the solar spectra on these photosynthesizers; why exactly most plants on our world are green is unknown with certainty, but it’s been speculated that plants tend to reflect green because the sun outputs most of its energy in that part of the spectrum, and reflecting that and absorbing adjacent colors helps to prevent scorching while still taking in most of the energy that’s available. If we follow this line of reasoning, then we should expect plants under a sun such as Sirius B (or even Sirius A) to be blue to perhaps purplish, not green. So you have this regolith of volcanic glass, towers of red and black stretching for miles up along this Dead-Sea-esque coastline, fog rolling in but with skies clear, the horizon blue but the zenith nearly black, the sun casting harsh sharp bluish light, with giant branching lichen dangling all over the place off those cliffs wherever some underground springs (perhaps driven by the extensive ice caves in this planet), blue in color.
The weather might be comfortable, the seas might feel familiar, the “plants” might even be soft and huggable, but it’s all distinctly alien, even though it’s rather closely based on the same building blocks as Earth’s biosphere.
Even more alien vibes come courtesy of the motion of the sun. With a 2:1 spin-orbit resonance, the planet completes two rotations per orbit, but the effects of orbital motion mean that an apparent solar day is twice as long, in this case being equal to a year. What this means is that when you add up these motions, there are periods in each orbit when the motion of the sun caused by the planet’s eccentric orbit overwhelm the rate of rotation, and as a result the sun stalls and retrogrades in the sky (sounds insane, but this actually happens on Mercury in our solar system). Twice a day, the sun would stall out and seem to go backward before resuming forward motion. On one of these peaks of eternal light near the south pole you’d see the sun circle eternally, but at specific points along the circle the sun would stall and the progression of shadows would seem to reverse course for a few minutes to maybe an hour. Really freaky.
And this effect of course is seen not only on the peaks of eternal light but across the whole planet, meaning that at certain locations experiencing multiple sunrises or sunsets per day might be common…a particularly pronounced effect compared to what you’d see on Earth, since atmospheric refraction is much lower, as is scattering of light, owing to the thin clear air. So as soon as the sun dips below the horizon the stars would peek out in nearly full glory. Already alien, but then you might notice that the sun rises back up again and the stars wink out, only for the sun to resume its downward course and the stars to come back out for the whole night. Again, really freaky.
Even with the deletion of the inner lava-dominated planet that I wanted to cause eclipses, this is heady sci-fi stuff that’s straight out of the classics, and I feel inspired as I continue to brainstorm for my world. I might want to dive deeper into Cerberus or perhaps explore more about Sirius A’s giant planets; we’ll see. For now I wanted to share the latest with you, because I think the Antarctic vibes and a lot of these details are really cool here. 🙂 More will be coming.