Argon Snows on an Ice Dragon Planet

“What about winter?” “You’ve already had it!” “We’ve had one, yes. What about second winter?”. On a planet with high axial tilt and/or an eccentric orbit, a short temperate summer can be envisaged, coupled with long cold winters beyond the ken of anywhere on Earth. Which is where my latest worldbuilding concept comes from. If a planet’s winters are truly exotic, dropping well below -100 degrees Fahrenheit, then the vast majority of the water-ice snow would occur in the fall and the spring. Where does that leave the heart of winter? As cold and dry as interior Antarctica, only the occasional ground blizzard for snowfall, right? Or does it?

Raining and Snowing Out Earth’s Air

Consider the major components of the atmosphere. Water vapor is a minor component, only 0.01 to 4% of the atmosphere, and produces appreciable precipitation. Carbon dioxide is 0.04% of the atmosphere and for all I know should precipitate in the heart of winter in parts of interior Antarctica (its freezing point is -70 degrees, and temperatures get much colder than that). As you pass below -100 and then -200 degrees, the water vapor and carbon dioxide left in the atmosphere will all freeze out as snow and join a very hard snowpack on the ground.

I’ve built a planet before, Belperev, featured in “Warp Dawn”, that has an extreme enough tilt and orbit for its winters to approach, but not exceed, the absolute limit of survival for Earth-like life: when oxygen starts to rain out of the atmosphere. That can only happen when it cools below oxygen’s condensation point, -297 degrees Fahrenheit. The freezing point for oxygen, when it starts to snow out of the atmosphere, is -361 degrees Fahrenheit. On Earth oxygen is 21% of our atmosphere, tens of times greater than water vapor’s concentration, so I can only assume precipitation would be correspondingly heavier than water-ice snow. The same sort of storm that gives you an inch of water-ice snow would give you a few feet’s worth of oxygen snow. Wow.

Interestingly, nitrogen isn’t terribly different. Nitrogen condenses at -320 degrees Fahrenheit, and freezes at -346 degrees Fahrenheit. Between -320 and -346 nitrogen rains out, and below -346 it snows out. Nitrogen is 78% of our atmosphere, so that would be a lot of rain and a lot of snow. Combined with the oxygen, this -350 to -380 degree range or so would produce truly extreme levels of snow I suspect. Enjoyment for Earth-like life would be limited by the atmosphere becoming thinner and less and less breathable the more it snowed out, to the point where eventually you would have to put on a spacesuit. Really puts a damper on the cool factor of having a second winter with an entirely new sort of snow.

Or does it? There is another significant component of Earth’s atmosphere: argon. The noble gas is 0.93% of our atmosphere, broadly comparable to water vapor in prevalence. We don’t think of argon in the same breath as water vapor because argon’s condensation point is -302 degrees Fahrenheit, far below the temperature range encountered on today’s Earth. But on an Earth analog with an exotic winter that could change. Interestingly, argon’s liquid range is very narrow at our 1 atmosphere of pressure; its freezing point is -309 degrees Fahrenheit, just a few degrees lower. So any argon precipitation would likely overwhelmingly be snow, unlike oxygen or nitrogen, which would (like water vapor) predominately tend to rain out, due to their wide liquid ranges at Earth-like atmospheric pressures.

It gets even better: -309 is slightly warmer than nitrogen’s boiling point of -320, and slightly colder than oxygen’s boiling point of -297. Most importantly, it’s considerably warmer than nitrogen’s freezing point of -346 and oxygen’s freezing point of -361. So there could be a climate with a stable temperature range in the heart of winter that’s cold enough for argon to snow out but not cold enough for oxygen or nitrogen to rain out much.

Argon’s snow-out would be comparable in terms of sheer mass to the water content of rains and snows on Earth. Several feet of argon snow accumulation would seem likely, though admittedly this is just a guess on my part.

Changing up Earth’s Atmosphere: toward an Argon Snowglobe

More interesting is the possibility of a different but still habitable atmosphere. In particular, in my post “Worldbuilding a Naked Jungle in Space”, I mention that for a story yet to be released I made a planet whose atmosphere was far richer in argon and much poorer in nitrogen than Earth’s. Instead of 78% nitrogen, 21% oxygen, and 1% argon it was 5% nitrogen, 63% oxygen, and 32% argon. Now that’s the kind of atmosphere that could lead to truly copious amounts of argon snow. It would also minimize any nitrogen rains that might mix in; presumably, like Earth water vapor, nitrogen and oxygen wouldn’t tend to rain out bar virga (which can be so beautiful!) until one got to the lower end of the liquid range.

The net effect? In that -309 to -340 range or so the atmosphere would still be breathable but the air would be like a snowglobe, puffy clouds pouring out ice crystals, only of argon, not water. Argon is monoatomic, so would probably form crystals more like shards or needles than the multi-sided flakes we see with water, but I can’t find much information on it, so I’m not sure. Videos and pictures I’ve seen show that argon forms clear colorless ice just like water does, so the basic form of the solid precipitation wouldn’t be very different. It would indeed be a second snow, a second winter.

Second Snows, Second Winters: more exotic habitable Environments

In a climate of this nature, where summers are temperate but winters drop to, say, -320, there would be copious water-ice snow as summer turned to fall, then a cold dry period until early winter (the equivalent of December), when the argon would start to snow out, continuing through the winter until the argon snowpack starts to melt and boil off in late winter (the equivalent of February), followed by another cold dry period until spring turned to summer, when the water snowpack melts off. Thus you get two distinct seasons of the year when you get frozen precipitation.

Really cool in my opinion, especially considering such an atmosphere and climate is technically a shirt-sleeve environment, habitable for humans! Sure, in the winter it gets extremely cold, but you wouldn’t need a pressure suit or a breathing mask, just warm clothing. Far warmer clothing than even what Antarctic expeditions wear, but in a speculative-fiction setting that’s no problem. In fantasy it could be the hide of an animal magical or mundane, in science fiction some far-out insulating material developed in a laboratory.

Toward Ice Dragons

I’ve been toying around with a medieval-style fantasy setting for all this, but more recently I’ve been thinking I might like to incorporate most of the ideas I worldbuilt for a fantasy-style setting into my far-future space opera setting. Among them would be the ice dragons as the native inhabitants of this planet: wyverns who have thick woolly white feathers, fearsome claws, and breathe not fire but ice: they have icy breath that freezes to death anything it touches.

Since it’s already down below -300 in midwinter, to have an insta-freeze effect at that temperature would take some peppy cryogenics, likely far colder than liquid nitrogen. “Breath” consisting of liquid hydrogen or even liquid helium would do nicely. We’re talking about temperature ranges from -423 down to absolute zero (-460); even for a human equipped for -300 degree weather that’ll turn them into a popsicle!

Bringing back the Belperevians: it’s been too Long!

I’m thinking the planet will be the site of a colony by some strange bedfellows: human dragon cultists and Belperevians, the latter group having been featured on their homeworld in “Warp Dawn”. This argon-snow planet will be a planet that reminds them of Belperev, and they will seek to establish a small population there. A small population for them still has a big impact, since these sauropod-like aliens have bodies up to a kilometer long! That’d be like Godzilla traipsing throughout the landscape!

I was thinking that the dominant native vegetation could be shallow-rooted plants that resemble the bromeliads, collecting water and nutrients from rainwater and storing them in great tanks in their trunks; perhaps they grow very tall, to proportions similar to a Belperevian forest. These plants might find the argon snow to be very useful. If they let it collect inside their water tanks, it’ll evaporate into a nearly pure argon atmosphere inside during the summer, which will asphyxiate any intruders; they could also release copious quantities of pure argon explosively to deoxygenate the surrounding area as a defense against predation. Hmm…come to think of it, with all those asphyxiated animal bodies around some of these plants might even turn carnivorous.

Anyway, the Belperevians have a matriarchal society not unlike elephants, whereas our dragon cultists are part of a culture that’s highly patriarchal, though matrilineal, along the lines I outline in a recent blog post. I’d love to touch on that sort of society in a story. Also in a recent blog post, I touch on the advantages of young parenthood, and a mechanism for assuring young marriage and childbearing: a custom where as soon as biological adulthood kicks in people spend all their time on dating, traveling far and wide in balls having fun dancing and meeting people. These debutante balls in my far-future setting for the race that has them would form a cosmic network, and the dragon cultists would establish a castle on a forbidding mountain range on this planet, holding their first debutante ball for Yule, amid the “second snow”, when it’s night constantly bar the near-constant lightning (argon-rich atmospheres produce more frequent lightning) plus whatever moonlight might be out there.

Patriarchal-Matrilineal Young-Marrying Dragon Cultists of the Far Future

I was thinking this culture that practically worships dragons as the most divine sort of beings would be influenced by what they discover about the ice dragons’ way of life: namely, that they are an all-female species who reproduce by parthenogenesis. Combined with their contact with the matriarchal Belperevians (which they hew close to; the cute big dinosaurs look up past an escarpment through the windows to see the little humans dancing in their little castle), this might inspire in their close-knit band a kind of feminist turn against their race’s ethos that the man commands and the woman obeys. Well, what if the local family in charge of the castle find that one of their own young debutante girls returns for their Yule ball and is even more deeply believing of their patriarchal worldview than ever, clashing with her liberated mother and her newly-egalitarian brother? Ah.

The latter is a particular problem, because this matrilineal culture practices the avunculate; mothers cohabit and raise their children not with their husbands, but rather with their brothers, the husbands merely visit for nightlong hot dates. This might sound weird to Western audiences, but 4% of the world’s cultures actually do this, the most famous case being the Mosuo’s “walking marriage” custom, where women take and dump male sex partners as they please.

This particular race practices an even more extreme form of the avunculate than any real-life humans do, because they’ve genetically engineered themselves so all pregnancies produce fraternal twins, one boy and one girl, and traditionally the twins are life partners for each other. So after she’s married on the spot at the ball, and crowned queen of the ball (her husband king of the ball) on account of being the first couple there to be wed, an event of great religious importance to that particular race, she’ll have to navigate her newfound differences with her brother.

The Ice Dragon crashes the Yule Ball

The Yule ball will be held with the hopes that the attendees from across the cosmos will be able to see the ice dragon in the distance, and they end up getting a much more up-close look than they bargained for: not just a fly-by, but a full-fledged dragon attack, no doubt brought on by the flurry of activity of the alien invaders, namely the humans. But the dragon doesn’t attack per se, she just flies around and terrorizes everybody.

Everybody panics, but only the girl realizes that there’s a pattern to the ice breaths, that the dragon is trying to communicate with them. She goes outside, against direct orders from her men (throwing away everything she stood for and was raised to do for what she knows in the moment is good and right), and offers her hand, with some valuable shiny pretty jewelry, and the dragon accepts this gift, and spits out an even more valuable gem for the girl in exchange. They talk, she pets the dragon, and the dragon flies off into the night.

Everyone becomes closer to each other as a result, with the boys being inspired by the girl’s example, her brother now willing to be the sort of brother she always wanted and expected him to be, with her own values becoming more nuanced as a result of her experience. Not exactly the epitome of progressive feminism, but I like it; I think it might be a fun little story to write. I always like to change things up, expand the world from tidbits hinted at or featured in previous stories, and do something kinda different, and this may well fit the bill.

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