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I'm thinking up a Mars or Venus type planet where the poles (or one pole) has a forest growing out of it due to a device that is used to make the planet more habitable by creating a oxygen friendly atmosphere.

However the atmosphere has not spread throughout the planet so it has mostly aggregated at the pole due to the device being there. Possibly a river could also be flowing out of the pole. The poles are full of icecaps containing water similar to Mars, and the melting of the ice caps has caused the river to flow out. Along the riverside is where the human colonies would be staying.

How feasible is this, and if not, does it tax suspension of disbelief too much?

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  • $\begingroup$ Welcome to worldbuilding. Please take the tour and visit the help center to make yourself familiar with our community and its standards. $\endgroup$ – L.Dutch Jan 21 at 6:43
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    $\begingroup$ Have you read Dune? What you're describing is very similar to the titular planet, mostly uninhabitable desert with less arid regions at the poles. In that series, there's a ring of mountains that helps control the climate at the northern region. $\endgroup$ – Christyn Jan 21 at 6:44
  • $\begingroup$ The only way I can imagine an artificial atmosphere being confined to the poles and not having spread to the rest of the planet (aside from the device somehow doing that too) is if the atmosphere were being dispensed at such an insane rate and volume that it is basically forcing the planet's existing climate and weather forces aside in the process. But even then, the atmosphere wouldn't remain confined for long, and certainly not long enough for forests to grow. (Not to mention such a terraforming process would probably have long-lasting negative consequences to the planet's weather systems.) $\endgroup$ – Abion47 Jan 21 at 19:45
  • $\begingroup$ Wow, I was not expecting so many answers in such a short period of time hahaha. I'd like to say thanks to everyone who answered this question and commented, every contribution has helped me really think about and revise the concept. Apologies also for the late comments I got a bit busy at college. I'll try to comment on all the answers so I can clarify my intents with the concept :) $\endgroup$ – Brandon Jan 24 at 17:03
  • $\begingroup$ @Christyn this will be embarassing to admit, but I actually have not read Dune although I plan on doing so sometime this year. I honestly don't know why I haven't read it this entire time. I haven't even watched the movie. Definitely time to pick that one up $\endgroup$ – Brandon Jan 24 at 17:07
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The planet would have to be very hot such that only the poles are temperate enough to support a forest. That s because poles are always colder than the rest of the planet.

The rest of the planet would be a scorching hot desert.

Remove the part about the atmosphere not spreading everywhere as it makes no sense (it violates the 2nd law of thermodynamics). Since the rest of the planet is inhospitable you don't really need that anyways.

A river flowing out of the pole is realistic, I don't see why that would be a problem. As you get further away from the poles, it would become thinner and eventually dissappear. So you would have a forest/arid/desert transition.

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    $\begingroup$ Worth adding that fossil evidence shows that the Earth had forests near the south pole at one point. Making this more than just feasible. See e.g. bbc.co.uk/news/science-environment-12378934 $\endgroup$ – Neil Slater Jan 21 at 10:19
  • $\begingroup$ You left me wondering what would that river look like.I clearly can imagine river slowing to a stream, then being a rivulet, but will it just... stop, like that ? In a puddle of mud ? like an eternal muddy countryside ? $\endgroup$ – Don Pablo Jan 21 at 13:11
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    $\begingroup$ @DonPablo Check the Okavango River, emptying into a desert :). $\endgroup$ – Blackhole Jan 21 at 14:13
  • $\begingroup$ 'Desert earth-like planet with forests at the poles'. Sure. On Mars or Venus? no. $\endgroup$ – Mazura Jan 21 at 14:40
  • $\begingroup$ @Neil Slater: I think you, and the authors of that article, have forgotten about plate tectonics. Antarctica had forests 100 million years ago, but was it anywhere near the South Pole? $\endgroup$ – jamesqf Jan 21 at 18:25
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How feasible is this, and if not, does it tax suspension of disbelief too much?

Points that trigger the rise of an eyebrow:

  • the atmosphere has not spread throughout the planet so it has mostly aggregated at the pole

Gases have no intrinsic shape. To contain them into a given volume you need a container. Else they spread around following pressure and concentration gradient.

  • the poles (or one pole) has a forest growing out of it [...] The poles are full of icecaps.

You can barely have moss and lichens in a tundra environment. On icecaps you can simply forget about any vegetation, let alone a forest. If you want forests, forget about the icecaps.

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    $\begingroup$ Gases have no intrinsic shape, aside from possibly on Uranus. I’ll concede that’s a hexagonal weather system that no-one really understands though. $\endgroup$ – Joe Bloggs Jan 21 at 16:11
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    $\begingroup$ I think you mean Saturn, no? en.wikipedia.org/wiki/Saturn%27s_hexagon $\endgroup$ – LambdaBeta Jan 21 at 18:13
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    $\begingroup$ Re forests and icecaps, see Greenland or the southern tip of South America. You have an icecap that is basically on the high interior elevations, with coastal valleys having trees & other vegetation. So if your planet's poles are mountainous, it might work. $\endgroup$ – jamesqf Jan 21 at 18:22
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Oxygen is a relatively light gas, and at 1 atm and room temperature the root-mean-square speed of each molecule is almost 2 kilometers per hour.

If you are oxygenating a planet that already has a ~1 atm atmosphere, you will get a higher local concentration of oxygen around the device.

If you are making an earthly atmosphere out of a near vacuum such as the martian atmosphere, you will only get breathable air after the whole planet has stabilized at a breathable pressure. If you do that from just one point at the pole you will either take millenia, or, if you do it fast (and bh fast I mean doing it in decades or centuries) you will have winds that will make colonization and forrests impossible. You'd have a better time seeding an atmosphere from multiple points in the planet.

If you start with a venusian atmosphere, first you have to lower the pressure by ~89 atm. Good luck with that.

Other than that, the Earth itself has had a lushing forrest on the south pole, back when dinosaurs roamed the planet.

Go back 100 million years ago and Antarctica was covered in lush rainforests similar to those that exist in New Zealand today," said Dr Vanessa Bowman who works with Francis at the University of Leeds.

"We commonly find whole fossilised logs that must have come from really big trees."

I totally stole the link above from a comment for another answer.

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  • $\begingroup$ Mars doesn't have enough gravity to hold an atmosphere and Venus is a terrible place. If only the question asked what caused Venus' atmosphere to runaway, then we could talk about what "a device that is used to make the planet more habitable" would be. $\endgroup$ – Mazura Jan 21 at 14:31
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    $\begingroup$ @Mazura we have plenty of questions about terraforming Mars. Yes, it will lose atmosphere faster than Earth, but it won't happen in a flash. Given a 1atm atmosphere it will hold it for millenia after you stop replenishing it. As long as you have a device as the one in the question, you can keep an atmosphere. $\endgroup$ – Renan Jan 21 at 15:09
  • $\begingroup$ Ok, "oxygen friendly atmosphere": complete. Still need a magnetosphere - or would plants not care about radiation so much? $\endgroup$ – Mazura Jan 21 at 15:19
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    $\begingroup$ Mars held on to a substantial atmosphere, and an ocean, for a billion years or so. Human species is, generously, maybe 10K years old. So give it a breathable atmosphere today, and it will last for 100K times the length of civilization. $\endgroup$ – jamesqf Jan 21 at 18:29
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    $\begingroup$ @Mazura I'll edit the question to add said detail about the device/Venus in. As of now the device in my mind is basically hand waving but I'd like to add detail to it; it doesn't have to be totally realistic but should at least not be completely infeasible. I got the idea for the concept from Total Recall, although what was given there as an explanation for that particular movie didn't really satisfy me, hence this question. $\endgroup$ – Brandon Jan 24 at 17:34
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Earth-like Desert planets are entirely feasible. In fact, models have suggested that such a planet could enjoy a habitable zone that extends much closer to its host star than a more aqueous one could.

Such a planet could be cold enough to possess ice-caps, but that will mean your deserts are also colder rather than hot. If you want forests at the poles, I'd suggest going with a hot desert planet instead. In that scenario, the majority of the planet is scorching inhospitable desert, and the poles possess temperate woodlands and marshes.

Having a river flow away from the lush polar region and end in the desert is entirely plausible, and the suggestion of the Okavango River as an example was a good one.

As to keeping the breathable atmosphere restricted to the polar region, this could be achieved by having a significant change in elevation between the lush pole and the surrounding desert. If the pole lies in a deep enough depression, it could harbour a dense, breathable atmosphere while the rest of the planet suffers from atmospheric pressure far too low to be breathable without assistance.

Keep in mind that having the pole in a deep depression makes having a river flow out of it nigh impossible.

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