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Some of the events in a story I'm thinking of have occur on a planet called Ascendia. Due to the world's backstory, it has several unusual traits.

Despite orbiting around a hot (roughly large F/small A class) star, it's a cold world - with average daytime temperatures of ~-50 degrees C at the equatorial regions. I assume this would probably mean that it orbits somewhere between 4.5-5.5 AU out from the system's star, since an F0 star has a habitable zone extending up to 3.7.

Although it has an oxygen-nitrogen atmosphere (either naturally or through terraforming) and an Earth-like pressure and gravity, its temperatures render it uninhabitable to any ordinary human settlers. The planet explicitly cannot be rendered conventionally habitable by any mix of greenhouse gases that would leave the atmosphere still breathable, as a major plot point in its history is that it was claimed by a faction of genetically-enhanced part-humans since nobody else had any use for it. Additionally, there are no planets in the habitable zone of the system or near Ascendia - it can be effectively considered on its own for the purposes of any analysis.

Ascendia's weather is usually calm and clear, but can sometimes be beset by "frostblade" storms, a phenomenon that can be compared to a massive blizzard which can engulf entire areas of the world for weeks - much like the dust storms of Mars.

So, my question is - is this planet feasible or possible as stated, or do I need to make compromises on some of its properties to keep the setting realistic?

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    $\begingroup$ "Massive blizzard": No, no way. As described the planet is frozen desert; there will be very very little precipitation. You may have strong winds, you may have dust or sand storms (even our Antactic has some ice-free patches), but you cannot have snow storms because there is almost no snow. $\endgroup$
    – AlexP
    Oct 12 '21 at 12:45
  • $\begingroup$ @AlexP unless there's enough volcanism to put water nontrivial amount of vapors in the atmosphere. Or winds so strong it avalanche ice-blasts its surface - each impacting particle creating one or more others. However, I see no way that can explain planet-wide storms. Mars has a very thing atmosphere, easy to put in motion by any tiny gradient of pressure, but hard to stop because there's not enough friction once it started. Venus has Sun constantly pumping energy into it. Jupiter has huge reserves of grav potential energy by the amount of gases still uncompressed $\endgroup$ Oct 12 '21 at 15:23
  • $\begingroup$ The reality-check tag specifically prohibits checks against Real Life and the help center states that questions can only be about fictional worlds. What this means is that you can't ask if something is "realistic" because that's literally not what we do here. You can ask if your idea allows for suspension of disbelief. Knowing all this, and realizing that Science Fiction is filled with worlds wonderful and fantastic, do you still have a question? $\endgroup$ Oct 12 '21 at 15:33
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    $\begingroup$ @JoinJBHonCodidact I don't see any such prohibition in either the tag wiki or the help centre. $\endgroup$ Oct 12 '21 at 17:48
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    $\begingroup$ It doesn't have to be impossible to safely terraform. It just has to be more expensive (or more time consuming) at the time they sent/created the modified humans. The O2 content, however, is problematic without something to generate it. $\endgroup$
    – ShadoCat
    Oct 12 '21 at 22:22
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Violent storms are possible on cold planets, as we know from the gas giants and the ice giants in our solar system.

What seems a bit odd is that your planet has no life, yet it has Oxygen in its atmosphere: Oxygen is a very reactive gas, and it would quickly react with other atoms to create oxides, unless there is some process replenishing it in the atmosphere.

On our planet that process is life-driven, and that is not possible on your planet. If maybe your planet has been recently terraformed with lot of Oxygen being pumped in its atmosphere that would be possible, but don't count on very long times of Oxygen rich environment without life.

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  • $\begingroup$ As with all the questions about atmospheres, it bears remembering that whilst atmospheric constituents are absolutely not stable over geological or astronomical timescales, you could still reasonably expect stuff to be fine over a mere million years. Especially on a distant iceball world where there aren't many oxygen sinks, and atmospheric escape rates will be low. $\endgroup$ Oct 12 '21 at 14:44
  • $\begingroup$ @StarfishPrime right, but the oxygen still has to have come from somewhere. The rate of oxygen depletion would definitely be minuscule on a human timescale, but it would still be much higher than oxygen generation, unless OP has some clever process up their sleeve to account for a lot of oxygen generation with no life $\endgroup$
    – Bitsplease
    Oct 12 '21 at 23:49
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    $\begingroup$ @Bitsplease doesn't really matter in the context of this specific question... the OP didn't ask about the atmosphere source, and suggested it might not be natural. Collapse of an artificial or natural ecosystem in the last few million years would be one possibility. $\endgroup$ Oct 13 '21 at 14:58
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Greenhouse gasses can be very potent

A greenhouse gas can have a global warming potential tens of thousands of times greater than carbon dioxide. For example, on a 20-year time frame, emissions of sulfur hexafluoride are 17500 times more potent than those of carbon dioxide. Sulfur hexafluoride is also so non-toxic that SF6 is injected into people's eyes to keep the retina in place in cases of retinal detachment. In order to lack access to SF6, the human settlers would have to lack access to sulfur (in which case they die because their proteins need it) or fluorine (in which case they probably have bad teeth, unless they've been genetically engineered to endure the travails of a system with zero fluorine).

There are other ways to warm the planet.

Orbiting mirrors have been proposed for Siberia. Wind power at the surface could warm and power underground colonies. Ordinary greenhouses of glass (or more likely ice) could sustain colonies. The imminent colonization of Antarctica, made inevitable by the combination of global warming of Earth and global cooling toward refugees, seems to promise interesting IRL worldbuilding scenarios over the next few decades.

Based on these things, I don't really believe your scenario works, unless there is a political level compromise in place, that leaves planets by fiat to those biologically capable of living there.

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