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In my military sci fi story in which a squad of private contractors have to contend with hostile creatures reliant on scent and mechanoreception to hunt, I wanted to keep the sci-fi 'hard' and plausible as I could--within the context of a story about space marines fighting space monsters of course--and wanted to build an ecosystem capable of explaining why mechanoreception developed as a primary sense over both sight and hearing.

After shopping around with Mist, Fog, low-light and Cave environments and running into a couple problems specific to each, I've settled on something like an unrelenting dust storm that covers the small backwater outpost the squad is sequestered in. There is intense noise and almost zero visibility, explaining why they creatures don't hear very well or have developed vision to hunt, despite the obvious advantage that enhanced eyesight provides predators. The landscape is relatively flat and of course, sandy, so it makes sense for the creatures to hunt via mechanoreception in a way modelled after the Central American Wandering Spider.

The Question What environmental conditions could make an extremely long-lasting sandstorm? At least a "season" if not, optimally, a year+? Central to the premise is the cabin fever that begins to grip some of the characters, for they've been stuck behind a shrinking force field for about six months.

Does the planet have to be tidal-locked? As I understand it, most dust storms only last up to an hour and generally "flatten out" at night, which I guess is a way to describe them weakening due to a lack of heat. Can I have a 24/7 dust storm that persists through the night? Would it be plausible to have it running, but perhaps weaken, at night?

I know I phrase my questions like "can I have" etc but I'm sure you understand what I mean. I want to go as 'hard' as I can, so that at the very least a discerning reader would be able to pick up on at least some level of development of the creature design and environment, rather than just 'I want THIS monster and THIS monster", so if anybody more learned could drop some science on me and explain the systems that would enable such a sandstorm, or why it simply not within the realm of possibility.

OH, this is NOT earth.

Thank you very much, in advance.

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    $\begingroup$ On Jupiter there are storms that last for centuries, so an 24/7 storm is possible. But I am not sure if it can happen on a rock planets. If possible, then you just need to add sand and the wind will do the rest. $\endgroup$ – Stefano Balzarotti Feb 13 at 12:42
  • $\begingroup$ Mars has dust storms that can last months and cover about the whole planet. $\endgroup$ – BlueCoder Feb 13 at 12:54
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Martian dust storms can last several weeks and encompass most of the planet. Mars' atmosphere is obviously a colder and much lower pressure than our own, but on the other hand there's less solar energy available to trigger and feed those storms in the first place. It may well be that if Mars were in Earth's place, the dust storms would be more energetic and longer lived.

The key thing is that the storms on Mars are due to very fine dust, which is easier to loft into the air and keep there.

There are problems with having thick, recurrent and long-lasting storms of this type, though. It rather requires the area to be very arid, and there needs to be a constant supply of dust. On Mars, there's nowhere for the dust to go. On Earth, such dust could end up in the oceans, or be rained out onto land. In the absense of an active hydrosphere, it becomes increasingly unlikely that complex surface life would have arisen on your world.

What might work is a combination of a massive and long-lasting storm, such as a hurricane forming on a very warm ocean or even a hypercane and prolonged volcanic eruptions (such as the Laki eruption that lasted for eight months). Driving winds and raining ash would certainly be a punishing environment, but in the quiet periods between storms and eruptions the ground would be extremely fertile which would encourage vegetation growth and immigration of animals from outside the affected area.

Handwaving mechcanoceptive predators doesn't seem like a major ask. Such creatures could have evolved in a variety of circumstances which needn't envolve continuous catastrophic weather conditions, but it may be that they are able to thrive in such conditions when other animals are less suited.

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    $\begingroup$ If the planet was honeycombed with caves that reached the water table, would that justify the existence of complex life whilst keeping the water far enough away to keep the surface arid? It would also be a reasonable source for the various mechanoreceptor species to develop $\endgroup$ – Kyyshak Feb 13 at 13:40
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    $\begingroup$ @Kyyshak there's a problem with the organisms at the bottom of the food chain, still. There's not a lot of energy to be had inside those caves, and huge and long lasting sandstorms make surface photosynthesisers a bit untenable which makes it awkward to see where the stuff the predators breathe is coming from. Soft-scifi worlds handwave this away, of course. $\endgroup$ – Starfish Prime Feb 13 at 13:51
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Two solutions come to mind.

  1. A thick atmosphere + lots of gaseous content. This could be achieved by a runaway greenhouse gas affect. Venus has very low visibility and is roughly earth-sized, so that's a good example. You would want to tone down the level of atmosphere though; Venus has 93 bar (earth is 1 bar).

  2. Alternative solution to having a perpetual storm would be: perpetual darkness. If your planet was tidally-locked with its star and rather close to the star, so that the side facing is too hot but the side facing away is habitable, then you would just have to give it a moderate atmosphere to block out starlight and voila, pitch dark. This doesn't eliminate hearing but that could also be solved by making this primarily an oceanic planet full of archipelagos; if you're near the beach you can't hear much over the roar of ocean.

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