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As a follow up to my previous question: Surviving a dark hycean world I ask this: how could life adapt to a tidally locked ocean world with thick atmosphere and perpetual storms? That's the definition of a dark hycean world by the way.

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I would like to add another method organisms could generate energy to the two proposed by Mike Serfas in the linked question.

Thermosynthesis- the generation of energy from heat (or more correctly, a heat gradient/differential). There are some related questions on thermosynthesis, and I’d recommend having a look at them. Thermosynthetic life would be found around heat gradients and would especially thrive around the border of the planet between dark and light zones. Some organisms to live on the border:

  1. Floaters –floats gain energy by floating in the ocean near the border ring using the gradient between the warmer surface waters (which warmed by currents from the heated side of the planet flowing into them) and cooler depths. Floaters would be the base of the ecosystem. Making way for more traditional complex life. (Could also have more traditional phytoplankton)

  2. Some of this complex life might have symbiotic relationships with floaters, acting in effect as a transport to other areas with heat gradients. Most of these would be very long or able to stretch out to fully exploit a heat gradient. Many might be adapted to dig burrows in which they would stand half-in half-out generating energy. (They'd still need to eat floaters or something else for obtaining molecules)

Lightning rod beasts are a creature that could live on the dark side. These creatures have metallic protrusions which funnel lightning from the frequent storms into their bodies, which they can convert a small percentage into energy for their use. In lightning storms a lightning rod beast makes a terrifyingly fast and tireless hunter. These could easily live on the dark side of the planet, as long as lightning storms are frequent enough. (Their evolution might be a bit of a stretch but hey) -They'd just need something to eat.

-about thermosynthesis on aliens worlds- might be interesting: https://pubmed.ncbi.nlm.nih.gov/14678664/

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  • $\begingroup$ Are you saying you would have large floaters using the temp gradient for energy and then smaller organisms attached to them to benefit as well? It's a little unclear $\endgroup$
    – Joe Smith
    Commented Mar 12, 2022 at 5:00
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Lets start by counting some things out. The tidal locking and constant storms means that photosynthesis is unlikely - on the one hand, cloud cover blocks a lot of sunlight, while on the other, constant exposure to the sun, clouds or no, would be deadly to most microbial life, especially when one accounts for the high temperatures of what would likely be a runaway greenhouse affect. The first stages of life would probably be extremophiles. You would have some living on the surface and in the atmosphere in spite of the sun's constant bombardment, and larger quantities living deep underwater around geysers and volcanoes. A few other such microorganisms might find ways to live on the edges of the planet's dark side in spite of the cold. Of these, the volcanic areas are most likely to host explosions of life; this could lead to Mariana trench style ecosystems, with sedentary predators similar to tube worms feeding off of the extremophiles that gather around the vents. A community of other creatures could conceivably evolve around such an environment. However, with microbial life as the main producers, there would be a hard limit on just how large anything surviving off of them or their primary predators could be, and also a limit on how far away from their breeding grounds anything could survive.

Without photosynthesis in the evolutionary history, sight would not be a primary sense, and might not be a sense at all. Smell would likely be very important, as would be touch and a sense of temperature. Magnetism might be important, depending on the planet's makeup and what materials are found in the underwater volcanoes where life gathers. Sound would eventually evolve out of touch, but wouldn't necessarily be important in a purely underwater environment. A rudimentary sense of radiation beyond what we know as visible light might be important, depending on the sun's activity and the viability of the planet's magnetic field.

All in all, if you're thinking carbon based life, probably no big creatures, probably nothing outside of water, probably populations limited to specific locations, probably nothing fast moving, almost definitely no eyes.

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  • $\begingroup$ Could we please keep thinking about this? I need more material. $\endgroup$
    – Joe Smith
    Commented Mar 6, 2022 at 5:13
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Life on one side only

Perpetual storms will cause the water on dark and bright sides be mixed continuously and lot of ocean currents (hot and cold) will flow. Therefore the water temperature may not reach extreme conditions but it may only be habitable on one side.

The planet has hydrogen-rich atmosphere, where oxygen or ozone may not be as abundant. It may host biomarker molecules like methyl chloride and dimethyl sulphide.

Crabs

enter image description here

Over millions of years, many crustaceans gradually may have grown to look more and more like crabs, a process called convergent evolution. So life might be in the form of crabs.

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  • $\begingroup$ Got off track there $\endgroup$
    – Joe Smith
    Commented Mar 7, 2022 at 3:23
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    $\begingroup$ I believe the process is called carcinogenesis. $\endgroup$
    – Daron
    Commented Mar 9, 2022 at 16:10
  • $\begingroup$ @Daron As written here (en.wikipedia.org/wiki/Carcinogenesis), Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by changes at the cellular, genetic, and epigenetic levels and abnormal cell division. $\endgroup$
    – imtaar
    Commented Mar 10, 2022 at 7:54
  • $\begingroup$ @imtaar That is the other kind of carcinogenesis. $\endgroup$
    – Daron
    Commented Mar 10, 2022 at 17:06
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Life would not have an issue evolving

Here on Earth, you can get photosynthesis at depths of up to 200 meters, but even the most violent of storms cause minimum turbulence at depths greater than 10-20 meters. So, even if you assume the atmosphere allows less light through and the storms are more violent, you should still have a pretty big band of depths where the water is still enough, and the light accessible enough for various forms of marine life to survive quite comfortably.

The only reason life on Earth often sees large die-offs after a storm is because this abrupt change in circulation causes the water to mix changing things like O2 levels, temperature, and saline concentrations over the course of the next several days... but if your world experiences constant storms like this, then the O2, temperatures, and salt levels would remain generally in equilibrium, even if that equilibrium is slightly different than in our oceans.

https://www.huffpost.com/entry/what-happens-underwater-during-a-hurricane_n_2066084 figure 2 https://www.huffpost.com/entry/what-happens-underwater-during-a-hurricane_n_2066084 figure 1 https://www.huffpost.com/entry/what-happens-underwater-during-a-hurricane_n_2066084

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