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Designing an environment inside the ice crust of an exomoon

  1. Jul 11, 2014 #1
    Hello. My name is Brian McKinley. I beginning work on a hard(ish) science fiction comic titled Verdant Spiral. I thought this would be a good place to get feedback to make sure my ideas are plausible. All feedback is welcomed, and thank you all in advance.

    The first story takes place on an exomoon orbiting a gas giant around the white dwarf G29-38. The surface of the moon is frozen over like Europa or Enceladus. I was inspired by images of methane bubbles trapped in frozen lakes to imagine something similar happening on a massive scale. hydrothermal vents maintain a liquid ocean under a thick icy crust. Cavities are cut upward into the icy crust and gases are trapped there. Once there is an atmosphere trapped there an ecology develops around it. That ecosystem continues to evolve and intelligent life develops, builds a civilization, dies out, humans come exploring.

    So what I've been wondering is the formation of these sort of cavities that could fill up with atmosphere possible? What shape would they be likely to take? Could the cavities be open to the ocean at the bottom?

    Variations on shape I had thought of:
    • The cavities are cone-shaped, big end up. Sort of like upside-down, inside-out island chains.
    • The cavities are stacks of flattened bubbles like the photos that inspired the idea.
    • The cavities are bell-shapped, big end down.

    If an opening to the ocean is plausible, then the idea with big end up is the descent through the cavity gets more and more claustrophobic and terminates in a small hot-spring area. With bell shaped I guess it would have to be a large lake or sea and the dramatic implications change.
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  3. Jul 14, 2014 #2
    What volcanic gases doesn't dissolve rather rapidly in water? O2 might be available from above due to photo-dissociation of the ice, but it'd rapidly dissolve in the water. Perhaps a plant-like organism of sorts create nitrogen bubbles, to store away rare nitrogen from the competition?
  4. Jul 15, 2014 #3
    So the main thing I need is a mechanism either physical or biological that will get gases out of solution? If I had a volume of air trapped below the ice, above the water, is there anything preventing that from being large in scale both in size and time?
  5. Jul 17, 2014 #4
    The ice cracking would be one problem, the gases being produced and then not dissolved would be another, N2/O2 behaves like that, CO2, SO2 and most other volcanic gases doesn't.

    Perhaps all oxygen-breathing life could exist and be symbiotic with the giant air-pocket plant, which lives under the ice and stretches it tendrils down to the black smokers below. It could even be some feat of bionengineering by a long lost civilization rather than something admittedly rather unlikely to evolve on its own.
  6. Jul 19, 2014 #5
    Interesting idea. There's already a rather pervasive plant involved - I might have to think about that some.
  7. Nov 21, 2014 #6


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    One thing to consider is the human visitors, they are going to be very advanced. If this story is taking place around another star then that means humanity has mastered long distance space travel and that is an enormous accomplishment. it means that we have either cracked FTL or we have perfected self sustaining environments and long term stasis or have generational ships. Any of these accomplishments mean you will have to really consider how different they are going to be from modern humans. to that end, it wont matter what the atmosphere inside the bubble is like as the humans should have the technology to explore any environment.

    If you want your humans to be closer to our current technology and civilization then I might suggest putting the story on Europa. It seems you are basing your moon heavily on Europa already so why not? it also puts the story right here in our solar system so humans could realistically be exploring it within the next century.

    Good luck.
  8. Nov 22, 2014 #7
    Definitely all things that I've been considering. Putting it on Europa would certainly simplify some things, but it would be at a trade off for other things. It's shocking how much of a rabbit hole "be more realistic" can be for a science fiction story–especially in a visual medium where I can't just leave it up to the audience's imagination what clothing and technology look like. But the thing is—making those decisions is what appeals to me in telling the story.
  9. Nov 24, 2014 #8


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    Yes I know there is a trade off between realistic and exciting. I get what you are saying about visual mediums. its always had to do sci fi that looks believable. in a book, the tech updates with the current reader as long as its open ended enough. Once you film something however its done. I still snicker at one of my favorite Time travel movies that features a flashback to the traveler's home period of 26th century Earth, and in the lab there is filled with these massive 80s style CRT monitors.

    My advice to keep it on Europa was simply to free you from that slippery slope of putting human travelers on a distant world but keeping them close enough to modern humans that you would give them a society readers would understand.
  10. Nov 26, 2014 #9


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    Interesting, I'm certain I read a slightly similar story in a sci-fi short story anthology. I can't remember the name. In that one, the aliens were aquatic, living in ocean-like cavities of fluid underneath the surface of Europa. The story was written from the perspective of the aliens, and humans aren't really mentioned, I think. The aliens were intelligent enough to have social interactions with each other, but did not have much technology or tool use. They had no knowledge of modern cosmology, so they developed their own superstitious ideas of cosmology centered around these cavities.
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