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Underground biosphere, what can be the possibilities?

  1. Apr 25, 2014 #1
    While the caverns of Earth isnt really lifeless, but as far as i know, only small beings can sustain themselves with the scarce food supply.
    What can be the hardness level of putting big animals into the underground caverns of an alien biosphere?
    I wondered about the plausibility of the following options :
    Maybe their biosphere could rather rely on heat energy of underground thermal waters than light?
    Maybe enough biomass could reach the underground from the surface the feed big fish and amphibians?
    Maybe bacteria could convert heat energy to light to feed regular plants?
    Should they feed on coal?
  2. jcsd
  3. Apr 25, 2014 #2

    Simon Bridge

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    It's about as plausible as living under domes on the surface - you'd just need to make sure the creatures have what they need.
  4. Apr 25, 2014 #3
    Living under domes on the surface - that means an artifical biosphere, that has to be maintained by sapient beings.
    The question is, could such an underground biosphere go on its own?
  5. Apr 25, 2014 #4


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    I don't see why you can't have some kind of underground ecosystem similar in principle to those surrounding hydrothermal vents.

    When I say "in principle" I mean - volcanic emissions being a source of energy. Whole system would be not trivial, as the presence of unlimited water and high pressure near hydrothermal vents helps deal with high temperature and toxicity of volcanic gases, which would otherwise kill animals around.
  6. Apr 25, 2014 #5


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    A obvious problem with underground systems is a food source. Unlike soil rock is pretty hard to break down, plant and fungi life would have a hard time settling in and without them animals wouldn't have much to eat in order to grow to large sizes.
  7. Apr 25, 2014 #6
    I would use geothermal energy dependent producers rather than plants and not more than three trophic levels, a plankton-like producer with a large population, a primary consumer and a secondary consumer (if scary monsters are really necessary).
  8. Apr 25, 2014 #7


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    My point was that might get you energy but what about biomass? Where is that going to come from?
  9. Apr 25, 2014 #8


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    Good point, I concentrated on the energy source, but that's not all.

    OTOH, apparently whatever system is there it has to be in some contact with the outside (I mean: it didn't evolve completely underground, more like it was colonized from above). That means some slow inflow of biomass is possible. Assuming "biomass conservation" (whatever got down there, stays down there) such system can slowly grow.

    I wonder what are the amounts of marine snow that reach the benthic zone.
  10. Apr 25, 2014 #9
    I would go with hand-wavium on that. :biggrin:

    Or on further thought:

    A class of plankton-like recyclers, along with the occasional visitor from outside the biosphere who would be eaten by the predators and the biomass 'assimilated' into the system. Its not a biosphere which would be likely to evolve though.

    And on further googling:
  11. Apr 25, 2014 #10
    Well I also thought about slow inflow, as well as some kind of underground planktons able to convert atmospheric (probably volcanic?) CO2 into biomass.
    Another thought was coal (mineral oil?), if something could digest it, a coal mine could be converted to lots of biomass.

    (It could have been artifically created at first, but it should stand on its own legs.)
  12. Apr 25, 2014 #11


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    CO2, water and a source of energy could get you carbohydrates sure but there are plenty of other nutrients needed that come from soil: nitrogen, potassium, phosphorous, calcium, sulphur, magnesium and a whole lot more. The lack of soil in a cave environment is going to be a big limiting factor, I can't think of a way off the top of my head for pedogenesis to occur in a cave.

    Activated charcoal is a form of edible coal used in medicine but I don't think it's nutritious at all. I'm not sure what the requirements would be for digesting coal but I have a suspicion it's unlikely to evolve. In addition coal just contains carbon, hydrogen, oxygen and sulphur so it only gets you one extra nutrient (the rest being present in air and water).
  13. Apr 25, 2014 #12
    I see the problems...

    Hmm, i thought about a great deluge happened on that planet. (caused by tectonic, volcanic activity something like that. well that part might be even pure handwavium )

    What if that washed lots of stuff into the caverns, filled them with hot water?
    Then gradually water level dropped and left a thin soil made by planktons, coralls fed on thermal energy?

    Or the caverns itself would only provide a relatively safe territory for the eggs of amphibians that go to feed to the hot underground lakes or see?
    (In those hot sees there would be much bigger competition and risks for the eggs.)

    Underwater life can go on without soil or sunlight.
  14. Apr 25, 2014 #13
    Some of these might help in getting the micro-nutrients and perhaps soil-formation:

    A lithoautotroph is a microbe which derives energy from reduced compounds of mineral origin. They may also be referred to as chemolithoautotrophs, a type of lithotrophs, reflecting their autotrophic metabolic pathways. Lithoautotrophs are exclusively microbes; macrofauna do not possess the capability to utilize mineral sources of energy. For lithoautotrophic bacteria, only inorganic molecules can be used as energy sources. Most lithoautotrophs belong to the domain Bacteria. The term "Lithotroph" is created from the terms 'lithos' (rock) and 'troph' (consumer); literally, it may be read "eaters of rock." Many lithoautotrophs are extremophiles, but this is not universally so.

    Lithoautotrophs are extremely specific in using their energy source. Thus, despite the diversity in using inorganic molecules in order to obtain energy that lithoautotrophs exhibit as a group, one particular lithoautotroph would use only one type of inorganic molecules to get its energy.

    Lithoautotrophs participate in many geological processes, such as the weathering of parent material (bedrock) to form soil, as well as biogeochemical cycling of sulfur, potassium, and other elements. They may be present in the deep terrestrial subsurface (they have been found well over 3 km below the surface of the planet), in soils, and in endolith communities. As they are responsible for the liberation of many crucial nutrients, and participate in the formation of soil, lithoautotrophs play a crucial role in the maintenance of life on Earth.
  15. Jul 31, 2015 #14
    Now I am thinking about a short SF story, where machines took over Earth, and people live like rats in the vast underground network of metro tunnels, sewers, transit pipes, rad shelters, parking garages etc.
    I thought the base of life would be hybrid (bio-machine) mushrooms, that feed on organic material and omnipresent electrosmog, radiowaves. Theese mushrooms feed rats, and provide other necessary material like nitroglicerin (against hunter robots), stuff that can be made to protective clothing, etc.
    Those this idea has anything to do with reality? (I dont intend to be very hard...)
  16. Jul 31, 2015 #15
    I think I watched some film with robots on top and humans deep below, that but with more acrobatics. ;)

    I see 2 ideas:
    1) the food chain gots big input of nutrients from outside:
    -bat cave
    -a river that goes underground

    2) Humans keep a source of energy that allow to have undergound greenhouses, presumably nuclear or geothermal
  17. Jul 31, 2015 #16
    Hmm, an underground nuclear power plant run by humans would be too much. What can be the lifetime of a small nuclear battery, if they only use it for lighting, can it be safe?

    About, the other... maybe due to global warming, the sea has flooded lower level tunnels, so humans have the upper level tunnels, and fish below?
  18. Jul 31, 2015 #17
    Caverns are lifeless? Thought there are bacteria 3 km deep into the rockbed like about everywhere on earth.

    Problem is, you can't just shallow litres of rock and filter out the microbes like a whale can do with plankton in the ocean.
    Density of biomass will likely be very low.
  19. Jul 31, 2015 #18
    Nuclear reactors are too expensive? I understand that taking a small one from a submarine is also out? Then what about:
    "Most RTGs use 238Pu, which decays with a half-life of 87.7"

    One more idea: keep this underground stream, but also have a possibility to generate some amount of hydropower?

    Anyway why not using energy from geothermals?

    This RTG could be man portable - it may be a local version of holy grail.

    You do not need necessary global warming. You could also use land reclaim in Holand style which is no longer maintained so sea returned.

    Metropolis flooded by sea, energy generated by tidal power plant and quest for finding a RTG? ;)
  20. Jul 31, 2015 #19
    A geothermal or nuclear power plant requires lots of infrastructure, and i think the survivors dont have that. (I also dont think they built a big city over a hotspot of Earth.)
    RTG is a good idea (I like that holy grail stuff :) ) but wouldnt the radiation poison the people around it?
    Tidal power, i think it is also right. :)
  21. Jul 31, 2015 #20
    Pu238 produces mostly alpha radiation, which is very easy to shield (dangerous only direct consumption / inhaling). However, if you use something more improvised, then theoretically heavy lead shielding should protect you... assuming that is not broken...

    You want a damaged one which would be both blessing and a curse? :D

    Tides would rather require a moon. (but there are a few other possibilities if you need it)

    Anyway, for my own story I toyed with a different idea, hard SF, maybe useful. Very long day night cycle (quite common on moons) or tilted planet. Then you have scorching heat wave during day (+50C?), freezing during nigh (-50C?). Aquatic life barely notices that, while humans can go out only during part of morning and a while after sunset. For most of the time they have hide underground. Continents are uninhabitable, while sea coast / islands are only very bad.

    Keep in mind that it produces energy continuously and it is irrelevant, whether it is actually use it or not.
    Last edited: Jul 31, 2015
  22. Aug 8, 2015 #21
    Ok, thanks for your help. :)

    I planned the following plot : the hero find a wounded girl, they live on fish, mushrooms and rats till they manage to reach a hive, that has some "energy source" (RTG or whatever) they have a greenhouse.
    The girl starts to speak about a Destiny. Then the robots attack the hive, they manage to escape with the help of nitro bottles, a pickaxe and a rifle.
    Eventually they reach the promised place : a renegade AI decided that the AI society became decadent, they need the humans, it experimented with some humans and created some cyborgs, and a nano-virus (self-replicating nanobots). Since the virus could destroy all AIs including it, it hesitated the employ it (or it wanted to create enough cyborgs to upload itself into cyborg bodies that protected from the virus), and others destroyed that AI.
    Generations later, one cyborg (the girl) gets out of hibernation (someone finds it, and opens it). Then with the help of the uploaded data they reach the hidden underground facility, and release the virus.

    Is that plan total nonsense or sounds a little bit reasonable?
  23. Aug 8, 2015 #22
    There are some reasons why there is a tiny limited number of survivors? (why they evaded attacks so far?)

    Who maintains that in workable state?
    No EMP?

    How the hell a nanobots distinguish between cyborg and robot? Shouldn't they start "chewing" plastic anyway? And in case of cyborg just leave the brain (without life support) behind?

    Why not using computer virus? To wipe most and cause damage to vital infrastructure, which would cause robot civilization collapse?
  24. Aug 8, 2015 #23
    Limited number of survivors : the AIs dont pay too much attention to hunt the remaining humans.

    EMP would require high technology. Maintaining that energy source... well Voyager is working since almost 40 years.

    Cyborg : with human body and a hybrid brain, that the virus dont recognize. I think the nano stuff is needed so switching simply to standalone mode isnt enough.
  25. Aug 8, 2015 #24
    Makes sense

    We have a different definition of high tech:

    The virus attack only the electronic brain? It is not in any casing?
  26. Aug 8, 2015 #25
    Okay, maybe some EMP grenade can be okay, but it isnt epic to solve everything with that, and they have a limited capacity.

    Even if the processor is in some case, it still needs ports of electrically conductive material to outside. The cyborg brain can be fully wrapped in living organic material the nano stuff dont digest.

    Or maybe it is better, that AIs became totally addicted to cloud computing, and one rather develops something entirely different to be able to operate standalone again?
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