KJW said:
mollwollfumble said:Humans land on a planet where the largest animals (non-standard biochemistry) are powered by nuclear reactors.
The planet has a high concentration of uranium and thorium ores in its crust.
This seems possible. What do you think?
What would such an animal look like, how would it evolve from lower life forms, what changes would be needed in its biochemistry?
Animals aren’t even powered by coal-fired power stations. How cells “burn” fuel is really quite fascinating. You should look up Citric Acid Cycle to see how acetic acid (in the form of acetyl-CoA) is converted to carbon dioxide.
Ta, yes. I’ve has a chart of the citric acid cycle since I was a teenager. It’[s fascinating.
I’ve only come up with a few follow-on thoughts since the original post.
1. An animal powered by a nuclear reactor, or even and RTG, could cook its own food. For instance if the radioactive material was in fine tentacle-like threads and it lived underwater then the water outside the animal would act as a moderator and reflector. And any prey caught by the tentacles could be pre-cooked before it is eaten.
2. In terms of deadliness, neutrons are deadlier than gamma rays, which are deadlier than beta rays which are deadlier than alpha rays. Natural radiation from uranium and thorium ores is predominantly alpha rays. Which makes them reasonably easy to insert into a semi-organic matrix. Uranium and thorium could be obtained by eating sand or clay containing particles of their ores. Or they could be strained element by element out of a general radioactive environment using a concentration method akin to kidneys in animals. I don’t happen to know if fast or slow neutrons are deadlier, fast neutrons penetrate further but slow neutrons have a much larger capture cross section.
3. The animal would want to eliminate or detoxify the more dangerous fission products, in particular caesium-137, iodine-131, strontium-90. Eg Iodine is less toxic if the animal doesn’t have a thyroid. Lime, calcium, ingestion helps to detoxify strontium. Or the animal could simply use silicon for bones instead of calcium. A modified kidney could be used to expel unwanted radioactives.
4. If the radioactive arrangements are in plates, such as in a mitochondria or golgi-body, then a collapse in inter-plate distance due to dehydration and/or gravity after death could give the necessary fast-neutron pulse to kill predators by radiation when the animal dies.
5. A full-blown nuclear reactor doesn’t have to be big, it can be basket-ball size (though I would have to check which isotope was used).
6. Natural chemicals in organic organisms, particularly carbon and water, provide good shielding against neutron damage.
7. The radioactives could be on tentacles, (to reduce radiation damage ro the main body), or on parallel plates (which by muscular separation and contraction is controllable), or centred in vesicles (particularly useful if grains of radioactive ores are part of the diet).
In summary:
- Having RTG energy inside an animal makes good sense, particularly if the animal lives in a cold climate.
- A full nuclear reactor produces neutrons that can be deadly, so would be less likely to find in an animal. And if found in an animal may be located at the tip of an arm far from vital organisms.
- There are intermediate systems that bridge the gap between RTG and nuclear reactor, so a nuclear reactor could evolve spontaneously.
- There are at least three positive aspects of having a nuclear reactor in an animal: pre-cooking food to improve its nutrient value, production of heat to help with cold climates, and toxicity which discourages predators.
- A silicon-based skeleton (like a glass sponge or a diatom) seems more appropriate than a calcium-based one, to avoid damage from strontium-90.