I’m mostly with you, but geothermal energy is always a possibility. Hot vents of all sorts have diverse ecosystems around them. You need an energy gradient of some kind to make it work, but any sort of water flow is effective, and relatively common underground. The source can then “radiate” nutrition to other areas without an energy source (animals swimming/flying/crawling, plants creeping, etc.).
Not enough to explain sandworms, but enough to keep a small local ecosystem going with smallish animals.
Another way you could get underground mobile life, handwaving away a different planet-load of other objections, is on a very, very low density, low gravity world.
One of the recent asteroid sample missions had a near-death experience when they tried to touchdown and found the thing was more the consistency of chiffon than beach sand. That possibility had been planned for and the onboard navigator retrofired instantly before they sank into the dust, never to be seen again.
Something like that at least solves the problem that dirt, at least Earth dirt, is much too dense / viscous / solid to tunnel through as a means of normal day to day locomotion. That asteroid dust wasn’t even as thick and unyeilding as room temperature/pressure water.
The rest of the ecosystem is left as an exercise for the would-be SF author.
The lack of surface water on Mars for so long means there may well be dust bowls full of fine grains that haven’t been compacted into sediment by water flowing through them. Or maybe dunes. The lower gravity will help, but I still would not want to be buried under 100 feet of Mars dust; that far down the stuff is going to be indistinguishable from a 50 foot pile of Earth sand. Hard to inhale/exhale down there.
OTOH, 10 feet down in uncompacted dust might be a plausible place for an ecosystem. The overburden buys enough protection from the UV/cosmic ray flux without being so dense that movement in it becomes impossible. Like Earth pond life, each dustbowl or dune field would be a separate closed system, but that’s no obstacle here.
I wonder a bit about this following ecological thought in general. This is top-of-head speculation here with no serious thought given yet. I’m hoping the general direction rings a bell w somebody, either yeah or nay.
…
Earth has some pretty cushy ecological niches. And some that are very very hard; so hard that they’re unoccupied insofar as we know.
In a world with fewer cushy niches, is capital-L Life going to end up pushing more aggressively into the unfavorable “nooks and crannies” trying to find any available purchase? IOW, could Earth life extend a bunch farther into our own extreme environments, but just hasn’t been cornered enough to bother trying?
Or at least not enough to bother well enough to not simply become promptly extinct prey for the lifeforms “smarter” (or sooner) enough to have occupied nearby niches that are more favorable.
Absent those favorable niches, just how far(ther) can Earth life (or Mars Life) go? We’ll find out in future centuries I’m sure.
Even if there’s no water compacting the dust, the burrowing animals themselves will do so. You can’t dig a burrow without either transporting the soil out the back of the tunnel (which would have its own issues, especially for long tunnels), or compressing the soil around the tunnel. Crisscross the “dust pond” enough times, and it’d pack as tightly as Earthly soil.
I think there’s some indication, in the extended universe, that sarlaccs aren’t native to Tatooine. That one was presumably brought there by Jabba, and kept alive by being fed people Jabba wanted to make an example of. Their native environment is much more lush, such that sarlaacs can survive on the occasional animal that stumbles in, sort of like a pitcher plant writ large.
On the other hand, though, krayt dragons do seem to be native to Tatooine (at least, we’ve seen at least two of them on the planet, loose in the wild, and it’s hard to imagine them having been deliberately introduced). And they’re both large enough to eat sarlaccs, and have a much more active (and hence Calorie-requiring) lifestyle.
This well constructed argument overlooks one detail.
Atomic bomb tests.
Thanks to atomic bomb tests, mutant giant ants, nuclear enhanced sea monsters, and of course, giant bats, giant spiders, and giant lizards have evolved to grow to immense sizes and survive outside their native habitat.
That was in the 1950s . By the 1980s and later it was chemical pollution (Prophecy, The Host)
It doesn’t matter. It just has to be something scary and new.
Actually, the scariest part is that either nuclear or chemical pollution, while it might cause gigantism, is more likely to produce cancers. Giant cancer-ridden ants would be self-defeating.
More credible explanations for giant underground monsters are awakening from suspended animation after a billion years, or recent exposure to radiation (which is well known for causing rapid gigantism), and of course the existence of Pellucidar which is almost as large as the outer world. With such options and more available it’s pretty lazy writing to just assume giant monsters are having a nice active life underground until suddenly uncovered.
Or being hatched. That’s the premise of Rodan and The Prehistoric Sound
(I love the last one. It’s cheesily bad, and goes by a number of names. What hatches is a roaring dinosaur, which is invisible. A great savings in effects work. The movie features the worst “iinvisible monster” effects you’ve ever seen. It’s also the debut film of Ingrid Pitt.)
I know the OP has said he isn’t really dissing Smaug, but didn’t Smaug live in an environment that had been highly modified by humans? I didn’t see an issue w/ Tolkien dragons seeking out whatever lairs they can, displacing others as they mature.
Now if we wanna talk impractical underground creatures - howzabout that Balrog with them WINGS?!
I wasn’t complaining about Smaug because, like bats, he doesn’t live all the time in his cave – he can come out and eat things outside. He just spends most of his time sleeping and conserving his energy (like my cats). He’s not violating the conservation of energy or anything. At least by not living completely underground with no obvious food input. We can discus his flying later.
As for Balrogs, them’s mystical creatures that live perpetually underground (except when forced out at the top of the Endless Stair by a Wizard), but I just assume that they have magical means of support, and don’t worry my head about them.
Are you SURE you want to bring up Balrogs and whether or not they have wings? It took long enough to tamp down that controversy last time.
“As Iluvatar is my witness, I thought Balrogs could fly!”
With a quick glance at the topmost wiki preview box there Darren, that thing sure looks like some hideous Tremors critter or Arrakis sandworm having just surfaced for a meal of humans. Not good.
