Bronchitis of the Earth — Microbes Living Deep Underground

    All life on earth, including you, your pets, your lawn, everything living out in the forest, swamps, all the fish in the sea – everything ultimately depends on the sun for its existence.  Sure, we don’t directly get our energy from the sun, but we eat organisms that do (plants).  All life on earth owes a giant debt to those lowly beings at the bottom of the food chain that can use photosynthesis to capture energy from the sun.  Almost.1

Deep-ocean life at volcanic vents posed an exciting challenge for G. I. Joe in 1983

You might have heard about the discovery of small clumps of life blooming around deep-ocean volcanic vents.  Aside from hosting beautifully strange looking plants and animals, what’s cool about these vent habitats is the fact that they do not depend on the sun – these little colonies use the geothermal energy released by the volcanic vent, so their ecosystem can exist completely independently of the sun.  If the sun blinked off tomorrow, we’d be in serious trouble, but these deep-sea vents wouldn’t even notice.

As it turns out, there’s a second type of habitat on earth that doesn’t depend on the sun – recently scientists have been surprised to discover microbes living deep underground, quite deep, like seriously deep – miles underground, waaay too deep to get any energy directly from the sun, or to eat any decayed organic material.  They’re completely cut off from anything fluttering down from the surface biosphere (or at least they were, until we discovered them with our drills).  What the hell are they doing down there?

These bacterial colonies ultimately get their energy from radioactivity, not from sunlight.  There’s a constant background of radioactivity in the earth’s rock, as radioactive elements like uranium decay and release energy.  Apparently this energy can break down groundwater, releasing energy that the microbes can exploit to make their own food.  (Specifically, the radiation breaks down water, releasing Hydrogen atoms that the microbes then use to convert sulfate molecules to hydrogen sulfide.  Why didn’t I think of that?)

Scientists have stumbled across a few of these microbial pockets in underground mines and whatnot.  From chemical analysis of the groundwater the microbes live in, they can tell they’ve been isolated for millions of years, in other words no chance of getting any energy or material from the surface, however indirectly.  These guys generally don’t do well in oxygen, so they tend to die when exposed to the surface atmosphere.  In fact they’re likely related to the first organisms to evolve on Earth, back before we had oxygen in our atmosphere – back then, anaerobic bacteria ruled the world, and oxygen was a poison to be avoided.  But while our beloved oxygen makes them scream, they can survive in harsh conditions that would fry us in minutes.  In fact, many astrobiologists are putting on their hardhats for a trip to the mines to see these guys, as their very survival implies life could potentially exist in similarly harsh climes on other planets.  (“Astrobiologist” is a title I would kill to have on my business card.)

One of the first scientists to propose the existence of deep-earth microbes was Thomas Gold, a scientist who I’m legally obligated to call a “maverick”.  He’s a guy who seemed to have his hand in one bizarre theory after another, starting with a competing theory to the Big Bang origin of the universe called the “Steady State Theory”.  As a child, I remember hearing about his theories on fossil fuels – he proposed the idea that petroleum didn’t come from decayed plant matter, was not in fact biological at all, and that vast quantities of it are dispersed throughout the earth’s interior.  Naturally this was a popular and optimistic theory to put forth when gas prices are rising.  He later suggested that bacteria might survive deep below the surface by munching on the vast hydrocarbons, and so was the first to advance the idea of organisms living that deep.  He likely didn’t help the critical reception of his ideas by 1) advancing so many other preposterous ideas, and 2) probably stealing this one from earlier Soviet scientists.

Geophysicist Tullis Onstott collects geologic samples using only his manly, ruggedly handsome chin

Years later, the crown of deep-underground microbe hunting has been passed to Tullis Onstott, a professor of geophysics at Princeton.   Onstott has made multiple deep-ground discoveries the hard way, by tagging along on deep mining projects and collecting water samples freshly released by the drill bores.  He’s made several trips to extremely deep mines in South Africa, and looks ruggedly handsome in his hardhat.

So let’s say you’re several miles beneath the surface of the earth, thousands of miles away from home.  It’s hot, harsh, and you’re only down there by the good graces of a mining company.  You’re wading around in groundwater seeping (and in some cases gushing) from the rock that ihas been down here for perhaps tens of thousands of years.  You recently discovered that you’re surrounded by ancient microbes that have never seen the sun and might as well be aliens.  Is there anything that might cause you to feel somewhat uneasy?  How about noticing worms moving around in the rock?

Onstott and Gaetan Borgonie discovered a new species of nematode worm living in the rock about a mile down, astoundingly deep for a complex multicellular animal.  The worms (which can be large enough to be seen with the eye) apparently feed on the various alien bacteria swimming around in the groundwater.

What are nematodes?   Tiny worms, basically – you’ve probably seen them before.  In fact they’re the most populous animal on earth – four out of five animals on the Earth are nematodes.  E. O. Wilson put this into perspective – if some wizard made everything on earth invisible except nematodes, you’d still be able to see a ‘ghostly outline” of Earth made from just nematodes.  Creepy, eh?  Its unclear as yet whether these particular nematodes are also truly cut off from the surface (sun-powered) biosphere, but even if they’re not, they’re impressive.  Having adapted to such harsh conditions, they now have superpowers such as being able to survive freezing, dehydration, extreme temperatures, and ad homeneim accusations of creepiness from some crappy science blog.

Does anything more complex live down there?  So far these creepy nematodes are the most sophisticated animal found this deep, and they’re vastly outnumbered by the unicellular microbes.  It would be pretty tough for anything more complex to live down there, considering the tight space, high pressure, and near-boiling temperatures.  But let’s indulge in some Wild-Ass Speculation anyway, and conceive of what it would be like for a sophisticated, intelligent multicellular organism living down there.

It’s possible that some existing animal down there could evolve larger and smarter, e.g. a nematode species decides to bulk up and hit the books.  But I think that would be unlikely – given the high pressure and tiny fissures in the rock these animals have to make their way through, there’d be a lot of resistance to a single organism growing larger.  But what about a colony of microbes communicating with each other, forming a loose collaboration as they burrow around in the rock, not unlike an ant colony?  Given the close cooperation among some insect colonies like ants or bees, some scientists speculate about how the entire colony could be considered one “superorganism”, in the sense that individual insects lose their individuality, sometimes being sacrificed for the greater good of the colony.  Sure, that sounds communistic, but also sounds somewhat like our own attitudes with our own cells — we can lose a couple here and there, no sweat.  Imagine some tight-knit social group of these microbes becoming more sophisticated over time, to the point where a complex colony of single-celled organisms starts looking like a diffuse multi-cellular organism.

This is still wild speculation, of course – there really aren’t many examples of this above the ground, much less miles below it.  Aside from insect colonies, the best-known example in the microbe world is the amoeba species Dictyostelium.  This guy normally flies solo, but in times of stress it will join up with other members of its tribe to fashion a multicellular “slug” creature – it will literally morph itself into a large complex organism, like the liquid-metal terminator reforming after a freeze & shattering.  While I don’t know that an anthill collective nor an amoeboid-slug are intelligent enough to inspire hope that my idea is possible, it’s fun to imagine how these collaborative colonies might become ever more complex to the point where they are essentially a large single organism.

Deep-earth microbes look quite alien, even to our modern sensibility

Believe it or not I haven’t yet gotten to the coolest part.  So we’ve agreed to picture a colony of deep-earth microbes learning to work together, eventually forming a close-knit collaboration strong enough that their individualness fades away and the entire colony can be reasonably seen as a decently intelligent single organism.  Here’s the cool part – remember, they’re living in solid rock.  When you think of intelligent beings living deep underground, you probably picture a hairy rock-creature living in a cave, living in spaces between the rocks – but the microbes we’ve found don’t live in caves, they live in the rock itself – they burrow their way through rock much like earthworms tunnel around in our backyard soil, or at the very least through microscopic fissures and cracks in the rock.  So this colony of microbes would not necessarily have to all be in direct contact with each other at all times – the colony would stay loosely aggregated as the individual microbes seep through the rock fissures, much as an ant colony exists spread out through the tunnels in the dirt.

So, to our hypothetical deep-earth Bolshevik microbe collective superorganism, solid rock would feel to it as air feels to us, or water to fish – just the medium they move around in.  This animal would be breathing and swimming around in SOLID ROCK.  If they came up to the surface to visit us, they’d have to bring “rock tanks” with them just to be able to breathe.  They’d probably be just as astounded to find us living outside of solid rock as we would be to find them, naturally assuming that no life could exist outside of a rock substrate.

Of course they’d move pretty slowly down there – we know that life for the microbes is slow given how little energy is available and how difficult it is to move around.  So they’d probably move very slowly, as their various body parts would have to wait for signals and whatnot to move around in the rock substrate.  They’d have much slower metabolisms than us surface-dwellers.  As such they’d probably have lives more akin to trees – they’d live quite long lives, and their sense of time passing would be on a much slower scale than ours.  Our own sense of how fast time moves is largely governed by how fast neural signals travel around our nervous system – on the scale of tens to hundreds of milliseconds.  If it took 10 minutes for a single neural signal to travel from our fingers to our brains, then that 10 minutes would feel like just an instance to us.  Similarly, to our underground dudes, a day or week would feel like just a few minutes.  If they could see us, we’d be buzzing around incomprehensibly fast to them, and would snuff out as quickly as we consider the lives of fruit flies.

This graphic nicely sums up the where these last couple paragraphs have headed.

Down there, there’s no sun to light up your environment, of course.  But the microbes living down there have ways to sense their environment, so surely our rock-breathing hypothetical life forms would have some analogue to our vision.  Perhaps to them the thermal glow of the interior of the earth would be their “sun” – they’d be able to sense their environment by somehow using thermal sensing to get around.  Or perhaps radioactivity – clumps of tasty radioactive material would “glow” to them.

All of this has gone past wild-ass imagination to become wild-ass bullshit, of course — as far as we know there’s just bacteria and tiny worms down there, & they hardly ever bump into each other.  There’s no evidence of anything more complicated than the nematodes.  The creepy, creepy nematodes.  That are probably creeping their way along in the dirt directly below where you’re sitting, right now.  And below them, millions upon millions of bacteria, munching on radioactive waste, mutating to become rock-breathing super-villains.  Who are likely already evolving to achieve consciousness…  maybe even a greater level of intelligence than ourselves…



1.   Please read the word “almost” in your best badass Liam Neeson voice.  That’s it?  That’s your Liam Neeson?  That sounded like Stan Humphries.  Sheesh.  Now I’m just embarrassed for you.

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