Hello, wee bug! Or: why a nuclear-powered bacterium may be the best hope for life in the universe...

>> Friday, October 17, 2008

Life is strange. I don't mean "life" as in what you're living, though that's probably strange enough, or at least almost everybody says it is. I mean "life" as in "living things," as in the great seen and unseen biomass that covers the Earth's dry surface and slips through her waters and curls up in the dark nooks and bowels you wouldn't think anything could survive in, if you thought of those corners and crannies at all.

Meet, for example (and if you haven't already), Desulforudis audaxviator, discussed in Monday's "Cosmic Log" science blog at MSNBC.com D. audaxviator lives underground, and not just underground--D. audaxviator is a bacterium that lives in dark, anaerobic conditions without any apparent access to nutrients from the surface or any direct or indirect reliance on photosynthesis at all: D. audaxviator uses natural, ambient radioactivity to break down water and minerals to produce hydrogen and sulfate and keeps its bad little self going on that.

Yes, it's a nuclear-powered bacterium living deep underground in a gold mine, having pretty much said "fuck you" to every other living thing on Earth three-to-ten million years ago.

Now, I think the obvious tricky part is whether D. audaxviator's ancestors evolved in what we traditionally deem an "earthlike" environment, warm and wet and maybe electrically-charged, or did life start somewhere in the bowels of the planet and eventually come up? One of the organism's discoverers, Dr. T.C. Onstott, notes in the "Cosmic Log" piece that D. audaxviator isn't itself a progenitor organism; in fact, it appears that the species has absorbed DNA from a number of bacterial species, DNA-trading being a not-uncommon activity for bacteria. But the possibility D. audaxviator settled in those radioactive rocks from above doesn't preclude the possibility it got there from below. Maybe we've been looking for the origin of life in the wrong places, by way of the wrong processes.

Here's why it's important: as best we can tell, and in all likelihood, warm, wet, rocky worlds in a star system's habitable zone are rare; and such worlds in an orbit where they happen to be shielded by outer gas giants that suck up all the cosmic afterbirth debris that could kill life off almost as soon as it starts must be rarer still. And should it happen that a necessary element to the formation of life as we know it is a goldilocks-just-so combination of tidal, rotational and axial stabilities that are brought about by having a plutoid-sized companion planet pulling away just so, well you can imagine that such worlds as ours may in fact be unique in their heritage and circumstance.

But darkness, radioactivity and water? Those, friends, are common. You might find conditions such as that on the inside of a brown dwarf's moon or in the deep core of a massive round rock zipping around the innermost orbit of a hot blue star or in an almost-frozen semi-cometary mass on the edge of a nearly-dead post-nova system. You might find life like that anywhere. And life, when it's there, evolves; I don't mean it ends up inventing cars and porn and religion--though it might do that, too, while it's up and about--I mean the descendants of an organism find and adapt to every available ecosystem, however hostile and unforgiving, and their descendants adapt and thrive and so do their descendants. Which at least raises the possibility some eventual descendant will sit or lie or splorch down with a container of a substance that has a mildly-intoxicating effect on its perceptual and cognitive faculties before a box that converts electromagnetic fluctuations into visible photons recreating images of distant amusements.

You're a little creature, D. audaxviator, but it's in you to upgrade our estimates of ne and fl. So I'm rooting for you, little bacterial dude; as cynical and pessimistic as I am--and I've never quite understood how somebody could get a whiff of the dreadful Fermi paradox and not be--you could be my new hero, little radioactive bug-in-the-rocks. Let's hope your great-grandparents came from the darkness beneath, wee one, and not from the bright above.


4 comments:

vince Friday, October 17, 2008 at 8:59:00 AM EDT  

To quote British geneticist and evolutionary biologist J. B. S. Haldane: "I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. Now my own suspicion is that the Universe is not only queerer than we suppose, but queerer than we can suppose."

mattw Friday, October 17, 2008 at 10:11:00 AM EDT  

I think it's interesting to read that you've supposed that life would evolve to create cars, porn and religion. Are those the penultimate achievements of any evolved creature?

Oh, and that stuff about the bacteria is pretty interesting too.

Eric Friday, October 17, 2008 at 1:24:00 PM EDT  

Matt: it was really more of an amusing way to frame the idea that evolution does not mean progress, as is commonly assumed. That is, as species evolve to fill environmental niches, they don't necessarily become more complex (including more intelligent), although there are reasons complexity tends to "ratchet" upwards.

One possibility is that we will eventually find that the universe is full of life in strange and (what we would now believe are) improbable places. Most of this life won't be intelligent, but if life is common it necessarily increases the chances of us finding intelligent life.

Maybe these two alternative scenarios illustrate (I hope):

1) The origin of cellular life is dependent on shallow pools of warm mineralized saline water (tidal pools) that are kept at reliable cycling temperatures and periodic gentle stirring by a sun at a just-so distance and a nearby orbiting plutoid of just-so mass and distance;

2) The origin of cellular life is something that can occur in complete darkness anywhere the raw materials for it are present using residual heat or heat generated by radioactive decay as a power source.

In the first scenario, life can originate in only a few places (possibly just one--ours); in the second scenario, life can happen nearly anywhere. Once life starts, Darwin tells us it will compete for new resources, with such competitions occasionally leading to virgin frontiers--environments where competition is nonexistent or weak, and therefore easy. In the first scenario, we are alone; in the second--not so much.

Religion, porn and cars are merely ornaments of the kind of interstellar life we might be able to contact if it exists.

(It might be remembered: our search for extraterrestrial intelligence is a search for beings like ourselves--that is, technology-using, RF-spectrum active, extroverted beings. An intelligent species that hasn't invented radio, or is content to meditate, or that has graduated to quantum communicators or somesuch, wouldn't be detectable by most current/past SETI projects. Perhaps, having a similar technological/psychological profile, such beings will also be into fast vehicles, gods and porn.)

Eric Friday, October 17, 2008 at 1:25:00 PM EDT  

Oh, and Vince: I've always loved that quote. I used to have the last part of it on a piece of paper tacked to my wall when I was a little kid, underneath my National Geographic map of the universe.

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