Thursday, October 16, 2008

The Living Dead

Meet Candidatus Desulforudis audaxviator, the bacterium that does it all: fix carbon, fix nitrogen, synthesize all essential amino acids, locomote — an organism that can exist totally independent of other life. It doesn't even need the sun. This fucker basically lives on sulfur, rock, and electrons*.

It's an obligate anaerobe, without even the most rudimentary oxygen resistance. A bug like βehemoth would kick its ass throughout most of the terrestrial biosphere (its natural digs are a couple of kilometers down in the crust, where no O2 has poked its corrosive little head for at least three million years). But that's not likely to be any kind of drawback out in space, and various talking heads are already nattering excitedly about the prospect of something just like this hanging out on Mars, or on the Saturnian moons.

It is cool. It is, quite literally, a complete ecosystem bundled into a single species, a biosphere crammed into two-and-a-half megabytes and a crunchy shell. Astrobiologists the world over have been creaming their genes for a week now. It's such a science-fictional little beast that its very name was lifted from a Jules Verne novel— but what really sticks in my mind about this little Swiss-army knife is a feature that's actually pretty common down there.

If it's anything like other deep-rock dwellers, D. audaxviator reproduces very slowly, taking centuries or even millennia to double in numbers. It's a consequence of nutrient limitation, but might we be looking at a kind of incipient immortality here? The textbooks tell us that one of the defining characteristics of life is reproduction. But if you think of life as the propagation of organized information into the future — the persistence of signal, rather than merely its proliferation — then reproduction is really just a workaround. The chassis that carries the information wears out, and must be replaced.

It doesn't take much, here at the dawn of Synthetic Biology, to imagine an organism with unlimited self-repair capabilities; something that can keep its telomeres nice and long, which sweeps away all those nasty free radicals and picks up the broken bottles in their wake, which replaces an endless succession of disposable Swatches with a solid gold Rolex which can hang in there for a billion years or more. Hell, you could even postulate some kind of Lamarckian autoedit option on the genes, so the organism can adapt to new environments. Or you could just limit your organism to extremely stable environments that don't require ongoing adaptation. Interstellar space, for example. Or deep in a planetary lithosphere. In some ways, this could be a superior strategy to conventional breeding; at least you wouldn't have to worry about population explosions.

I wonder if, somewhere down there, D. audaxviator or something like it has given up on reproduction entirely. Maybe it keeps the machinery around as a kind of legacy app that no one uses any more and just ticks slowly onwards, buried beneath all that insulating and protective rock, unto the very end of the planet.

The textbooks would call it dead. I'd suggest our definitions may need an upgrade.

*Of course, the fact that it can live independently doesn't mean that it evolved independently. A bunch of its genes have been cadged from Archae via lateral transfer. Its genes also contain anti-viral countermeasures; whether it siphoned those off incidentally from donor species or actually uses them to guard against parasitic code, there's obviously a history of contact with other life in this bug's family tree.

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Friday, August 17, 2007

We Don't Need No Steenkin' Carbon

Okay, now here's a paper to kick your paradigms a little off-kilter: self-replicating, mutating complex structures built from inorganic dust, kick-started into a form of rudimentary "metabolism" by charged plasmas.

For want of a better word, Life. Inorganic life. Spawned from starting conditions reasonably common in deep space, if I'm to believe the commentary.

Of course, the results are just out, and so is the jury. We don't want to get too carried away; lots of nonliving structures superficially resemble life in a variety of ways (ball lightning, Fox's microspheres from the fifties — I even wrote a children's story once premised on the thought that fire might be considered a life form under the right circumstances, although the logic of that argument was about as feeble as the story itself). And for every thought-provoking Hoyleian thought-experiment into sentient clouds, there are ten third-rate episodes of Star Trek and Space: 1999 that trotted out the ol' energy-being trope for no better reason than that a blob of blue light was even cheaper to render than a guy in a rubber mask. There's a certain hokey taint to the whole concept.

Still. Those of you who read Maelstrom may remember the definition "Self-replicating information shaped by natural selection", based on (and slightly mutated from) a line I stole out of Dawkins's Blind Watchmaker. Tsytovich et al's "inorganic living matter" seems to meet that standard, at least. And since I'm presently gearing up to build a deep-space lifeform or two of my own, I for one welcome the arrival of our new dustbunny overlords...


Wednesday, April 25, 2007

"It's 20 light years away. We can go there."

Now that's the kind of attitude I like to see coming from a legitimate authority-- to wit, Dimitar Sasselov of the Harvard-Smithsonian Center for Astrophysics, quoted in today's NY Times. He was talking about Gliese 581c, a potentially earth-type planet orbiting a dim red dwarf in the constellation of Libra. 1.5 time Earth's radius; 5 times the mass. Mean temperature somewhere between 0 and 40°C, solidly in the Goldilocks Zone for liquid water. A type of planet thought by Sasselov to be not only congenial to life, but more congenial than Earth.

Of course, you probably know this already. It's on boingboing, after all, and Yahoo, and and Nature, and a thousand other websites. (Science, my usual go-to source for this kind of thing, is still asleep at the wheel as of this posting.) What you probably don't know, however, is that there's a pretty specific real-world connection between Gliese 581c and Blindsight.

You see, we don't really know all that much about 581c yet. We got a mass, and we got a distance-from-primary, and we got an orbital period (11 days), and we got all of that by watching Gliese 581 wobbling slightly as its planets tugged gravitationally on its sleeve. We don't even know if 581c has an atmosphere, and if so, whether it's closer to ours or Venus's.

But there are plans to find out, and they involve the use of a suitcase-sized Canadian satellite called MOST (also known as "The Humble", by virtue of its teensy dinner-plate of a mirror). Despite its small physical size, MOST is well-suited for picking up the atmospheric signatures of extrasolar planets, and it'll be turning its glassy eye towards Libra in the near future. The Principle Investigator behind the MOST is a guy name of Jaymie Matthews, who acted as my unpaid astrophysics consultant (well, paid in pizza and beer, I guess) for Blindsight.

And now, after helping me chase aliens through my own brainstem, he's gonna be looking for real ones at Gliese 581. How cool is that?

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