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Acetylene Based Life on Titan?
mindpixel writes "Astrobiology Magazine's Leslie Mullen has a fascinating interview with funky science dude David Grinspoon about the possibility that there may exist a whole new biology on Titan where the extreme cold slows normally explosive reactions to a biologically useful pace." From the article: "What's really new in our paper is that we go into the question of energy sources. If there's life there, what's it going to eat? What kind of food is there? And it turns out there's abundant food because of all this photochemistry in the upper atmosphere, where methane is being turned into other organic molecules. Some of those organic molecules are very energy-rich, and one that we consider in the paper is acetylene. We know it's being made in the atmosphere, we know it's raining down on the surface, and it's been detected at the surface with the Huygens probe. We calculated that, if acetylene is reacting with the hydrogen gas to turn it back into methane, quite a bit of energy is being released. So that's our basis for saying there is something to eat on Titan. We don't know if there are any customers, but there's something on the menu."
Even just from the summary, it would seem that the life itself is not acetylene-based, just the food the life would eat.
I am scientifically inaccurate.
--Greg
Biology 101 - The characteristics of life (Iowa state uni)
Except that our small green guy would be LONG dead from terrible burns. We get burned at 110*F or so -- the chemistry of our bodies and verily the very structure of our proteins are affected by temperatures above that, just as temperatures too low do not allow our metabolic processes to continue.
Titan is COOOOOOOLD. Acetylene is much MORE reactive, such that at our "room temperature" it reacts much too easily and much too violently. Our bodies don't work at those temperatures, becuase you can't get oxygen to react (or many other of our normal chemical reactions). But, the article says, they think acetylene chemistry could work at that temperature.
But heat up those chemicals to our normal temps, and fffffffffffffffffffffft!
- Peter
INsigNIFICANT
I think you're missing the point. How reactive the specific chemicals are depends on the temperature to a large degree. Acetylene is more reactive (too reactive) at Earth standard temperatures. On Titan, the temps are so cold as to freeze use solid in minutes, but acetylene remains liquid and could still react with other hydrocarbons. How that plays into over metabolysm and reflexes (which seems to imply macroscopic scales) depends on the reaction energies of those specific hydrocarbon reactions relative to the ambient temperatures.
This reaction doesn't make any sense.
Sure it does. C2H2 + H2 --> CH4 is exothermic by about 300 kJ/mol. That is, 300 kJ of heat are released for every mole of acetylene consumed.
Maybe it's confusing because we usually think of energy-releasing respiration-type reductions in the context of our nice highly oxidizing atmosphere? So that most reactions we think of as "energy producing" are combustion reactions, combinations of hydrocarbons with oxygen? But there's no free oxygen on Titan, so that's out. Nevertheless, there are zillions of chemical reactions that produce energy.
And on that note, I have to say the existence of some chemical reaction that can generate energy seems pretty much a given on any planet with an abundance of light elements and temperatures nontrivially above 0K. How could it be otherwise? The universe has hardly had time to reach complete chemical equilibrium...
So I guess I'm underwhelmed by the realization that this or that chemical reaction could power life. I'd think there's always a chemical reaction that can produce mere energy. That's the least of life's problems, maybe.
The trick, as I see it, lies more in figuring out what system of complex chemical reactions under Titanian conditions could mimic the Terrestrial transcription-translation-replication pas de deux our nucleic acids and proteins execute to regenerate and duplicate themselves indefinitely.
Here's one problem with Titan I see on general thermodynamic grounds: I would argue one of the key aspects of DNA/protein chemistry is the primacy of hydrogen bonds, which have an energy comparable to Earth's average temperature. That makes much of its chemistry nicely reversible -- you can build proteins or digest them, bind with DNA or unbind, and so on, by exerting only small control forces, e.g. by using enzymes.
Alas, the temperatures on Titan are only about 100K, so that's right out. At those temperatures hydrogen bonds are stronger than steel, so to speak. Their chemistry is no longer easily reversible.
But what else is there? It's hard to think of any chemistry which is easily reversible -- easily controllable -- at 100K, because there isn't anything even remotely like a chemical bond with energy that low.
Maybe life -- in the sense of self-replicating large molecules -- is pretty much impossible except where the temperatures are near the energy of a hydrogen bond, which -- aha -- means temperatures near the melting point of water.
Because the Huygens probe had many platinum-covered appendages, this (catalyst) triggered out the chemical reactions depicted in the OP, which heated the probe much more than expected (it is notorious that the probe's temperature was well above manufacturer's predictions during all descent).
:-)
Then once on ground, this heating continued, and Huygens whose batteries had been designed to last "the 3-hours descent + some margins" in a -150 degree environment, lasted indeed six hours more for being much hotter...
Hervé, part of the Huygens technical team
OK, as we are not april 1st now I wonder wether I shoulnd't have posted anonymously
Herve S.
The reason it smells is because it's not pure acetylene. Pure acetylene has a rather sweetish smell. In fact, for a brief period it was used as an anaesthetic (yes, really) until the rather unfortunate side effects became all too obvious - No, I don't know why they didn't catch on straight away.
The *nasty* smell comes from impurities, the major one is phosgene which smells horrible and is pretty poisonous, to boot.
DG: By ultraviolet light and also by interactions with Saturn's magnetosphere. There's a lot of energy up there. Then the acetylene is raining down and getting buried....
Other than that small confusion in the heads of the interviewers, I find the concept of acetylene based life very intriguing.
I, for one, welcome our new acetylene metabolizing overlords.
fast as fast can be. you'll never catch me.
Prions aren't alive.