h a l f b a k e r yCogito, ergo sumthin'
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The original Miller-Urey experiment passed an electrical current and UV radiation through a mixture of heated chemicals to see if organic compounds would form, to test the hypothesis that life could have arisen in this way if the early atmosphere was rich in the compounds in the mixture. It ended up
producing various carbon compounds, some of which were organic such as glycine.
I'm personally very sceptical about the possibility of silicon-based biology, but obviously i've never tested it and i'm fairly sure no-one else has in this way. The original mixture in the Miller-Urey experiment was water vapour, ammonia, hydrogen and methane. Only one of these needs to be replaced to turn this into a fairly reliable test for the possibility of silicon-based life. So, take this mixture, replacing methane with silane, do the experiment again, and see what you get. This assumes that silane can occur naturally.
If it does turn out to make new compounds, it might even be a useful method for synthesising them.
I'm pretty sure this wouldn't work, which is sort of the point.
Experiment with silca-based life.
http://www.youtube....watch?v=2aUTYnPwmz8
[bungston, May 01 2009]
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A little wandering around the Internet tells me that silicones (made from silicon) are roughly analogous to common carbon-based compounds, and are as inert as all get-out. The rubbery key-covers that you may be touching right now are silicone. The rubbery implants that you probably are not touching right now are silicone. |
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Silicon compounds are common enough, but not that lively. Go ahead with the experiment, but I'm not financing it. [ ] |
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Well exactly. I'm pretty sure very little would happen. It probably wouldn't be all that expensive to do, but i think you'd end up with a few odd chemicals which were complete dead ends. Then again, maybe silane is the wrong place to start, since i don't know if that exists in the interstellar medium. |
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It would probably depend a lot on other reactive species and
on temperature and pressure. Lots of people have pondered
silicon-based life, so there must be some plausible
chemistry. |
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//I'm pretty sure this wouldn't work, which is sort of the point.// |
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I don't think a negative result would tell you much. Silicon-based life could exist with a very odd chemistry far removed from our current knowledge of organic chemistry and the makeup of faraway planets. I think it's worth a try though. [+] |
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//I'm pretty sure this wouldn't work, which is sort of the point.// |
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It might indeed not tell you much, but it has to start from building blocks which are known to exist for it to be investigated. On reflection, i think there should be other silicon stuff too, as is found in the interstellar medium, and i made a list: carbides, nitride, monosulphide, carbonitride and naphthocyanine. I still feel suspicious that these things will either just sit about doing nothing or just turn into silica with boring stuff.
[MB], i think there probably is once it's been kick-started, but it has to get to the stage when the kind of substances feasible have been formed. I'm not aware of anything like amino acids or purines and pyrimidines. Lipids, yes. |
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I'm bunning because I'm dumb enough to have thought the title was a typo and have now learned something. (+) Very strange that methane is so common and silane is so rare, that alone seems to cast doubt on the success, but as you said that is sort of the point. |
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There are problems with a Si based biochemistry. First of all there don't seem to be commonly occurring catalytic reactions for manipulating Si here on earth, and they would be very useful to living organisms here on earth as Si is very common in the soil in various forms. Obviously there is a need for dramatically different conditions of temperature, pressure, or chemistry for Si life precursors to occur. Sensibly the most favorable conditions would need to be present in this experiment, as our one good example of "a place where live developed" seems to have very favorable conditions for the reactions that give rise to life (they occur with startling frequency which is why the apparatus was a success.) |
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IIRC, Si-Si bonds are not as strong as C-C bonds. They'd never survive the tension necessary to create many proteins. |
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I suppose this is really an attempt to falsify the hypothesis that there can be silicon-based biochemistry in particular circumstances. The problem with it is that the circumstances may be too specific for it to work properly. For all i know, there may be exotic situations when unusual silicon compounds could be generated spontaneously.
I don't think it'd even get as far as chains of silicon. I actually think you'd just get silica and the like. |
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Water vapor is not reactive enough - maybe substitute HF (hydrogen fluoride) for this experiment ? |
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Hasn't the biggest discovery relating to the Miller-Urey experiment been the discovery of biologies linked to hydrothermal vents? Miller-Urey was investigating almost exclusively atmospheric phenomena (evaporation, lightning, rain) with no thought to deep-sea processes (which is reasonable since nobody knew they existed then) - certainly an interesting experiment in that it showed how a complex physical arrangement can synthesise complex chemical compounds. |
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If you were certain that silicon compounds wouldn't form using this same atmospheric process, there are other processes you might try - including volcanic ones (vents), magnetic ones (imagining interesting things happening in the whorls of Jupiter) or other suitably outlandish physical arrangements. |
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[Batou], the problem i have with that is trying to envisage a process without technological intervention which would lead to the appearance of hydrogen fluoride. I tried to come up with a plausible scenario once of a planet with free fluorine in its atmosphere, and concluded that it couldn´t be done. Maybe i´m wrong. Sulphuric acid is common on other bodies in this solar system and the presence of deposits of fluorite on a planet with liquid sulphuric acid might end up with hydrogen fluoride, so maybe, yes. I think chlorinated compounds are a lot more likely though.
[Zen_tom], you may very well be right. The challenge would then be to imagine a possible scenario. I have seen it suggested that certain hot Jupiters would at least have silicate clouds, but how is the silicon going to get free from it? Ionisation maybe. |
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[19thly], I agree about scenarios for producing HF naturally ... your suggestion of fluorite/sulfuric acid is rather plausible. I was only thinking about an analogue to water vapor in terms of reactivity to the other ingredients, otherwise as others have observed above it will probably end up as SiO2. I don't think chlorine is reactive enough to affect silicon usefully. Best to try this anyway, with several different starting mixes. [+] ! |
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Thanks. I was really thinking of the possibility of free halogens in itself. There is such a thing as tetrachlorosilane. Also, an entire ecosystem made of synthetic biochemicals would be rather fun too. |
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just wait another thousand years and dig into the trash layer from this century..... |
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Glycine has a track record of being part of critters - likewise the other molecules that the in vitro primeval ooze generated. If your silane experiment did generate some Si- containing molecules, how would you know if they were suitable building blocks for life akin to glycine? Unless you did a mind meld with the experiment afterwards and it told you ... "pain...". |
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"NO KILL I"
If the compounds reduced were unable to bond to each other in any substantial way, or in another way form a larger scale structure, i see that as an insurmountable problem. I do think it's possible for plasma-based information processing to happen as a result of non-biological processes, but whether a biochemical system could arise from silicon i don't know, but my degree of belief is low. Maybe a dust-based plasma or some kind of electrical process. |
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You've also got foaming, repeated sloshing into tidal shallows, and I wondering whether standing vibration waves might produce nodes at which more unusual bonds might develop. |
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There must be a lot of unanticipated situations which are exotic to us but really quite common. I sometimes wonder about the magnetospheres of gas giants, for example. |
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I'm a fan of gas giants too. |
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I've often thought the full phase diagram of water - including the high pressure ice phases - is very enlightening. If one basic compound can show that much variation in its behaviour, surely it's reasonable to suppose that there might be other pressure and temperature regimes
where complex structures can form and evolve into something that we might call life. |
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Most of the interior of Jupiter is thought to be fluid. The pressure in the centre is over 100 million atmospheres and the temperature is probably over 10,000 degrees C. That covers a lot of bits of phase diagram. If we want to find completely alien biochemistries then gas giants could be the best place to look. |
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Of course this is speculative. There's one situation where we know for sure that life can exist, and understand something about the details of the molecules that make it up. That's why we search the skies for water, Earthlike planets, amino acid precursors, and such things. |
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But it's interesting to think that the Jovians, in their own search for alien intelligence, might have summarily dismissed the Earth as a mere rock, many orders of magnitude too small to be worth more than a cursory glance. |
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[+] for giving me an excuse to write something about this. |
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This is probably one for "Am i mad or not", but i sometimes wonder if there's a complex process of some kind in Saturn's magnetosphere, near the poles.
[Bungston], just noticed your link. I'll have a look now. |
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OK, i've now spent rather too much time on the Star Trek wiki, and it seems fossils of silicon-based insects will be discovered on Mars only a dozen years from now. I also know a lot more about a Hungarian actor called Janos Prohaska than i ever did before. Thanks, [bungston].
Actually, the Martian insect thing does make me think of one way in, sort of. Biogenic silica exists and silicon is present in some cartilage, plants and protists. I wonder how much scope there is for that in organic life forms. Probably not a lot, since it just seems to be silica and silicic acid. |
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