I was wondering if silicon based life is possible (or been found)? I know that life that we know of is carbon based because of the half filled valence shell electrons that allow so many different ways of covalent bonding.
So, since Silicon had four valance electrons, is life based on silicon possible? Has it, or any examples, been found?
Probably not…
As I understand it the binding energy of silicon is a lot higher than carbon, so even with the 4 valence electrons, silicon life would have either very slow metabolisms (on the scale of aeons and aeons- it would erode before it could metabolise anything), or be at such high energy levels that any sub compounds would be to unstable to be useful…
Some smarter doper will be along shortly to either clarify or refute my humble attempt here
regards
FML
Certainly no examples have been found - all lifeforms currently known are believed to be descendants of a single origin event - which happened to be (or perhaps could only have been) carbon-based.
Indeed. It’s all about CHON.
I am not that smarter doper, however, to add to what you’ve said above - one of the problems with silicon as a carbon-analogue is the different material properties of some of the compounds - for example: carbon dioxide is a gas - miscible with air, soluble in water.
Silicon dioxide is… sand. more difficult to excrete into an earth-like environment. Not necessarily impossible, but certainly presents additional challenges in handling.
Also, silicon is a lot bigger than carbon. This may sound like a silly thing, but the thing is, carbon can have multiple bonds relatively easy; silicon, not so much. The list of organic (from a root meaning “life,” but meaning C-based) families of compounds that have multiple bonds is much larger than that of those which don’t.
(My MS is in Theoretical Chemistry; look, pretty pictures of molecules!)
In the classic story “A Martian Odyssey” by Stanley G. Weinbaum, an Earth explorer comes upon a trail of pyramids on Mars that grow steadily latger. Each pyramid has been broken open. When he gets to the end of the line, he finds the largest pyramid, unbroken. As he watches, it breaks open from within and a vast, amorphous blob exits, moves over a pyramid spacing, and settles down. It begins to produce quartz blocks, that it begins to pile around itself. It was a silicon life-form, and it was essentially “exhaling” silicon dioxide (quartz) instead of carbon dioxide, and simply piled it up around itself until it ran out of room.
It’s a great story, for sure, but I’m sure it overlooks quite a lot of the detail.
Not sure what you mean, but if you’re saying that Weinbaum didn’t look much beyond the simple fact of SiO[sub]2[/sub] respiration, I agree. But he wasn’t trying to create a detailed lifecycle and a believable chemistry for a silicon-based lifeform. It was pretty much background material of “odd stuff we saw on our trip to Mars”… The real story was him and Tweel and a sympathetic treatment of an extraterrestrial.
Frank Edwards, in one of his “Strange” series of books recounted a 19th century scientist/tinkerer who did indeed create silicon-based critters (crickets? frogs?). Unfortunately, he never revealed the secret behind his process.
No mention yet of that wonderful Roddenberry documentary on the Horta?
RR
They were insect-things. Edwards wasn’t the only one to write about it (and, as a word of caution, you shouldn’t trust Edwards. I don’t mean in that he writes about weird things – lots of people do that. It’s that Edwards can’t even get the story straight. He tends to “misremember” things, or misreport them, or just plain make things up.) I have the story in other books, and it all goes back to Andrew Crosse:
That’s one of the things Edwards got wrong.
Even if you take Edwards at his word, though, these don’t qualify as silicon-based. Crosse, as described by Edwards, used a big chunk of iron oxide in his experiment (I know – I duplicated it in my basement lab as a kid. My attempt to Create Life in the Laboratory didn’t work, though. It’s Not Alive!!!)
Somebody need to bring up A G Cairns-Smith. His theories of clay-based abiogenesis use crystallography, not chemical bonds, to form complex structures, but do involve silicates as replicators. The theory isn’t favored as much as it once was, but I don’t believe it’s entirely discredited either. The replicator for “life” does not necessarily have to be chemical.
In terms of more conventional chemistry, long-chain silicon compounds aren’t very stable. Types of long chain silicones using alternating silicon and oxygen atoms are more stable, and have been suggested for alternate biochemistries, probably in radically different environments than on the Earth. The wiki alternative biochemistry writeup mentions that silicones might be more favorable in sulphuric acid rich environments. IIRC, one stumbling block is that in radically different environments where water is not liquid, you have to come up with an alternate liquid transport, or postulate life processes without one.
ETA:
If we are going to play “fair” concerning silicon based life in other environments, we probably should disallow carbon-based liquid transports, or insist that the proposal include why organic chemistry based life wouldn’t work in those environments. No seas of liquid methane.
BTW, I can’t believe that the wiki article on alternative biochemistries has a long section on fiction without mentioning Hal Clement.