What Silicon-Based Life Might Be Like

Nancy_A writes "While the world as we know it runs on carbon, science fiction's long flirtation with silicon-based life has spawned a familiar catchphrase: 'It's life, but not as we know it.' Although non-carbon based life is a very long shot, this Q&A with one of the U.S.'s top astrochemists — Max Bernstein, the Research Lead of the Science Mission Directorate at NASA headquarters in Washington,D.C. — discusses what silicon life might be like."

Comments

Easy

[ericloewe]

A large clump of silicon that lays eggs and produces and extremely corrosive acid to chew through rock.

Re:Easy

[Snard]

For those who don't get the reference: http://en.wikipedia.org/wiki/Horta_(Star_Trek)

Re:Easy

[DataDiddler]

NO KILL I

And they'll also have a tenuous grasp of English grammar, at best.

Re:Easy

[3vi1]

I'm a doctor, not a bricklayer!

Re:Easy

[Runaway1956]

What's funny about attempts to visualize other types of life forms is, we tend to visualize those life forms in our own environmental terms. That is, we tend to assume some basic atmospheric conditions, pressure ranges, and temperature ranges. We "assume" certain basic conditions that resemble our own conditions.

Silicone? How about we break the cycle by trying to visualize silicone under hundreds of thousands of tons of pressure, and thousands of degrees, with and atmosphere of ammonia? Or, alternatively, in a vacuum at tens of thousands of degrees? Partial pressure atmospheres at near 0 degrees kelvin?

Of course, the question arises then, how and why are mankind interacting with such creatures under such conditions?

Of course, I was enamored with the idea of "living rock" as I child. Some story I read mentioned it, and I had the idea that some rock was really alive. Of course, it isn't - or IS IT?!?!? Nothing says that we are smart enough to recognize alien life when we see it. Geologic time and man's time are so different, that we might not even recognize that a rock actually breathes, or moves, or reproduces. Again, let's step outside our own familiar conditions. Assuming that time might be entirely different for some other life form in conditions that are inimical to us, why would we hang around long enough to collect the data necessary to determine that this or that rock really is alive?

I certainly don't have any answers about the existence of life outside our own experience. But, it amuses me to see the almost idiotic assumptions that people make when considering and debating the possibility. “It’s life, but not as we know it” How about the possibility that a face to face meeting with another life form might be fatal to one or both of the participants in the meeting? His environment is a poisonous atmosphere (to me) and my own body radiating heat might be fatal to him!

Re:Easy

[meerling]

We have a lot of divergent lifeforms from what was taught when I was little.
They used to say nothing could survive in the vacuum of space, the bottom of the ocean, in geysers, highly acidic conditions and so many other places. If they knew about the oceanic geothermal vents (like the black smokers) back then, they'd have sworn they would be lifeless.
Now of course, we have the entire category of Extremophiles that live in those very places and conditions.

Additionally, we have lifeforms that have copper based blood instead of iron, ones that respire sulfur instead oxygen, and diatoms build their skeletons/shells/cell walls out of silica. And now they may have found one that exchanges its phospates for deadly arsenic and lives.

All in all, there are significant portions of life on this world that was considered science fiction several decades ago. Does that mean it's possible that life in other parts of the universe can be very different than ours? Sort of. It means that our understanding of what is necessary for life is incomplete due to our exposure to only our own type of biology. There may be very strange biochemistry out there, but most of it that we might recognize as life will probably be similar to ours. (That's the biochemistry, not the form, or if intelligent, culture.)

Caps Lock Elevates Accessibility

[papar]

I love it how Dorminey IS CONSTANTLY YELLING HIS QUESTIONS AT BERNSTEIN. Oh good God I can't even get this post past Slashdots caps filters!

Why not here?

[vlm]

Why not evolve Si life here?

Dorminey — WHERE ARE THE LARGEST CONCENTRATIONS OF SILICON HERE?
IN SAND?

Bernstein — In sand or rock. There are literally megatons of silicate minerals on Earth.

Talk to a geologist like my ex roommate. I knew there was something fishy about that so I checked the actual numbers:

http://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth's_crust

Silicon 277200 ppm second only to oxygen
Carbon 300 ppm second to pretty much everything but vanadium and stuff like that. By weight the earth has about as much Rb as C.

For all intents and purposes the earth is not the idea place for a carbon based life form. Its the equivalent of a unit train full of high fructose corn syrup tank cars for a silicon lifeform. If they can't form here and absolutely gorge themselves on what to them would be the equivalent of a giant pizza, there is not a more ideal place out there to form...

The reason why we're made out of relatively rare C instead of tremendously available Si is C chemistry is incredibly better than Si chemistry for bio, or heck, chemistry in general. The fine article didn't give it enough justice or maybe the editors edited out the chemistry rants. Lets just say that Xe biochem is not all that more unlikely or difficult than Si biochem would be (in other words, nearly totally freaking almost incomprehendibly impossible vs just merely incredibly extremely impossibly unlikely)

It all has an air of speculative fantasy fiction, like trying to intellectually debate if its easier to make vampires, werewolves, or zombies...

Re:Why not here?

[meglon]

Better yet, talk to an organic chemist. First day of organic our prof detailed why silicon based life is a non-starter. Make chains of carbon and you get such an incredible variety of things that they make up over half the compounds known; make chains of silicon and you get: more sand.

Re:Why not here?

[Rei]

There's more ways to form a complex compound than just Si-Si-Si-Si... chains (which, as you note, tend to oxidize into crystaline silicon dioxide). As a random example as proof, look at silica gel. Si-O-Si-O-Si-O... etc. Chain it pretty much as long as you want, functionalize the side chains, etc.

When it comes to LNAWKI (Life Not As We Know It), I think a lot of people lack creativity to a tremendous degree -- envisioning the situation as altering only one parameter (say, substituting silicon for carbon but otherwise keeping the chemical structures roughly the same).

Re:Why not here?

[thomst]

vlm answered the musical question:

Why not evolve Si life here?

Thusly:>/p>

Carbon 300 ppm second to pretty much everything but vanadium and stuff like that. For all intents and purposes the earth is not the idea place for a carbon based life form.

Incorrect, I'm afraid.

If you exclusively look at the abundance of carbon in the Earth's makeup, you miss the most crucial aspect of hydrocarbon-based biochemistry: the abundance of water as a solvent for hydrocarbons, particularly here on the surface of the planet, where the incredible profusion of possible compound-producing reactions benefits tremendously from sunlight as a source of energy input to trigger the making and breaking of hydrocarbon bonds.

A world where carbon is greatly more abundant - but water is largely absent - wouldn't necessarily be more conducive to the evolution of life.

The reason why we're made out of relatively rare C instead of tremendously available Si is C chemistry is incredibly better than Si chemistry for bio, or heck, chemistry in general. The fine article didn't give it enough justice or maybe the editors edited out the chemistry rants. Lets just say that Xe biochem is not all that more unlikely or difficult than Si biochem would be (in other words, nearly totally freaking almost incomprehendibly impossible vs just merely incredibly extremely impossibly unlikely)

This, on the other hand, is a much better point ... and, IMnsHO, one deserving of an "Insightful" upmod.

Re:Why not here?

[sFurbo]

No, you don't get sand. The silicon equivalent of organic compounds are polysilanes, not polysiloxanes. Making them seems to have been a rather popular niche in the 70's. However, they are unstable, as Si can form more then 4 bonds, so isomerisation is much more rapid than with carbon.

The reason 90 % of the known compounds are organic is because a) there is amble supply different carbon-based compounds to manipulate, as life has made sure, and b) they are more interesting as pharmaceuticals then inorganics. Based on pure chemistry, boron is nearly as versatile as carbon, but starting blocks for boron chemistry is harder to come by, as is funding.

Re:Why not here?

[Anonymous Coward]

OK, I would concede the general point that it somewhat depends on how one defines "life", but I would still argue that the grandparent posts are largely correct:

As noted above, the fact remains that Si - Si bonding is much weaker than C - C bonding due to the relative positions of these elements in the periodic table, which means that any kinds of polymerized molecular species that you might want to try to kick off life with still probably wouldn't last as long in a primordial environment as their carbon-based counterparts. They're more susceptible to being broken up into shorter-chained fragments by UV radiation, cosmic rays, etc.

Things like repeated Si-O chains simply require more factors to be favorable: both elements in the same place, physical conditions that favor sufficiently large quantities of specific silicon oxidation over any other process, etc. Not saying it's impossible, but it just seems significantly less likely to be the dominant chemistry than comparatively strong organic polymerization processes, particularly given the cosmic elemental abundance distributions (i.e. where you get silicon & oxygen in sufficient quantities, you probably get enough carbon as well).

Re:Why not here?

[Beryllium Sphere(tm)]

Long Si-O-Si-O chains are all through the mineral kingdom, forming chains, linked chains, sheets, 3-D cages, and I don't know what else.

Worried that the bonds are too stable? Evolve it in a hotter environment.

Re:Why not here?

[meglon]

Unfortunately, imagination isn't the issue, chemistry is. Silicon simply doesn't do what carbon does when it forms bonds. Substituting silicon into place of carbon chains would not yield molecules that do the same thing, act the same way, or even look the same (silicon is a much larger atom).

Re:Why not here?

[polymeris]

where you get silicon & oxygen in sufficient quantities

Everywhere on the earth's crust?

I don't actually understand enough about the chemistry of Si & C to make a direct comparison, but regarding the issue of bonding strength you mention, wouldn't other factors, like temperature and pressure affect this? Possibly even making Si-based life fitter for some environments?

Mammals?

[TeknoHog]

They better be mammals, otherwise all those nice silicon-based polymers are udderly wasted.

Re:There was a pretty insightful comment

[houghi]

Silicon life forms may actually need to be designed by intelligence because of how hard it is to get a stable start up in environments.

That is what many religions say about life in general.

Where will the anus be?

[Anonymous Coward]

Just wondering.

Re:There was a pretty insightful comment

[Rei]

The problem is of people envisioning silicon-based life in a manner that's too similar to carbon-based life. Silicon life, if ever found, is essentially guaranteed to not have any long Si-Si-Si-.... chains; they're not stable. The silicon equivalent in terms of stability is Si-O-Si-O-Si-O... etc (silicone). Silicon also has some fascinating complex chemistry in the form of silanols, which can form membranes, catalysts, and all sorts of other fascinating stuff... so long as they don't get too hot or in too acidic or basic of a chemical environment.

silicon based religions

[allo]

will believe the universe only exists since 1.1.1970.

Re:silicon based religions

[Snard]

If there is no Silicon Heaven, then where do all the calculators go?

Stupid rocks

[sgt scrub]

There should have been a question like "is there an environment that might make it more plausible for Silicon life"? What about planets that are molten or have oceans, lakes, and rivers of acid. Why would an intelligent rock walk around in place where they will become immobile? Sounds like something only dumb rocks would do.

Re:There was a pretty insightful comment

[chew8bitsperbyte]

The difference is, religions typically believe their "creator was, and always has been". OP (I believe) realizes that humans evolved without a "divine touch" and is talking about a possible next step in evolution. Just because "nature" doesn't make it happen, doesn't make it any less significant. We are a product of nature and evolution after all.

Actually...

[denzacar]

How about we break the cycle by trying to visualize silicone under hundreds of thousands of tons of pressure, and thousands of degrees, with and atmosphere of ammonia? Or, alternatively, in a vacuum at tens of thousands of degrees? Partial pressure atmospheres at near 0 degrees kelvin?

Max Bernstein mentions something very similar to that in TFA.

Dorminey â" DO YOU THINK THAT SILICON-BASED LIFE MIGHT EXIST SOMEWHERE OUT THERE?

Bernstein â" Maybe deep below the surface of a planet in some very hot hydrogen-rich, Oxygen-poor environment, you would have this complex silane chemistry. There, maybe silanes would form reversible silicon bonds with selenium or tellurium.

 
 

How about the possibility that a face to face meeting with another life form might be fatal to one or both of the participants in the meeting? His environment is a poisonous atmosphere (to me) and my own body radiating heat might be fatal to him!

A biochemist's vision of such an encounter, for your listening pleasure.

Re:There was a pretty insightful comment

[tuxicle]

so long as they don't get too hot or in too acidic or basic of a chemical environment.

Isn't this also true of carbon-based proteins (usually what membranes and catalysts are made of)?

What I said there

[mbone]

If you think about it, the people claiming that advanced civilizations would create self-replicating Von Neumann machines that would spread throughout the galaxy, are really claiming that carbon-based life would create (and maybe be supplanted by) silicon-based life. In the same way that RNA-life may have been necessary to get to DNA-based life, carbon-based life may be a necessary pre-condition for silicon based life. (We might think of those Von Neumann machines as robotic spacecraft, but those that can evolve would likely supplant those that cannot, and in a few billion years take on forms that we cannot predict.)

We don't know

[uvajed_ekil]

Although non-carbon based life is a very long shot...

Isn't this a really big assumption? Sure, we haven't seen any non carbon-based life, but we also haven't found carbon-based life on more than one little planet.