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Earth May Harbor a Shadow Biosphere of Alien Life
An anonymous reader sends us to Cosmos Magazine for a speculative article arguing that a 'shadow biosphere' may exist on Earth, unrelated to life as we know it. If such non-carbon-based life were found here at home, it would alter the odds for how common life is elsewhere in the universe, astrobiologists say. "The tools and experiments researchers use to look for new forms of life — such as those on missions to Mars — would not detect biochemistries different from our own, making it easy for scientists to miss alien life, even if [it] was under their noses. ... Scientists are looking in places where life isn't expected — for example, in areas of extreme heat, cold, salt, radiation, dryness, or contaminated streams and rivers. [One researcher] is particularly interested in places that are heavily contaminated with arsenic, which, he suggests, might support forms of life that use arsenic the way life as we know it uses phosphorus."
It's life, Jim. But not as we know it.
Or the researcher is secretly needing arsenic to do his more brilliant colleague in the old Victorian-era way, having learnt from too many Agatha Christie novels.
...may exist on Earth but we won't be able to look for it until we define it.
Sounds pretty clear to me. Maybe rocks are intelligent. How would we know? Has anybody thought to ask?
http://michaelsmith.id.au
I think everyone who's ever seen the original Star Trek Episode "Devil in the Dark" (the one with the Horta, the silicone-based rock creature that Spock mind melds with to share its emo about being a rock) has been waiting for some scientist to start looking for these things.
On behalf of all trekkies from Boomer to Gen X, it's about damn time.
Interesting theory, but I seem to remember my biology teacher discussing silicon-based life, and how it was much less likely to develop as carbon atoms produced much more stable molecules, especially on planets like Earth with water and nitrogen/oxygen atmospheres. Carbon-based life just "works" better on Earth.
On planets with radcially different environments there's probably a lot of potential for life that's totally different from ours, but I think it's fairly unlikely for us to discover it here.
You can advertise in this sig from as little as £99.99 a month!
You can pry my bottle of Head & Shoulders from my cold, dead, carbon-based hands! Now get those freakozoids out of my beloved state!
Not an expert in biology, but unless these contaminated areas have been contaminated for a very long time (read tens of thousands of years), and are quite large, the chances for life to have sprung up seem very, very slim. Current life needed millions of years to gain a firm foothold and start building up complexity. Lucky meteorites aside, starting from zero is bound to be hard.
If the experiment succeeds (here or elsewhere), and something "life-ish" is found, the results will still be tricky to classify. Can a given chemistry lead to increasing complexity, or is it just a dead end? Without hindsight, this seems like a very difficult question.
We are born in flesh
that there is tea in china, there is no tea in china, it's all tealess, really
TFA means coke could be an alien form of life?
imagine all these poor little aliens who have been snorted until now...
@neonux
this is how life as we know it uses phosphorus
some of these arguments often sound plausible until you examine the mechanics for life. water for instance, has unique properties not shared by any other compound - the ability to be neutral, liquid at reasonable temps and be able to transport other elements. the same goes for carbon. nothing else is going to be able to put together a tangible life form.
If you mod me down, I will become more powerful than you can imagine....
"From (water) As does (all) some other type of life begin" - (Orange) Yellow Catholic Bible
http://transformativeworks.org/
If such non-carbon-based life were found here at home, it would alter the odds for how common life is elsewhere in the universe, astrobiologists say.
Magic! If we find such life here, then the rest of the universe will change!
I think you meant...
It would alter our understanding of the odds. It might even alter the odds of success in our search for life elsewhere, since ostensibly we would be looking in more places of greater variety.
What it most certainly will not do is suddenly make that type of life appear elsewhere in the universe. Well, unless we are ready to assume an EdTV universe. It is awfully convenient that we're not really able to leave our solar system. Hmm....
I can easily believe that much of the fundamental chemistry of this "alien" life could be different. I'm sure there are plenty of ways to chemically move energy around that don't require phosphorous. One thing I think we will find is a constant though is that life will be carbon based*. It's just not possible to make a wide enough range of complex molecules with any element other than carbon. Even if we look at the next best atom for making complex molecules, silicon, and the simplest lifeforms we know about the molecules that allow it to function are way beyond what can be created.
This limitation isn't because we haven't looked hard enough it's a fundamental property of the orbital structure of carbon which makes it behave significantly differently to all elements. Therefore it's probably safe to assume that all the life we find will be based on carbon.
* There is, I feel, scope for non-carbon based life based around metals but it will have been created rather than evolved completely naturally - what we would currently call a machine.
I used to have a better sig but it broke.
Actually I don't think it would alter all that much really. It's probably true that there are simple organisms on this planet that are not carbon-based, or that survive without DNA, but simply haven't been discovered.
On the other hand, if we've lived with them all this time, and not noticed, how important can they be? A cause of many diseases, perhaps. A cure for many diseases, perhaps. None of that would be earth-shattering; we know there are new species, new causes and cures for diseases in rain forests, yet we care so little that we allow those rainforests to be destroyed.
When most people speak of alien life, they're talking about advanced, sentient alien life. A lot of this "life on mars" or "shadow biosphere" stuff is nothing more than sensationalism.
You obviously haven't had any good LSD.
I dream of a better world... one in which chickens can cross roads without their motives being questioned.
Nurse Tate: I'll get the lubricant...
Dr. Paulson: No time for lubricant!
Harry Block: There's ALWAYS time for lubricant!
the quote's off topic but it's a cinematic classic
this is how life as we know it uses phosphorus
This needs a 'funny because its true' score
In space no-one can hear your vuvuzela.
http://www.newscientist.com/article/mg19826533.600-early-life-could-have-relied-on-arsenic-dna.html tried looking up some examples of non carbon based life on earth that I'd heard of but couldn't find any however the ecology of undersea volcanic vents pretty much threw most ideas about heat tolerance and toxins being a problem out of the window.
Build a Man a Fire, and He'll Be Warm for a Day. Set a Man on Fire, and He'll Be Warm for the Rest of His Life.
I, for one, welcome our new shadowy overlords.
Can you start posting ones which aren't all conjecture?
I don't know, can I ?
“Common sense is not so common.” — Voltaire
Awwww, way to piss in my Cheerios :(
Can you start posting ones which aren't all conjecture?
I don't know, can I ?
Perhaps. But maybe not.
When I was in the army, my unit had a guy who claimed to have seen a dragon.
I don't think it was purple though.
Er, you mean politicians?
Actually area available for life to live in is not really what we should be comparing. Most scientific theories regarding the creation of a life are based upon a very particular requirements, life will not for example simply spring up in the middle of your back yard. If these 'contaminated' areas contain a higher concentration of locations where life could form then this could skew results.
Regardless, even if the odds are astonishingly small (or appear to be) I don't see the harm in looking. A life form based on an entirely different structure than our own may have a far more pronounced effect on our understanding of life than any number of discoveries based on the same structure as our own.
Scientific proof for the existence of ghosts now just around the corner?
You can't swap silicon for carbon in DNA. Silicon doesn't have the same talent for directionally bonding to itself. You can get get multiple bonds if you stick an oxygen in between, but the oxygen always has electron pairs that make it open to attack. There is no equivalent of the stable and inert paraffin chain.
If you were to have silicon-based life, then it would probably not use chain molecules. Suppose you had a planar silicate structure that catalysed the formation of a similar layer on top of it. The layers might then separate or exfoliate and then catalyse other copies of themselves. Some formations would be more stable, or would come out of solution at lower concentrations, and thereby 'predating' on less successful conformations by lowering the conentration of valuable components, and causing the other to go back into solution.
This is pretty dull sort of life - it isn't really much more than crystallization. No antennae, no ray-guns, no 'greetings earthlings, we come in peace'. However, carbon-based life was probably a pretty dull affair before the cell wall. It would have relied on random variations in ambient chemistry and temperature to do anything, and a lot of time must have been spent waiting for the right conditions for the next move. The simpler viruses are more like big chemicals than small creatures.
I remember a Scientific American article from about 1983 where it was argued that some of the lamellar structures that you can get in pre-cambrian clays may have been just such a system. No easy way of telling now, of course, because carbon based life would probably have killed it off. If it could be said to have been alive in the first place.
"They're made of meat."
"Meat?"
http://home.earthlink.net/~paulrack/id82.html
I think the idea is that if you kill off all the carbon life in some river, the (preexisting but uncommon) other life is much more likely to flourish and be plentiful there. Same way that we get antibiotic resistant bacteria.
SIGSEGV caught, terminating
wait... not that kind of sig.
I fail to see how non-carbon-based life is possible
If you want to find the shadow biosphere on Earth just search for otherkin
Maybe rocks are intelligent. How would we know? Has anybody thought to ask?
The creative forces behind this video have put some thought into it.
I went to eat some animal crackers and the box said, "Do not eat if seal is broken." I opened the box and sure enough..
dark basements below older human habitation? im sure theyll find a new asexual species resembling man...
I am very sucseptible to "let's have another drink"
I don't know what the original article said (the site is thoroughly slashdotted), but finding life based on alternative chemistry won't "alter the odds" - it will just alter our computation of the odds. That immediately raises my suspicions since it suggests that the article was written by a journalist rather than a scientist, and consequently that it might be severely distorted.
Having said that, there are a lot of possible alternative chemistries that don't involve non-carbon-based life: substituting arsenic for phosphorus as mentioned here need not also substitute something else for carbon, so the most likely possibility is that such life would be carbon based but still "alien." As far as we know now, at Earthly temperatures and pressures carbon is a far more plausible basis for life than anything else, and so far we haven't even found much that's very promising at other temperatures and pressures. But I'm not at all sure that we have sufficiently explored alternative temperatures and pressures to rule them out as possible habitats.
I didn't find it on Google, but about 30 years ago I read an account of a creature like a giant sand dollar that was dislodged from the deep ocean by an undersea earthquake. I can't verify it until I find a reference, but I recall that the scientist examining it found that it was largely silicon, hydrogen, and sulphur (and decayed rapidly giving off H2S). His theory was that it was silicon based life - and that its chemistry required deep ocean temperature and pressure to remain stable. (Note that there are carbon based ocean creatures able to process silicon to create SiO2 structures.)
"Alien" means "not from here." If our planet harbors a resident life form which we're not aware of, that doesn't make them alien. It just makes us ignorant.
It's not a lie. It's the truth with lossy compression.
Can a given chemistry lead to increasing complexity, or is it just a dead end?
Why is "increasing complexity" a requirement for life? It's clearly a requirement for evolution, but I don't see any reason why something "lifelike" but alien might not have a very simple "maximum complexity" compared to standard carbon-based earthly life forms.
How do we kill that which has no life?
Note that Carl Zimmer wrote about this exact research in greater detail about a year and a half ago in Discover magazine. Take a look: http://discovermagazine.com/2007/jul/aliens-among-us/ The story even includes the line about "life as we don't know it"!
In the sense of the article volcanic areas on our planet can typically be classed as contaminated and have been so for millions of years.
Especially sub sea volcanic vents are known to harbour life forms that are really special and studies have only just started.
"The likes of Facebook and WhatsApp are free to those whose privacy is of zero value."
Now where have I heard this before? Oh yeah! http://www.sciam.com/article.cfm?id=are-aliens-among-us
The world is made by those who show up for the job.
Isn't there stuff down there that uses sulfur like we use carbon?
sudo mount --milk --sugar
It seems like organic life would be most likely since its made of up lighter molecules which are more common in the universe, ie there's are lot more carbon around than there is silicon.
Chief Science Officer Spock also had a close relationship with Kirk, but he would only call him "Jim" on rare occasions when he would let his Vulcan-logic show-no-emotion guard down for a a nanosecond. I am sure it would be "It's life, Captain, but not as we know it." Also, the determination of whether alien entities were life was a Science Office job, not a Medical Officer responsibility, as the Medical Officer was quick to point out the things that were outside his job description.
For a moment I read the article text as 'Cosmo Magazine', and assumed a 'shadow biosphere' was some sort of new eco-friendly eyeliner. God I need a vacation.
life is a tragedy to those who feel, and a comedy to those who think
This just in: War kills people, and unfortunately, that's the truth.
I'll bet you're a lot of fun at parties. At the risk of some redundancy, I'll post this again in case you missed it when dkleinsc posted it the first time.
Unfortunately this isn't really evidence of anything, as grasses contain large amounts of silica, presumably for strength and protection. Whether an organism goes down the calcium carbonate or the silica route depends on its habitat. Oysters are "largely calcium carbonate", but they are definitely not a calcium-based life form.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
Life is carbon based. That's it. You can't detect non carbon based life, because it isn't life. As we have never seen anything life-like that isn't carbon-based, the definition of life has always been carbon-based. You may find something non-carbon based that can do some similar to life things, but it's simply not life. This isn't semantics although it seems so, it's just a fact. You don't get to redefine a scientific truth simply to fit your needs.
I'll bet you're a lot of fun at parties.
I'm reminded of the time I complained that tomorrow is not, in fact, always a day away, in fact it's almost never that, and sometimes less than a second away.
"Tomorrow, tomorrow, I love you, tomorrow, you're on average 12 hours away..."
"Convictions are more dangerous enemies of truth than lies."
You are assuming that life has to exist as it does on earth. I am interpreting your statement thus: in the 10-20 billion years the universe has existed, no other combination of temperature and chemistry has given rise to life in the entire universe.
If life arose out of a different base chemistry, and survived a comet/meteor launching impact, and then another impact with earth, it would not have terrestrial earth competition for the resources it consumes. Given the age of the universe, the 1st condition seems plausible. The second and third conditions are less plausible when applied to Earth alone(I would never state that it did not happen anywhere/when in the universe), but the fourth condition is also plausible.
Asimov: "Not as we know it". Magazine of Fantasy and Science Fiction, Sept 1961.
Reprinted in View from a Height, Doubleday, 1963.
Asimov did his usual concise job of working through alternative chemistries. Better than this article in my opinion.
The meaning is you-less.
"Life" is just the organized processing of energy that perpetuates itself through a system that generates local order even at the expense of global entropy, at some degree of complexity. All life that humans have recognized so far also typically replicates its independent units, even if there are a few exceptions (mules and other sterile offspring), but that's not necessarily a requirement. Some degree of complexity both in composition and in interactions with the environment is also necessary, which is why viruses are at the boundary of life and "mere organic chemistry", and prions outside it, while whole ecosystems (or the Earth entirely) are usually considered "life", but rather collections of life. However, those subjective boundaries are more a measure of human understanding of life, and have gradually grown more inclusive as we've learned more.
Wherever we find such objectively measurable systems, we have found a candidate for life. Where those systems fail to meet our subjective requirements of complexity, we can either learn to expand our sense of life, or we can learn more about the nature of that artificial boundary.
None of that prevents us from recognizing life that's not based on carbon chemistry. Anywhere we see the entropy/enthalpy dynamics that define life, we can recognize it. Just as we discovered the ecosystems independent of solar energetic that are powered by geothermal flows, we can discover other life that is not in the chain that starts with sunlight. Regardless of what kind of chemistry is at work in it, or its other dissimilarities with familiar life. We just have to look for it, and be ready to recognize it when we find it.
--
make install -not war
Reminded me of "The Dreaming Jewels"; an old sf novel by Sturgeon in which the author speculates that a completely foreign species exists on the earth, but is invisible simply owing to the slightness of its impingement on our ecosphere.
Of course the whole problem with all this is we do not have a good definition for "life" or "intelligence".
For "intelligence", what do you think about this one?
Intelligence: is the capacity to generate new information consistent with information previously assimilated or generated.
You can find an explanation about here.
I think you are absolutely right. It seems that many people cannot understand how special the carbon atom is. They assume that our life being based on carbon wouldn't exclude life based on other atoms somewhere else.
Not true. There's a special, unique property in the carbon atom orbital structure that allows very complex structures. No other atom has that quality, unless some basic constants of the universe were changed. It's like comparing a set of Lego blocks with a box of marbles.
The same goes for temperature, to get life one needs a liquid solution that lets molecules interact. With a solid there's no interaction, with a gas the molecules don't stick together, so one needs a liquid for transporting the elements of life. If a planet is too cold or too hot life will not appear. These are some basic limits on the physics and chemistry that will allow for complex chemistry to gradually evolve.
And the funny thing is that we have both theory and experiment telling us that life isn't very common in the universe. We haven't found any sign of life in either Mars or Venus, which a hundred years ago many people thought would certainly have life. If planets like Venus and Mars, that are very close to the Earth in their characteristics, didn't create life, then one should assume that our position is very special.
The only kind of life that isn't carbon based is going to HAVE to be created by something that was carbon based, somewhere up the chain. It's not going to happen spontaneously like carbon-based life, unless it happens somewhere where the laws of physics and chemistry are drastically different.
It's very simple: You need water and you need carbon. First of all, for life, you need complexity. For the kind of life we're familiar with, this complexity comes in the form of DNA, RNA, proteins, carbohydrates and other macromolecules that life uses. All of these require water as the solvent again, for reasons based on chemistry (hydrogen bonding, van der waals forces, and ionic bonds, etc, all of which play crucial roles in protein function and no other suitable, naturally occurring solvent will do the job and, to my knowledge, there's no artificially developed solvent yet that can do the job either.)
The macromolecules of life MUST be carbon-based because no other element can operate as a backbone for such complex and large molecules. You can make large molecules based on other backbones, but they are repetitive structures lacking complexity that life requires. As these structures get more complex, they tend to lose their stability.
Organic and inorganic chemists have tried all sorts of bizarre stuff in bizarre circumstances. Using high pressures, high heats, low pressures, low heats. If there was anything else that could function like carbon, I'm pretty sure we would have found it.
On the other hand, throw a few basic organic and inorganic materials together in a jar and add some heat and electricity, and you start producing some of the basic building blocks of life. It's easily reproducible.
Non-carbon life is a pipe dream created by sci-fi authors and it should remain in the realm of sci-fi.
Since we don't know the extent that potential cohabitating forms of life would compete with carbon life for a similar commonly assumed set of material and energy resources, as a first step I would settle for detecting unexpected changes in water chemistry after carbon life is removed from the system. We cannot at this point understand what "flourish" or "plentiful" mean in the context of a previously unknown system of life. It may be that mineral life would flourish or fail in the absence of carbon life.
There may be broader symbioses in play between carbon and perhaps a mineral system of life, which would provide insights into how plants came to rely on rare magnesium ions to be able to pull slightly less rare carbon from the environment into our known food webs, and also how macroscopic organisms were able to durably evolve to rely on dietary minerals found in rare to trace quantities on the Earth's surface for essential biological functions.
There are 1.1... kinds of people.
You can find a brief description here.
The article suggests that the hydrogen was produced only when rocks crack, meaning that the microbes' food supply was meager and sporadic. Now Freund has discovered a chemical process in Earth's crust that may produce enough hydrogen to feed a mass of underground life larger than the mass of all living things at the surface. "[T]he rocks around them will replenish the hydrogen supplyÃÂ--indefinitely, over eons of time," said Freund.
Talk about a shadow life form.
The diversity and expression of human opinion is essential to human survival.
In Soviet Russia life forms primarily take sustenance in the form of once distilled vodka.
We have no idea how long it usually takes life to arise. Speculation is generally that it would take a long time, but it isn't really something that can be proved.
Looking on Earth is a bit of a pickle, as new life has to deal with things like old life and free oxygen, which are both things that old life has been dealing with for billions of years.
Nerd rage is the funniest rage.
CREATION TOOK EIGHT DAYS
I nearly understand it, thanks for an excellent explanation.
I keep thinking about that Mad Cow Disease... that was crystalline and seems more like the sort of thing being talked about here than a regular virus...
Okay, this is going to drive me insane. I know I've heard this quote since I was a kid (or a teen at least), so I went online to "prove" to you that that's how it originally was, with "Jim" instead of "Captain" because I was convinced that was the case. One problem: I can't find any evidence that the line or anything like it was actually ever uttered in the series.
Where does this "quote" originate from? You can find variations of it all over the web, but I can't find the source at all. I even found a site that had scripts for TOS, the animated series, and the movies, and I couldn't find any part of the line in a context that resembled the quote. Is this just one of those crazy pop-culture things were a line is attributed to someone who never said it, like now Sherlock Holmes never said, "Elementary, my dear Watson" in any of Doyle's works?
If it's for-profit but free, you're not the customer -- you're the product (e.g., the Slashdot Beta's "audience").
I'm pretty sure it was a ToS episode where they find a silicon-based critter that tunnels through rock.
Cthulhu loves you.
... They are hard to find!
--- I am known for the ones who want to find me on the net. Is that a privacy risk or a privilege? One might wonder..
A film student somewhere made Bisson's short story into a pretty decent short, starring, oddly, the guy who hosts Discovery Channel's Cash Cab. http://www.youtube.com/watch?v=gaFZTAOb7IE
I looked it up, from "The Devil in the Dark." The quote isn't exactly as it's most commonly said:
KIRK: I see. Mister Spock give us a report on life beneath the surface.
SPOCK: Within range of our sensors, there is no life, other than the accountable human residents of this colony beneath the surface. At least, no life as we know it.
If that's it, then it's exactly like the "Elementary, my dear Watson" quote, a common mangling. Also, it means that both posters were wrong. It's neither "Jim" nor "Captain" there. Weird.
If it's for-profit but free, you're not the customer -- you're the product (e.g., the Slashdot Beta's "audience").
Life can be thought of as a localized reversal of entropy. A mule is a more complex thing--it contains more information--than what it consumes to continue. The same cannot be said of fire.
Build a man a fire, he's warm for one night. Set him on fire, and he's warm for the rest of his life.
Where did you get that idea? I see no grounds for requiring increasing complexity for evolution, and indeed, since the overwhelming majority of life on this planet is microbial, as it always has been, there is fair evidence against such a claim.
Consider a range of lifeforms which randomly become more or less complex over time, but have a minimal level of complexity needed to sustain life. Some will become less than minimally complex and die out directly (in the real world, these may be obligate parasites whose host organism then becomes extinct or able to expel their parasites) ; some will randomly become more complex ; some of the more complex organisms will then randomly become less complex while others become randomly more complex.
Over time, you will have an increased range of complexity in your population, but the modal degree of complexity will likely remain where you started - near the degree of minimal complexity.
Just to be clear - I'm not disputing that the complexity of the most complex organisms has increased with time (Adams : "the wheel, New York, wars, and so on") ; I'm disputing that increasing complexity is a necessity for evolution to occur. (It's one of the less common lies that Muslim and Christian fundamentalist proselytes bring out to try to scare people away from thinking about evolution.)
(Jewish fundamentalists may falsely deploy the same argument - I've not met such, yet, so can't speak for what lies they tell.)
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
Where did you get that idea? I see no grounds for requiring increasing complexity for evolution, and indeed, since the overwhelming majority of life on this planet is microbial, as it always has been, there is fair evidence against such a claim.
"Complexity" in this context should be understood to say little or nothing about the physical size of the organisms or their multi- or unicellular nature. It is, rather, a comment about the size of the potential gene space for the organisms. Humans tend to think of "complexity" in very anthropomorphic terms, but even modern prokaryotes are still pretty complex organisms and have an enormous potential gene space. If the biochemistry of the life-forms does not allow for very much diversity (remember we're talking about life that presumably does not use DNA or RNA and possibly not even any of our amino acids), there is very little for evolution to work with. It's not hard to imagine a situation where such organisms might relatively quickly reach their maximum potential and evolution - even microbial evolution - effectively stops.
We haven't found any sign of life in either Mars or Venus
"In" is right. We've barely looked *on* them yet, much less *in* them. I think when we start looking *in* planets (or moons) for life, *that* is where we shall find it.
DNA is a Turing machine. You, however, being dynamic and emergent, are not.
http://www.nasa.gov/centers/ames/news/releases/2002/02_37AR.html .
DNA is a Turing machine. You, however, being dynamic and emergent, are not.
Hmmm, I did mention size ("microbes"), but as I was meaning it as a shorthand for an ill-defined "genetic complexity space" as you're thinking. I would have been more accurate to say that most life on the planet is (probably) still prokaryotic. If you count mitochondria and chloroplasts and the more-recently described methane- and hydrogen- generating organelles of certain organisms, and if you swallow Margulis' assertion that ER/ myosin-actin fibrils, centrioles and intra-cellular transport networks are degraded spirochaetes, then you can probably take out the "(probably)" in the previous sentence.
On SlashDot, you never know the level of the person you're corresponding with. For all I know, you might actually be Margulis!
True ; I refer the honourable gentleperson to the comments I made a few moments ago.
That was implicit in the general discussion, but barely perceivable in the actual article (typical SlashDot ; RTFA is so uncool!). It would take a vastly more confident chemist and/ or biochemist than I am to examine the mechanisms of a novel biochemistry and to deduce it's limits. Bearing in mind that while we're confident of our understanding of basic protein synthetic pathways, we don't really have a clear understanding of how our own genomes control gene activation and/ or suppression ...
It took the best part of a quarter-century from Crick and Watson's discovery of the basic structure of our biochemistry before Ohno's concept of "alternative reading frames" was described and demonstrated ; the consequences of this are still being worked out, along with considerably more esoteric ways of using genomes. That should give serious pause for thought before declaring that "X" other biochemistry "does not allow for very much diversity".
Ummm, actually I do find it quite hard to imagine such a situation. The minimal complexity of an organism is quite substantial - 9000-odd genes is the sort of size Venter et al are looking at? - so if you're going to have a successful organism of ANY biochemistry, then you're going to have to be dealing with quite significant chunks of genetic material (be it DNA, or patterns on the edges of spiral defects in clay minerals [example only, don't take it seriously]. At that point, it gets hard for me to conceive of a system that isn't going to be prone to re-reading the same data block twice, or writing the same block twice. At which point you're in the territory of gene duplication, which is certainly a mechanism for generation of new functions, followed by new diversity.
Nope, you're going to have to work a lot harder to convince me that any genetic system has an inherent upper limit on diversity, where the biochemistry continues to work. As has been pointed out, DNA/ RNA/ amino acid biochemistry can work well enough to survive low pH and high temperature (at least, for some of it's life cycle), and to endure low temperatures for protracted periods of stasis. I don't think that it's going to work at a bright-orange heat though - the RNA would fatally dehydrate. And I wonder what's the upper limit of pH that our co-b
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"