Talk:Hypothetical types of biochemistry/Archive 1

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Archive 1

Machine Life

What, no reference to self replicating machines? —Preceding unsigned comment added by 71.93.61.178 (talk) 13:51, 22 December 2010 (UTC)

This article is on hypothetical biochemistry. Speculations on self replicating machines are likely to focus on bio-mechanics, or the simulation of life processes with purely mechanical structures. at a smaller scale, mechanics and chemistry may merge, so if someone has speculated on nanoscale mechanical life forms, that might be applicable here, but only if there is some chemical reaction occurring.Mercurywoodrose (talk) 20:40, 18 January 2011 (UTC)

Edited the Other Solvents intro

I added two paragraphs. Could someone take a look at the last two paragraphs in the intro, and tell me if they look good? 96.242.163.72 (talk) 16:58, 5 July 2009 (UTC)

Not being based on anything

I believe the article should mention that it is possible for an organism not to be based on anything. For example, their protiens may use everything from hydrogen to uranium if they find if profitable. For example, earth life is DOMINATED by carbon, while other life forms moy only show a bias towards carbon, or silicon. Statue2 (talk) 21:32, 29 January 2008 (UTC)

I think the point of "basis" is that elements with certain properties are absolutely necessary for life, and if an organism has a higher amount of one of those elements than another, then the life is "based" on that element. Though, here's a proposition for addition to the page. Basis on more than one element? tehgrisp (talk) 21:20, 25 June 2008 (UTC)
If you think about it terrestrial life is based on multiple elements: Carbon, Hydrogen, Oxygen, and, to a lesser extent, Nitrogen. I don't know why Carbon receives so much attention... —Preceding unsigned comment added by Ummonk (talk • contribs) 20:14, 27 December 2008 (UTC)

Examples from fiction

It occurs to me that Michael Crichton "The Andromeda Stain" includes a crystaline life form which causes blood to clot. Could this be added to the list of fiction life forms? --ManInStone 15:09, 19 June 2007 (UTC)

Also, Diane Duane has a silicon based life form in "high wizardry" Statue2 20:53, 17 September 2007 (UTC)


"Carbon Chauvinism" debate

This is even better than radical anti-speciesism! Now i can call people 'Carbonists'! --MichaelTinkler

This article gives the impression that 'carbon chauvinists' believe that carbon is the only possible basis for life solely because that is what life is based on on Earth. I would think most 'carbon chauvinists' would hold that only carbon-based life is possible, not just because that is how life is on Earth, but also because carbon based compounds are more common in the universe in general, and they form more easily and are more versatile than silicon-based compounds. -- SJK

On the other hand, is it really chauvenism if the person has a good, solid reason for his or her bias? :)

I would say it is too narrow-minded to say only carbon based life form is possible because we could only find carbon based life form on earth. The condition on earth probably could only support carbon based life because of the atmospheric temperature, pressure and oxygen in the air. It is not impossible that there are organisms in other worlds that breath chlorine or hydrogen sulphide or swim in a ocean of molten lava or liquid hydrogen.

Imagine this. When a carbon based life form jumps into a pool of magma in a volcano, it just burns to ash and dies. When a silicon based life form (assuming there were one) leaves the confine of the magma, it just solidifies and dies too. No scientist can enter the magma and survive, then how can anyone disprove the possiblity that non-carbon based life exists in the center of the earth? Likewise for hostile world such as venus, or even the core of a star, there may be life forms that we don't and will never recognize.

This is a *REALLY* important point. It ought to be made in the article. We ought to accept our vast ignorance of how life on earth works. For instance until a few years ago the existence of deep-ocean-bottom life forms near volcanic vents that used chemosynthesis for energy rather than the sun's photosynthesis was unknown. This was good old fashioned regular right handed DNA life, right up to clams and crabs (pretty damn high up the chain), but the genus are distinct, and all the energy comes out of the volcanic vent not from the sun. This would have been considered fantasy just 10 years ago.

This is idiotic. No, if "magma life" exists in silicone based forms and leaves, only to "die" by soliditfying, we would STILL be able to examine it and understand that it was life.

Nice try though, what with that fail of biology. I swear, its just as idiotic as the morons who believe anyone who states that an extraterrestrial race is more likely to be warlike and agressive is "just baised because thats what we humans believe". What "we humans believe" has no effect on what we can observe to the best of the ability in the Universe we live in. If someone tells you "oh, there can ONLY be carbon lifeforms" then you can spout this pointless "carbon-chauvanist" response. But stating its the most likeliest of existence because of what we can observe from OFF of this planet is not. 121.215.56.12 (talk) 06:35, 26 December 2008 (UTC) Harlequin

Well, we should be saying that we don't have enough information to predict what life would be like elsewhere. Ummonk (talk) 20:17, 27 December 2008 (UTC)

Pretty good integration, *but*:

  • there is already an article on artificial life so this section should be retitled
  • most people refer to a 'clanking replicator' as a robot, or would if they met one
  • the initial example of creation-by-intelligence listed carbon nanotubes as the basis, which is sstill carbon (and of course can be used structurally and for computing as well, depending ont he type, so maybe this should be mentioned in the carbon section?) - it's not as clear now that intelligence required to build a "clanking replicator" could be ANY oif the above forms on ANY planet.

- trying not to be a Carbonist

The "artificial life" section of this article is focused on the context of non-carbon biochemistries, which is not the same as the existing artificial life article. Likewise, a "clanking replicator" is a subset of robot; there are many robots which are not clanking replicators (in fact, all currently-existing robots are not clanking replicators). And finally, the fact that carbon nanotubes are indeed carbon is mentioned in the article; the reason for their inclusion is that it's a different _form_ of carbon than any known life currently uses. I don't think any of these points need major amendment. I'll add that intelligent life could construct life based on the other non-"machine" biochemistires as well, though. Bryan
There, just did a little tweaking. The "artificial life" section starts out with a very general paragraph which doesn't specify "machine-type" artificial life, and the ending paragraph "Scientifically, the relevance of this possibility is that high intelligence in a transition species may be the means by which an otherwise-impractical basis for life gets started, after which it can continue to evolve by more natural means." is also nonspecific, is that what you were after? Bryan

Shouldn't the section on artificial life mention possibility of non-material forms of life (such as those simulated in a computer) or at least state that it is dedicated only to material forms of life?

All forms of life are "material", and the use of the phrase "artificial life" or "genetic algorithm" for symbol processing are basically and utterly WRONG - a profound bias we should not introduce, and one we should not apologize for simply ignoring. Wait long enough, and the stupidity that passes for "genetic algorithm" or "artificial life" in software only will simply go away since it is irrelevant to genetics, or life. It just mirrors current biases about those.

Question: it is theoretically possible to simulate a live creature by simulating it down to every last atom. Is such simulation alive? Is it unethical to torture it? Nikola 15:43 2 Jun 2003 (UTC)

No. Not because you can't do that to simulate life (assuming, for the sake of the exercise, that we have the technology to perform the exact duplication), but because at that point you don't have a simulation of life, you have life itself. Tannin
OK, fine, so there could be silicon-based life ;) The next question is: at which level of simulation does the simulation become alive? Cellular? Tissue? Organs?
Depends! If the simulation is as smart as a dove (the stupidest bird, considerably more stupid than a mammal), then you cannot treat it arbitrarily – and then you are obligued to exhibit some humanlike consideration towards it. But on the other hand: if you simply stop the simulation, and save it to HD for future, nobody can say anything. Be very careful to not implement a nerve system that you overactivate – that would be gravely unethical. You will be regarded as a very evil creation god, and only the most sinister such simulated life will worship you. Said: Rursus ☻ 07:44, 29 July 2008 (UTC)

speaking of carbon chauvinism, the section on ammonia seemed to me to have a POV. not i'm not joking. can anyone see the irony here in an article about alternate biology claiming that the conditions for ammonia are "unusual" for terrestrial life; WELL DUH, IT ISN'T "USUAL" LIFE. i'm sure it is entirely possible that life can form with both different chemistry AND conditions, especially seeing as the different compound would require different pressures and temperatures to function. like wise for any argument based on the cosmic abundance of a compound; there's still sh*tloads of it - the universe is a pretty big place Motorbyclist 11:55, 22 April 2007 (UTC)

The debate on whether non-carbon-based lifeforms exists or not seems to be ignorant of some basic precepts of chemistry:

1) Intermolecular forces. For those who are not up to speed, there are a few types: London dispersion forces and dipole-dipole action.

The reason carbon and water work so well as molecules which life uses as a building block and a solvent is that carbon is just small enough that it can bond fairly easily to four other molecules and produces bonds that are extremely difficult to break without high energy investment. Carbon is more stable than other Group 4A elements and other elements that might have been considered as alternative biochemistry. Long carbon molecules, even if they contain polar components such as carbonyl functional groups, exert a good deal of force by virtue of the fact that they have a gigantic amount of London dispersion force from their electrons.

Water is an excellent solvent because its polarity is so profound by virtue of the orientation of its hydrogens and the electronegativity of the hydrogen-oxygen bond (oxygen, nitrogen, and fluorine are the three most electronegative elements in the periodic table). It undergoes hydrogen bonding and has a vapor pressure and melting point and boiling point at levels compatible with carbon-based life.

Ultimately, the only truly plausible non-Earth biochemistry is another chirality. —Preceding unsigned comment added by 96.241.20.217 (talk) 19:56, 19 May 2009 (UTC)

Serious problem

The title of this article is Carbon chauvinism (the connotation of chauvinism leads me to believe this is not only a neologism, but a pejorative one), and this term is defined in the opening para as the belief that carbon is the only possible basis for life.

But then, the entirety of the rest of the article is devoted to theoretical bases for life that are not carbon-based.

In other words, this article spends its entire time discussing the opposite of the title!

An article with this title should be spending its time explaining the basis of the belief that all life must necessarily be carbon-based, not the opposite. My suspicion, though, is that anyone in a position to write such an article in an NPOV fashion would not be using this term for the title.

I dont know whether to send to cleanup or deletion.

- Keith D. Tyler [flame] 21:32, Feb 17, 2005 (UTC)

Renaming from carbon chauvinism to non-carbon biology is a good move in that it now accurately relects the actual content of this article. However, there are a large number of links in other articles pointing to Carbon chauvinism which gets redirected here. Some of them seem to be looking to link to an article that describes non-carbon based life, but others refer to a supposed bias against the idea of non-carbon biology. The article on life for instance has this statement:

"All life on Earth is based on the chemistry of carbon compounds. Some assert that this must be the case for all possible forms of life throughout the universe; others describe this position as 'carbon chauvinism'."

Once the final status of this page is decided (for instance, merged with astrobiology) we might need to clean up some of these dangling links that refer to the old content of the article, since the context of the above link is now misleading. Personally, I think carbon chauvinism is a loaded term. It also seems to be rarely used. But, some wiki pages link to the term with the expectation that it will be defined. The term is even used in non-carbon biology itself without being defined:

"In addition to carbon compounds all currently known terrestrial life also requires water as a solvent. Although not strictly "carbon chauvinism" since water doesn't contain carbon, it is sometimes assumed that water is the only suitable chemical to fill this role and so similar issues apply."

This article (or wherever the content gets moved to) might benefit by mentioning the debate over the possibility of non-carbon based life. The article currently lacks arguments on why carbon based life is seen as most likely. There are a couple of interesting points in the [ET life FAQ].

--Mu301 14:43, 26 Jun 2005 (UTC)

Wrong figures for abundance

Finally, of the molecules identified in interstellar space as of 1998, 84 are based on carbon and 8 are based on silicon. Moreover, of the eight Si-based compounds, four also include carbon. This suggests a greater abundance of complex carbon compounds throughout the cosmos&hellip

I question whether the above statement is accurate. Are we talking 84 individual molecules, or 84 varieties of molecules? If the latter is correct, which seems likely, then it does not suggest a greater abundance, but rather a greater variety of complex carbon compounds. It says nothing about abundance, which I suspect is most critical for providing adequate resources for life. If so, does anyone have data on what relative abudances are for carbon- and silicon-based molecules identified or theorized in interstellar space? -- Jeff Q 07:08, 20 May 2004 (UTC)

The source is this, I believe: [1]. I'm sure it's referring to varieties, since there's no way to detect individual molecules. As for abundance, [2] indicates that there's 3.5 times as much carbon in the universe as a whole as there is silicon - don't know if that's by mass or by moles. So it looks like both abundance and variety may be true. Bryan 07:31, 20 May 2004 (UTC)
Bryan, thanks for the speedy and excellent references! I agree that [1] suggests it's varieties and not abundance. I think [2], though, doesn't provide nearly the punch about abundance that the rest of the quoted passage above ("… providing less of a foundation upon which to build silicon-based biologies") implies. One might read it and think there aren't enough complex silicon-based molecules to bother about. I'm guessing that there are at least 2-3 orders of magnitude more mass contained in stars than there are in planets, but it's the tiny amount of planetary mass where we concentrate our search for life. Compared to that, a mere factor of 3.5 seems insignificant. It leaves an incredible amount of mass to harbor potential silcon-based life. (It doesn't change the other arguments, but this particular one probably shouldn't sound so strong.) -- Jeff Q 07:56, 20 May 2004 (UTC)
I agree, though since the FAQ link above is referring to the interstellar medium I suspect the universal abundances are more relevant than they would be if it was just planets. If nobody beats me to it, I'll try tweaking the wording when I get home tonight (I'm just zooming through while eating breakfast at the moment :) Bryan 15:11, 20 May 2004 (UTC)
I didn't mean to imply that planetary mass has anything to do with this question. I was just using the star/planet mass ratio to point out that two factors of the same order of magnitude are practically equal when one considers other astrophysical ratios. I was thinking that if the actual abundance of carbon molecules was several orders of magnitude more than those of silicon, I would be less inclined to look for silicon-based biochemistry, but with only a 3.5:1 ratio, they're practically even competitors. (Of course, this doesn't account for the other logical arguments presented in the article that favor carbon. It's just that this argument didn't sound very strong to me.) -- Jeff Q 17:31, 20 May 2004 (UTC)
Good point. I'll make sure to mention the actual numbers in the article. Bryan 04:18, 21 May 2004 (UTC)

I have changed the carbon - silicon cosmic abundance ratio to "roughly 10 to 1" rather than 3.5 to 1. Check [3] [4] . Also see this chart [5] which you can find in a lot of spots; C is clearly an order of magnitude greater than Si. I did find the 3.5 ratio once, [6], which may be the source of the error. I only noticed this because I just set down a book (Faint Echoes, Distant Stars) which also lists the 10 - 1 figure. Anyhow, I'll take four sources ahead of one. Note too, that 10 to 1 corresponds to the 84 to 8 molecule ratio mentioned earlier in the paragraph.

Regarding the above discussion, an order of magnitude is an order of magnitude: carbon and silicon are not "even competitors" when it comes to abundance. Marskell 07:36, 24 July 2005 (UTC)

Astronomers have identified stars with unusual abundances of various elements. For example, Fomalhaut has an unusual abundance of fluorine. I wonder if this would significantly improve the likelihood of life using an otherwise rare element on a planet orbiting that star? —Preceding unsigned comment added by 99.9.112.31 (talk) 14:45, 17 March 2010 (UTC)

Merge debate

A single article or category should be created that encompasses all hypothetical extraterrestrial biospheres and biochemistry. Thus this article should either be edited to specify its name or be rename or moved to a better more generalized name.

This topic may fit better under Astrobiology and could be placed as a sub-topic of astrobiology. If not then either move all the topics in this article that are not specifically related to non-carbon biology or rename the article to take into account those topics. For example replacement of water with ammonia or another fluid medium or the replacement of oxygen for biological oxidation reactions with another oxidizer (such as chlorine or sulfur compounds) is not strictly related to non-carbon biology and in most hypothesis and science fiction involving a biosphere with such differences carbon biology is still used. --BerserkerBen 22:35, 16 May 2005 (UTC)

"astrobiology has been criticized for being unimaginative in the tacit assumption that Earth-like life presents the most likely template for life elsewhere" (Astrobiology article)

So Non-carbon lifeforms are simply out of the scope of Astrobiology as a contemporary science (or would-be science, depending on your POV) because it does not, in fact, try to study them much. That is one of its failures.

One the other hand, the Astrobiology article should clearly have something about the fact that there could be lifeforms of other kinds but that we just don't currently investigate them. Or maybe something about the assumptions of astrobiology researchers or something... I'll have a look at the Astrobiology talk page.Jules LT 18:08, 12 August 2005 (UTC)

Er... nobody seems to care. I enriched and reorganized the Astrobiology quite a bit, and I do not think that non-carbon biology can fit in there. For one thing, it is maybe still bigger than astrobiology, so it would flood it. If nobody objects in the next couple of days, I will remove the "to be moved" tag (or ask for its removal, if that's an administrator's work).Jules LT 07:05, 18 August 2005 (UTC)

Fine enough but I still thin something needs to be done: Exotic solvent based life and exotic oxidizer utilizing life are usually referred to as carbon based, and the real life examples we have of such things are of course carbon based, having these topics under this title is a erroneous. Either change the name to something more general or move those topics to somewhere. --BerserkerBen 12:14, 18 August 2005 (UTC)

Ben is right that this article is still mis-labelled. It's basically Life as We Don't Know It rather than strictly Non-carbon biology. And Jules is right that this would swamp Astrobiology. What about two smallish articles: Non-carbon biology and Non-aqueous biotic solvents? Anything not strictly related would not be included. There's stuff here about AI, for instance, which is probably redundant and can be dropped or moved. Marskell 13:15, 18 August 2005 (UTC)
I don't see why any of this stuff should be removed from Wikipedia outright, if there's something that doesn't fit into existing articles then other articles that it does fit into should be created. Bryan 15:50, 18 August 2005 (UTC)

What sections of the article deal with carbon-based biology? Please point them out specifically. - Keith D. Tyler 21:52, August 18, 2005 (UTC)

None of these sections deal with carbon-based biology. Sections 1 to 3 are rightly covered as non-carbon biology. Section 4 could provide the basis of (my) suggested Non-aqueous biotic solvents article. Section 5 could be moved toArtificial Intelligence or partly dropped if it's redundant. Section 6 is largely sci-fi and can be moved to various articles or dropped. Looking at it again these solutions make a lot of sense. Marskell 22:30, 18 August 2005 (UTC)
What do you mean "none", I just pointed them out above didn't I, let me repeat:"Exotic solvent based life and exotic oxidizer utilizing life" all of these place no prerequisite that nucleic acids/amino acids/charboydrates/fatty acids are not used, in fact here on earth we have life that use exotic oxidizers, life forms that oxidize with nitrates and sulfates, life forms that reduce rather the oxidize, ect, we have life that use exotic solvents (all of which though consist of water as the major component though). What about the issue of different chirality and/or exotic organic molecules in exobiology, were am I suppose to put that? I think a article is need to cover hypothetical and sci-fi biochemistry of aliens, a exobiochemistry or something--BerserkerBen 23:22, 18 August 2005 (UTC)

In the spirit of boldness, I have moved this page to "Alternative biochemistry." Hopefully this is a broad enough name that all of the various topics currently discussed in the article are covered by it. Bryan 00:56, 19 August 2005 (UTC)

Sorry Berserker, mis-interpretation. I only meant that section 1 to 3 do indeed deal with alternatives appropriate to the (now former) title and the rest of it doesn't. Of course you're right life forming in exotic solvents are as likely to be carbon-based as anything else. I sometimes think silicon and ammonia get mentioned in the same breath so often (ie., onExtraterrestrials) that people may make the mistake of assuming they necessarily occur in tandem. Anyhow, the new title is better though there may still be too many eggs in one basket here. Marskell 07:26, 19 August 2005 (UTC)
Incidentally, I'm working on a page User:Marskell/Planetary Habitability which maybe of interest to people floating around the AstroBio pages. Plz have a look if you like and add suggestions to my talk page. Marskell 11:41, 19 August 2005 (UTC)
I love you Bryan, and I want to have your baby! :-P Anyways I think I’ll move some of the information from extraterrestrial to here, maybe extraterrestrial article can have information on hypothetical alien morphology, Astrobiology will be the actual science of course and only link to those two articles for the more radical concepts. --BerserkerBen 16:54, 19 August 2005 (UTC)

I agree with the new name, it seems that it encompasses all that this article is and gives rise to some more expansion. Nobody seems to be thinking about merging this article with astrobiology anymore so I removed the ugly tag. The article has been renamed to something more inclusive already and nobody had a bad reaction to it (except, arguably, a strange declaration of love, but I guess that counts as positive ;-) ) so I'm removing the tag from the Talk page, too. Action was taken before the consensus, but then again... Wiki is about being bold :-DJules LT 16:15, 29 August 2005 (UTC)

Separate science and fiction

As I added my beloved Discworld trolls to the silicon-based life section (they brought me here in the first place) I reflected that I hadn't included them here in the first place because it didn't feel serious, but a Star Wars fan didn't have such qualms, so I couldn't resist anymore.

Seeing how the fiction feels sometimes a bit out of place to me in the first sections but is the major part of the last ones, I thought about putting all of it in a separate section, or even on another page, but after all I think it's alright as it is.

I mentionned the talk page in my edit comment, so I thought I might put this in anyway... maybe someone will think of a good solution.Jules LT 21:09, 26 August 2005 (UTC)


Boron, Molybdenum, Tungsten

Is life possible of compounds consisting of Boron, Molybdenum or Tungsten? Are life forms possible, which use Mercury as solvant?

I've looked into the feasibility of a boron biochemistry myself (albeit briefly). The trouble is that boron suffers from a very low cosmic abundance. It forms some interesting molecular cage structures though, and has a good ability to catenate, so it should be considered.
Molybdenum and tungsten (amongst the other transition metals) pose other problems. They have excellent coordination and (in some cases) catenation ability, but transition metals tend not to form stable enantiomers -- in other words, D and L isomers will tend to flip back and forth. The inability to form stereospecific compounds may hamper their ability to form biomolecules
As for a mercury solvent, that is an interesting idea. Life from a metallic solution. Very interesting... It would rely on an environent where elemental mercury could form, mind you.
--Xanthine 13:28, 14 July 2006 (UTC)
The rarity of Boron would lead to a rather interesting ecology, if a biochemistry is possible. Presumably life would evolve methods of concentrating boron compounds. Perhaps plant-analogues would form symbiotic relationships with small insect-sized creatures who would gather boron-rich materials, such as dead organisms and feces. At any rate, it seems to me that if life evolved beyond small unicellular organisms, it would have to concentrate in small "islands" of life surrounded by vast lifeless regions, as opposed to Earth, where life is essentially universal. These islands would also be rather isolated from each other, and would have to have some method of counteracting the forces of erosion which would otherwise tend to remove the crucial boron Nik42 06:47, 18 August 2006 (UTC)


An interesting ecology indeed... Sadly, unless there's some kind of cosmic phenomenon (perhaps during stellar system formation, for instance) to concentrate levels of boron on a single planet, this topic seems relegated to the realms of the hypothetical...
--Xanthine 10:37, 22 August 2006 (UTC)

Chlorine

In the Other exotic biochemical elements section of the main article chlorine is proposed as an alternative to oxygen. How can this be true? Chlorine is vastly different from oxygen. It generally accepts only 1 electron instead of 2 in bonds and is highly elecronegative. It is essential for oxygen to be able to establish covalent bonds with 2 other atoms. Chlorine can not do that. Also chlorine forms alot of ionic bonds and pulls electrons from other atoms. Explanation?!? --BorisFromStockdale 04:05, 25 March 2006 (UTC)

Personally, I agree. Chlorine exhibits a lot of ionic character, making it's covalent bonds rather poor. However, on the other hand, the two elements aren't quite as different as might be immediately apparent. Chemically, Chlorine and oxygen have similar electronegativities (oxygen is also capable of forming ionic bonds and pulls electrons from other atoms), and the two are both capable of forming Van der Waals bonds. Granted, chlorine would be unable to play a directly analogous role. A Chloride (-Cl) group could emulate the functionality of a hydroxy (-OH) or ketone (=O) group, but not an ether (-O-).
--Xanthine 13:42, 14 July 2006 (UTC)
The explanation is that it shows up in fiction a lot, therefore we should cover it even if it's not scientifically plausible. Go ahead and point out the problems with it in the article, that's what we're here for. Bryan 15:34, 14 July 2006 (UTC)
It just redox chemistry, useful energy can be extracted, as long as you have something that can be oxidized or reduced. Here are some examples:
Here the systems we use:
CxHyOz + O2 <-> CO2 + H2O + Energy
Here a system deep sea/ground bacteria use:
CxHyOz + S <-> CO2 + SH2 + Energy
Here is a potential system in a high halogen environment:
CxHyClz + Cl <-> ClH + CCl4 + Energy
The only problems are that a halogen environment would be very different from ours; note hydrochloric acid is a by product, such a world would be highly acidic let alone corrosive with that much chlorine around, then again maybe their are aliens that believe a oxygen environment is unlikely. --BerserkerBen 19:24, 14 July 2006 (UTC)
Just imagine the alien professor explaining to his students how 'water molecules break the fragile bonds in their phosphorus-nitrogen body chemistry, making life on a planet like Earth impossible'. :)
I think the biggest argument against is that a halogen-rich environment is rather unlikely, due to a relatively low cosmic abundance. That said, it's a big universe out there... --Xanthine 15:45, 17 July 2006 (UTC)
How about the opposite of a oxidizing environment, a reducing one: here the example:
CxHyOz + H2 <-> CH4 + H2O + Energy
Methogenic bacteria here on earth do this, although they generate hydrogen from a fermentation pathway. Image a world high in hydrogen, probably a larger planet then our own (hopefully with a solid surface). I can’t at this time access data on the energetic’s of such a reaction so I don’t know how much energy it could produce, I’m doubtful it can produce as much energy as oxygen do to hydrogen’s lower electronegativity. --BerserkerBen 00:40, 18 July 2006 (UTC)
I like your thinking... I've spent some time considering reducing environments, myself. The most outlandish place known to fit that description is actually the jovian atmosphere. Just consider the possibility...
As far as I'm concerned, if the geochemistry is capable of supporting a metabolism, a biochemistry cannot be ruled out -- especially anywhere there are unexplained chemical species present. Interestingly, this is actually the case on most of the planets we've explored.
--Xanthine 10:09, 18 July 2006 (UTC)
Well I have finally got back to this and here is the pchem on using alternative energy:
  1. C6H1206 + H2 <-> CH4 + H2O + 623Kj/mol
  2. C6H1206 + Cl <-> CCl4 + H2O + 1207Kj/mol
  3. C6H12O6 + O2 <-> CO2 + H2O + 2799Kj/mol
  4. C6H12O6 <-> 3C02 + 3CH4 + 128Kj/mol
  5. C6H12O6 <-> 2C2H50H + 2C02 + 64Kj/mol
It just plug and chug ethalpies, glucose was used as the standard. Because the ethalpy values were all made under standard temp and pressure here on earth they might not very accurate on alien world with very diffrent pressures and tempatures. Also glucose might not be a common biomolecule especially on a halogen world where chloride might be in the place of oxygen. Even so I think the values give a descent estimate as to what the energetic would be. Numbers 5 and 6 are just methogenic and common fermentation here on earth which many simple single cell life forms live off with ease. Hydrogen would only provide 10 times as much energy as common fermentation, oxygen of course provides ~40 times as much, although aerobic metabolism in biochemistry is about 40% efficient and fermentation is about ~70% efficient, so in real life aerobic metabolism only provides about 20 times more energy then fermentation.
Beside all that I think we need alot more about alternative metablisms like chlorine, hydrogen, etc. --BerserkerBen 15:54, 20 October 2006 (UTC)
Some of this should be in the article, and I've heard so much about Chlorine as an alternative to Oxygen, so Chlorine deserves its own subsection. Said: Rursus ☻ 07:53, 29 July 2008 (UTC)

More Fuel for the carbon debate

Has it been considered in this article (or anywhere else, for that matter) the possiblility of alternative carbon-based biochemistries?

Logically, just because a lifeform has a carbon biochemistry doesn't mean that it would necessarily replicate using DNA, require water or utilise lipids and saccharides. It is entirely plausible that carbon-based life may form in a non-Earth environment and utilise a wholly different biochemistry.

Does anyone have more information on this subject? --Xanthine 13:16, 14 July 2006 (UTC)

Look up chirality, that alone makes it possible alien life could be identical (Carbohydrates, lipids, nucleic and amino acids) to us but complete opposite.--BerserkerBen 19:30, 14 July 2006 (UTC)

The subject of a lot of science fiction, combined with the Cambrian Explosion, and a good point. Although I was thinking more along the lines of alternative nucleic acids (such as PNA). Or DNA, with (for the sake of argument) a sugar-sulphate backbone, instead of sugar-phosphate. Just pondering the feasibilities... --Xanthine 15:40, 17 July 2006 (UTC)
I've seen PNA before for use in DNA tags, the problem with it is that without the repulsion of the phosphates the tempature and energy needed to denature PNA double stands would be very high (not a problem for very high temperature environments) and thus the rate and energy needed for replication could be much higher. An advantage would be that nitrogen would be more abundant then phosphorus.--BerserkerBen 00:52, 13 December 2006 (UTC)

Grunts in Halo

In the Halo video game series, a race of Covenant aliens named "Grunts" by humans require a breathing apparatus while fighting the humans in an Earth-like atmosphere. According to the novelizations of the video game, the Grunts' apparatus allows them to breathe the methane they need to survive.

why would this make the grunts methane based? just because they breathe something other than oxygen doesn't change their biochemistry, does it? --Philo 11:10, 12 December 2006 (UTC)

I don't think it makes them methane based (carbon is carbon) Their biochemistry can be what ever the authors describe it as, at least they (the authors) have stated that they breath methane. Methane though does not make real sense as a oxidizing or reducing biological agent: if they are reducing lifeforms that breath in hydrogen and breath out methane that would make sense.--BerserkerBen 00:42, 13 December 2006 (UTC)

Ben, while you are right about them being carbon based, I see no reason that they could not be chemoautotrophs that fix carbon from methane. --Savant13 20:36, 21 October 2007 (UTC)
I see what your saying: they could breath in methane if they also eat sulfur and oxidize the methane with the sulfur. But this does not make sense because they could just eat biological matter to fix the carbon, unless they don't have a GI track? --BerserkerBen 13:07, 8 November 2007 (UTC)

news story about life

http://www.cbc.ca/technology/story/2007/07/06/life-space.html

Said someone at an unknown time after 7 July 07. I've read it. The article is about a NASA sponsored report. The article doesn't claim very much at all, and provides no real clues or news. It simply says: the NASA report reports that we searched too narrowly for life before the eartlings' exploration of Titan, that the bichemistry have changed lately, and that "weird" kind of life might exist here and there (Titan, Enceladus or so), and that, most importantly: ... [tadaaa! Imagine trumpets and likewise dramatic music] ... NASA needs more founding for searching for weird life. (As by being read between the lines). It's a political statement: "more money to us"! Said: Rursus ☻ 08:22, 29 July 2008 (UTC)

Another reference

Hi! You might take a look at this article, as an additionnal ressource: The Limits of Organic Life in Planetary Systems Committee on the Limits of Organic Life in Planetary Systems, Committee on the Origins and Evolution of Life, National Research Council

which can be found for free at

http://www.nap.edu/catalog/11919.html —Preceding unsigned comment added by 132.203.241.19 (talk) 05:29, 3 September 2007 (UTC)

Most unique dedication of all times:
Dedicated to
Non-Human-Like Life Forms, Wherever They Are
but I can reveal that my neighbors' cat, is most probably in a bush nearby, lurking for birds which he isn't going to catch, because he (named "Pingu"), is too satiated from food from humans. He speaks with humans though, but not much more than "meaw" and "miau". Said: Rursus ☻ 08:33, 29 July 2008 (UTC)
Collection:
"Heteroatoms [meaning deviantly bounding atoms in an environment of a specific kind of environment, f.ex. O and N as regards to C, Ga, As as regards to Si] create opportunities for reactivity by activating carbon-carbon and carbon-hydrogen bonds, in general by offering a place for electrons to go during a reaction sequence. Oxygen and nitrogen are frequently used in terran life for this purpose.Indeed, virtually every pathway in central metabolism exploits the electrophilicity of carbon doubly bonded to nitrogen or oxygen (C=N or C=O), or the electrophilicity of phosphorus doubly bonded to oxygen (the core of phosphate metabolism and terran bioenergetics)."
"Metabolism cannot occur in a system that is at thermodynamic equilibrium." [I agree!]
As compared with water, ammonia’s increased ability to dissolve hydrophobic organic molecules suggests an increased difficulty in using the hydrophobic effect to generate compartmentalization [separation of hydrophilic from hydrophobic, implying cell membranes, etc.] in ammonia, relative to water.
... more to add. Said: Rursus ☻ 09:47, 29 July 2008 (UTC)

Two Things

1. I removed the P Files tag because the subject of the article is not paranormal, but rather discusses the subject from a scientific standpoint.

2. Why does the article not address alternative carbon-based biochemistries? Methane breathing is a possibility.

--Savant13 23:17, 11 October 2007 (UTC)

Side note about hydrogen fluoride

The acidity of HF should not be a big threat to HF life based hipothesys.

HF is an acid when compared with water, but the water itself is an acid when compared with ammonia. I've heard about HF being protonated in a pretty similar way than water, giving H2F+ (compare with H3O+, hydronium ion = water protonated).

Someone with Chem-knowledge can verify it?

[sorry my bad English - it's not my native lang.] 201.21.182.211 (talk) 07:35, 21 February 2008 (UTC)

Also the article says HF has a pH around sulfuric acid but isn't HF a weak acid —Preceding unsigned comment added by 219.64.92.211 (talk) 05:34, 29 April 2008 (UTC)

Not really; usually, if an acid doesn't contain oxygen, it has a high (5-7ish) pH; but because Fluorine and Chlorine are very eletronegative, their non-oxygenic acids, HF and HCl, are classed as "strong" (around pH 2 for a normal solution). --Wtrmute (talk) 14:40, 13 May 2008 (UTC)
I think that those values of high pH are off, whether you mean high in number (the scale goes to 14) or acidity (a substance is neutral with a pH of 7 and a weak acid with a pH of 5). Though don't count my words as much, I'm ignorant of the science. tehgrisp (talk) 21:20, 25 June 2008 (UTC)
I apologise; I meant the pH is high for an acid, which means it will hover close to 7 (beyond that it will become alkaline). A high pH would be associated with weaker acids and stronger bases. I should have worded my comments better. --Wtrmute (talk) 23:38, 23 September 2008 (UTC)
I'm not a chemist, but I use to use a university chemistry book as a sleeping pill – confirm:
  • HF is a weak acid – it is very etching however ... ,
  • H2F+ fluoronium easily forms and is a ionic analogue to H2O
But as far as I'm concerned, the acidity is not a trouble – it is currently (2008) believed that the original life on earth was thermophile, and there are known acidophiles. The main point, as I see it, is that cells shall be able to form in a colloidal environment, the Terrestrial life based on the duality between polar and non-polar polymers, water constituting the polar one (polymer as regards to the water molecule complexes as in water ice), and aliphatic hydrocarbons the non-polar polymers. The cells seems to be ballons of double-skinned assemblies of non-polar lipids, swimming around in a liquid polar environment, and containing a similar, but not equivalent polar inner environment, where energetic chemical reactions are catalyzed and buffered so as not to turn into combustion. If HF can play the same role as H2O, then maybe... but not if HF is a great polymer eater. Said: Rursus ☻ 08:11, 29 July 2008 (UTC)
Acidity is relative. Here on Earth we water based creatures consider water to be neutral. However HF could just as well be considered neutral, and water a base... 67.174.254.136 (talk) 17:09, 1 September 2008 (UTC)
Oops, forgot to login before posting... Here is my signature: Ummonk (talk) 17:12, 1 September 2008 (UTC)

Methane and Sulfur as solvents?

I just read the Isaac Asimov article, Not as We Know It; The Chemistry of Life [7]. He mentioned that on very cold worlds methane might take the place of water. Of course, methane is nonpolar so lipids would have to take the place of proteins.

He also mentioned the possibility of fluoro-organics dissolved in liquid Sulfur, or Fluorosilicones dissolved in other Fluorosilicones. Neither was mentioned in the article.

Sociotard (talk) 01:24, 25 June 2008 (UTC)

Use of the words "Animal" and "Plant" improper?

To me, and perhaps to others, it seems a problem that the terms "animal" and "plant" are being used to describe extraterrestrial life. This is because the terms refer to phyla, and extraterrestrial life, especially those of alternate biochemistries, would almost certainly be in other kingdoms, domains, or some new, larger group in taxonomy. Where the terms are used in the article, I propose that heterotroph/autotroph, or perhaps producer/consumer, be used. tehgrisp (talk) 21:06, 25 June 2008 (UTC)

Yeah, most likely, if we do discover extraterrestrial life, we'll have to create a new taxonomic level, something like "world" or maybe "empire" to continue the analogy of kingdom and domain. Still, I think "plant" and "animal" would be fair enough colloquial terms. Sure, biologists would create their own terms to refer to the multicellular photosynthetic organisms of the Alpha Centauri Ac world, but I think most people would simply say "plant". (Actually, maybe biologists would still use the term "plantae" there - after all, names can be duplicated between the animalia and plantae kingdoms, e.g., erica the plant genus and Erica the animal genus (or, indeed, this page). So, why not permit such homonymy between different "worlds"? At any rate, that's pure speculation, since we haven't found any extraterrestrial life. But, I imagine if we found enough extraterrestrial ecosystems, we'd run out of names pretty quickly! (Not to mention, can you imagine the nightmare of working out priority with relativistic travel and lengthy travel times, if FTL travel proves impossible?) Nik42 (talk) 00:39, 27 October 2008 (UTC)

HF

Removed this line: "However, HF suffers from the fact that it is an acid, with a pH similar to Sulfuric acid. See hydrofluoric acid. "

pH is concentration/solvent dependent, and so this line is meaningless. --Rifleman 82 (talk) 07:48, 24 July 2008 (UTC)


Minor point, but it bothers me

At the end of the "Alternative atmospheres" section, there is a paragraph discussing motile photosynthetic lifeforms and sessile "animals." My first qualm arises from that I'm not certain -- though think I see why it was put there -- that this paragraph belongs in this section (it still really has nothing to do with atmospheres), or, for that matter, in this article: it my opinion it would be more appropriate in something like "Alternative biomechanics," which leads to my second qualm. The statement is more or less incorrect: sessile heterotrophs could be considered as analogues for anything from fungi to sponges, and, while there are no known actively motile, multicellular, photosynthetic lifeforms proper (the number of qualifiers in that statement alone should be an alert), there are still animals that undergo symbiosis with unicellular photosynthetic lifeforms.

The reason I bring this up here is twofold. First, I see that this article has a long and complicated history of reclassification and role-changing, and I'm not certain I want to become embroiled therein :) . Second, I would appreciate some opinions and viewpoints on my qualms from some of the regulars. Cheers, Ngorongoro (talk) 16:16, 25 October 2008 (UTC)

Several Typos

Some sentences here have incorrect grammar. E.g.,

"just after been out of dying stars, because it's the most reactive element." " And the two firsts couldn't be thought to be found in" 129.59.89.150 (talk) 18:43, 31 March 2009 (UTC)

Phosphorus pentasulfide and Mercuric bromide

A chemistry journal had a letter which suggested these two substances as good choices for alternative biochemistries because they have a broad liquid phase and can dissolve many different substances. Unfortunately I didn't record the journal title or author. And it didn't mention how these could be abundant enough on a planet's surface, but they would be interesting. 69.212.37.239 (talk) 15:54, 11 May 2009 (UTC)NotWalter

Not quite good enough...

I noticed this in the section "Other exotic biochemical elements"

"The existence of Methane-based life is proposed as a reason for the production of methane in the absence of organic chemicals on Jupiter's moon Titan.[9]"

Which might make sense, except that (1) methane is not an element; (2) Titan is not Jupiter's moon; (3) Organic chemicals are found in Titan's atmosphere; (4) The citation provided doesn't go anywhere. Kalidasa 777 (talk) 13:04, 13 June 2010 (UTC)

Which is more common?

At least two theories claim to be the most common hypothesis. How can that be measured anyway? 72.14.165.102 (talk) 21:41, 2 August 2010 (UTC)

Define life

To make this article about HYPOTHETICAL types of biochemistry, as opposed to SPECULATIVE types of biochemistry, we need to purposefully broadly define life.

Before posting on any page about topics like this, you must first ask yourself these questions: What defines life? What makes something living different from something that is not living? In other words, what is the FUNDAMENTAL difference between life and non-life?

After we get that definition, we can begin to hypothesize about alternative biochemistries, not speculate about it.

97.77.49.169 (talk) 04:39, 31 October 2010 (UTC)

Biochemistry is the chemistry of life, but we don't any clear definition of what life is. We have clear definitions of emergent properties of life, but not what life is in itself. That is the relevance of this section. 97.77.49.169 (talk) 04:40, 31 October 2010 (UTC)

Archiving messages

You may want to consider setting up an archive, possibly using a bot, since most of these messages are dated. All is One (talk) 17:47, 3 December 2010 (UTC)

Arsenic dispute

Regarding the arsenic-phosphorus dispute, please use the discussion at Talk:GFAJ-1 instead of starting another thread here. Thanks. Dysmorodrepanis (talk) 13:46, 8 December 2010 (UTC)

What matters here is not the actual truth of the claim but verifiabilty that the hypothesis itself has been published. See wp:truth. I don't doubt the theory's unlikeliness, given the size difference of the atoms, and I greatly welcome your added criticism. The proper response is to give both sides, not just what each of us judges to be the correct side. μηδείς (talk) 20:55, 4 February 2011 (UTC)

Life Based On Sub-Atomic Chemistry

An article from The Science Times in 1988 suggests that Frank Drake's theories about life on neutron stars (used in the Robert L. Forward novel Dragon's Egg) may have enough scientific credibility to be included in this article's Non-planetary Life section. The novel is already mentioned in the fiction section, but the theory itself is not yet included above. Can anyone identify reasons why it should not be moved up?

An Earthshine (talk) 20:42, 9 June 2011 (UTC)

OR issue

I found a couple of comments about the question of OR in this article posted on the page Wikipedia:No_original_research/Noticeboard, and have added a comment there myself. Kalidasa 777 (talk) 12:02, 14 June 2011 (UTC)

Yes, I am guessing that most of the content is reporting on some book(s) that speculate on the same themes. So I did not cut anything. --Smokefoot (talk) 12:23, 14 June 2011 (UTC)

Chlorine life claim

Whilst updating myself (via Google) on the progress of last year's arsenic-based life debate I've stumbled upon several articles purporting that there is a type of E.Coli bacterium that has been bred to use a compound called 5-chlorouracil as opposed to thymine in their DNA.[8] I'm curious if someone with more technical expertise in the field could take a look at some of the literature on this phenomena and update the article? Thanks! --MarcZimmer (talk) 18:10, 7 October 2011 (UTC)

I should note the 2011 in science article has a brief mention of this as well. Here is a link to the paper: [9]. --MarcZimmer (talk) 18:13, 7 October 2011 (UTC)

High-temperature solvents

Are there any suggested high-temperature solvents? The non-water solvents mentioned in the article all seem to be possibilities only in environments with temperatures lower than those on Earth. --JorisvS (talk) 20:15, 13 February 2013 (UTC)

experimental creation?

I am not sure if this has happened but I do not see it mentioned in the article. It seems like it is a plausible experiment and if it has been attempted this article would seem like an appropriate place for covering it.--Jrm2007 (talk) 20:22, 26 May 2013 (UTC)

Some other fictional alternate biochemistry stuff

the novel Grass, by Sheri Tepper, also deals with alternate chirality, though that fact isn't revealed until the end of the book, so I'm not sure if it should be included.

Dragon's Egg by Robert Forward involves life on a neutron star. I'm not sure how much it goes into the actual biochemistry, but they might be worth mentioning in some way if they aren't already.

Thoughts? Tamtrible (talk) 04:40, 18 February 2014 (UTC)

Alternate respiration

It seems like the article could potentially use a little more discussion of alternate respiration chains. There's mention of chlorine instead of oxygen, but not any coherent mention of other likely respiration cycles. In particular, if you had a solvent other than water, you might reasonably expect another respiration chain to be likely, if the world has something like plants (that fix carbon using photosynthesis or whatever other energy source) and animals (that consume that fixed carbon and respirate it back). If there's no water available for the equation, then some alternative pathway would be required.

Anyone have sources or informed speculation on the subject? Tamtrible (talk) 08:23, 19 February 2014 (UTC)

Citation needed

In the first paragraph of http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry#Other_types_of_speculations, there is a "citation needed" about blue light granting more photosynthetical yield, and while I do not want to edit it myself, because there might be better reason for it than I know, I believe that this is not really something that needs a citation, but more of a fact, because blue light simply has more energy than yellow or red light.

217.121.176.170 (talk) 19:22, 16 September 2014 (UTC)

Panspermia

Noticed a statement about the panspermia hypothesis in the intro, although at present there is nothing about panspermia in the body text. I don't think this is relevant as it stands.

I wouldn't be opposed to having something in the body text exploring the relation between panspermia hypotheses and alternative biochemistry hypotheses. Jonathan Lunine has argued that finding microbes on Titan with radically different chemistry would imply they were NOT related to Earth life via a panspermia mechanism such as meteor transfer. Conversely, the more sweeping versions of panspermia hypothesis would seem to rule out radically different chemistries — if living things are all over the universe, and they are all related to each other, then their biochemistries would presumably be rather similar...

As with everything in WP, if we're going to discuss this in the article, we will need citations. Not just about panspermia itself, but about the relation between panspermia and alternative biochemistries. Kalidasa 777 (talk) 00:54, 19 March 2015 (UTC)

I think you are right, and I too was tempted to delete it last week. Besides, if life on Earth was transported here by some panspermia mechanism, it cannot be used to explain "alternative biochemistries" because there is none of those on Earth. BatteryIncluded (talk) 01:01, 19 March 2015 (UTC)
Great minds think alike. :) Kalidasa 777 (talk) 03:19, 19 March 2015 (UTC)

Life with extra bases, or with different selection of amino acids

I was surprised to see that it suggests the idea of "mirror life" but then doesn't mention the idea of life that uses a different vocabulary of amino acids or that uses extra or different bases from Earth life. Or even life that uses XNA instead of DNA?

Some of the material that could be referred to:

Alien Life Could Use Endless Array of Building Blocks

First life with 'alien' DNA

World’s first artificial enzymes created using synthetic biology

There are many more - those are just a couple I happen to have open in my browser at the moment in a discussion I'm having with someone about it which is how I ended up here. I think this is a good page on wikipedia and use it often and only just now noticed that though it mentions just about everything else, doesn't seem to mention this possiblity (or have I missed it somehow?).

I can understand of course that that's not the main focus of this article, are more specialist ones elsewhere in wikipedia - but I feel it should be touched on (unless I've missed it?). Robert Walker (talk) 23:28, 25 June 2015 (UTC)

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Pop culture/fiction section

This section has grown to a monstrous length that rivals the article itself. It has become an indiscriminate list of miscellaneous mentions of extraterrestrial life, however, WP:IPC indicates that: A litany of innumerable novels, TV shows, and films [...] is not useful to anyone. Topics of this level of world importance or broad generality never need pop-culture lists; if a cultural references section is present, it should be reserved for major, in-depth treatment with lasting significance, and be written in paragraph form. The two main works that have reached a significant level of social consciousness are, perhaps, Star Trek and Star Wars. I am shortening the list with the aim to condense it further to the most relevant or significant works, and write it later in prose if possible. Cheers, BatteryIncluded (talk) 19:24, 13 September 2015 (UTC)

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"Life as We don't Know It" listed at Redirects for discussion

A discussion is taking place to address the redirect Life as We don't Know It. The discussion will occur at Wikipedia:Redirects for discussion/Log/2021 September 19#Life as We don't Know It until a consensus is reached, and readers of this page are welcome to contribute to the discussion. signed, Rosguill talk 17:29, 19 September 2021 (UTC)

Ammonia and other solvents problem: ice

One other problem with such solvents is that, unlike water, they don't float when they freeze. Therefore a planet with such oceans would see arctic-style icecaps sink, and the end result would be the locking up of much of the oceans into a solid mass. I'll see if I can dig out a RS for this. Tfdavisatsnetnet (talk) 01:27, 6 August 2023 (UTC)

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