# Sulfur-based life **URL:** \ **Category:** Factual Questions\ **Created:** [December 20, 2002, 11:52pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140 "2002-12-20T23:52:15Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Sauroposeidon](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@Sauroposeidon](https://boards.straightdope.com/u/Sauroposeidon)\ **Post date:** [December 20, 2002, 11:52pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/1 "2002-12-20T23:52:15Z")
I heard from a friend that a form of life was found here on Earth that was sulfur-based instead of carbon-based, implying life formed at least twice. Is this true? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [December 21, 2002, 12:18am UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/2 "2002-12-21T00:18:44Z")
No. There are however some kinds of [bacteria](http://www.xrefer.com/entry/463647) (carbon-based, like all other life on Earth) that are able to metabolize sulphur. ---
**Author:** ![Tamerlane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tamerlane/32/7602_2.png) [@Tamerlane](https://boards.straightdope.com/u/Tamerlane)\ **Post date:** [December 21, 2002, 12:28am UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/3 "2002-12-21T00:28:12Z")
In addition to bacteria there are also certain invertebrates that have a sulfide-utilizing anaerobic metabolism, like Echiuran worms on mud flats or some of the thermal rift critters ( my old Animal Phys. professor was big on this ). - Tamerlane ---
**Author:** ![Speaker\_for\_the\_Dead](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@Speaker\_for\_the\_Dead](https://boards.straightdope.com/u/Speaker_for_the_Dead)\ **Post date:** [December 21, 2002, 12:29am UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/4 "2002-12-21T00:29:55Z")
Is it possible to have life based on any element? Could I have an iron-based life form? Calcium? Neon? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [December 21, 2002, 12:35am UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/5 "2002-12-21T00:35:23Z")
> [@](#): > > \*Originally posted by Speaker for the Dead \* > \*\*Is it possible to have life based on any element? Could I have an iron-based life form? Calcium? Neon? \*\* No. The reason life is carbon-based is that carbon is able to form bonds with 4 different atoms, so that it is able to form extremely complex compounds. Only elements that can form 4 bonds, and which are also fairly common, are likely to be able to form the basis for life. Silicon can also form 4 bonds, and it has sometimes been speculated that it could potentially provide the basis for life forms. But so far this is just science fiction. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [December 21, 2002, 12:38am UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/6 "2002-12-21T00:38:51Z")
[Silicon-based life.](http://www.angelfire.com/on2/daviddarling/siliconlife.htm) > [@](#): > > At first sight, silicon does seem a promising organic alternative to carbon. It is common in the universe and lies directly below carbon in the periodic table of elements, so that much of its basic chemistry is similar. For instance, just as carbon combines with four hydrogen atoms to form methane, CH4, silicon yields silane, SiH4. Silicates are analogues of carbonates, silicon chloroform of chloroform, and so on. Both elements form long chains, or polymers, in which they alternate with oxygen. In the simplest case, carbon-oxygen chains yield poly-acetal, a plastic used in synthetic fibers, while from a backbone of alternating atoms of silicon and oxygen come polymeric silicones. > > Conceivably, some strange life-forms might be built from silicone-like substances were it not for an apparently fatal flaw in silicon’s biological credentials. This is its powerful affinity for oxygen. When carbon is oxidized during the respiratory process of a terrestrial organism (see respiration), it becomes the gas carbon dioxide-a waste material that is easy for a creature to remove from its body. The oxidation of silicon, however, yields a solid because, immediately upon formation, silicon dioxide organizes itself into a lattice in which each silicon atom is surrounded by four oxygens. Disposing of such a substance would pose a major respiratory challenge. ---
**Author:** ![scm1001](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@scm1001](https://boards.straightdope.com/u/scm1001)\ **Post date:** [December 21, 2002, 1:10pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/7 "2002-12-21T13:10:44Z")
not quite true colibri. Depending on the pH, silicon is quite stable in the form of soluble silicates, and could be easy transported or excreted. Sodium silicate solutions used to be used for preserving eggs and waterproofing. However, make the pH too acidic and you will get lots of insoluble silica. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [December 21, 2002, 4:57pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/8 "2002-12-21T16:57:39Z")
It’s been a while since I took chemistry, but wouldn’t silicon have weaker bonds than carbon due to its larger atomic radius? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [December 21, 2002, 6:25pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/9 "2002-12-21T18:25:14Z")
> [@](#): > > \*Originally posted by scm1001 \* > \*\*not quite true colibri. Depending on the pH, silicon is quite stable in the form of soluble silicates, and could be easy transported or excreted. Sodium silicate solutions used to be used for preserving eggs and waterproofing. However, make the pH too acidic and you will get lots of insoluble silica. \*\* OK, none of the drawbacks to silicon absolutely rule it out, they just make it a much more unlikely basis for life than carbon. Silicon has lot of other drawbacks, including lack of chirality (handedness) in its compounds that give them less specifity in reactions than carbon compounds have. [This site](http://nai.arc.nasa.gov/astrobio/feat_questions/silicon_life.cfm) has more info on silicon’s drawbacks. Here’s an article that discusses some other alternatives to carbon-based life: [Carbon chauvinism.](http://www.wikipedia.org/wiki/Carbon_chauvinism) ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [December 21, 2002, 6:31pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/10 "2002-12-21T18:31:59Z")
> [@](#): > > \*Originally posted by ultrafilter \* > \*\*It’s been a while since I took chemistry, but wouldn’t silicon have weaker bonds than carbon due to its larger atomic radius? \*\* Yes. [This site](http://www.ess.sunysb.edu/fwalter/AST248/week6.html#sec2) has more info on silicon’s chemistry: [quote] . . . Si is not as versatile as C. It does not readily form double and triple bonds (since the atom is larger, the bonds must “bend” or “stretch” more to reach - this takes more energy and makes the bond less stable). [ul] [li]Si-Si bonds are half the strength of C-C bonds, so long Si chains are weaker than long chains of C. [/li] [li]Si-H and Si-O bonds are stronger than Si-Si bonds, while C-H and C-O bonds are about as strong as C-C bonds. [/li] [li]Si-O chains (silicones) are very stable, and not highly reactive. They make good lubricants. [/li] [li]SiO2 (quartz) is very stable and insoluable, unlike CO2. It is the major constituent of sand. [/li] [li]Si does not form rings (aromatic compounds, like benzene C6H6), unlike C.[/ul][/li][/quote] ---
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [December 21, 2002, 7:16pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/11 "2002-12-21T19:16:27Z")
I think there is a sulfur-based lifeform living in my dog’s intestines. ---
**Author:** ![Epimetheus](https://avatars.discourse-cdn.com/v4/letter/e/c4cdca/32.png) [@Epimetheus](https://boards.straightdope.com/u/Epimetheus)\ **Post date:** [December 21, 2002, 8:47pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/12 "2002-12-21T20:47:33Z")
> [@](#): > > \*Originally posted by KidCharlemagne \* > \*\*I think there is a sulfur-based lifeform living in my dog’s intestines. \*\* Really? You sure it isn’t living in YOUR intestines? I know how blaming it on the dog goes. 😉 ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [December 21, 2002, 10:07pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/13 "2002-12-21T22:07:01Z")
We already have silicon-based life forms. Not yet sentient, however. But it’s coming. ---
**Author:** ![Revtim](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/revtim/32/1042_2.png) [@Revtim](https://boards.straightdope.com/u/Revtim)\ **Post date:** [December 21, 2002, 10:44pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/14 "2002-12-21T22:44:20Z")
If you’re talking about computers **Hari** , I’m going to disagree that they can be considered lifeforms. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [December 21, 2002, 11:15pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/15 "2002-12-21T23:15:15Z")
There was quite a buzz a few years ago when it was discovered that some undersea vent creatures use elemental sulfur, rather than oxygen, as the final electron acceptor. In other words, they use sulfur to burn their metabolic fuels. IIRC all these creatures were bacteria. However the tube worm’s lifestyle surprised everyone: > [@](#): > > the giant tube worm known as Riftia.\_ These beasts can grow to be 1.5 m in length and 3.8 cm in diameter.\_ However, the low surface area to volume ratio of the worm and the relatively low concentration of dissolved organic material in the water would not seem to be able to support such a large creature.\_ More careful observation revealed the presence of elemental sulfur crystals on the outer surface of the worm’s body.\_ This is significant because elemental sulfur is one of the products of sulfur-reducing chemosynthesis.\_ Microscopic examination of these animals revealed that chemoautotrophs were present inside the cells of the worm and were serving as the primary food source What Sauroposeidon’s friend said was probably a version of this story that had been mangled by too many tellings. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [December 21, 2002, 11:18pm UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/16 "2002-12-21T23:18:53Z")
:smack: Here’s the link for the tubeworm quote from [The Wild World of Chemoautotrophs](http://www.arches.uga.edu/~jmdavid/). It’s a wild, Wild World ! ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [December 22, 2002, 1:33am UTC](https://boards.straightdope.com/t/sulfur-based-life/144140/17 "2002-12-22T01:33:21Z")
The reason that you would expect any alien species to be carbon-based is just pure probabiltiy, I imagine that carbon based life, being more efficient, would have many more times the chance of suriving than silicon based life.