Talk:Titan (moon)/Archive 4

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Evidence of Alien Life Found!

Scientists found evidence of methane and alien life in saturn's biggest moon Titan. View the link for more credible sources and information.

Click Here to view more info. —Preceding unsigned comment added by 66.176.103.151 (talk) 18:18, 5 June 2010 (UTC)

I've added some material but I need someone with credentials to look over it and see if I got the science right. Serendi^podous 19:23, 5 June 2010 (UTC)

The title is misleading no evidence of alien life. Just speculation. --68.209.227.3 (talk) 02:46, 6 June 2010 (UTC)

No there's evidence, it's just not particularly conclusive evidence. An earlier paper made a prediction concerning the affect of a methanogenic lifeform on Titan's atmosphere, and that prediction has been verified, sort of. Serendi^podous 05:49, 6 June 2010 (UTC)

A wee bit more about this subject from Chris McKay himself. It deserves mention, but it needs to be balanced. I'd do it myself but this is well outside my wheelhouse. - Jack Sebastian (talk) 23:27, 8 June 2010 (UTC)

I think it's outside all our wheelhouses. Thanks for that, it will take some time to unpick, but it REALLY needs to be added. Serendi^podous 08:09, 9 June 2010 (UTC)

Hm. There seems to be a contradiction there. In that article, McKay says,

Benner et al. (2004) first suggested that the liquid hydrocarbons on Titan could be the basis for life, playing the role that water does for life on Earth. Those researchers pointed out that "... in many senses, hydrocarbon solvents are better than water for managing complex organic chemical reactivity".

However, in his 2005 article he said that methane was a poor solvent. I don't get this. Serendi^podous 22:44, 10 June 2010 (UTC)

Which 2005 article? I wonder if it's the technical physical chemistry definition of poor/good solvent for polymer molecules. Water is considered a "poor solvent" technically for proteins, but this is a good thing, because it allows proteins to collapse into definite structures. --Cyclopia^talk 01:35, 11 June 2010 (UTC)

This article. Can't access the full text from here, so I can't dig up the appropriate quote I'm afraid. Serendi^podous 05:26, 11 June 2010 (UTC)

I should be able to access it from the department -give me the time to breakfast and cycle there :) --Cyclopia^talk 08:59, 11 June 2010 (UTC)

The article can be found here. Ruslik_Zero 11:59, 11 June 2010 (UTC)

Ok, gave it a look. My initial guess was wrong, but no problem. The 2005 article acknowledges that, apparently, liquid methane is not a good solvent for organic substances. The end of the article says, however: Although we have shown here that the energetics of methane-based life on Titan may be favorable there are two important difficulties to consider related to such life forms. First, the low temperatures imply very low rates of reaction. However by the use of catalysts life can speed up any thermodynamically favorable reaction. The second, more problematic issue is the low solubility of organic substances in liquid methane. Because water is such an excellent solvent we have no experience with how life adapts and works with sparse solubility. It is possible that active transport and organisms with large surface to volume ratios could mitigate this problem..

However the other article (Benner 2004, [1])says: Further, hydrogen bonding is difficult to use in the assembly of supramolecular structures in water. In ethane as a solvent, a hypothetical form of life would be able to use hydrogen bonding more; these would have the strength appropriate for the low temperature. Further, hydrocarbons with polar groups can be hydrocarbon-phobic; acetonitrile and hexane, for example, form two phases. One can conceive of liquid/liquid phase separation in bulk hydrocarbon that could achieve Darwinian isolation.

The reactivity of water means that it destroys hydrolytically unstable organic species. Thus, a hypothetical form of life living in a Titan hydrocarbon ocean would not need to worry as much about the hydrolytic deamination of its nucleobases, and would be able to guide reactivity more easily than life in water.

This is understood by preparative organic chemists, who prefer non-aqueous solvents to water as media for running organic reactions in the laboratory. For example, in a recent issue of the Journal of Organic Chemistry, chemists used a solvent other than water to run their reactions over 80% of the time. Chemists avoid water as a solvent because it itself is reactive, presenting both a nucleophilic oxygen and an acidic hydrogen at 55 molar concentrations. Thus, in many senses, hydrocarbon solvents are better than water for managing complex organic chemical reactivity.

There are therefore two faces of the issue: one is that methane can be a better solvent from the structure and reactivity point of view, allowing stronger hydrogen bonding and easier enzymatic reactions. The fact that it is however in general a worse solvent for organic molecules creates another set of problems. I hope it helps. --Cyclopia^talk 11:49, 11 June 2010 (UTC)

There comes a time when I have to throw up my arms and say, "This is beyond me". I just don't have the level of chemistry required to unpick those quotes. Serendi^podous 16:04, 11 June 2010 (UTC)

Here is the 2004 paper in case anyone can work it out. Serendi^podous 08:36, 12 June 2010 (UTC)

Well, easily put, hydrocarbon solvents and water have different sets of pros and cons. Water dissolves things overall better: this means that it is easier, say, to distribute substances in a cell. But it is so good that it makes a bit hard for big molecules to acquire the right structure (even if it is definitely possible, given that it happens every day). A hydrocarbon solvent would require some trick to permit small molecules (metabolites etc.) to go to and fro in an organism, but it makes easier for structures to form. Does it make sense? --Cyclopia^talk 18:45, 13 June 2010 (UTC)

OK, I've had a go at rewriting it. Let me know if it works. Serendi^podous 09:19, 15 June 2010 (UTC)

Sounds nice to me. --Cyclopia^talk 19:50, 15 June 2010 (UTC)

In my opinion the argument for methane (or other hydrocarbon solvents) is flawed. The assertion seems to be that enzymatic reactions may plausibly occur in a methane solvent at subzero temperatures, however, this pressupposes enzymes. In the 2004 paper linked in the comment prior to this one, the authors conclude that for folding, and thus enzymes, an amide backbone is probably needed, and the very idea of metabolism and life requires enzymes. But nonpolar solvents are extremely unlikely media for proteins to fold in, and so in my opinion, the argument counters itself. I have not read the full paper but i'll do so as soon as i have time and add any further comments. Silasmellor (talk) 01:27, 13 June 2010 (UTC)

Since we're speculating... actually, some proteins fold properly in nonpolar solvents -and all membrane proteins do in fact fold (at least partially) in a non polar environment. I'd say it is possible to have a "reverse folding", where hydrophilic residues constitute the buried core and hydrophobic residues an exposed one. (Hmm, nice project. I'd have to talk about it to my supervisor). --Cyclopia^talk 18:35, 13 June 2010 (UTC)

Yes, i suppose that is true, but what about the backbone dipole? Secondary structures such as alpha helices form rapidly when proteins fold, as the backbone hydrogen bonding is favorable, but the same does not count for beta sheets - For a peptide backbone in a methane (or other nonpolar solvent) any hydrogen bonding would be favorable, to neutralise the dipole, so how could long distance secondary structures such as beta sheets form? any protein would just coil into a helix immediately, and those helices associate to bury hydrophilic side chains - a "hydrophilic effect" as opposed to a hydrophobic one. I agree that the side chains could be "reversed" essentially, but i don't see how the backbone is accomodated. Another difficulty is active sites - i realise that nonpolar solvents are good for chemical catalysis, but would a polar active site in an enzyme, existing in a methane solvent, not run the risk of binding its substrate too tightly?? Silasmellor (talk) 21:14, 13 June 2010 (UTC)

Very good questions. For folding (and evolution of folding for non polar solvents) I'd say this paper could be a good starting point. For catalysis, I don't know exactly, but I definitely remember in my biotechnology classes to have learnt that enzymes are successfully used in non polar environments for chemical synthesis, so it must definitely be possible. --Cyclopia^talk 21:22, 13 June 2010 (UTC)

Thanks for the paper, was going to ask you if you had any i could look at! Let me read it and i will respond :) Silasmellor (talk) 00:11, 14 June 2010 (UTC)

A more serious problem is availability of chemical elements. After all suitable proteins can evolve over billions years. Unfortunately only three elements are abundant in the atmosphere of Titan: nitrogen, carbon and hydrogen. Oxygen is also present but scarce (CO at 1×10⁻⁵ and possibly NO). All other elements are trapped as essentially immobile solids on the surface (in water ice and rocks). Can a life be built from just three or four elements? Are sulfur, phosphorus and some metals necessary? Ruslik_Zero 16:40, 14 June 2010 (UTC)

Carbon, Nitrogen and Hydrogen are the constituents of all but 2 of the 20 common amino acids. Granted, lacking phosphorous and sulfur restricts the amount of chemistry that can be done, so it may be a serious restriction. Gauging it from the available gases in the atmosphere may not give a very good indication. Most of the metals used by life today probably originate from the earths crust for example. Metals are definitely important for life on earth, about a third of all enzymes one or more metal ions for catalysis. On earth, life probably originated at the interface between sea and crust, ie the seafloor, giving a rich medium, and so while atmospheric gases are important, and they tell us about the concentration of solutes in the seas, it is not necessarily indicative of the exact environment it would originate in. Silasmellor (talk) 19:24, 14 June 2010 (UTC)

Methane/ethane is a non-polar solvent, which can not dissolve salts, so there is no way metals can be incorporated into organic matter. They will remain in the rock. Ruslik_Zero 19:37, 14 June 2010 (UTC)

Thats a good point. This poses problems for chemiosmosis as well... Silasmellor (talk) 20:25, 14 June 2010 (UTC)

Pending changes

This article is one of a small number (about 100) selected for the first week of the trial of the Wikipedia:Pending Changes system on the English language Wikipedia. All the articles listed at Wikipedia:Pending changes/Queue are being considered for level 1 pending changes protection.

The following request appears on that page:

However with only a few hours to go, comments have only been made on two of the pages.

Please update the Queue page as appropriate.

Note that I am not involved in this project any more than any other editor, just posting these notes since it is quite a big change, potentially.

Regards, Rich Farmbrough, 20:41, 15 June 2010 (UTC).

Circulatory

By definition, circulatory is an adjective meaning of or relating to the circulation of blood or sap. As such cannot be used to in reference to the atmosphere. Mkdw^talk 19:27, 28 June 2010 (UTC)

No, it is the adjective of "circulation", which means "moving in a circle" and is very often used to describe not only convective cells but also pennies and newspapers. Serendi^podous 19:29, 28 June 2010 (UTC)

Actually not quite. You are talking about circulation as a noun, and its other adjective (there's a reason the word has two adjectives) circulative as the word you describe above. Granted circulatory and circulative stem from the word circulation, they do not have the same usage and are not interchangeable which is why we have the variation. You will note that circulation has many unique definitions (Merriam-Webster's Dictionary), but circulatory (Merriam-Webster's Dictionary) makes the specification. Also the American Heritage Dictionary makes this distinction as well as the Concise Oxford English Dictionary (which is not on the web for free access). Most non-complicated dictionaries will merge the two definitions and link circulatory to circulation, but make the effort of marking noun, adverb, or adjective. In any matter, in meteorology "atmospheric circulation" is the correct term, and notably only 444 examples of "atmospheric circulatory" are found in a SET, which could easily be argued the confusion over the proper usage, to a comparative 568,000+ examples of "atmospheric circulation". No examples exist for circulative as you say above which is used to describe more journeys of a specific physical objects than its described movements as a whole. "The blood circulates in the circulatory system". Mkdw^talk 20:30, 28 June 2010 (UTC)

Almost all adjectives and nouns have different meanings even if they are related... An expense has a totally different meaning than expensive. Noun and adjective. If they meant the same thing we wouldn't have adjectives... Doesn't your profile say you're a research major? 207.6.232.25 (talk) 23:32, 28 June 2010 (UTC)

Actually, yes, and I just did a piece of research I should have done before I started. There is no need, Mkdw, to bring up a reversion of a single anonymous edit on the article talk page. That guy probably will never post here again, and if he does you can make the argument on his talk page. Serendi^podous 06:37, 29 June 2010 (UTC)

Units of measurement

This article is one of many which needs some sort of conversion capability so that users can convert metric measurements to common equivalents. For instance its atmospheric pressure is 146.7 kPa. Which is how many atmospheres, how many psi and how many Torr? Someone I suppose decided that these articles didn't need conversions, however that particular hubris defies the rules of both general accessibility and good manners. 12.150.232.116 (talk) 02:35, 6 October 2010 (UTC) Sorry I wasn't logged in.Trilobitealive (talk) 02:37, 6 October 2010 (UTC)

scientific articles, as a rule, use metric, because science uses metric. Serendi^podous 19:18, 6 October 2010 (UTC)

Thanks for the reply. I'm aware the fact that many scientists use metric. I'm also aware that many computer scientists use binary coding and hexadecimal calculations but in their articles they provide decimal conversions where needed. The primary goal of Wikipedia is to provide good articles which are readable to an eclectic group of readers. To meet that goal it is common practice among a large number of editors (except in articles like this one) to provide conversions. Regards and thanks again. Trilobitealive (talk) 23:43, 6 October 2010 (UTC)

Also (hoping to not be too tendentious in the process), but if obligatory metrification is the only justification for refusing to provide conversions in these articles, Torr is a metric unit of measure and a lot more understandable to most of us than kilopascals.Trilobitealive (talk) 00:56, 7 October 2010 (UTC)

Please use kilopascal in preference to torr, but convert to atmospheres as well! Graeme Bartlett (talk)

Spoken Wikipedia audio recording

I've updated the Spoken Wikipedia audio recording to reflect changes made to the article. I also added a "Statistics" section to read the infobox. Please let me know if I've made any mistakes. Thanks. --Mangst (talk) 00:54, 17 October 2010 (UTC)

Thank you very much for your efforts. You are a rare breed. Serendi^podous 01:26, 17 October 2010 (UTC)

Thanks, and thank you very much for the barnstar! --Mangst (talk) 20:03, 17 October 2010 (UTC)

Titan's volume

Most planet and moon articles give the object's volume in their infoboxes. Though the article states that Titan has a larger volume than Mercury, the article does not state what the volume is. Anyone know? – Quadell ^(talk) 19:57, 15 November 2010 (UTC)

It can be added. Most volume statements are just the radius worked into the equation for calculating the volume of a sphere: 4/3πr³ Serendi^podous 20:25, 15 November 2010 (UTC)

Thanks for the fix! – Quadell ^(talk) 20:31, 23 November 2010 (UTC)

CRYOVOLCANO

I have an Image of a quote possible cryovolcano. The image is not in the article. Should I put it in? Mocha2007 (talk) 19:10, 4 December 2010 (UTC)

Which image is it? There have been a lot of possible cryovolcanoes which have been disproven. Serendi^podous 19:16, 4 December 2010 (UTC)