Talk:Titan (moon)

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Current status: Featured article

Only natural satellite with a dense atmosphere?[edit]

This article states that Titan is the only known natural satellite with a dense atmosphere. When I click on the link to 'natural satellite', I am told that moons (because they orbit planets) and planets (because they orbit stars) are 'natural satellites'.

So what's the deal? Is the article wrong about Titan being the only such body, and should be changed to say the only *moon*, or is the definition of 'natural satellite' in the other article wrong? I'm fairly certain Earth and Venus qualify as having 'dense atmospheres', and if they don't the gas giant worlds obviously do. I don't have the qualifications to know what the right answer is, but clearly something is messed up. 74.75.153.248 (talk) 02:29, 9 September 2016 (UTC)

The article makes it abundantly clear in the first lines that a natural satellite is defined as orbiting a planet. Where did you find the rest of your statement? Double sharp (talk) 03:18, 10 September 2016 (UTC)
Yes, the word "moon" is used scientifically to refer to only one natural satellite: the one that orbits the earth. Colloquially, of course, a "moon" can refer to a natural satellite that orbits another planet. If you can think of a way to enhance clarity, by all means, be bold.
Kortoso (talk) 17:39, 4 November 2016 (UTC)

Mistake in surface pressure?[edit]

(7.3 times more massive atmosphere per unit surface)*(surface gravity 0.14g)=(surface pressure 1.02 times that of Earth's), not 1.45 times as it's stated in the section "Atmosphere". Something is wrong. (Oleksiy.golubov (talk) 13:35, 27 July 2011 (UTC))

Four years later--does anyone have an answer to this good question? Loraof (talk) 21:26, 16 November 2015 (UTC)
Why would that simple multiplication be an accurate calculation? --JorisvS (talk) 21:33, 16 November 2015 (UTC)
Your response doesn't answer the question--could you explain what additional factors are involved? I'm not an astrophysicist, although the original poster @Oleksiy.golubov: identifies himself as one on his user page, so I take him seriously. His simple multiplication seems plausible to my untrained mind: the amount of mass pressing down on the surface times the surface gravity equals the weight. Is it wrong to say that the surface pressure is not proportional to the weight? Loraof (talk) 23:50, 16 November 2015 (UTC)
I don't have all the answers, but without an explanation, it doesn't look all too credible to me. That's why I responded like that, to get more information about it. I do know that I have never heard anyone say Titan's surface pressure is roughly that of Earth, and hence I suspect that the calculation is wrong or oversimplifies things. --JorisvS (talk) 10:11, 17 November 2015 (UTC)
I found this in Surface pressure:
Pressure (P), mass (m), and the acceleration due to gravity (g), are related by P = F/A = (m*g)/A, where A is surface area. Atmospheric pressure is thus proportional to the weight per unit area of the atmospheric mass above that location.
So the OP's calculations appear to be correctly done, given the inputs. Yet the original source confirms the (contradictory) numbers in our article for pressure, air mass, surface area, and surface gravity. I guess maybe there's a typo in one of the numbers in the source—I don't see how else to explain the discrepancy. Loraof (talk) 19:47, 17 November 2015 (UTC)
Or maybe the formula is an oversimplification. I can easily imagine that the cloud deck cases a discontinuity in the pressure profile. The total mass per surface area is rather the integration over the mass profile of the atmosphere, which, in turn, is directly related to the local pressure and temperature via the ideal gas law (to good approximation). --JorisvS (talk) 11:29, 18 November 2015 (UTC)

@JorisvS:, it doesn't help. I'm speaking of the most basic definition of pressure, P=F/S, and the expression of gravity force, F=mg. Whatever the gas law, the clouds, the composition, - nothing matters. Well, I can propose some mechanisms that will crash my argument, but they all are too exotic. (We must get forces additional to mg. Either centrifugal forces of rapidly rotating atmosphere, or alteration of g with height in a too thick atmosphere. Or we are outside equilibrium because the atmosphere is rapidly evaporating... Problems with averaging of these formulae due to height alterations are also possible, but very improbable as variations of height on Titan are minuscule.) I don't know what is wrong. The origin of the contradiction lies in Table 5.1 in p. 130 in Coustenis. We might want to check the mass of the atmosphere indicated in the table from independent sources. Oleksiy.golubov (talk) 14:54, 21 November 2015 (UTC)

@Oleksiy.golubov: "Nothing matters"? Seriously? Of course it does. We don't need additional forces at or around the surface to create a deviation from your simple calculation. Planetary atmospheres are not in equilibrium. They are only irradiated half the time and there is differential heating with height due to inhomogenities in composition (e.g. the ozone layer with on Earth, Titan's cloud deck). Figure 5.2 on p. 132 shows that the pressure does not fall off exponentially with height, which is something your simple calculation does assume. I don't know if that's sufficient to explain the inconsistency, but it does show that we need a more sophisticated way of determining whether there is an inconsistency. --JorisvS (talk) 16:06, 22 November 2015 (UTC)
@JorisvS:, seriously, nothing matters. I don't assume exponential density profile. Nor homogeneous composition. It's like when you are standing on weighing scales: you know your mass, you know the surface area of the scales, thus you know the pressure experienced by the scales. All your arguments sound like "You can't know the pressure for sure. It doesn't depend solely on your mass. It depends also on how tall you are an what material your body is composed of". Even if there were vertical motions of the atmosphere (which are by far negligible as |dv/dt| << g), it would be like you jumping on the scales: the mean weight <F> indicated by the scales stays the same, as <F>-mg = <dp/dt> = 0 (p is momentum). Oleksiy.golubov (talk) 19:22, 22 November 2015 (UTC)
No, your analogy is flawed. It is not about vertical motions in the atmosphere. We're talking about the mass of the atmosphere, which always is the mass in every piece of volume of atmosphere (i.e. density) summed (i.e. integrated) over the relevant volume. And if the density profile deviates from what would be expected from hydrostatic equilibrium, then so would the total mass. However, looking more closely at our source makes it ugly: The surface pressure was measured directly (p. 130) and the total mass of the atmosphere "determined from surface pressure and acceleration due to gravity". They do give the note that "the average conditions are a very complex derivative of these basic parameters, ...". The first part strongly suggests that they simply have made a mistake, but the note seems to suggest that maybe their stated total mass is correct after all, but without any explanation why. Either way, this should definitely be investigated more closely.
In Figure 1 of [1], at low altitudes the pressure can be seen to increase more rapidly than the trend at high altitudes (or should this rather say "at high altitudes the pressure can be seen to decrease less rapidly than at low altitudes"?). Maybe this hints at that the used "average conditions" (ahum; if so this would be a misnomer) from the note deviate quite a bit from the basic parameters (which, of course, we are using). Information on this appears to be rather sparse. Maybe we should contact the authors and ask them about this? --JorisvS (talk) 18:01, 23 November 2015 (UTC)

Mistake in surface gravity?[edit]

Surface gravity is currently listed as (0.14 g) (0.85 Moons), however it's very prominently stated in the intro text that "Titan's diameter is 50% larger than Earth's natural satellite, the Moon, and it is 80% more massive". Other details also state that Titan's volume is (3.3 Moons) and its mass is (1.829 Moons).

How can it have more mass than The Moon, yet have less surface gravity? Is this a mistake or is there some piece I'm missing here? Jack insomniac1911 (talk) 20:16, 29 May 2015 (UTC)

See surface gravity for explanation. Ruslik_Zero 20:37, 29 May 2015 (UTC)
The surface gravity is indeed correct based on the provided values, using g=m/r2, and the values are correct. I would assume, based on the values, that since radius is also used in calculating this, that since Titan may have a higher mass than the Moon, it still has a larger volume. As a result, it has a lower surface gravity. exoplanetaryscience (talk) 20:41, 29 May 2015 (UTC)
I am sure that atmosphere density, altitude and gravity cohefficient play a role in that too, so I'd like to see a reference if changed. BatteryIncluded (talk) 01:07, 18 November 2015 (UTC)
Atmospheric density is irrelevant. Altitude is always zero at the surface, where surface gravity is measured. As @Exoplanetaryscience: says, the formula is surface gravity = body's mass divided by the square of the body's radius. Thus (with rounding error) with all variables measured relative to the Moon's values, Titan's surface gravity relative to Moon = 1.8 Moon masses ÷ (1.5 Moon radii)2 = 0.8, which up to rounding error is the value given in the article. Loraof (talk) 14:56, 18 November 2015 (UTC)
The intuition is that, while Titan is more massive than the Moon, Titan's surface is farther away from the center of gravity (the center of Titan) than is true on the Moon. These two considerations work in opposite directions. Loraof (talk) 14:59, 18 November 2015 (UTC)

"Ih"?[edit]

What is "Ih" in the following (in sub section Cryovolcanism and mountains)?

... may be caused by ice Ih ...

It is not explained. --Mortense (talk) 22:43, 14 November 2015 (UTC)

It is linked in Bulk characteristics. Double sharp (talk) 04:57, 17 November 2015 (UTC)

Battery-NOT-included-in-his-brain removed my bit on PSCs without reading it. This is a talk page pal, not you personal back yard. I put in several mistakes which you did not spot. This article is in a tug of war between several idiots who have no real knowledge on the subject of gravity nor geophysical fluid dynamics. Probably time to report it.27.33.251.24 (talk) 05:44, 30 December 2015 (UTC)

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Polyimine[edit]

New paper mentions polyimine, which does exist, but has no Wiki article yet.

Citing experimental and observational data, the researchers note the abundance of hydrogen cyanide in Titan's atmosphere. This is a hydrogen-bonding molecule that may combine with other molecules on the surface to form polymers, including polyimine. Using quantum mechanical calculations, the scientists demonstrated that polyimine has electronic and structural properties at very cold temperatures that could potentially facilitate prebiotic chemistry in conditions like those on the surface of Titan, especially in tidal pools near the large seas.[1]
The chemistry of hydrogen cyanide (HCN) is believed to be central to the origin of life question. Contradictions between Cassini–Huygens mission measurements of the atmosphere and the surface of Saturn’s moon Titan suggest that HCN-based polymers may have formed on the surface from products of atmospheric chemistry. This makes Titan a valuable “natural laboratory” for exploring potential nonterrestrial forms of prebiotic chemistry. We have used theoretical calculations to investigate the chain conformations of polyimine (pI), a polymer identified as one major component of polymerized HCN in laboratory experiments. Thanks to its flexible backbone, the polymer can exist in several different polymorphs, which are relatively close in energy. The electronic and structural variability among them is extraordinary. The band gap changes over a 3-eV range when moving from a planar sheet-like structure to increasingly coiled conformations. The primary photon absorption is predicted to occur in a window of relative transparency in Titan’s atmosphere, indicating that pI could be photochemically active and drive chemistry on the surface. The thermodynamics for adding and removing HCN from pI under Titan conditions suggests that such dynamics is plausible, provided that catalysis or photochemistry is available to sufficiently lower reaction barriers. We speculate that the directionality of pI’s intermolecular and intramolecular =N–H…N hydrogen bonds may drive the formation of partially ordered structures, some of which may synergize with photon absorption and act catalytically. Future detailed studies on proposed mechanisms and the solubility and density of the polymers will aid in the design of future missions to Titan. [2]

Is it any one of these:?

Kortoso (talk) 18:46, 6 July 2016 (UTC)
Probably this entry instead;
17:27, 11 July 2016 (UTC)

References

Too many entries on the channels[edit]

A few editors have done entries on the liquid-filled channels, causing repetition on the information. If a main editor can consolidate this info it will be appreciated, otherwise I will delete the redundancies. Cheers, BatteryIncluded (talk) 15:42, 12 August 2016 (UTC)

What is the availability of oxygen on Titan?[edit]

Looking for more sources relating to the availability of oxygen—atomic, molecular, or in combination with other elements like oxide silicates etc.—on Titan?

With a serious and funded program now underway to develop (at scale) some interplanetary transport technology, the Interplanetary Transport System currently under development by SpaceX, and with Musk having already mentioned potential missions to Enceladus, Europa, and Pluto, am wondering what raw materials might be available for obtaining oxygen on Titan? N2e (talk) 16:25, 4 October 2016 (UTC)

From the article: "Titan is primarily composed of water ice and rocky material". So, lots of oxygen. The other moons (and rings) are also largely water-ice, with less gravity, so Titan wouldn't be a prime target for water/oxygen. Water is everywhere past the main belt. Tbayboy (talk) 18:19, 4 October 2016 (UTC)

Mountain names[edit]

According to JPL, "By convention, mountains on Titan are named for mountains from Middle-earth, the fictional setting in fantasy novels by J.R.R. Tolkien" (jpl.nasa.gov). I'm not sure where to put this little tidbit of information in the article, though. — Loadmaster (talk) 15:44, 24 October 2016 (UTC)

It could go in the Titan (moon)#Cryovolcanism and mountains section. If there was a mapping paragraph, it could go there, but "mapping" does not exist here yet. Graeme Bartlett (talk) 23:56, 24 October 2016 (UTC)
I added a couple of sentences at the end of that section. I notice that currently only a couple of features are mentioned, none of them mountains or hills. — Loadmaster (talk) 16:22, 31 October 2016 (UTC)

ENGVAR[edit]

I noticed the article was written in a mixture of spelling dialects. This cannot be. Per this version it seems the article was written in American English. Per MOS:RETAIN it should therefore remain in this dialect unless a conscious decision was made to change it. --John (talk) 16:26, 4 February 2017 (UTC)

Lead cites[edit]

Per WP:LEADCITE I moved cites out of the lead. --John (talk) 19:09, 4 February 2017 (UTC)

A "significant" atmosphere[edit]

"Titan is the only known moon with a significant atmosphere." What does that mean, a "significant atmosphere"? How high must the pressure be for an atmosphere to be significant? It is true that most moons only have a surface boundary exosphere at best, which can be ignored for most practical purposes. But Triton's atmosphere tells a different story. Its pressure of about 1.5 Pa is rather low, but at least measurable. It is dense enough for the nitrogen in it to behave like a gas. You can see the atmosphere at Triton's horizon. There are even clouds in it. Four things you can't say of the trace atoms surrounding our own Moon or Ganymede. I would definitely call that a significant atmosphere, however tenuous. Steinbach (talk) 10:32, 17 March 2017 (UTC)

Sub-Saturnian point[edit]

I'm not happy with this sentence:

Because of this, there is a sub-Saturnian point on its surface, from which the planet would always appear to hang directly overhead.

Yes, I realise the point it is trying to make but it is doing do in an over-strong and clumsy manner: Titan has measured eccentricity and thus its sub-Saturnian point moves over the course of an orbit within a well-defined region of the surface, as for the more familiar example of lunar libration. Indeed, the reference for the sentence following regarding longitude specifically refers to the average sub-Saturnian point. Even if we had no measured eccentricity the conclusion would not flow automatically from the simple fact of a synchronous orbit (as implied by the overly-assertive "Because of this") simply because of the mere possibility of there being eccentricity to throw into the mix.

I'm not sure the best way to rectify this - my initial impression is that if it is toned down and clarified to something correct it gets diluted to a point not worth making and therefore better snipped entirely. Thoughts, anyone? 3142 (talk) 18:01, 25 March 2017 (UTC)

The article also notes that the sub-Saturnian point is also the Greenwich of Titan, so if it moves, then the 0 longitude must be some average. Serendipodous 19:46, 25 March 2017 (UTC)

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"The only [...]": really?[edit]

The article states: "Titan is the largest moon of Saturn. It is the only moon known to have a dense atmosphere, and the only object in space other than Earth where clear evidence of stable bodies of surface liquid has been found."

Is s it set in stone that no other moons exist on any other planet in the solar system? Or at the very least, is it highly likely that no other moons exist orbiting any other planet?

Finally, of all registered moons, have all of them been as thoroughly observed as Titan was?

Failing a definitive answer to the questions above, I'd precede the quotation with "Currently": "Currently, it is the only moon known to have [etc etc]"

There are certainly a lot of other moons that we have not seen, but they must all be very small rubble piles, and certainly much too small to hold on to any atmosphere. Double sharp (talk) 10:52, 18 September 2017 (UTC)
First, the complaint is un-necessary because the word "known" is already included. Titan is described as the "only moon known" to have a dense atmosphere. The word "known" indicates the current state of human knowledge. Furthermore, unless there are moons found orbiting planets as yet undiscovered at great distance far beyond Neptune, there is zero chance that there are "currently" unknown moons with dense atmospheres. This is simply a statement of scientific fact: Titan is the only moon with a dense atmosphere in the Solar System (to the orbit of Neptune and far beyond). — Preceding unsigned comment added by 2600:1000:B12F:37AD:4496:BD1:B881:BA32 (talk) 17:43, 18 January 2018 (UTC)

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Sixth "ellipsoidal moon"[edit]

The article begins (third sentence) by saying that "Titan is the sixth ellipsoidal moon from Saturn". Linking to a mathematics article on ellipsoidal is worthless. No one uses this language to describe Titan EXCEPT Wikipedia. The concept of an "ellipsoidal moon" is presumably fallout from Plutonian irredentism. — Preceding unsigned comment added by 2600:1000:B12F:37AD:4496:BD1:B881:BA32 (talk) 17:37, 18 January 2018 (UTC)

I removed the sentence. Again, this was not a "normal" or "common" description of Titan. It was a Wikipedia-ism without support.2600:1000:B120:B65:44C8:F791:F62A:B550 (talk) 19:08, 19 January 2018 (UTC)
The difference between the "roundish" moons (which have room for actual geology, being more than rubble piles: Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Iapetus) and the others is certainly well-established in the literature. It was probably more often referred to as these moons being in hydrostatic equilibrium than being ellipsoidal, but this presents difficulty as data from Cassini has shown that among these, only Rhea and Titan are currently in HE. I will note that "ellipsoidal" also poses problems, because of Methone. So this distinction is certainly not a "Wikipedia-ism without support", and it is also not Plutonian irredentism to note that there is some difference between gravitationally rounded objects and the others. What poses a difficulty is the language we need to use to describe this with. Double sharp (talk) 07:12, 20 January 2018 (UTC)
You agree that referring to these potentially geologically-active moons as ellipsoidal is not as useful categorization. You also are aware that hydrostatic equilibium is not a well-defined categorization for the moons of Saturn. That's fine then. Referring to Titan as the "sixth ellipsoidal moon" is not effective --even outside Wikipedia. You also mentioned that that the difficulty is the language used to separate the major moons from the minor moons (beyond those vague words "major" and "minor"). That's true, too. There is no well-established language that separates the moons of Saturn into categories like this unambiguously. The bigger problem is that this language difficulty you describe is not Wikipedia's problem. A Wikipedian editor should not make up expressions and categorizations, like "ellipsoidal moon", that are not found in the scientific literature. That's basic and fundamental to Wikipedia. When a Wikipedian editor invents his or her own terminology or categories, then that's what I call a Wikipedia-ism.174.199.32.8 (talk) 20:31, 20 January 2018 (UTC)
I do not agree that "ellipsoidal moon" is a Wikipedia-ism. It is simply an adjective "ellipsoidal" applied to a noun "moon", and reliable sources can be found for each claim (that it is ellipsoidal, and that it is a moon). Similarly, referring to iodine as a "volatile nonmetal" would not be a Wikipedia-ism, since it is volatile and it is a nonmetal. And, in fact, there is a quite adequate adjective we can use: "gravitationally rounded", as in List of gravitationally rounded objects of the Solar System. I will edit the article to use that, since it is accurate. Double sharp (talk) 02:48, 21 January 2018 (UTC)

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