Talk:Titan (moon)

Sub-Saturnian point

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. Serendi^podous 19:46, 25 March 2017 (UTC)

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

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)

Yes, "known" being included is the kicker. MaximusEditor (talk) 20:45, 16 September 2020 (UTC)

Sixth "ellipsoidal moon"

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)

Surface: what's it made of?

I've been looking for clear descriptions of what the surface is made of. For instance, the intro details how the atmosphere is mostly nitrogen, there's dunes, rivers, lakes of methane & ethane, cryovolcanos - but not clear what the solid part of the surface is made of. The cutout diagram shows a green layer of 'normal ice' just under the yellow surface skin - but what's that skin like? The section on 'Surface Features' doesn't help much. Little hints like "There is also evidence that Titan's ice shell may be substantially rigid, ...", ice shell could be any layer. Finally in the Impact craters section we get this confession: "Pre-Cassini models of impact trajectories and angles suggest that where the impactor strikes the water ice crust, a small amount of ejecta remains as liquid water within the crater."

From these clues, I've figured out that the non-lake surface is made of water ice. That should be stated in the intro, clearly. And I know it's not pure water ice. If I was walking around in my space suit, and picked up a "rock", it wouldn't look like a clean ice cube, it would look dirty or at least opaque. Just like granite doesn't look like clear glass. Somebody must know some details about this.

PS: I use the term "water ice" because, when you're talking about the outer planets, lots of things are frozen solid. As in the term "ice giant". OsamaBinLogin (talk) 19:04, 11 August 2019 (UTC)

The short answer is that scientists don't know, but have a good idea. The dense atmosphere complicates the use of orbiting spectrometers. The Huygens probe was not a "lander" but an atmospheric probe that happened to make it all the way to the ground, so we have more info on the atmospheric composition than info on the surface. It did, however, collect images and info on the physical properties of the surface, but not its chemical composition (no soil samples analyzed). You are correct in that there is a strong suspicion on the existence of a mix of ices on the surface (cryovolcanoes were imaged, I think), but these surface ices are also mixed with wild and complex kinds of organics collectively called tholins, so there is not one kind of surface "composition" one could quote at this time. Fortunatelly, Dragonfly (spacecraft) was selected for launch, and your questions will begin to be answered soon after landing in 2034. Cheers, Rowan Forest (talk)

There is some surface composition data from Huygens and Cassini. One of the Huygens instrument suites was "Surface Science Package", although it would have worked better if the probe had landed in a lake or sea, and it got material not chemical properties of the surface. The Gas Chromatograph and Mass Spectrometer made a sort-of chemical composition measurement. The inlet was heated and close to (or against) the surface, and they got a measure of whatever surface materials were evaporated by heat from the inlet. And, despite the atmosphere, the Cassini VIMS instrument did get plenty of surface spectra. Unfortunately, they are actually of the surface and the atmosphere, and require lots of modeling to get the surface contribution. So there is data, it just has lots of "ifs" and "assumings." It's basically a mix of hydrocarbons, nitriles and cyanogens, but the details are uncertain. That wasn't a big surprise. Haze particles which grow big enough settle to the surface. There's probably a few places with bare rocks, and the depth and exact composition of the gunk varies spatially. Now, is any of that worth adding the article, and if so, how much of it? — Preceding unsigned comment added by Fcrary (talk • contribs) 22:11, 27 September 2019 (UTC)

Titan as the 6th of 7 gravitationally rounded moons.

This is a continuation of the comments I made for my January 17th Edit: I have read this paper (Thomas P.C. (2010)) and while the author does note that Iapetus does not have a rotation period consistent with being in equilibrium on page 397, he also notes the moon as being an “oblate spheroid” which is consistent with gravitational rounding. It should also be noted that on page 399 in the list of “irregularly-shaped satellites” Iapetus is not included. Therefore I argue that while Iapetus may not be technically in hydrostatic equilibrium it is obviously highly gravitationally rounded, which is consistent with other Wikipedia articles. Therefore, Titan is the 6th of 7 gravitationally rounded moons of Saturn.Violettsureme (talk) 23:41, 17 January 2021 (UTC)