Talk:Ganymede (moon)/Archive 1

Image
The link/caption under the image looks crappy. dark blue on black, only the word "image" is visible on mine, and it shouldnt be in italics. - Omegatron

I changed it, but it could probably be standardized, along with the other moons, planets, or any images, i guess. - Omegatron

Adjectival form
The OED has "Ganymedean" (no pronunciation given) for 'a follower of Ganymede', but its Latin source (Ganym&#275;d&#275;us) is for anything pertaining to Ganymede. Therefore 'Ganymedean' would serve as a general adjectival/denomymic form.

The pronunciation to be expected from the Latin long vowels is gan'-i-mi-dee'-un. Generally, when dealing with classical names ending in a long e like this one, the spelling -ian is used to prevent the stress from shifting to that long-e penult. However, this alternate form of the word (*Ganymedian gan'-i-mee'-dee-un) is unattested. kwami 01:44, 2005 Jun 24 (UTC)

It has been noted that both Ganymede and Europa have tenuous atmosphers of Oxygen. Would this Oxygen be breathable (if warmed up to say zero farenhite) by us?

Idea for an image
Since the article states that it can be seen with the naked eye, are there any GFDL images of said moon? Or even a simulated recreation of what it'd look like?  young  american (ahoy-hoy) 02:02, 25 August 2006 (UTC)

Visible by eye?
Is this for real? I can see that it's magnitude of 4.6 makes it potentially visible, but I would think that Jupiter's glare might be a problem. If it was visible, how come not a single ancient astronomer seems to have noticed, and we had to wait for Galileo to come along with his telescope? Deuar 17:44, 19 March 2007 (UTC)

None of the other wikipedia pages dealing with the galilean satelites say that any of them are observable by the naked eye. I also always understood that being so close to jupiter, they are not individually visible. 66.7.119.190 23:56, 19 May 2007 (UTC)

Interesting question. A Google search turned up only three references to this. One of them is unclear, another I'm suspicious of, and I'm not sure the third is relevant.

This planetarium website says that Ganymede is "...the only moon outside of our own large enough to be seen with the naked eye." That doesn't specifically say whether it can be seen; just that it's large enough.

This page discusses anecdotal evidence of seeing the Galilean satellites with the naked eye. It claims to be from "Sky and Telescope, December, 1976, pp. 482-84". It sure looks good, but it's on this Denis Dutton's personal web site, I wouldn't expect him to write for Sky and Telescope, and I can't turn up any evidence of the article outside of his web site. Does anybody have an old copy of Sky and Telescope? Anybody want to do some library research?

Oh, yeah, one more reference: Ganymede may be/have been visible during a rare occultation of Jupiter by Earth's Moon.

- Ken g6 03:16, 5 June 2007 (UTC)

Gan De reported to have seen one of the moons of Jupiter. I am the one that added Callisto since, as I stated on my edit summary, "Ganymede is twice as bright, but Callisto orbits further out from the planet and Jupiter is several hundred times brighter than either." Callisto orbits at 1.8 Gm / APmag 5.6 and Ganymede orbits at 1 Gm / APmag 4.6. -- Kheider 17:26, 8 November 2007 (UTC)

Volcanic activity
Hi, is Ganymede volcanic? --Kjoonlee 13:01, 1 July 2007 (UTC)

In the past, it was. Now, it isn't. Might be something to add to the article. Shrewpelt 12:28, 3 December 2007 (UTC)

Source:

Atmosphere
The atmosphere was not found in the mid-1980s but 1972. See Ganymed (Mond) for correct citation.--CWitte 14:03, 5 August 2007 (UTC)
 * Done it myself...--CWitte 15:02, 6 August 2007 (UTC)

For later

 * http://www.sciencemag.org/cgi/content/abstract/273/5273/341 Ozone
 * http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-45SJBFT-S&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=0f02ac9d6f555792867a10b6226c53df Oxyegen: Lat and Long.
 * http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-45MFXR8-2H&_user=1790654&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000054312&_version=1&_urlVersion=0&_userid=1790654&md5=65f01a1f1b272850bfc1cfb7cdd2e00b Polar caps. Marskell (talk) 13:54, 13 January 2008 (UTC)

Merge attempt
Cratering is seen on both types of terrain, but is especially extensive on the dark terrain: it appears to be saturated with impact craters and has evolved largely through impact events. The brighter grooved terrain contains much fewer impact features, which have been only of a minor importance to its tectonic evolution. The density of cratering indicates an age of 4 billion years for the dark terrain, similar to the highlands of the Moon, and a somewhat younger age for the bright grooved terrain (but how much younger is uncertain). Ganymede may have experienced a period of heavy cratering 3.5 to 4 billion years ago similar to that of the Moon. If true, the vast majority of the impacts happened in that epoch, while the cratering rate has been much smaller since then. Craters both overlay and are cross-cut by the groove systems indicating that some of the grooves are quite ancient. Relatively young craters with rays of ejecta are also visible. Ganymedean craters are quite flat, lacking the ring mountains and central depressions common to craters on the Moon and Mercury. This is probably due to the relatively weak nature of Ganymede's icy crust which can flow and thereby soften the relief. Ancient craters whose relief has disappeared leaving only a "ghost" of a crater are known as palimpsests.

Requested move

 * The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section. 

The result of the proposal was no consensus to move the page, per the discussion below. Dekimasu よ! 00:30, 27 January 2009 (UTC)

Ganymede (moon) → Ganymede — It strikes me that the moon is by far the most recognizable meaning of the name "Ganymede" and probably qualifies as the WP:PRIMARYTOPIC. As such, it would make sense to give it the main page and move the current Ganymede page to "Ganymede (disambiguation)". — Dragons flight (talk) 01:00, 22 January 2009 (UTC)

Survey

 * Feel free to state your position on the renaming proposal by beginning a new line in this section with  or  , then sign your comment with  . Since polling is not a substitute for discussion, please explain your reasons, taking into account Wikipedia's naming conventions.


 * Oppose. I think the mythical figure is the most recognizable use of this name. I'm open to persuasion, but I need some actual data to change my mind. --Akhilleus (talk) 01:57, 22 January 2009 (UTC)
 * Ganymede (moon) gets 2.4 times as much traffic as Ganymede (mythology).  I'll give you that there is some interest in the myth, but I'd be stunned if the myth is more recognizable than the moon.  Dragons flight (talk) 02:05, 22 January 2009 (UTC)
 * Likewise, there seem to be substantially more Google hits for Ganymede moon than Ganymede myth or any other myth related terms I tried. Dragons flight (talk) 02:10, 22 January 2009 (UTC)
 * Not sufficient; we do not want a plurality, but an overwhelming majority. Septentrionalis PMAnderson 20:18, 22 January 2009 (UTC)


 * Oppose, per reasons at Europa. kwami (talk) 02:32, 22 January 2009 (UTC)
 * Oppose. There are many other things named Ganymede. Anthony Appleyard (talk) 06:16, 22 January 2009 (UTC)
 * Oppose - As Ganymede may refer to a number of things, and there is clearly no obvious "primary topic" here. --DAJF (talk) 06:42, 22 January 2009 (UTC)
 * Oppose I have explained why WP:PRIMARYTOPIC requires much more than a plurality at Talk:Europa. Septentrionalis PMAnderson 20:18, 22 January 2009 (UTC).
 * Oppose. If any move were to be made, the mythological character should be the primary. All of the others are his namesakes. •Life of Riley (talk) 04:43, 23 January 2009 (UTC)
 * Oppose per PMAnderson. older ≠ wiser 11:26, 23 January 2009 (UTC)
 * Oppose - As someone with experience of both astronomy and LGBT studies, I'd say that the 'primary meaning' of the name 'Ganymede' is highly contextual, and no straighforward assumption can be made. AlexTiefling (talk) 16:41, 23 January 2009 (UTC)

Discussion

 * Any additional comments:

DragonsFlight is scattering these polls all over the place. The discussion is at Talk:Europa (moon). kwami (talk) 02:17, 22 January 2009 (UTC)


 * I'm doing exactly two, which you obviously had no problem finding, and which are listed consecutively at WP:RM. Serendipodous raised an issue potentially unique to Europa, so it makes sense to do them separately in my mind.  Dragons flight (talk) 02:28, 22 January 2009 (UTC)


 * Oh, okay. kwami (talk) 02:32, 22 January 2009 (UTC)
 * The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Does "Not Necessary" Principle and Cornerstone of Wikipedia Override NPOV?
Neutral point of view is a fundamental Wikimedia principle and a cornerstone of Wikipedia. All Wikipedia articles and other encyclopedic content must be written from a neutral point of view, representing fairly, and as far as possible without bias, all significant views that have been published by reliable sources. This is non-negotiable and expected of all articles, and of all article editors. For guidance on how to make an article conform to the neutral point of view, see the NPOV tutorial; for examples and explanations that illustrate key aspects of this policy, see Wikipedia:Neutral point of view/FAQ.

Information suppression

A common way of introducing bias is by one-sided selection of information. Information can be cited that supports one view while some important information that opposes it is omitted or even deleted. Such an article complies with Wikipedia:Verifiability but violates NPOV.

However, "not necessary" is being used as a way to suppress information and override NPOV.Sophergeo (talk) 11:41, 20 March 2009 (UTC)
 * I do not understand why are you trying to add exactly the same statement three times? Ruslik (talk) 12:06, 20 March 2009 (UTC)
 * Since it's the redundancy you ojbects to, I'll make the appropriate change.Sophergeo (talk) 14:03, 20 March 2009 (UTC)
 * Removed piped link from direct quote. Doubt that they were referring to Carey's defunct hypothesis. Vsmith (talk) 19:32, 20 March 2009 (UTC)
 * UnsourcedSophergeo (talk) 20:24, 20 March 2009 (UTC)
 * Indeed, the source does not state that they were referring to Carey's hypothesis. Therefore we don't imply that with a piped link within a direct quote. Vsmith (talk) 20:50, 20 March 2009 (UTC)
 * Carey was never linked to. Why are you implying a link to Carey?Sophergeo (talk) 22:00, 20 March 2009 (UTC)
 * Assuming someone were to link to Carey, is there a Wikipedia rule against linking to Carey?Sophergeo (talk) 22:03, 20 March 2009 (UTC)
 * I am a little confused by why there are two paragraphs needed to discuss the formation of grooved terrain, particularly when the second explains the issue much better than the paragraph Sophergeo and Vsmith are debating. Obviously, trying to connect radius expansion as the result of differentiation is in no way related to Carey, and implying that via links is a non-starter.  The two paragraphs should be merged in some way.  Definitely look at the Collins et al. paper as a potential guide for adding this info.  Volcanopele (talk) 21:25, 20 March 2009 (UTC)
 * Volcanopele, Carey was never linked to. Who linked to Carey?Sophergeo (talk) 21:58, 20 March 2009 (UTC)
 * You do, when you keep linking to Expanding Earth. This is not the appropriate link as that refers to a defunct theory about terrestrial tectonics that isn't applicable here.  Volcanopele (talk) 22:44, 20 March 2009 (UTC)
 * I didn't link to Carey. The peer-reviewed articles in Nature and Science say "global expansion" so I linked to expansion.Sophergeo (talk) 23:05, 20 March 2009 (UTC)
 * Er - no, you did not link to global expansion - rather you inserted a piped link to Expanding earth which is about Carey's old hypothesis. Vsmith (talk) 23:19, 20 March 2009 (UTC)
 * Encouraging POV Forks such as global expansion is a violation of NPOV (one of the three cornerstone's of Wikipedia) and against the spirit of Wikipedia.  A POV fork is an attempt to evade the neutrality policy by creating a new article about a certain subject that is already treated in an article, often to avoid or highlight negative or positive viewpoints or facts. This is generally considered unacceptable. The generally accepted policy is that all facts and major points of view on a certain subject are treated in one article.


 * If you are unfamiliar with Wikipedia policies, see the guideline Wikipedia:Content forking for clarification on the issues raised in this section.Sophergeo (talk) 23:31, 20 March 2009 (UTC)


 * Seems we have a user "cherry-picking" a quote and pasting it into an article without considering the existing text (the other paragraph). The articles he referenced would be valid sources, but the way he is using them is problematic. I would reccomend removing the quote and perhaps working the info into the existing text if it enhances the section. Vsmith (talk) 23:19, 20 March 2009 (UTC)
 * I agree it seems we have users "cherry picking" for the purpose of supressing information. A common way of introducing bias is by one-sided selection of information. Information can be cited that supports one view while some important information that opposes it is omitted or even deleted. Such an article complies with Wikipedia:Verifiability but violates NPOV.  Neutral point of view is a fundamental Wikimedia principle and a cornerstone of Wikipedia. All Wikipedia articles and other encyclopedic content must be written from a neutral point of view, representing fairly, and as far as possible without bias, all significant views that have been published by reliable sources. This is non-negotiable and expected of all articles, and of all article editors. For guidance on how to make an article conform to the neutral point of view, see the NPOV tutorial; for examples and explanations that illustrate key aspects of this policy, see Wikipedia:Neutral point of view/FAQ.Sophergeo (talk) 23:30, 20 March 2009 (UTC)
 * It does not violate NPOV to make sure that wikilinks are appropriate and provide context for the reader. Linking to Expanding Earth does not provide that context and isn't appropriate for the discussion of Ganymede tectonics.  If anything differentiation would be the most appropriate link, but the text would need to be reworded.  The papers cited are appropriate, but perhaps a better reading by of the article is needed before linking to irrelevant wiki articles.  Volcanopele (talk) 23:43, 20 March 2009 (UTC)
 * What would you have us link to instead of expansion? Encouraging POV Forks is a violation of NPOV (one of the three conerstones of Wikipedia) and against the spirit of Wikipedia. A POV fork is an attempt to evade the neutrality policy by creating a new article about a certain subject that is already treated in an article, often to avoid or highlight negative or positive viewpoints or facts. This is generally considered unacceptable. The generally accepted policy is that all facts and major points of view on a certain subject are treated in one article.  If you are unfamiliar with Wikipedia policies, see the guideline Wikipedia:Content forking for clarification on the issues raised in this section.Sophergeo (talk) 00:22, 21 March 2009 (UTC)
 * Well, at the present time there is none for explaining the Ganymede-specific process. I guess it would need to be explained in this article, rather than linking to an article that doesn't provide useful context and isn't appropriate for this purpose.  Volcanopele (talk) 01:02, 21 March 2009 (UTC)
 * Actually the explanation is called "expansion." It is verified and sourced by the reliable information provided which some editors are attempting to suppress.Sophergeo (talk) 01:40, 21 March 2009 (UTC)
 * Although there are supporters, it is WP:FRINGE and it violates conservation of mass, which makes it untenable. See also WP:PSCI. Awickert (talk) 05:33, 21 March 2009 (UTC)
 * "The ArbCom ruled that the following should generally not be characterized as pseudoscience:


 * Questionable science: "Theories which have a substantial following, such as psychoanalysis, but which some critics allege to be pseudoscience, may contain information to that effect, but generally should not be so characterized." Furthermore, your unverifiable and unsourced personal POV opinions and straw man fallacies do not justify the suppresion of verified and reliable information.  This is an encylcopedia.Sophergeo (talk) 05:50, 21 March 2009 (UTC)


 * To save on copying and pasting, and because I already replied to another version of your above comment there, I will address your comments in the future at our original debate on talk:subduction. For the meantime, please refrain from personal attacks. Please do not state that my comments are "POV opinion": besides being redundant, my opinion is my opinion, but my arguments are based on physical principles. For a convenient source, I use Geodynamics. Awickert (talk) 06:13, 21 March 2009 (UTC)
 * I am sorry if you interpreted my comments as a personal attack. My intention is to attack POVs only and the suppresion of information, not you personally.  As far as science is concerned, my focus, there is no subduction on Ganymede.


 * Martin, P., et al., Why Does Plate Tectonics Occur Only On Earth?, Physics Education, 43, Pages 144-150, 2008 "Beware the man of only one Book" -- Aquinas Sophergeo (talk) 06:38, 21 March 2009 (UTC)
 * Yes, I 100% agree. no present-day subduction on Ganymede. Thanks for your apology - my point was that it is better and more important to confront differing ideas and debate than to unilaterally say that they are no good. So when I say that I think Expanding Earth is wrong, I do so because I do not see the evidence required to believe it is occurring, or any relationship to physical constraints. It is not because it is a theory that is not taught. Awickert (talk) 06:52, 21 March 2009 (UTC)
 * Personal POVs, strong as they may be, do not justify suppression of information.Sophergeo (talk) 07:42, 21 March 2009 (UTC)
 * What I'm trying to say (here and at subduction) is that I am not presenting my ideas. I am presenting facts, and we will get nowhere if you summarily dismiss everything I say. The fact I present is that due to conservation of mass, either the expanding body is adding mass from the inside or that it is decreasing in density. This is a fundamental physical principle that can be easily sourced, look at the Wiki page for sources if you decide to not believe me. Because of this, either (a) you, the contributor, need to describe how your sources satisfy fundamental physics, or (b) the contributions that you have will be treated as fringe science until there is a viable mechanism. Awickert (talk) 09:11, 21 March 2009 (UTC)
 * I'm not dismissing everything you say. Say whatever you want; the fact that Ganymede has expanded in it's geological history does not justify suppression of verifiable and reliable information.Sophergeo (talk) 09:34, 21 March 2009 (UTC)
 * You clearly are dismissing it, as you do not address a single argument I make. One last time: will you answer a direct question about how your work does not contradict much more well-accepted work on conservation of mass? If so, I will stop being a roadblock. If your only available response is POV and information suppression, I am forced to decide between your sources and a fundamental physical principle. Your sources will not win with me or anyone else, and therefore will be considered WP:PSCI, and will not be able to have a higher standing than astrology as per "Generally considered pseudoscience". Awickert (talk) 09:43, 21 March 2009 (UTC)
 * The fact that Ganymede has expanded in it's geological past does not in any possible way violate the conservation of mass and your claim that it does is unverified, unsourced, and irrelevant as far as NPOV and information suppression are concerned. Even if it was sourced, it would not justify information suppression of other POVs or violations of the NPOV cornerstone.  As far as your pseudoscience claims are concerned, "The ArbCom ruled that the following should generally not be characterized as pseudoscience: Questionable science: 'Theories which have a substantial following, such as psychoanalysis, but which some critics allege to be pseudoscience, may contain information to that effect, but generally should not be so characterized.'"Sophergeo (talk) 10:00, 21 March 2009 (UTC)
 * We don't know that it expanded, and there are more than "some critics" against expanding planets. Tell me how it conserved mass: was material added from the interior, or did it decrease in density? And give a source. Humor me. Or leave this conversation and humor me at plate tectonics, either way. Awickert (talk) 10:11, 21 March 2009 (UTC)
 * A slight expansion of Ganymede is possible due to phase transitions in ice as is frequently mentioned in literature. I modified the added part to clarify this. However any expansion in access of a few percent is infeasible. Ruslik (talk) 10:20, 21 March 2009 (UTC)
 * I thought we had come to agreement and now you are starting another edit war? What about NPOV?Sophergeo (talk) 10:21, 21 March 2009 (UTC)
 * The source sources that you cited say about expansion of 1-6%, not more. I added information about this. I see no justification in this POV tag. Ruslik (talk) 12:22, 21 March 2009 (UTC)
 * I cited three sources so you are ignoring 66% of them. Please do not remove the POV tags until the NPOV dispute is resolved. Sometimes people have edit wars over the NPOV dispute tag, or have an extended debate about whether there is a NPOV dispute or not. In general, if you find yourself having an ongoing dispute about whether a dispute exists, there's a good chance one does, and you should therefore leave the NPOV tag up until there is a consensus that it should be removed.Sophergeo (talk) 17:40, 21 March 2009 (UTC)
 * All your sources only discuss minor expansion on the order of a few percent. I do not understand what you trying achieve by POV tag. Unless you can find a reliable source that says something different, this tag will be quickly removed. Ruslik (talk) 18:02, 21 March 2009 (UTC)
 * Why don't you want the verifiable and reliable links to be included in the article? I thought this is an encyclopedia.  An encyclopedia with rules which state, "Neutral point of view is a fundamental Wikimedia principle and a cornerstone of Wikipedia. All Wikipedia articles and other encyclopedic content must be written from a neutral point of view, representing fairly, and as far as possible without bias, all significant views that have been published by reliable sources. This is non-negotiable and expected of all articles, and of all article editors."Sophergeo (talk) 18:25, 21 March 2009 (UTC)
 * Just a guess: it could be because he did include the reliable sources, but that they don't say what you say they do. Awickert (talk) 18:34, 21 March 2009 (UTC)
 * Your characterization of Nature and Science as unreliable is unsourced and does not justify information suppression.Sophergeo (talk) 19:03, 21 March 2009 (UTC)
 * Please, stop making false statements about opinions of other editors. The sources are reliable, but you are misrepresenting them. Ruslik (talk) 19:09, 21 March 2009 (UTC)
 * I have addressed the same comments earlier, yet you continue to bring them up. Why? Please do not continue to copy/paste from one talk page (where the issue has been addressed) to another. This is unproductive and spam. Awickert (talk) 19:32, 21 March 2009 (UTC)
 * Thank you Ruslik. I think this resolves this issue as far as including information about how differentiation and phase transitions have effected Ganymede's radius and how this may result in the tectonism seen.  This would seem to resolve the NPOV problem by presenting the currently accepted theories for Ganymede's bright terrain formation.  The POV is not needed.  --Volcanopele (talk) 18:31, 21 March 2009 (UTC)

RFC notification
I have initiated a request for comment on the Expanding Earth hypothesis at Talk:Expanding Earth. Please leave a comment there, or a statement if you were involved in the debate. Thank you, Awickert (talk) 05:07, 22 March 2009 (UTC)

Organic?
Im no geologist, but this line

"The dark terrain, which comprises about one-third of the surface,[38] contains clays and organic materials that could indicate the composition of the impactors from which Jovian satellites accreted.[39]"

seems to indicate life exists or once did on Ganymede. I understand it can also refer to carbon containing compounds, but also means having properties relating to life. Perhaps a clairification is in order? 62.68.66.138 (talk) 07:12, 18 August 2009 (UTC)toolazytologin
 * Organic materials are not necessary imply life. There are most likely of non-biological origin. Ruslik_ Zero 17:38, 18 August 2009 (UTC)

Discovery Date
User:Katydidit has been repeatedly been editing the article in order to include the incorrect discovery date of January 13. I have reverted these edits twice now, and per the No 3 revert rule, I am bringing up this potential conflict in the Talk page of this article. January 13, 1610 was the date this article used for the discovery of Ganymede. However, this date is erroneous based on re-constructions of Galileo's observations and Galileo himself certainly never argued that he discovered Ganymede on a latter date than all the others. Galileo's first observation of Ganymede took place on January 7, 1610 NOT January 13, and the current version of this article reflects that. The only significance of January 13, 1610 is that is when Galileo first saw all four Galilean satellites in a single observation (when two moons weren't appearing as a single point of light, as on January 7 with Io and Europa). --Volcanopele (talk) 03:13, 13 January 2010 (UTC)

You won't even read your own sources that confirm it was Jan. 13, 1610 when Galileo FIRST SAW Ganymede, and I noted that in my change. Why not read the source where the author notes (from either of those sources) he first saw Ganymede on Jan. 13, 1610 at 16:50 (UTC), six days after? Plus, Astronomy (Jan. 2010) notes the same thing about the six days later with Galileo first seeing Ganymede. READ your own sources, please, and look at the current January issue Astronomy, p. 49! Katydidit (talk) 06:29, 13 January 2010 (UTC)

You confirmed Galileo did NOT see Ganymede on Jan. 7, because it was hidden by another 'star' (another Jovian moon), and that confirms what he says about it on Jan. 13. Therefore, Jan. 7 is *incorrect*, as you yourself noted. Katydidit (talk) 06:31, 13 January 2010 (UTC)
 * No, Ganymede was first observed on January 7, it was not hidden by any 'star' (another Jovian moon). The re-constructions by Wright (Ganymede is the white dot in those re-constructions) and by other authors such as Stillman Drake in Galileo at Work: A Scientific Biography on page 153 show that Ganymede was first observed on January 7, then seen again on January 8, 10, 11, and 12 of 1610.  On January 7, Io and Europa were seen as a single point of light; Ganymede appeared as a distinct point of light to the west of Jupiter.  January 13 was the first time Galileo distinctly observed all four Galilean satellites AT ONE TIME.  He had observed each satellite several times, those he only saw two or three at a time, or two appeared as a single point of light in his telescope.  That DOES NOT mean that he discovered Io, Europa, and Callisto on January 7 and then somehow didn't see Ganymede for several more days.  I have no idea where Astronomy magazine got their source on that.  Maybe Wikipedia... --Volcanopele (talk) 06:40, 13 January 2010 (UTC)

Martin Ratcliffe and his associate got it from the same sources you keep (incorrectly) citing for the mistaken Jan. 7 date. BTW, how come you ignored Wikipedia's own timeline that also said that about Jan. 13 and Galileo seeing and IDENTIFYING IT--until you (incorrectly) changed it to Jan. 7? Just because he *may* have seen a point of light doesn't mean he saw it as another moon. Otherwise, he would have realized it was the 4th moon right then, instead of not until Jan. 13.

In his own words below:

http://hsci.cas.ou.edu/images/barker/5990/Sidereus-Nuncius-whole.pdf (p. 38)

Jan. 7, 1610 "...three little stars, small but very bright, were near the planet;..."

Who are you going to believe now, you or Galileo's own words? Katydidit (talk) 06:51, 13 January 2010 (UTC)
 * Yes, I am using Galileo's own words, that he saw three little stars, one of which was Ganymede. Hence Ganymede's discovery date is January 7.  If you say that Ganymede's discovery date is January 13, then ALL of the Galilean moons were discovered then, apparently...  as he didn't recognize any of them as going around Jupiter on January 7  And yes, I corrected Wikipedia's timeline, which had the incorrect date.  --Volcanopele (talk) 06:57, 13 January 2010 (UTC)
 * Just in case other editors are confused here, on January 7, Galileo observed and noted in both his notes and two months later in his book Sidereus Nuncius three stars in a line with Jupiter, parallel to the ecliptic. Two stars appeared to the east of Jupiter, and one star to the west.  Based on modern calculations of the positions of Jupiter's satellites at the time of Galileo's observations (see Wright), the two stars to the east of Jupiter were Callisto and a combined Io and Europa, which were too close together for Galileo to separate with his 20 power telescope.  The star to the west of Jupiter was Ganymede.  At the time, he just thought they were background stars.  He continued to observed Jupiter and the three stars for the next few days.  Jupiter and the stars shifted positions with each observation.  First, he thought Jupiter was moving strangely, then he realized that the stars were the ones that were moving (as he observed on January 12 when they moved with respect to one another).  During this time, he saw with his lower powered telescope at maximum of three stars.  That DOES NOT mean that he only ever saw Io, Europa, and Callisto until January 13.  On January 7, he saw a combined Io and Europa as a single point of light.  On January 8, he missed Callisto because it was so far from Jupiter it was out of his field of view.  On January 10, Ganymede and Europa appeared as a single point of light and Io was lost in Jupiter's glare.  On January 11, Io and Europa were transiting Jupiter, so they were lost in the planet's glare.  On January 12, Callisto was lost in Jupiter's glare.  So again, before January 13, he had seen all four at least once, just not all at one time.  And Galileo most definitely saw Ganymede on January 7.  --Volcanopele (talk) 07:12, 13 January 2010 (UTC)
 * I also see that the date has been reverted back again. This is not in keeping with WP:3RR--Volcanopele (talk) 07:18, 13 January 2010 (UTC)

I cited a third/fourth source that confirms it *was* Jan. 13. Two writers (one a contributing editor) of Astronomy magazine in the current Jan. issue. Don't like it? That's a shame you won't listen to the two sources you cite plus an editor with Astronomy mag. Katydidit (talk) 09:00, 13 January 2010 (UTC)
 * Once again, no, you are not reading those sources. Both of my sources show that it was discovered on January 7, including a third, Galileo at Work by Stillman Drake.  Ganymede was discovered on January 7.  Again, I am afraid the editor of Astronomy is wrong on this.  Okay, let's back up... Why is January 13 considered the discovery date?  Galileo observed and noted Ganymede in his notes and in Sidereus Nuncius on four occasions before January 13.  There is no question about that.  You seem to be arguing, well he observed three stars on January 7 and only three until January 13.  But that does not mean that those three were the same three moons, as I mentioned in my reply above, they changed over the course of his observations.  So where did the discovery date for Ganymede you quote, January 13, come from.  Despite what you say, both my sources support the January 7 date, which just based on evidence backing up that statement in both Wright's website and the book by Drake.  You can quote Astronomy magazine all you want, but these other two sources use evidence to back that up.--Volcanopele (talk) 09:14, 13 January 2010 (UTC)

If what you say is true, than what is the other moon of Jupiter Galileo did *not* see initially on Jan. 7? Did Galileo do the naming of the first 4 moons himself, or was that done shortly afterwards by another astronomer? I quoted your two sources using the words in the sources you cited. Neither of them mention the exact names of the 3 (with two of them so close together he thought it was one moon that was the 4th?) moons Galileo first saw on Jan. 7 *or* later on the 13th. As the sources note, he never saw all 4 until Jan. 13th. Therefore, he only saw 3 previously because his tiny 2" telescope wasn't large enough to resolve the two 'stars' together he saw that were two moons looking fused together to him as only one. Is that true, or not?  Katydidit (talk) 09:24, 13 January 2010 (UTC)

The other source you cited (http://www2.jpl.nasa.gov/galileo/ganymede/discovery.html) says the same thing, but never identified which 3 moons he saw previously, so you can't say it was specifically Ganymede on Jan. 7, "On January 13, a fourth star appeared." Katydidit (talk) 09:28, 13 January 2010 (UTC)
 * On January 7, he observed Io and Europa as a single point of light because his telescope could not distinguish the two. He definitely saw both on January 8 as separate points of light as well as Ganymede, with Callisto being the odd moon out (it was at its eastern elongation point, so it was out of the field of view of Galileo's telescope)  Simon Marius named the moons well after he realized there were four. Galileo did the same (I, II, III, and IV) once he figured out their orbital periods.  By the publication of Sidereus Nuncius, he hadn't figured out which moon was which in his observations.  He had noted that the outer satellite had a period of about half a month by early March 1610 (see the conclusion of Sidereus Nuncius).  On Wright's site, he uses colors to denote the moons.  The white dot is Ganymede.  Orange is Io, Blue is Europa, and Pink is Callisto.  He did see only three, but the identities of those three changed from day to day, as I noted above (I can see now that part of the confusion here is not seeing the key for Wright's illustrations which are located on the page before it, I apologize for not making that clearer).--Volcanopele (talk) 09:35, 13 January 2010 (UTC)
 * And I hope I haven't angered you too much with this (I am definitely nominating this for the Lame Edit Wars page). To be honest, while I think the evidence does bear out that January 7 is the date Ganymede was first observed by Galileo, there is some confusion in the sources I've found via Google.  Did Wikipedia use January 13 because that's what the sources said, or do the sources say January 13 because that's what Wikipedia said?  The NASA page for Ganymede says January 7.  I've found others that say January 11.  --Volcanopele (talk) 09:51, 13 January 2010 (UTC)

I was going to add that Jan. 11 date you cited with nasa's web detail on Ganymede. What are you going to do *now* about the correct date to put on Ganymede's page? Kinda calls into question the whole Jan. 7 date where supposedly he saw all 4 moons with his tiny 2" diameter 'scope, but the evidence indicates he did NOT, until at least Jan. 11; if not the 13th. You going to write them, and *demand* NASA change it to Jan. 7, too? ( http://www2.jpl.nasa.gov/galileo/ganymede/fact.html#stats ) "Discovery: Jan 11, 1610 by Galileo Galilei" Katydidit (talk) 10:04, 13 January 2010 (UTC)

PS: NASA mentions Jupiter has only 16 moons here: http://www2.jpl.nasa.gov/galileo/jupiter/jupiter.html and again here: http://www2.jpl.nasa.gov/galileo/Jovian.html#king although Wikipedia lists a few more--63 moons for Jupiter here, with details [edit: NOT dates here] found: http://en.wikipedia.org/wiki/Jupiter%27s_moons

Who(m) do you trust now? Katydidit (talk) 10:12, 13 January 2010 (UTC)
 * LOL, I will not tell them that their 10 year old page from the Galileo mission is wrong, since their current page for Ganymede is right ;) It doesn't call into question, but it does point out an issue that seems to have occurred before, what dates one should cite for the discovery of the Galilean satellites.  What this just shows is that one can apparently find sources that say a specific date to support January 7, January 11, or January 13.  So to distinguish between these conflicting sources, we have to look at the evidence, what moons did Galileo observe during his observations in January 1610?  When did he first see Io, Europa, Ganymede, and Callisto?  Based on the Wright website and Drake's book, Ganymede was definitely first seen on January 7; it was the only moon to the west of Jupiter as noted by Galileo.  That maybe the only clear cut one...  Drake and Wright differ in their identifications for the other two stars. Drake says that the two stars to the east of Jupiter were Io and Europa, rather than the two being seen as a single star, and that Galileo missed Callisto.  Wright says that Galileo saw Io and Europa as a single star, and saw Callisto furthest to the east.  On January 8, Drake and Wright both agree that Galileo missed Callisto far to the east, and saw Io, Europa, and Ganymede (another pre-January 11 and January 13 observation of Ganymede) to the west of Jupiter.

As far as the number of moons... 63, that NASA page dates from the early part of the Galileo orbital tour of Jupiter (1996 or so), before the vast majority of Jupiter's outer moons were discovered. --Volcanopele (talk) 10:16, 13 January 2010 (UTC)

Dates listed here: http://en.wikipedia.org/wiki/Timeline_of_discovery_of_Solar_System_planets_and_their_moons Katydidit (talk) 10:21, 13 January 2010 (UTC)
 * Exactly, most of the outer moons were discovered since 1999 (mostly the much smaller, harder to see kind). Thanks for listing another page on Wikipedia that needs to be corrected...  again, WHY is there is such a conflict in dates?  Was there some older analysis of which moons Galileo saw and when?  I am still curious where the origin of "Ganymede was discovered on January 13" came from?  --Volcanopele (talk) 10:33, 13 January 2010 (UTC) (It is 3:34 am here, so I think I am going to have to call it a day)

I am still curious how you (or anyone else, for that matter) can tell for sure Galileo actually saw Ganymede on Jan. 7, when there is no ID on the diagrams or text in your two sources on which ones he actually saw, and when. There are no labels on those Jupiter-moons diagrams showing the names of them and which-is-which and how they changed over those days from Jan. 7-13. If you can't do that to 100% precision and the logic on how it can be accurately done, then there is no choice but to at least accept this compromise: allow the date of discovery of Ganymede (or one other moon of your logic/choosing) to be shown as "January 7-13" instead of only specifically as January 7 for all four. The only thing that seems to be 100% certain on what we know what Galileo saw, was he saw all four sometime in early-mid January 1610; between the 7th and 13th. That is my view on it from the sources you cite, plus the Martin Ratcliffe and Alister Ling in Astronomy (Jan. 2010), p. 49, quote: "The great Italian scientist spotted Io, Europa, and Callisto January 7, 1610, and Ganymede 6 days later." If you can somehow torture the data only from your two sources to logically have it appear specifically that all four were somehow seen by Mr. G. only on January 7, despite the quote from him on January 7, "...three bright stars," (from Sidereus-Nuncius), I'd like to see how you can do that. You can't go by what another book's authors say in your sources when it is not apparent to the looker-upper on your two sources there are no actual IDs given of the moons; and how did Drake/Wright agree (or know?) Ganymede was the only 'star' west of Jupiter at that time so Galileo had to see it on the 7th? Drake and Wright can't even agree on the whole deal on when Mr. G. saw what-and-where, so if you by some miracle do it, you deserve a medal--to say the least. Katydidit (talk) 12:18, 13 January 2010 (UTC)


 * The Wright web page: lables the moos via color (the key is given here: ), Io orange, Europa turquoise, Ganymede white and Callisto pink. The Drake book, p. 153:  labels the moons: Io I, Europa II, Ganymede III, and Callisto IV. Both sources label the  point of light that Galileo drew to the right (West) of Jupiter on the January 7th diagram as Ganymede. Paul August &#9742; 15:52, 13 January 2010 (UTC)

It would appear to me that the above is good evidence for a precovery observation of Ganymede on January 7. I do not see a reliable source stating that this was a discovery of Ganymede on that date. Observations that are not identified as being of a new object, but are later realized to have been prior observations of one are not considered to constitute a discovery. This is why Comet Shoemaker-Levy 9 is named after the Shoemakers and Levy rather than being named after Kin Endate, S. Otomo, or Eleanor Helin, all of whom had taken earlier photographs that, after the announcement of the discovery, they examined and realized included the comet.--Noren (talk) 20:05, 13 January 2010 (UTC)
 * Yes, but you could make the same argument for ALL the Galilean satellites, since Galileo didn't identify the individual moons in his own observations. He says he observed three stars on January 7.  He noted that they were in a line with Jupiter.  He noted all three 'stars' the same way (though those three have been found to be all four moons, with one being Io and Europa in a close conjunction).  He didn't say that two were moons of Jupiter, and he didn't know where the one to the west came from.  I'm not sure how you can call this a precovery observation.  I already pointed to the current NASA page for Ganymede, and the IAU considers the discovery date for Ganymede to be January 7.  --Volcanopele (talk) 20:14, 13 January 2010 (UTC)
 * Where is the IAU opinion documented? Paul August &#9742; 21:25, 13 January 2010 (UTC)
 * here --Volcanopele (talk) 21:27, 13 January 2010 (UTC)


 * You realize that implies Io and Europa should then be dated January 8, instead of January 7 as with Ganymede and Callisto.
 * You can't have it both ways in saying all four should still be dated January 7 now, when your appeal to the IAU authority shows something you insist didn't occur. I'll expect a change to Io and Europa's discovery dates (from you?) on their respective Wiki pages with the IAU as the new/additional reference. Katydidit (talk) 23:24, 13 January 2010 (UTC)
 * I won't do it, call me sentimental, but I would not object to other editors doing that. I disagree with them on their conclusion, but I agree, it would be NPOV for me to object to the dates for Io and Europa to be changed.  --Volcanopele (talk) 23:40, 13 January 2010 (UTC)
 * Okay, I've edited the Io article to reflect the date the IAU cites. --Volcanopele (talk) 23:48, 13 January 2010 (UTC)

Well it makes some sense. Obviously Callisto (16 day orbital peroid) and Ganymede (7 days) move the slowest given that they orbit furthest from Jupiter. So Galileo had an easier time tracking them night to night. Io (1.7 days) and Europs (3.5 days) both whip around Jupiter very fast. Even with a small (modern) telescope, it is easy to see how much both Io and Europa move in a single hour. I think the IAU's solution may make as much sense as any. Besides, given how far Callisto orbits from Jupiter, it is quite likely that some acute visioned observers had seen Callisto (and/or Ganymede) long before Galileo ever did. -- Kheider (talk) 07:18, 14 January 2010 (UTC)

File:Ganymede g1 true.jpg
Question. File:Ganymede g1 true.jpg is different from commons:File:Ganymede g1 true.jpg. Most other Wikipedias are using the image on Commons. Is it better to use the one here on Wikipedia, or should that be uploaded to Commons under a different name, or perhaps even simply deleted and the Commons version used instead? Angus McLellan (Talk) 22:51, 24 September 2010 (UTC)
 * It looks to me like someone fiddled with the colors on the commons version. If you look at its history, it originally looked like the local copy. --Patteroast (talk) 07:52, 25 September 2010 (UTC)

Relevance
A reference I added was removed because it didn't seem to have any relevance. The article, named Saturn's moon Rhea has thin atmosphere, says "Oxygen exospheres have been seen at Jupiter's moons Europa and Ganymede, but this is the first time such a detection has been made in the Saturnian system." We already knew Ganymede had a thin atmosphere, but an atmosphere can be divided into different layers; troposphere, stratosphere, mesosphere, thermosphere and exosphere. It appears like these moons have only a exosphere, which the article seem to confirm. All I did was adding a reference to it. But, if one think that the article can be trusted without it, then there is no reason to add any links. 84.210.60.115 (talk) 16:55, 2 February 2011 (UTC)
 * That Ganymede has only an exosphere was known since 1980. The article already contains all necessary references, it only does not use the word 'exosphere'. Ruslik_ Zero 17:16, 2 February 2011 (UTC)ym

Robert A. Heinlein and others
Scifi author/legend Robert Heinlein wrote several books with characters who were from colonies on Ganymede. I wonder if this might be relevant to the article? Canine virtuoso (talk) 20:41, 13 January 2012 (UTC)
 * No. His book (Farmer in the Sky)is very entertaining and well-written (he was the "Dean" of sci-fi, after all) but it has no bearing on reality. You can't terra-form Ganymede and with the dangerous radiation of Jupiter's inner moons it would be extremely hazardous to go there and just walk around on the surface. And as for finding ancient alien artifacts there, well . . .   HammerFilmFan (talk) 00:33, 28 February 2015 (UTC)

Largest moon
It appears that the claims in this article and the article on Titan(moon) are conflicting in that they both claim the respective moon to be the largest in the solar system. As I am not an astronomer, I don't know which is actually true, but clearly one of them is not correct.83.111.108.83 (talk) 06:38, 10 December 2013 (UTC)
 * Excuse my dyslexia, Titan is claimed to be the largest moon of Saturn. Never mind. Have a nice day :) 83.111.108.83 (talk) 06:40, 10 December 2013 (UTC)

Ganymede vs Moon gravity
It says the gravity of the moon is more than Ganymede's gravity which is right,but how come Ganymede has greater escape velocity than the moon,how is this? — Preceding unsigned comment added by Alhadialika (talk • contribs) 00:01, 22 February 2014 (UTC)


 * The Moon is denser, so it has a steeper gravitational well, hence more surface gravity, but Ganymede is more massive, so it has a deeper and wider gravitational well, hence the higher escape velocity. Tbayboy (talk) 05:28, 22 February 2014 (UTC)

Ganymede visible by naked eye?
The sentence below does not seem right, even if referenced. Gallileo needed a telescope to see Ganymede, yet the Chinese saw it with naked eyes? Trivia? Fringe? I rendered it invisible but did not delete it without your input: "According to Chinese astronomical records, in 365 BC, Gan De discovered a moon of Jupiter with the naked eye, probably Ganymede. (Astronomical content of American Plains Indian winter counts),(Ancient Astronomy in Modern China)." Thanks, -BatteryIncluded (talk) 19:50, 2 May 2014 (UTC)


 * They also said that Peking was apparently able to replicate the results, thought how you could see anything through the air of Beijing I don't know. But lots of objects discovered with telescopes are visible to the naked eye under optimal conditions:  Vesta, Uranus, etc.  — kwami (talk) 00:06, 3 May 2014 (UTC)
 * Both Callisto and Ganymede are visible to the naked eye (for someone with excellent vision) if you block the glare of Jupiter behind something. -- Kheider (talk) 00:14, 3 May 2014 (UTC)

To do

 * Convert remaining references to Citation Style 1 templates.
 * Fix 'coauthors' parameters.
 * Add missing authors.
 * Fix works and publishers.
 * Add archive URLs where available.
 * Add format=PDF.
 * Fix duplication errors created by citation bot.
 * Combine duplicate references. -- 79.67.241.235 (talk) 13:15, 3 May 2014 (UTC)


 * Once again, thank you for cleaning all the references. It is the core of Wikipedia. --BatteryIncluded (talk) 18:08, 3 May 2014 (UTC)


 * Thanks. More recruits are needed though. There are a very large number of articles needing work - both filling in additional details and fixing errors. -- 79.67.241.235 (talk) 19:40, 3 May 2014 (UTC)

Images in this article are magnificent
Someone really did a good job with some of the artistic representations and diagrams. This could really be a feature article. Cliffswallow-vaulting (talk) 08:23, 3 August 2014 (UTC)

One Image from this article just won "Featured Image of the Day" for all of Wikimedia Commons!
The cut-away diagram of Ganymede (showing it's internal ocean and other layers) won "Feature Image" today on all of Wikimedia Commons. Congratulations! Cliffswallow-vaulting (talk) 08:19, 3 August 2014 (UTC)

Underground water in Ganymede moon
Hubble telescope has the found the best evidence for underground salty ocean in the Jupiter's largest moon. The subterranean ocean has more water than all the Earth's surface. read more here:

http://phys.org/news/2015-03-hubble-underground-ocean-jupiter-largest.html

MansourJE 06:46, 13 March 2015 (UTC)
 * You mean Jupiter's moon. HammerFilmFan (talk) 20:09, 20 March 2015 (UTC)

Infobox image
The current infobox image has the left edge of Ganymede cut-off/not photographed. This means that Ganymede's disc would continue beyond the image and outside the infobox, which gives it a weird kind of overly cropped look. This is my main problem with it. Aside from that, it is of rather low resolution. I tried to replace it, but was reverted because 'an actual photo is better than a computer-generated image'. Everything being equal, I would agree. However, the problem with this photograph makes it, in my opinion, unworthy of the infobox. --JorisvS (talk) 07:16, 5 April 2015 (UTC)
 * Would you prefer File:Ganymede, moon of Jupiter, NASA.jpg (from PIA01299) over the current image? (It's the same image, "enhanced" a bit to make it higher contrast although somewhat less life-like, rotated a little and with the cropping on the left artificially masked) WolfmanSF (talk) 07:46, 5 April 2015 (UTC)
 * Although that has that unnatural bland gray there and looks like an ellipse, not an image of a partly lit imperfect sphere (cf. File:Mercury in color - Prockter07 centered.jpg), I think that would be less conspicuous in the infobox. --JorisvS (talk) 10:34, 5 April 2015 (UTC)
 * There are actually three versions of the photo available (the other is File:Ganymede g1 true.jpg (from PIA00716). I would be happy to go with the PIA01299 version. Does anyone else have strong preferences one way or another about the infobox image?  For reference, the images are reproduced below. WolfmanSF (talk) 20:04, 5 April 2015 (UTC)

Merge discussion at Talk:Life on Ganymede
There is an ongoing discussion at Talk:Life on Ganymede about whether to merge Life on Ganymede into Ganymede (moon). Any reasoned comments would be helpful. A2soup (talk) 15:20, 16 August 2015 (UTC)

Surface area
The article states that the surface area of Ganymede is 87.0 million km2. This is not possible, unfortunately I don't know the correct figure. — Preceding unsigned comment added by 2600:8805:5A00:22CC:8827:5E42:E6AD:7DFF (talk) 21:35, 22 April 2016 (UTC)
 * Just calculate the surface of a sphere: 4*pi*r^2. This gives 87.2 million km2, so yeah, it is possible. --JorisvS (talk) 22:37, 22 April 2016 (UTC)

External links modified
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Comparisons in first paragraph
Currently, the first paragraph presents a jumble of comparisons and statistics to express Ganymede's size. These comparisons do not have a logical order, are partially redundant, and state the same thing in several different ways. As it stands now, the paragraph presents the following facts about Ganymede's size, in the following order:


 * 1) it is the largest moon of Jupiter
 * 2) it is the largest moon in the solar system
 * 3) its diameter is 8% greater than Mercury's
 * 4) its mass is 45% of Mercury's (note % used differently than in 3)
 * 5) its diameter is 2% greater than Titan's
 * 6) its mass is 2.02 times greater than Earth's Moon's
 * 7) it is the most massive planetary satellite
 * 8) it is the ninth largest object in the solar system
 * 9) it is the largest object in the solar system without an atmosphere

Also note that information not about its size is interspersed among these facts. I think it is clear some streamlining and organization is needed here. I would suggest the following facts in the following order (note that each fact would not be a separate sentence - as is already the case, they would be in the same sentence when logical):


 * 1) it is the largest moon of Jupiter
 * 2) it is the largest moon in the solar system
 * 3) it is the most massive moon in the solar system
 * 4) its diameter is 2% greater than Titan's
 * 5) it is 10% more massive than Titan (comparisons to Mercury diameter and mass might be better here, but in that case Titan should not be included for concision)
 * 6) it is the ninth largest object in the solar system
 * 7) it is the largest object in the solar system without an atmosphere

Do people agree that a reorganization is needed? Have any better suggestions? I don't think this is the most controversial change, so I plan on making it pretty soon. Pinging. A2soup (talk) 18:37, 25 January 2017 (UTC)
 * I tried reorganizing it, but a bit differently that you suggested. I think it's a good idea to stress its unique properties by putting them first. I also think the comparison to Mercury is apt, because the idea of a moon being larger than a planet is counterintuitive. WolfmanSF (talk) 22:25, 25 January 2017 (UTC)
 * I changed it around some more. I like your mention of its unique properties, but think they should go after some more comprehensible facts so as not to disorient the non-scientific reader. I removed size comparisons to anything besides Mercury - I think making comparisons to multiple celestial bodies is too busy and too much detail on a single point for the very first paragraph. IMO, comparisons beyond the one to Mercury (which is really acting as "fun fact" or "hook" to draw the reader in) should go in the Ganymede (moon) section, which actually needs expanding. A2soup (talk) 16:02, 26 January 2017 (UTC)
 * I further condensed it. It is the tenth largest object in the solar system if you count the sun, so I removed that fact as it seems less significant. I also removed the other fact about lacking an atmosphere as all but one moon lacks an atmosphere. 24 April 2019‎
 * No, it is the 9th largest including the Sun, and your second action is also not justified. WolfmanSF (talk) 03:13, 24 April 2019 (UTC)
 * True, but the second sentence is still badly worded and lacks a citation. Is the asteroid belt an "object" that Ganymede is larger than? What designates a "significant atmosphere"? Nuclearrrabit (talk) 14:42, 24 April 2019 (UTC)
 * The rules for English sentence construction may be more flexible than you realize. Also, not every statement requires a citation. Try to exercise a degree of common sense. WolfmanSF (talk) 17:07, 24 April 2019 (UTC)
 * See Exosphere for perspective on the atmosphere issue. WolfmanSF (talk) 17:31, 24 April 2019 (UTC)

Here are the surface atmospheric pressures of the members of the 9 largest Solar System objects that have a surface, ranked by pressure:

Clearly, there is a major divide between Mars and Ganymede. WolfmanSF (talk) 23:11, 24 April 2019 (UTC)

Ganymede Lander/Laplas-P mission
Hello,

I'm about to finish the translation-adaptation of this article on the French Wikipedia. However, I don't understand what's the real name of the planned Russian mission. This article says it's Ganymede Lander (GL) while the last known source talks about Laplas-P.

I'm very confused. Are we even sure it's the same mission? Do we have to change its name in this article ? — Foldo (talk) 18:24, 16 February 2017 (UTC) — Preceding unsigned comment added by Feldo (talk • contribs)
 * Both Ganymede Lander and Laplace-P seem to be two differnt neames for the same mission, from what I can tell. There only seems to be one seriously proposed Ganymede lander mission from my search, and that is Laplace-P Caelus5 (talk) 01:36, 24 February 2017 (UTC)

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 * Added archive https://web.archive.org/web/20080227015923/http://lasp.colorado.edu/icymoons/europaclass/Zahnle_etal_1998.pdf to http://lasp.colorado.edu/icymoons/europaclass/Zahnle_etal_1998.pdf
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Superior conjunctions of Io, Europa and Ganymede; periapsis and apoapsis; the animation
There appears to me to be an inconsistency between:
 * the statement: "The superior conjunction between Io and Europa always occurs when Io is at periapsis and Europa at apoapsis. The superior conjunction between Europa and Ganymede occurs when Europa is at periapsis."
 * the animation of the motions of the moons which shows Europa in superior conjunction with Ganymede at a moment when it is also in superior conjunction with Io.

If Europa is simultaneously in superior conjunction with (by which I understand: is on the opposite side of Jupiter with respect to) both Io and Ganymede then it must (if the statement is true) be both at apoapsis and at periapsis, which is impossible. So either I am misunderstanding something or there is something wrong with either the statement or the animation. There is a reference for the statement. If someone has access to the referenced book then they could check that the statement is in fact supported by the reference. The animation is consistent with the illustration (2T) of Io–Europa–Ganymede resonance used on the Orbital resonance page; but are the illustration and the animation accurate as to phase in their depictions of the motions of the three moons?

If it turns out that the animation needs correcting then which is also used on the Orbital resonance page also needs to be corrected.

Jdthood (talk) 12:17, 9 December 2018 (UTC)


 * The statements in the article were not taken directly from the source and were misleading. The correct description is that Io and Europa are aligned on the same side of Jupiter when Io is at periapsis and Europa at apoapsis, while Europa and Ganymede are aligned on the same side of Jupiter when Europa is at periapsis. Thanks for pointing out the problem. WolfmanSF (talk) 00:05, 10 December 2018 (UTC)

"third" ?
"It is the third of the Galilean moons..." In what sense is it the third? Whatever sense it is, we need to say so. IceDragon64 (talk) 23:25, 20 January 2019 (UTC)
 * This has been clarified, although it would have been obvious to nearly everyone. WolfmanSF (talk) 00:33, 21 January 2019 (UTC)