Talk:Europa (moon)

From Wikipedia, the free encyclopedia

Europa (moon) was a good article candidate, but did not meet the good article criteria at the time. Once the objections listed below are addressed, the article can be renominated. You may also seek a review of the decision if you feel there was a mistake. Date of review: 28 September 2006

WikiProject Echo has identified Europa (moon) as a foreign language featured article. You may be able to improve this article with information from the Portuguese or Russian language Wikipedias.

Featured on Template:March 2 selected anniversaries (may be in HTML comment)

---

	To-do list for Europa (moon):	edit  · history  · watch  · refresh
Here are some tasks you can do: Add more inline references to the sources you have used (i.e., use the <ref name="name"> notation. This helps readers looking for more information find the specific source that might help them the most. A copyedit for grammar and clarity. Expand and cite the Possible life section

Contents 1 Continent Europe naming 2 Ice thickness and composition 3 Axial tilt 4 Data for Europa 5 Naming (and Etymology) of the Galilean satellites 5.1 Galilean moon names 5.2 Fact garble in Etymology section 6 geysers 7 Pronunciation 8 Orbital inclination to the ecliptic = 25,04 degrees? 9 Atmosphere 10 Additions + let's make an FA 11 Units of Eccentricity 12 Description of Age 13 life on Europa 14 Greenberg 15 Terrestrial Microorganisms Could Survive the Trip? 16 GA review 17 GA re-review 18 source for the etymology 19 Failed GA 20 Possible life on europa 21 Not Epsom 22 Eccentricity 23 Is something missing?

[edit] Continent Europe naming

The continent 'Europe' was named after the word 'Ereb'. 'Ereb' means 'land of sun set' in ancient greek/latin.

Where does that come from? I thought the name of the continent had a mythological origin. Also, "ereb" isn't what you'd expect for either a Latin or a Greek word. --kwami 00:26, 11 Apr 2005 (UTC)

---

[edit] Ice thickness and composition

This article states:

 "It has an outer layer of water ice thought to be around 100 km 
 thick

then later says:

 "...based on this and on the calculated amount of heat generated 
 by Europa's tides it is predicted that the outer crust of solid 
 ice is approximately 10-30 km thick, which could mean that the 
 liquid ocean may be as much as 90 km deep underneath."

Am I correct in assuming that the first number refers to the thickness of the water AND the ice, combined? Not just the "water ice"?

I'm fairly certain that the first statement is referring to water ice as opposed to other ices, somewhat common in the outer solar system. But yes, it would include the liquid water as well. --Patteroast 22:02, 17 Apr 2004 (UTC)

I doubt that, because i presume: 1. the surface is water ice, 2. the interior becoming warmer inwards, which means that more volatile ices are melted earlier than the water ice, and being lighter will ascend towards the surface. I think, iff the numbers 100 and 90 are correct, that 100 refers to the layer of H₂O, 90 to the subpart of H₂O that is liquid, and therefore, implicitly, that the solid H₂O layer is 10 km. Those figures seems to me to still be pretty accurate, although i think i remember that arguments exist that the water ice layer must be thinner than that. Rursus 13:00, 7 February 2007 (UTC)

NASA states that Europa's oceans may be up to 50 km deep at the deepest point. What's the citation for the 20 - 30 km deep?

NASA who? Anderson et al. (Europa's Differentiated Internal Structure: Inferences from Four Galileo Encounters, Science 281, 2019-2022) find the H₂O layer is ~80-170 km thick based on Galileo gravity data (the whole water + ice layer, not just the ice layer), and nominally about 100 km thick. Subtract your favorite ice shell thickness, and you get the liquid ocean thickness.

[edit] Axial tilt

I noticed that this page does not have a value for Europa's Axial tilt...Does anyone know this value?

Unknown, but predicted to be very small, (9.65±0.69)×10⁻²: Bills, B.G., Free and forced obliquities of the Galilean satellites of Jupiter, Icarus 175 (2005) 233–247.

[edit] Data for Europa

I removed the paragraph below because it reiterates the article, or is trivially calculated from data in the table. None of the other Galilean moons have a similar paragraph.

Data for Europa:

• Surface Gravity (Earth = 1): 0.135
• Orbit Speed: 13.74 km/s
• Escape velocity: 2.02 km/s
• Surface Composition: Water Ice

—Herbee 16:45, 15 Jun 2004 (UTC)

In case you were curious why that was there, originally most of the planets and moons had a list of facts similar to this before the Wikiproject to give them all a uniform table started. I guess this just got missed during cleanup. :) Bryan 00:55, 16 Jun 2004 (UTC)

[edit] Naming (and Etymology) of the Galilean satellites

[edit] Galilean moon names

 "Although the name "Europa" was suggested by Simon Marius soon
  after its discovery, this name and the names of the other Galilean
  satellites curiously fell into disfavor for a considerable time..."

I've heard speculations that Marius invented the names just to annoy Galileo. These names probably weren't considered appropriate as they were named after the lovers of Zeus -- especially with the case of Ganymede, who was male. --Jyril 23:07, Feb 27, 2005 (UTC)

Ganymede was a godified servant of the olympian gods, not anything else! Basta!! Those rumors don't respect myth. Rursus 13:22, 7 February 2007 (UTC)

[edit] Fact garble in Etymology section

Before doing anything about the text:

1. I claim that Jupiter I, II, a.s.o. numbering refers not to the from-in-to-out order of the satellites, but to the discovery order, and in cases of simultaneous order, to an arbitrary but static order kept by the astronomer collective (a so called convention). This means that explaining the introduction of the modern person names, to be caused from confusion created by new discoveries, is an erroneous discourse (fact garble).
2. I claim that the numbering is still used for some unexplicable reason (maybe redundancy as per linguistics??, or as a discovery order mark), such as for example in "Astronomy - structure of the Universe", Roy & Clarke, ISBN 0-85274-082-4, page 112.

Now, my trouble is this: i wish to change, which necessitates deleting the above mentioned explanation, but i wish to replace it with a reasonable explanation of why the Io/Europa/Ganymedes/Callisto tetrad is used nowadays? So my question is:

WHY??! did the convention change from Jupiter II to Europa??

Said Rursus 13:22, 7 February 2007 (UTC)

[edit] geysers

shouldn't the geysers be mentioned? kwami 12:30, 2005 May 6 (UTC)

I don't think there are geysers on Europa. You may be thinking of Enceladus or Triton. The Singing Badger 19:16, 10 May 2005 (UTC)

Yup, eruptions off the limb of Europa were imaged by Voyager, and recognized some weeks after the flyby. Not as numerous as the Ionian eruptions, of course. I don't recall anything similar from the Galileo mission. kwami 10:14, 2005 May 30 (UTC)

Could you verify that claim? As far as I know, geysers on Europa are still hypothetical. Galileo orbiter tried to detect them, but was unable to find any. Galileo images show very smooth plains between the cracks suggesting that there may have been active cryovolcanism recently. But no active geysers/cryovolcanos have been detected.--Jyril 13:47, May 30, 2005 (UTC)

I've been unable to find anything online. I remember the interpretation of the plumes on Europa's limb was rather speculative. Perhaps it turned out to be something else, which wasn't news, so there was no followup to the story? I'll keep looking, or try writing someone at JPL. kwami 17:21, 2005 May 30 (UTC)

Heard back from the NSSDC:

It is believed that the "plume" seen on Europa was actually an artifact of the Voyager vidicon system. A search for plumes using Galileo found none, so the question of geysers on Europa is still open. —kwami 03:45, 2005 Jun 17 (UTC)

Correct. See section 5.2 of: Pappalardo, R.T., et al., Does Europa have a subsurface ocean? Evaluation of the geological evidence, J. Geophys. Res. 104, 24015-24055, 1999.

[edit] Pronunciation

Instead of the pseudo-phonetic transcription, I replaced it with what seems to me as a reasonable phonemic transcription and a a sound file of my own Americanized English. I've intentionally avoided using any special IPA characters for stress and vowel length since they have a tendency to look very odd in some browsers. Change this if you want, but try to at least keep it phonemic, or we might get more disputes over which is to be conidered correct. Don't take the sound file as an excuse to start bickering over the merits of various varieties of English. It's not supposed to be canon, and anyone listening to the sound file will at once know how to pronounce it in their own dialect/accent.

Peter ^Isotalo 13:13, May 29, 2005 (UTC)

We have the same cross-dialectical spelling pronunciation for all of the moons of the solar system and most of the first thousand asteroids. Add the IPA if you like, but don't delete the other. kwami 19:36, 2005 May 29 (UTC)

Oh, for crying out loud... Did you even notice that it wasn't accepted too well by non-native speakers? I was trying to avoid that.

Peter ^Isotalo 09:41, Jun 5, 2005 (UTC)

If you put in an IPA pronunciation, people start complaining about dialect chauvinism. (Maybe not a problem with Europa, but certainly a problem elsewhere.) Plus, half the English-speaking world doesn't have a clue what the IPA even is, let alone are able to use it. Rather than learn, they'll just ignore it. If it's useless for half the population, and contested by the other half, why should we try to make it the sole representation of English pronunciation? If you can figure out a way to transcribe into the IPA so that it represents all major English dialects, that would still only address half the problem. (I'm missing too many low vowels to attempt it.) Ideally we would have both. kwami 09:59, 2005 Jun 5 (UTC)

Pseudo-phonetic orthographic transcription seems like something people could fight about for ages as far as I can tell. At least IPA is as close to a neutral standard as one can get, and it is certainly not something exclusisve to English speakers. Now, if you actually take some time and read the transcription you'll notice that I deliberatly made it phonemic instead of phonetic. In other words, it's perfectly dialect-neutral.

Peter ^Isotalo 22:56, Jun 6, 2005 (UTC)

Yes, but it's only dialect-neutral for Europa. Your approach won't work for all the moons, because English dialects differ in their phonemic inventories, unless you specify that there is not a one-to-one correspondance between sound and symbol. Then people will argue with you about that, claiming that the IPA is supposed to be one-to-one.

We've also had very few problems with the spelling pronuciations. (A couple people didn't like the digraphs ah and oh, so we changed them to aa and oe, but that's it.) I don't see any problem with having both. At least now you have something to work with, which wasn't the case when I started. Oh, by the way, the spelling pronunciation is also phonemic, not phonetic (pseudo or otherwise). kwami 23:37, 2005 Jun 6 (UTC)

Couldn't keep my fingers away: let's spell [ju:rəʊpə] in Swedish: Joreupö, or German: Juröupö, or French: Yujeu-ou-peu? Twirling his moustaches, does: Rursus 16:29, 9 February 2007 (UTC)

P.S. The adjectival form Europan is fairly common in the literature. kwami 02:31, 2005 Jun 24 (UTC)

[edit] Orbital inclination to the ecliptic = 25,04 degrees?

Europa's orbital plane is practically the same as Jupiter's equatorial plane which is tilted only 3 degrees with respect to its orbital plane, which itself has an inclination of only a little more than one degree; so the tilt of Europa's orbit as referred to the ecliptic plane should never exceed a few degrees, as it is the case for the other three Galilean satellites as well. The figure of 25 degrees may be the tilt of Europa's orbit with respect to the celestial equatorial plane and not to the ecliptic, anyway, I suspect none of these needs to be mentioned under the "orbital characteristics" label. Just the inclination to Jupiter's equator is fine, and the celestial coordinates of Europa's north pole may be added if necessary. Allison Connors 29 June 2005 19:07 (UTC)

Well spotted. The mistake had spread, and is now fixed. Thanks!

Urhixidur 2005 June 30 03:06 (UTC)

[edit] Atmosphere

A far as I know, the "recent observations" using the Hubble Space Telescope that revealed a tenuous oxygen atmosphere were made in 1994 and the results published in 1995 (just google 'hubble europa oxygen'), so this is old news. I'm modifying that part. --201.236.39.22 01:54, 18 December 2005 (UTC)

[edit] Additions + let's make an FA

I have expanded the beginning of this page and created two small sections on etymology and orbital characteristics. There is some redundancy between the table and the body now but I think this is acceptable, given that many will simply sit down to read a page and not pick through charts and tables and what not.

Also, while I assume there's some attempt to standardize the natural satellite pages, I'm thinking Venus offers a good template for what we might do here and I have arranged the sections to this end. It's our only planet or satellite Featured Article at the moment and I see no reason why Europa can't be our second. Marskell 09:51, 3 February 2006 (UTC)

[edit] Units of Eccentricity

Eccentricity is a dimensionless number; surely expressing it in degrees is incorrect?

83.67.5.25 17:44, 2 March 2006 (UTC)

Definitely incorrect. Degrees make no sense here.--Jyril 18:17, 2 March 2006 (UTC)

[edit] Description of Age

This content in the "Surface" section doesn't make sense to me. "...the surface is about 60 million years old (plus or minus a factor of 3)." Does it mean from 20 to 180? Or 57 to 63, or what? Factors usually involve multiplication/division - not plus/minus. Peter 01:58, 31 March 2006 (UTC)

Usually, yes, but in this case, no. The intent is 20 - 180 Myr. See the work of:

Zahnle, K., L. Dones, and H. F. Levison, Cratering rates on the Galilean satellites, Icarus, 136, 202-222, 1998. Zahnle, K., P. Schenk, H. Levison, and L. Dones, Cratering rates in the outer Solar System, Icarus 163, 263–289, 2003.

[edit] life on Europa

There doesn't seem to be too much in that article about the possibillty of life on Europa. There should be secetion about the possibilty of there being life on Europa.--Scott3 01:07, 7 June 2006 (UTC)

Wikipedia isn't the place for speculation. We have no idea if anything is swimming around beneath the ice, and probably won't know for a long time. All we know is that the ocean either isn't or is inhabited, which is like CNN saying that Osama bin Laden is dead or alive.[1]--Planetary 08:24, 29 August 2006 (UTC)

WP:NPOV: "Assert facts, including facts about opinions — but don't assert opinions themselves." It is quite reasonable for us assert that other's have speculated on life, without presenting any given speculation as fact. Surely we can find the material for the suggested section or too add to the paragraph already present in exploration. Marskell 08:46, 29 August 2006 (UTC)

I agree that it is quite resonable to add facts about arguments for life on Europa. There are many articles in Wikipedia based on theories, that have only logical proofs. Matt. P 10:19, 31 August 2006 (UTC)

[edit] Greenberg

To mention this person 4 times in a section were he is representing only one half of the comunity is a little to much! Others do also research and they are not listed four times.--Stone 09:00, 10 August 2006 (UTC)

Agreed--edited out.

[edit] Terrestrial Microorganisms Could Survive the Trip?

Was it really necessary to crash Galileo into Jupiter? I would think that the icy cold vacuum of space, along with cosmic rays, would have killed any microorganisms present on the spacecraft.

Planetary protection deals with this problem. Experimental work points out, that Bacillus subtilis and deinococcus radiodurans are able to survive nearly anything. Horneck, G., Bücker, H., Reitz, G. (1994). "Long-term survival of bacterial spores in space". Adv. Space Res. 14 (10): 41–45. DOI:10.1016/0273-1177(94)90448-0. 

[edit] GA review

This article nearly satisfies the qualifications. I have some suggestions for improvement before I approve it as a Good Article.

• Cut down a little on the back-story of Europa in the Etymology section. Some of that seems to be unnecessary trivia. What would be useful is info on why it was named Europa, and who first named it.
• "This heats the body, and allows for geology" (Orbital characteristics section). This statement seems a little ambiguous, perhaps a little expansion on this thought would help clarify things for the casual reader.
• Add citation(s) to the Internal structure section.
• Instead of specifying which scientists believe what (Subsurface ocean section), simplify to something like "Some scientists believe(citation)...however, others argue(opposing citation)..." -- Its pretty much a universal consensus -- Nbound
• The image on the left in the Possible life section seems disruptive to the flow of the article: consider moving it and/or replacing it.
• In general, more inline references to the sources you have used (i.e., use the <ref name="name"> notation. This helps readers looking for more information find the specific source that might help them the most.-- The current format seems to work fine =S -- Nbound
• A minor copyedit for grammar and clarity. -- added tag =) -- Nbound
• Fix Etymology naming garble. (see above!) Rursus 13:30, 7 February 2007 (UTC)

Feel free to leave a message on my talk page if you have any questions or disputes.-Runningonbrains 12:58, 25 September 2006 (UTC)

[edit] GA re-review

I would advise against merely putting a {{cleanup}} tag on the article. This article does need a copyedit to remove fragment sentences, split run-ons, a few spelling errors. I am only permitted to keep this nomination on hold for 7 days, and trust me, from working on my own articles, cleanup tags get nothing done. I would suggest either doing it yourself, or contacting someone you know to do it. Unfortunately it would create a conflict of interest if I made any major changes, otherwise I would offer. A few more things:

Galileo imaging team member Richard Greenberg has used his research group's analyses of Voyager and Galileo images of Europa to argue that Europa's geological features also demonstrate the existence of a subsurface ocean^[1].

While the Galileo spacecraft is wikilinked, at least a brief mention of what it is should be included in the article. This occurs a few more times in the article at various points.

(Its was called the "Galileo probe" earlier in the article" -- Nbound 01:57, 27 September 2006 (UTC))

Adding a brief phrase like "the Galileo probe, which orbited Jupiter and studied Europa in (time)," would suffice. -Runningonbrains 03:11, 27 September 2006 (UTC) (fixed -- Nbound)

One thing I missed before, Possible life is a stub-section, and has no citations. This should be fixed.

And while this isn't required, I do recommend using the <ref name="name"> notation for major facts. Even if the source is referenced somewhere else, if someone wants to know more information about a certain aspect of Europa it greatly helps to have a reference nearby.

If you feel it would be a rush to get all this done in less than a week, I would suggest just re-nominating this article at a later date. In the time between, I would suggest requesting a peer review, to get more than just my opinion on the quality of prose in this article. As it stands right now, I do not believe this is quite a good article, however, with some tweaking, it could easily make it.

-Runningonbrains 04:23, 26 September 2006 (UTC)

[edit] source for the etymology

i didn't mean to start an edit war by putting back the {{fact}} tag.. but i don't think it's to much to ask to cite a source somewhere in the etymology section? i mean, that information has to come from somewhere.. the argument that it isn't cited on the other wikipedia articles isn't valid, i don't think, since they aren't very well referenced either. Mlm42 11:10, 27 September 2006 (UTC)

Marazzini C. (2005). "The names of the satellites of Jupiter: from Galilio to Simon Marius". Lettere Italiana 57 (3): 391-407.  and literature in there!--Stone 11:43, 27 September 2006 (UTC)

[edit] Failed GA

This article is not quite a Good Article. However I have created a "To do" list at the top of this page. When these are done (aside from the references, which is not required, only a suggestion), re-nominate the article, and it should pass fairly easily. -Runningonbrains 19:14, 28 September 2006 (UTC)

[edit] Possible life on europa

I do not like it to put a big section into a enceclopedia article about something real like europa, which is so far from reality like the hypothesis about life on europa. Make a new article saying highly fictional hypothesis or science fiction or what ever. Everybody arguing that scientists come up with this does not make it more real. The Scientist play with scientifical fantasy about things they have no date. Everybody who belives in these hypothesis should first read an Science article about the life on Mars publishe few jears bevor the Mariner probe destroyed all hopes. This article states life on Mars as a fact and only deals whit the exact way the martian oecosystem works. Be careful with all this and wait for the landing operation planed for this century!

• Salisbury F. B. (1962). "Title: Martian Biology". Science 136 (3510): 17-26. 

If anybody wants to extand the life on europa section here is some literature!

• Kletetschka G, Getty SA, Shields M, Li J, Mikula V, Wasilewski P (2006). "Title: Microbial origin of life on Europa". ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE 36 (3): 328-330. 
• Raulin F (2005). "Exo-astrobiological aspects of Europa and Titan: From observations to speculations". SPACE SCIENCE REVIEWS 116 (1-2): 471-487. 
• Chyba CF, Phillips CB (2002). "Europa as an abode of life". ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE 32 (1): 47-68. 
• Zolotov MY, Shock EL (2004). "A model for low-temperature biogeochemistry of sulfur, carbon, and iron on Europa". JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS 109 (E6): E06003. 
• Kempe S, Kazmierczak J (2002). "Biogenesis and early life on Earth and Europa: Favored by an alkaline ocean?". ASTROBIOLOGY 2 (1): 123-130. 
• Irwin LN, Schulze-Makuch D (2003). "Strategy for modeling putative multilevel ecosystems on Europa". ASTROBIOLOGY 3 (4): 813-821. 
• McKay CP (2002). "Planetary protection for a Europa surface sample return: The ice clipper mission". SPACE LIFE SCIENCES: EXTRATERRESTRIAL ORGANIC CHEMISTRY, UV RADIATION ON BIOLOGICAL EVOLUTION, AND PLANETARY PROTECTION ADVANCES IN SPACE RESEARCH 30 (6): 1601-1605. 
• Chyba CF, Phillips CB (2002). "Europa as an abode of life". ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE 32 (1): 47-68. 
• Mood S. (1983). "Life on Europa". Astronomy 11 (12): 16-22. 
• Gaidos EJ, Nealson KH, Kirschvink JL (1999). "Biogeochemistry - Life in ice-covered oceans". SCIENCE 284 (5420): 1631-1633. 
• Chyba CF, Hand KP (2001). "Planetary science - Life without photosynthesis". SCIENCE 292 (5524): 2026-2027. 
• Kargel JS, Kaye JZ, Head JW, Marion GM, Sassen R, Crowley JK, Ballesteros OP, Grant SA, Hogenboom DL (2000). "Europa's crust and ocean: Origin, composition, and the prospects for life". ICARUS 148 (1): 226-265. 

--Stone 07:16, 29 September 2006 (UTC)

[edit] Not Epsom

The Subsurface ocean section equalled Magnesium sulphate (MgSO₄) with Epsom salt (mineral), which is not correct, since chemical compound names (MgSO₄) use to refer to many minerals, defined by approximate chemical composition, crystal structure, crystal water and similar crystal lattice extra molecules. I'm not quite sure, but i'll wager a great deal on the bet that the MgSO₄ on Io, is not exactly Epsom Salt. Hehe (giggering evilly, does: Rursus 13:44, 7 February 2007 (UTC))

[edit] Eccentricity

The eccentricity of Europa is 0.0101 according to JPL's Horizons website and the books The Planetary Scientist's Companion, Planetary Sciences, and Europa: The Ocean Moon. I have not been able to find any reference for the number given, 0.0094.

128.32.149.56 17:43, 28 March 2007 (UTC)PtysGrl

It's great that you have a reference - put the new number in! and add the reference in line...

The only reasons the previous eccentricity edits were reverted was that 1) they broke the infobox format (eccentricity did not appear at all); and also 2) because the infobox should just have the actual observed eccentricity, while discussion of what part is forced etc should go somewhere in the text. Deuar 19:24, 28 March 2007 (UTC)

I tried to edit the page, which I guess means I broke it. Sorry! This is the first experience I have had editing a wiki page. If you (or anyone else reading this) could change the eccentricity, that would be great. I am clearly incompetent when it come to wikis.

I checked the reference given in the page, and it does link to a website with the value of 0.0094. However, it is generally accepted (and cited in the literature including a different webpage by the same people) that Europa's eccentricity is 0.0101. I pointed out the free and forced eccentricity simply because I thought might clear up why some older references state that the eccentricity is zero. Any eccentricity observed for Europa IS the forced eccentricity, and it's value is 0.0101, not 0.0094.

Aha, makes sense. Deuar 16:20, 30 March 2007 (UTC)

Sorry once again for the troubles!

Hey, don't worry, it wasn't a major problem. I really hope you don't get discouraged — we can use people who check the facts. They say that one of the main principles of Wikipedia is to Be Bold!.

I see that the reference for the 0.009 value is a NASA factsheet, and these tend to be out of date. Deuar 16:20, 30 March 2007 (UTC)

[edit] Is something missing?

Have a look at these sentences from the article - "Europa is also being gravitationally pulled in different directions by Jupiter and by other satellites of the planet (tidal flexing). This gives the body a source of heat and energy, allowing the subsurface ocean to stay liquified, and driving subsurface geological processes.[7]"

As far as I know tidal flexing has nothing to do with heat generation. Is there a sentence missing from the article?61.68.183.41 18:05, 28 March 2007 (UTC)

Tidal energy is dissapiated during the flexing (a classic example is to take a paper clip and bend it back and forth several times. The center of the bend will be hot). I will clarify this. Michaelbusch 18:10, 28 March 2007 (UTC)