| Revision as of 23:51, 9 March 2006 editKeenan Pepper (talk | contribs)Autopatrolled, Administrators19,056 edits →Pronunciation← Previous edit |
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English pronunciation . |
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== Atmosphere == |
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|action2date=09:46, 2 June 2006 |
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An atmosphere exists around every larger body of the solar system. The substantial information which is missing here is the pressure / density of the atmosphere. ] 18:52, 18 Mar 2005 (UTC) |
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:The press release announcing the discovery gave no information on the atmospheric properties, only that it is "substantial", whatever that means. --] 20:13, Mar 18, 2005 (UTC) |
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Although the planetary society article says "a million million times less" which means a factor of 10<sup>12</sup>, it's actually a factor of 10<sup>11</sup> if the number of 200 to 300 million atoms/molecules per cm<sup>3</sup> stated in the same article is correct. I think one order of magnitude does matter. ] 01:55, 23 September 2005 (UTC) |
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{{WikiProject Astronomy|object=yes|importance=Top|solar_system=yes|ss-importance=High}} |
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{{old move|date=16 June 2022|destination=Enceladus (moon)|result=not moved|link=Special:Permalink/1095314267#Requested move 16 June 2022}} |
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== False color image == |
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{{Annual readership}} |
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==Cassini flyby of plume == |
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The data gathered by Cassini in her final flybys in October (E21) and December 2015 (E22) are expected to yield some clues regarding the chemistry of the moon's ocean and prospects for some form of biochemistry. The data may not be published until December 2016, it seems.... |
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: Cassini did a final flyby of Enceladus in late October that targeted the chemistry of the plumes directly. The INMS team, which includes Glein, is searching for molecular hydrogen in that plume, which would be chemical evidence of active serpentinization. An absence of molecular hydrogen would be a sign that the serpentinization is extinct. The data analysis from this flyby may be completed in time for the American Geophysical Union's fall meeting in December. Glein added that the planned NASA mission to Europa includes advanced descendants of both the CDA and INMS instruments, meaning that in a decade or two, scientists can start to make these same measurements at Europa. This will allow us to better understand the importance of serpentinization across the Solar System. |
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I definitely prefer the old picture over the new false color image. I will revert, if nobody objects! ] 13:15, 27 Apr 2005 (UTC) |
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http://www.space.com/32021-how-life-friendly-is-enceladus-ocean.html |
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Done. ] 13:55, 28 Apr 2005 (UTC) |
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:Yes, on ] the concensus was that the main image of a body should look as realistic as possible. Specifically, false-colour images were considered inferior. In fact, apparently you were the one who reverted that one. :-) --] 17:52, Apr 28, 2005 (UTC) |
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::I'm not at all sure that the current image has true colors whatever that means. Enceladus, with its extremely high albedo, is actually bright white or gray, not brown like in this image which looks like a colorized one. But I've to admit that the current image looks much better.--] 19:45, Apr 28, 2005 (UTC) |
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Yes, there should be a better picture, since this is an old Voyager image, I believe. I will take a look at the JPL/Cassini image archive. ] 19:58, 28 Apr 2005 (UTC) |
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I can only find raw images, close-up images of the surface, or false color images that are better than the Voyager image. All other visible light images from the whole moon have less resolution. However, those pictures show a white surface! Should we replace? ] 20:14, 28 Apr 2005 (UTC) |
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Personally I would include both on the page. Most of the images I have added following my revisions earlier this month are high resolution images that don't show the whole disk and perhaps one of the full disk images from Cassini could be added to highlight the blue cliffs of Enceladus (to go along with the high resolution image I have for that purpose. ] 17:37, Jun 20, 2005 (UTC) |
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== Mass and Density Figures == |
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I have updated the mass and density numbers for Enceladus based on a given by Zibi Turtle last month (not my only source of that information, but it is the only public mention of the change that I am aware of). The density figure is now 1.6 g/cm<sup>3</sup>, compared to the previous value of 1.3. This update is based on the Cassini NAV team's assessment of the reconstructed trajectory of Cassini following two recent flybys. This makes Enceladus denser than the other Saturnian mid-sized icy satellites, suggesting that it is composed of more iron and silicates that those other moons. I'm planning on making a mention of this in the article itself. ] 22:06, 01 Jun 2005 (UTC) |
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There have been a few updates to the mass numbers lately by other members, mostly because I forgot to change the source on some more recent figures. I have once again put in the more recent numbers (1.08x10^20 kg; 1.61 g/cm^3) based on the GM numbers in the Cassini pck SPICE kernels. I have now linked to the source of those numbers, but the calculations are my own. If others want to check my work, go ahead, just make sure to read the documentation in the source document on the units used for GM (gravitational constant times the mass), so you do the right conversions. I also used a different radius for density, escape velocity, and surface gravitational acceleration from the March 9 flyby. ] July 6, 2005 19:54 (UTC) |
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== Major changes coming == |
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I am working on some major edits to the Enceladus article after having spending the last week working on Enceladus images. The edits will be confined to the "Physical Characteristics" section, plus a new section on the history of Enceladus exploration. The Physical Characteristics section will have the following outline: |
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* Interior |
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* Surface |
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** General Geology |
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*** Voyager 2 results |
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*** New Insights from Cassini |
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** Impact Craters |
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** Tectonics |
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** "Planitia" |
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** Cryovolanism? |
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* Atmosphere |
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This would generally follow an inside out approach to discussing this satellite. The atmosphere section will largely remain intact as it is now, though I may de-emphasize the "current events" nature of the section. |
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Just wanted to give a heads up to the changes I am working on. |
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- ] 19:29, Jun 3, 2005 (UTC) |
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: I have updated this article again, to attempt to fold in some of the results from the July encounter and from the plume images from November. As such, I have removed the atmosphere section. It is now becoming increasingly clear that the Magnetometer, UVIS, and INMS instruments didn't see an atmosphere, per se, but a plume emanating from the south pole, made of water vapor and dust. So, I have folded the information in the atmosphere section into the cryovolcanism section, where I feel it belongs. ] 23:23, 2 December 2005 (UTC) |
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== Temperature == |
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What is Enceladus' surface temperature? Googling seems to mostly repeat the tidbit mentioned here, that is to say 70 K. But that's way too hot for the albedo of 0.99! 70 K implies an albedo of 0.67-0.68; an albedo of 0.99 implies 29 K (but that value is very sensitive to the actual albedo at that point). Anyone have an actual measurement they can quote? |
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] 2005 July 5 03:43 (UTC) |
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says it was measured in February. What was the result? |
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] 2005 July 5 03:45 (UTC) |
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:I recently read a source with temperatures derived from Voyager IRIS data. I'll need to find it again and post the information here. In terms of Cassini results, I don't think the Cassini CIRS results from the flyby have been posted, and certainly not temperature data, AFAIK. |
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:Also, don't forget that other factors contribute to surface temperature, including surface roughness, as well as albedo. |
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:] July 6, 2005 19:44 (UTC) |
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::Okay, found it, from : |
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::"The High albedo of Enceladus results in a colder surface than most of the other satellites, with a calculated subsolar temperature of 75 +/- 3 K, and an average temperature of ~51 K. ] July 6, 2005 23:07 (UTC) |
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:::I have found that the original source of the 75 +/- 3 K value comes from a paper by R. Hanel et al. (1982)., using infrared data from the IRIS instrument. This temperature results in a bolometric bond albedo of 0.89±0.02 and a phase integral of 0.89±0.09 (as opposed to the geometric albedo of 0.99). ] July 7, 2005 20:53 (UTC) |
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:I've updated the page with the temperatures from the refererence above. I'll look into the albedo issue some more, particularly how that temperature was estimated, and see if I can find a better estimate, but that is the only mention of surface temperature I have found thus far in the literature. ] July 7, 2005 20:35 (UTC) |
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::Using an emissivity of 0.9, a geometric albedo of 0.91 gives a mean T of 51 K; if we stick to a geometric albedo of 0.99, then the emissivity has to go down to about 0.1 to reconcile the temperature. Not altogether impossible, just unlikely (the calculation is, understandably, very sensitive to the geometric albedo value as it nears 1). |
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::] 2005 July 8 00:24 (UTC) |
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:::That calculation isn't supported by the geometric albedo observed by both ground-based and spacecraft observations which consistently show an albedo of 0.99±0.01 (Franz and Millis 1975, Cruikshank 1979, Smith et al. 1982, Buratti and Veverka 1984, Buratti 1988). For temperature measurements, it is the bond albedo that is important here, not the geometric albedo. Bond albedo is also known as the spherical albedo, and is the fraction of the total incident solar radiation—the radiation at all wavelengths—that is reflected or scattered by an object in all directions. As I said above, this value is 0.89±0.02, which is consistent with the value you came up with. ] July 8, 2005 19:01 (UTC) |
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:::Found an even better reference, Verbiscer and Veverka 1994, which reported that the single-scattering albedo (another way of saying geometric albedo), is 0.997±0.001 for disk-resolved images (value an average of all terrains). ] July 8, 2005 19:37 (UTC) |
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:Another problem has occured to me regarding the temperatures reported here. What exactly constitutes a max, mean or min temperature. Is the max the average sub-solar temperature, the min the average midnight temperature, and the mean the average between the two? Is the max the maximum surface temperature (as a result of differences in thermal inertia/volcanism), the mean the average sub-solar temperature, the min the average nighttime temperature? What is the convention at wikipedia, if there is any? ] 17:30, July 20, 2005 (UTC) |
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== Energy source for cryovulcanism partially molten core? == |
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The energy budget for Enceladus's cryovulcanism, and suggested energy source are discussed briefly in a Science news article at . I'll let someone else write it up; it's past my beddy-bye time. ] 12:00, 8 January 2006 (UTC) |
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:Never mind, I got it. Also covers a possible subsurface ocean, which is what that life comment may have been about. ] |
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=="Debunking evolution"== |
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The fact that Enceladus is geologically active has been used by Creationists to supposedly debunk evolution, since they say that Enceladus has not cooled yet and therefore must be young and recently-created. See . - ] 14:47, 16 February 2006 (UTC) |
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:Yuck. Those people are really desperate. I'm sorry for the people who actually listen to them.--] 15:43, 16 February 2006 (UTC) |
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== Surface water == |
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It looks like ] is going to report at 2pm EST (about one hour from now) that there's liquid ] near the surface of Enceladus. -- ] 17:51, 9 March 2006 (UTC) |
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:Does the water that is released escape from the planet, or does it eventually settle back down? I didn't see at what velocity is is released. Also, if there is life in that water, I woner if it might be possible to send a probe to sample the water that is released to see if there are any microorganisms.--] 20:09, 9 March 2006 (UTC) |
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== Image == |
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Is this image copyright? |
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http://solarsystem.nasa.gov/multimedia/gallery/Enceladus_PIA06254_full.jpg |
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its picture of Enceladus with a very good resolution showing high details of it |
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would be nice to put this picture on the article |
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] 21:27, 9 March 2006 (UTC) |
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== Geologically Active == |
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Is it too much of a stretch to include Venus alongside Enceladus, Triton, Io and the Earth? |
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It does present some kind of vulcanism. ] 21:42, 9 March 2006 (UTC) |
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:Yes, it is, because active volcanisim, although widely suspected, has not been confirmed on Venus. ] 21:56, 9 March 2006 (UTC) |
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==Pronunciation== |
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Why specify pronunciation when it's incorrect? Enceladus is a Greek word, and would be pronounced ''eh-nke-lah-dos''. In Latin it is ''eh-ncheh-lah-doos''. If Anglo-Saxons want to continue to badly pronounce words (another blatant case is that of scientific names of animals and plant)... but please don't confound other language people reading the English Misplaced Pages]. |
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:For one thing, Misplaced Pages should not be prescriptive, but descriptive. We have no business telling people what is correct and incorrect. For another, ''ενκέλαδος'' is a Greek word but ''enceladus'' is definitely an English word, and is pronounced {{IPA|}} according to the rules of English orthography. —] 22:22, 9 March 2006 (UTC) |
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::Now, the question is whether many English speakers actually pronounce it {{IPA|}}. If so, then it should be given as one of two alternate pronunciations. Personally I've never heard that pronunciation. Anybody? —] 22:26, 9 March 2006 (UTC) |
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::Actually, the word "ενκέλαδος" does not exist in Greek. The n "ν" is replaced with a gamma "γ" when followed by k. The word is pronounced en-geh-lah-thos, the ng part as you would pronounce "anger." And delta is pronounced as th in "the", "then" etc. Not as d. -] |
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:::I was just about to say that! You beat me to it. —] 23:51, 9 March 2006 (UTC) |
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The data gathered by Cassini in her final flybys in October (E21) and December 2015 (E22) are expected to yield some clues regarding the chemistry of the moon's ocean and prospects for some form of biochemistry. The data may not be published until December 2016, it seems....
level-4 vital article is rated FA-class on Misplaced Pages's content assessment scale..jpg){kind=small}
