Wikipedia:Featured picture candidates/A day on Io
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[edit] A day on Io
- Reason
- A composite of a full day rotation on Jupiter's moon Io.
- Articles this image appears in
- Io (moon)
- Creator
- NASA Voyager and Galileo spacecraft
- Support as nominator --DurovaCharge! 05:26, 25 May 2008 (UTC)
- Oppose Please forgive me if I'm missing something or if it isn't really a defect, but the object appears oval in shape... shouldn't it be round. I think the aspect ratio is wrong. Capital photographer (talk) 08:09, 25 May 2008 (UTC)
- Comment The aspect ratio is wrong when played on the MediaWiki applet, but it's OK when played with mplayer. I think ffmpeg2theora was putting 640x480 in the metadata but encoding the actual file in the correct 640x440. Anyway, I've gone back to the original NASA mpeg and re-encoded it with ffmpeg2theora -x 640 -y 440 and it seems to fix the ratio problem. Time3000 (talk) 10:27, 25 May 2008 (UTC)
- Comment Thanks for fixing the aspect ratio. However, the South pole is now sliced off, and the color balance has changed. Pete Tillman (talk) 03:08, 26 May 2008 (UTC)
- Maybe try a different browser? I see the South Pole on my system and the color balance looks the same. DurovaCharge! 06:07, 26 May 2008 (UTC)
- I can't see any difference in the colour balance, but I just noticed that the new version's only about 4s long. I think the problem with the south pole being cut off is the mediawiki applet when it's a thumbnail - it always cuts off the bottom 10px or so as a scrubber. Anyway, I've re-encoded it again so it is now 640x480, with padding instead of scaling (to fix both aspect ratio and south pole issue). This time I used an intermediate step of very high quality (about 4000kbps) MPEG-4 (so I could use the ffmpeg options to sort out the aspect ratio and padding) and then ffmpeg2theora to convert to ogg/theora. The length is slightly different (NASA's original mpeg wasn't sure whether it was 25 of 30fps) so it's now 28.8s instead of 24s, but I don't think it makes much difference to the animation. The re-encoding has also had the side effect of making the file appear the right length instead of 25mins when using the mplayer plugin on firefox. Time3000 (talk) 11:54, 26 May 2008 (UTC). Sorry about the huge comment, feel free to ignore it ; ).
- Maybe try a different browser? I see the South Pole on my system and the color balance looks the same. DurovaCharge! 06:07, 26 May 2008 (UTC)
- Support Alternative 2. Can't help the MediaWiki problems, but it's a feature-worthy clip.--ragesoss (talk) 01:33, 27 May 2008 (UTC)
- Comment Nice idea. I just have trouble believing that Io is a perfect sphere. It's probably an irregular shape, maybe slightly oval, but definitely with some bumps on the surface by the looks of it. Can we not produce such a rendering? I know there are ways to apply raster graphics textures as depth maps on a 3D object. Papa Lima Whiskey (talk) 08:01, 28 May 2008 (UTC)
- If the Earth were scaled down to six feet in diameter, Mount Everest would be a thin coat of paint. All the substantial moons and solid rocky planets are near-perfect spheres. Io is a Galilean moon; it's got enough mass to be spherical, and any aberration wouldn't be visible in a scaled representation as small as this. DurovaCharge! 11:53, 29 May 2008 (UTC)
- Earth is not a good reference for several reasons (much larger, has an atmosphere, has liquid on the surface), but even so, Earth has bumps far larger than mountains. Earth has a reference about why Mount Everest isn't actually necessarily the highest mountain, for instance. I don't think we need to argue about the fact that in the nominated image, the texture is projected on a perfect sphere. As for the rest of your argument, can I put a [citation needed]? Also, please note that the photograph at the top of the Io (moon) article suffers the same problem. You can verify this by the fact that no "anti-aliasing" is present, i.e. the borders were drawn as hard pixels by a computer program that does not support anti-aliasing. Meanwhile, my argument about non-perfect shape would seem to be supported by Image:Iosurface.jpg and Image:Tvashtarvideo.gif, which are also in the article. Papa Lima Whiskey (talk) 13:09, 29 May 2008 (UTC)
- I agree that Earth isn't a perfect reference, but the same argument can be applied more validly to the Moon (a similar size to Io - 1700km radius compared to Io's 1800km). From Earth, the only way to tell that the Moon is not a perfect sphere is to look at it through a telescope or binoculars at a bit where shadows from crater walls etc. are visible. For this video of Io, the light source is in the same direction from Io as the 'camera', so no such shadows appear. It would be possible to use a normal map of Io's surface to simulate these, but because of the direction of the light source, there's really no point.
- Earth is not a good reference for several reasons (much larger, has an atmosphere, has liquid on the surface), but even so, Earth has bumps far larger than mountains. Earth has a reference about why Mount Everest isn't actually necessarily the highest mountain, for instance. I don't think we need to argue about the fact that in the nominated image, the texture is projected on a perfect sphere. As for the rest of your argument, can I put a [citation needed]? Also, please note that the photograph at the top of the Io (moon) article suffers the same problem. You can verify this by the fact that no "anti-aliasing" is present, i.e. the borders were drawn as hard pixels by a computer program that does not support anti-aliasing. Meanwhile, my argument about non-perfect shape would seem to be supported by Image:Iosurface.jpg and Image:Tvashtarvideo.gif, which are also in the article. Papa Lima Whiskey (talk) 13:09, 29 May 2008 (UTC)
- If the Earth were scaled down to six feet in diameter, Mount Everest would be a thin coat of paint. All the substantial moons and solid rocky planets are near-perfect spheres. Io is a Galilean moon; it's got enough mass to be spherical, and any aberration wouldn't be visible in a scaled representation as small as this. DurovaCharge! 11:53, 29 May 2008 (UTC)
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- The image and video you link to don't show that Io isn't a perfect sphere. Io is volcanically active, hence the change in surface in the image. The video is of a volcanic eruption in progress, but the plume hardly counts as a part of Io's surface. From Io (moon): "As a by-product of this activity, sulfur, sulfur dioxide gas and silicate pyroclastic material (like ash) are blown up to 500 km (310 mi) into space, producing large, umbrella-shaped plumes...". You might just as well say that the Earth's atmosphere is a part of the Earth's surface. Time3000 (talk) 14:34, 29 May 2008 (UTC)
- It's good that you bring up the moon, as the featured picture I added to the nomination should convince you of its unevenness. The fact that Io's surface changes is irrelevant, as photos and videos are frozen in time. This animation should accurately represent the point in time when the probe passed. A natural satellite is a 3D object. This candidate animation fails to capture planet shape and surface structure, and so it fails on the grounds that it is inaccurate. Papa Lima Whiskey (talk) 15:20, 29 May 2008 (UTC)
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- I have to disagree again - firstly, the animation you linked to and the data used for this video were taken by different probes (this video - Voyager 1 and Galileo (spacecraft); the animated GIF - New Horizons). When Voyager flew by Io there was an eruption, but there were plenty of times during the Galileo mission when there were no eruptions which would be visible on this scale. Still, if you want to oppose, go ahead : ). Time3000 (talk) 16:57, 29 May 2008 (UTC)
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- Once again, your comments come across as irrelevant. The fact that one of the pictures I cited shows an eruption has nothing to do with the fact that the surface of Io is not as even as you claim, clearly visible in both the cited pictures, and a consistent property of Io, regardless of when the pictures are taken. In fact, the time between those two exposures substantiates my argument: Io is not a perfect sphere, and this property is invariant through time. From one of the sources cited in the article: We have identified 115 mountain structures (covering ~3% of the surface) and 541 volcanic centers, including paterae (calderas and dark spots) and shield volcanoes. The average length of an Ionian mountain is 157 km, with the longest being 570 km. The mean height of Ionian mountains is 6.3 km, and the highest known mountain is Boösaule Montes (17.5+/-3km). Papa Lima Whiskey (talk) 21:54, 29 May 2008 (UTC)
- The image and video you link to don't show that Io isn't a perfect sphere. Io is volcanically active, hence the change in surface in the image. The video is of a volcanic eruption in progress, but the plume hardly counts as a part of Io's surface. From Io (moon): "As a by-product of this activity, sulfur, sulfur dioxide gas and silicate pyroclastic material (like ash) are blown up to 500 km (310 mi) into space, producing large, umbrella-shaped plumes...". You might just as well say that the Earth's atmosphere is a part of the Earth's surface. Time3000 (talk) 14:34, 29 May 2008 (UTC)
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- Oppose given the above argument. Papa Lima Whiskey (talk) 15:20, 29 May 2008 (UTC)
- Support alt 2. The composite does make it look almost perfectly spherical at the edges but the images themselves quite clearly show that it is pockmarked and it's a pretty impressive achievement to be able to watch a complete rotation of a distant satellite. Pstuart84 Talk 15:30, 31 May 2008 (UTC)
- There are tools that allow you to use textures as elevation maps. Papa Lima Whiskey (talk) 10:29, 1 June 2008 (UTC)
Not promoted MER-C 07:02, 2 June 2008 (UTC)
