Rev 126 - Feb 4-22, 2010 - Mimas (main target), Tethys, Iapetus, Calypso and mutual events too |
Rev 126 - Feb 4-22, 2010 - Mimas (main target), Tethys, Iapetus, Calypso and mutual events too |
Feb 15 2010, 05:59 PM
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#61
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Senior Member Group: Members Posts: 2492 Joined: 15-January 05 From: center Italy Member No.: 150 |
Feb, 14 sequence animation:
Note the curious sudden illumination change on Epimtheus from a body on the right, perhaps from Janus itself (strange geometry, however) -------------------- I always think before posting! - Marco -
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Feb 15 2010, 06:33 PM
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#62
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
Note the curious sudden illumination change on Epimtheus from a body on the right Looks like "sunset" to me. -------------------- |
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Feb 15 2010, 06:37 PM
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#63
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Senior Member Group: Moderator Posts: 3234 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Nice catch about the change in illumination on Epimetheus. I doubt it is from Janus since that moon is clearly on the OTHER side of Epimetheus from those craters. I think we are just seeing a slight bit of rotation on Epimetheus, and the Sun is setting on the far rims of three impact craters just beyond the evening terminator.
I have to admit that I started to doubt that explanation since I suddenly thought that north might be up, so the terminator we are seeing would be the dawn one... But nope, south is up in your animation, so my explanation holds... -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Feb 15 2010, 07:16 PM
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#64
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Member Group: Members Posts: 813 Joined: 29-December 05 From: NE Oh, USA Member No.: 627 |
I do not usually throw in attachments so bare with me...
But in this Mimas image I am not convinced all the low albedo stuff is due to shadow. It is from NAC image N00151508. Also if you look at dilo's colorized global image you can see a few darkish spots in the high phase region. Kinda like the Rhea ring impactors but more dispersed (not in a line)? Interesting. Craig |
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Feb 15 2010, 07:45 PM
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#65
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Senior Member Group: Members Posts: 2091 Joined: 13-February 10 From: Ontario Member No.: 5221 |
Wow this stuff is truly great. Honestly if it wasn't for the central peak Herschel almost looks like it formed some other way. It's just so irregular and different from other big craters, like on the moon or Callisto.
Mysteries abound! |
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Feb 15 2010, 07:50 PM
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#66
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
Compare it to Rhea. Many of the larger craters on that moon are also irregular.
Mass wasting and slumping the crater walls of Herschel seem evident. EDIT: Looking at the picture that Craig posted it seems that there is a tendency for the walls to form and slump along parallel lines going from lower left to top right. -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Feb 15 2010, 08:01 PM
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#67
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Lord Of The Uranian Rings Group: Members Posts: 798 Joined: 18-July 05 From: Plymouth, UK Member No.: 437 |
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Feb 15 2010, 08:19 PM
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#68
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Member Group: Members Posts: 102 Joined: 29-January 10 From: Poland Member No.: 5205 |
- Full quote deleted. Use the "add reply" button at the bottom of the page. -
Nice work ! Your animations show rotations of this monns -------------------- Adam Hurcewicz from Poland
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Feb 15 2010, 08:56 PM
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#69
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Senior Member Group: Members Posts: 2492 Joined: 15-January 05 From: center Italy Member No.: 150 |
Grat animations, Ian! (original quality is clearly better than mine...)
Gordan, you were right! -------------------- I always think before posting! - Marco -
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Feb 15 2010, 09:06 PM
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#70
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Member Group: Members Posts: 102 Joined: 29-January 10 From: Poland Member No.: 5205 |
-------------------- Adam Hurcewicz from Poland
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Feb 15 2010, 09:08 PM
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#71
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Member Group: Members Posts: 128 Joined: 28-October 08 From: Boston, MA Member No.: 4469 |
What we're seeing here is these two co-orbitals exchanging orbits, correct? It seems natural to think that the switching of orbits would need to cause temporary redirections of the moons from their normal elliptical orbits, and therefore the observed rotations and exposure of hidden surfaces to the sun.
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Feb 15 2010, 09:23 PM
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#72
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Member Group: Members Posts: 916 Joined: 4-September 06 From: Boston Member No.: 1102 |
I'm not exactly sure where they are in the process of exchanging orbits, but I think the relative movement we see here is mainly the changing perspective of Cassini as it rushes by.
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Feb 15 2010, 09:34 PM
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#73
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Solar System Cartographer Group: Members Posts: 10201 Joined: 5-April 05 From: Canada Member No.: 227 |
This is not the orbital switch. There are several factors - the moving spacecraft, the moons moving relative to the sun and to each other.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Feb 15 2010, 09:37 PM
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#74
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Member Group: Members Posts: 128 Joined: 28-October 08 From: Boston, MA Member No.: 4469 |
But changing the observer's perspective couldn't account for the change in illumination of the subject. We must be seeing physical rotation of the moons themselves relative to the sun.
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Feb 15 2010, 09:38 PM
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#75
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Solar System Cartographer Group: Members Posts: 10201 Joined: 5-April 05 From: Canada Member No.: 227 |
"in this Mimas image I am not convinced all the low albedo stuff is due to shadow."
These patches don't look unusually dark in images with more overhead lighting, which you can see further up the thread. - but there are real dark spots in places further east. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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