Titan's topography, strange.... |
Titan's topography, strange.... |
Apr 12 2009, 12:44 PM
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#1
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
Recent article in Science by Zebker et al.:
Zebker et al. Science in press, "Size and Shape of Saturn's Moon Titan". doi: 10.1126/science.1168905 (published online April 2, 2009) Link to abstract (pay-for article): http://www.sciencemag.org/cgi/content/abstract/1168905 Article on spaceref discusses this paper: http://www.spaceref.com/news/viewpr.html?pid=27912 Figure 3 from the Science article is a global elevation map relative to barycenter. Key points of article:
"Xanadu seems to be systematically lower than other parts of the equatorial belt, and not uplifted like most mountainous areas on Earth." (quote from Fig. 3 caption in article) -Mike -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Apr 23 2009, 08:01 AM
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#2
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
After sleeping on it I'll now try to be more explicit about why I have difficulty with Jason's quasi-static scenario above.
I have no knowledge of how far sand particles must travel to build a dune sea or the streamlined teardrop shapes around islands, but we can see how far it must have travelled to clear Xanadu. To do that, any sand that formed in the middle of it must have drifted through at least one Xanadu radius. If the global eastward drift were much less than that we would see positive accumulations of sand on [i]both[/ sides of Xanadu, not just the western side. Instead we see a depletion of sand on the eastern side. I think that implies that the global eastward drift at least equals, and may exceed, the flow rate associated with the albedo cleaning process. In other words each sand particle must have drifted, over the history of the sand seas, a distance at least comparable with the dimensions of the sand seas themselves, and possibly much further. That in turn suggests that if Xanadu did not occasionally flush there should by now be a very much bigger pile of sand at its western margin. |
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