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 21 2009, 03:06 AM
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#2
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
If Xanadu is "self-clearing" then the dune particles must be going around the southern edge of Xanadu. (The dune pattern in W Xanadu indicates a southern flow)
So you'd expect to see an ISS-dark and RADAR-dark dune sea somewhere along the southern margin...but you don't. One possibility is if there is a temperate/polar bright deposit that forms faster than the dune seas move. So instead of dark dune seas forming, there are bright smooth deposits that form in the temperate regions in south-central Xanadu. In effect the dune seas get "tamped down" and covered up by an ISS-bright atmospheric deposit. So limited "equatorial dunes" in the temperate regions, the deposit seals up the sand supply. So in the big picture of timing of features on Titan, that would imply: Temperate/polar atmospheric deposits>dune seas>other process (save cryovolcanic outlflows) This seems to fit not only Xanadu but the rest of the temperate regions in general. I'll bet that the normalized brightness of Mezzoramia is still not as dark as that of Shangri-La. (Another piece of evidence, look at craterforms: not much in polar/temperate regions, some in dune seas, but pretty much everything exposed in Xanadu) -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Apr 21 2009, 08:06 AM
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#3
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
If Xanadu is "self-clearing" then the dune particles must be going around the southern edge of Xanadu. Not necessarily. There may be no flow across or round Xanadu at this particular epoch but rather a very gradual encroachment at its western margin. When eventually enough of it is covered a lot of sand may cross in a relatively short period. I do think though that there must be some net leakage of sand to temperate latitudes where maybe it becomes damp and less mobile. A lot of dark streaks seem to be diverging from the tropics. RE "The dune particles do not form in the atmosphere" EDITED LAST PARA: I expressed myself sloppily there, and thanks Jason for pointing that out. On the respective particle sizes of haze and sand, I'm not forgetting that there must be a processing step or five to get from the former to the latter, if that is indeed what happens. The point as it relates to this discussion, though, is whether all parts of Titan receive equal doses of the raw material for making sand or whether it has a more localised origin. I was merely pointing out that the albedo winds idea is consistent with virtually any origin for the sand particles, including an atmospheric source for the material, whereas some other conceivable explanations for their uneven distribution might rely on localised sources and sinks. |
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