Titan's Equatorial Sand Seas |
Titan's Equatorial Sand Seas |
May 7 2007, 03:53 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 |
I’ve put together a sequence of events that could explain the morphology of the Equatorial Sand Seas. (An example basin similar to Shangri-La is shown)
This could explain the ria-like topography [http://en.wikipedia.org/wiki/Ria] on the Eastern shore, as well as the VIMS dark blue western parts of the Sand seas, and the placement of the dark brown unit on the Eastern parts of the sand seas. 1. Basin formation. 2. Water-ice sand deposition [slowly, suddenly?] forms an ice-sand margin 3. Mobile dark brown dune sands deposit on E side, depositing inland up W facing valleys. :attachment] The dark brown sands will blow in following the predominantly W winds and make a dust coating on low-lying terrains on the eastern margins. This will be visible by VIMS and ISS as the dark-bright margin, placed “inland” from the "real margin" and will accentuate the local topography as seen by optical instruments. This accentuation on the E margin will make the Equatorial Sand Sea visible margin look “swoopy” and windblown (in effect, it is) from the dark basin. Similarly, the W margin will have a dark blue zone that appears blown from the western bright areas. On the Eastern shore, the RADAR images will place the smooth-dark/mottled gray boundary far to the W of the VIMS brown dark-bright margin. (RADAR should be able to penetrate a thin coating of dark sands). The features in the limbo zone have been covered by dark sands, perhaps not enough to form dune structures, but enough to cover up the ice-sand margin, the near shore terrain, and perhaps even some of the underlying bright terrain. This makes the deposition sequence in the Equatorial Sand Seas: 1: Basin formation 2. Major water ice sand emplacement 3. Dune sands cover up low-lying downwind valleys (enough to mask visible imagery) Other Equatorial Sand Sea basins should look very similar around Titan: Shangri-La, Belet, Senkyo, Fensal and Quivra. Local winds may play a bonus role, but the overall trend of dark sand deposition up valley should be towards the E. For example: the false-color image in Figure 6 of the Soderblom paper seems to imply a predominant wind vector in Fensal and Quivra to the ESE. [I’m pretty sure all this has been described in pieces before, but it gave me a really great excuse to play with PowerPoint. ] -Mike -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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May 24 2007, 01:00 AM
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#2
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Senior Member Group: Members Posts: 1887 Joined: 20-November 04 From: Iowa Member No.: 110 |
Would the strength of these tides tides vary with latitude? If so I can see this as an additional reason for the lakes being concentrted at the poles. Stronger tides at low latitudes could result in liquid filled basins being enlarged by tidal motion. Eventually they could reach the point where increased evaporation or seepage caused them to dry up.
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May 26 2007, 01:29 PM
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#3
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Member Group: Members Posts: 613 Joined: 23-February 07 From: Occasionally in Columbia, MD Member No.: 1764 |
Would the strength of these tides tides vary with latitude? If so I can see this as an additional reason for the lakes being concentrted at the poles. Stronger tides at low latitudes could result in liquid filled basins being enlarged by tidal motion. Eventually they could reach the point where increased evaporation or seepage caused them to dry up. Yes - the strength varies with latitude (and longitude) - specifically with distance from the subsaturn point. A brief intro to tides on Titan and their effect on lakes (from 1993 - it includes some predicted landforms that, er, well, havent been borne out by observations so far, let's say - but it lays out some useful fundamentals) is at http://www.lpl.arizona.edu/~rlorenz/craterlakes.pdf Tides are generally weaker at high latitudes. I dont think tides explains why we find liquids where we do (but they may be responsible for the lack of wave-type features on shorelines like sandbars - tidal displacement of the waterline is larger than typical waveheight..) |
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