The two faces of Titan's dunes |
The two faces of Titan's dunes |
Jan 23 2012, 08:38 PM
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#1
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
ESA press release today: http://www.esa.int/esaCP/SEMX5NH8RXG_index_0.html
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Jan 23 2012, 11:13 PM
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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 |
No comments? OK I'll post one. This is a fact-reporting article (observations, correlations) and at that it succeeds perfectly. It offers a tentative tying up of a number of loose ends. To me that's less convincing because we don't have all the ends yet so tying ends up now may mean making wrong connections. Lots of questions beckon, as always with Titan. If the dune material descends from the hydrocarbon haze this presumably happens at all latitudes, so what happens to it north and south of the tropical dune zone?
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Jan 24 2012, 01:18 AM
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#3
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
Atmospheric sintering is just one of the possible ways of making dune particles.
(Remember, it's still not known exactly what is in the dune particles. RADAR dielectric constant suggests 'organic' (not ice). VIMS, which only sees the first few microns, suggests some aromatics with benzene-like stretches near 5 micron are present?) To really determine composition, some type of in-situ separation/then characterization would be needed. (LC-MS/MS Orbitrap). This will be a really neat problem for a future mission. Even uglier, atmospheric chemistry on Titan isn't the same everywhere. Some recent CIRS data shows that the concentrations of different atmospheric materials vary widely by lattitude (multiple orders of magnitude). So the starting ingredients for the atmospheric chemistry is different in different locations. That could also have an effect on what gets constructed in the atmosphere and then deposited on the surface. So you'd want to send that LC-MS/MS Orbitrap down to different places. Titan's surface will taste different depending on your location. That might be one possible explanation for polar zones being different than equatorial zones. -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Jan 30 2012, 07:26 AM
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#4
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Member Group: Members Posts: 699 Joined: 1-April 08 From: Minnesota ! Member No.: 4081 |
... Lots of questions beckon, as always with Titan. If the dune material descends from the hydrocarbon haze this presumably happens at all latitudes, so what happens to it north and south of the tropical dune zone ... and of course in the Xanadu region which lies WITHIN the tropical zone at a LOWER elevation than the surrounding dune seas and presumably is OLDER geologically than the dune fields! |
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Jan 30 2012, 01:18 PM
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#5
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
and of course in the Xanadu region which lies WITHIN the tropical zone at a LOWER elevation than the surrounding dune seas and presumably is OLDER geologically than the dune fields! We had an extended discussion about that in this thread: http://www.unmannedspaceflight.com/index.php?showtopic=5953. See especially Ralph Lorenz's albedo-driven winds suggestion in post 11 and many posts following therefrom. |
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Feb 26 2012, 08:07 PM
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#6
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
Interesting article in Science Daily on the formation mechanism of linear dunes, with possible application to Titan: http://www.sciencedaily.com/releases/2012/...20224140615.htm
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Mar 2 2012, 01:24 AM
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#7
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
Some more stuff on sticky longitudinal dunes (some behind a paywall, bummer):
Rubin and Hesp, Nature Geoscience 2 (2009), 653 - 658. Multiple origins of linear dunes on Earth and Titan. doi: doi:10.1038/ngeo610. Pay-for article: http://www.nature.com/ngeo/journal/v2/n9/full/ngeo610.html An abstract discussing linear vs. bidirectional winds: http://adsabs.harvard.edu/abs/2009AGUFM.P51G1193R And a FREE article on Interplanetary dunes : Bourke et al., Geomorphology 121 (2010) 1–14. Extraterrestrial dunes: An introduction to the special issue on planetary dune systems. 10.1016/j.geomorph.2010.04.007 Link here. -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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