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Titan's changing lakes
nprev
post Oct 8 2009, 09:36 PM
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Gotcha. I'm definitely thinking flash floods are possible in Huygen's neighborhood, but not long-term standing bodies of liquid.


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ngunn
post Oct 8 2009, 09:53 PM
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QUOTE (nprev @ Oct 8 2009, 10:13 PM) *
Huygens sure looks like it's sitting in a flood channel...maybe an arroyo?


It seems ages since I posed the question: Where is Curien Station? Is it for once and all the latitude and longitude where the probe landed, or does it move when Huygens gets washed along a bit, maybe even buried? (The first option is itself problematic as we now know, due to the variable rotation state of Titan's floating crust.)

I think a typical surmise just now would be that at any given tropical location floods are more like millennial events than seasonal ones. The changes now unfolding at high latitudes are exciting enough but, as VP points out, we need to watch for a few years more before anyone can do more than make informed guesses about the big picture. That's what's so great about this amazing active world. Everyone has a ringside seat at the show and nobody knows what may happen next.
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Juramike
post Oct 8 2009, 11:27 PM
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QUOTE (ngunn @ Oct 8 2009, 03:38 PM) *
Oh well, I had to ask. smile.gif


Here's my shot at Fig 2b trying to zero near the "Spooky Dude" formation.
From: Jaumann et al. LPSC 40 (2009) Abstract 1599.

Attached Image


Graphic is of Fib 2b masked and infilled with a hue/saturation adjusted and contrast adjusted and Gaussian blurred [0.5 pixels] Fig 2c - Fig 2a (after masking line & text area and underfilling with vortex-modified Karoschka mosaic).

Looking forward to the full article....

[EDIT: Even with this hack job, one can see that the R1, R2, and R3 balance out to the correct colors. So if the Spooky Dude formation is in the VIMS, it could be either R1 (bright region terrain) R2 (blue region) or something else that spectrally resembles either of those. R3 (brown region = dune material) can be safely ruled out.]


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djellison
post Oct 9 2009, 04:33 PM
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Some posts have been removed from this thread, as they contained links to and images from data that should not yet have been in the public domain.
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titanicrivers
post Oct 10 2009, 03:01 PM
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Check out Photojournal http://photojournal.jpl.nasa.gov/targetFamily/Saturn from today. Posted are two superb figures that were presented by Alexander G. Hayes at the Division for Planetary Sciences meeting of the American Astronomical Society on Oct. 6, 2009. Olvegg has posted the links to the presentations earlier in this thread (post #49).
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ngunn
post Oct 25 2009, 09:48 PM
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VIMS sees specular reflection from Kraken Mare:

QUOTE:

After more than 50 close flybys of Titan by the Cassini spacecraft, it has become clear that features similar in morphology to terrestrial lakes and seas exist on Titan’s surface. Widespread evidence for fluvial erosion, presumably driven by precipitation of liquid methane from Titan’s dense atmosphere is also apparent from these data. Lake-like features have thus far only been observed in Titan’s polar regions. Of these presumed lakes, liquids have only been conclusively identified in Ontario Lacus, a relatively small lake in Titan’s south-polar region. As Titan progresses into northern summer, the much larger lake-like features in the north-polar region identified in Radar data, are becoming directly illuminated for the first time since the arrival of Cassini. This allows the Cassini optical instruments to search for specular reflections to confirm the presence of liquids in these presumed lakes. On July 8th, 2009 the Cassini Visual and Infrared Mapping Spectrometer (VIMS) successfully detected a specular reflection in the north-polar region of Titan. The signal is restricted to the VIMS channels at ~5 µm where most of the incident light reaches the surface without being scattered by aerosols in Titan’s atmosphere. By mapping these observations onto the RADAR image from the T19 flyby, the VIMS specular reflection was found to be associated with the western part of Kraken Mare, one of Titan’s large northern lakes, indicating the lakes surface is mirror like, strongly suggesting it is liquid.

(with thanks to 'Gish Bar Times' for the link to these abstracts).
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ngunn
post Oct 25 2009, 10:50 PM
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And there's so much more - here:

(struggling to post a link that works)

http://agu-fm09.abstractcentral.com/planner.jsp

OK that works. Now: Browse / Friday / Planetary Sciences and you're there.
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ngunn
post Oct 26 2009, 12:01 AM
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Personal anecdote: perhaps not many people remember their 57th birthday as one of the best. I do. Not only did we have this VIMS observation of northern lakeshine, but also the Ontario SAR:

QUOTE (Sunspot @ Jul 2 2009, 02:27 PM) *
Ontario Lacus......... at last biggrin.gif


The SAR of Ontario Lacus was long expected and advertised, but the VIMS Kraken Mare specular reflection was not mentioned in the July 8 Mission Description or in the 'Looking Ahead'. I wonder if it also was expected, or purely serendipitous?
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ngunn
post Oct 26 2009, 01:34 PM
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Another morsel from the conference abstracts. Anything to do with timescales on Titan always grabs my attention. This one was hiding outwith the dedicated Titan sessions. Because of the difficulty of linking to these abstacts I'm going to try posting a series of short QUOTES from:

Geomorphic Analysis of North Polar Channel Networks on Titan, and Implications for Active Tectonics and Persistence of Relief Structures
R. Cartwright1; J. A. Clayton

"Assuming constant 1.5 m depth liquid hydrocarbon flow during the summer (wet) season, we estimated that roughly 19,800 Titan years are required to lower Basin A down to its minimum relief."

"recent tectonic uplift could help explain why this region displays variable relief, as well as contorted and constricted channel networks"

UNQUOTE

If I understand correctly this implies that typically the relief confining Titan's lake basins only formed within the last million (Earth) years or so, or else the basins are continuously deepening themselves at a pace that matches erosional degradation of the topography. The timescale tallies quite well with the ages of terrestrial lakes, relatively few of which go back more that a million years.
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Jason W Barnes
post Oct 26 2009, 02:00 PM
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QUOTE (ngunn @ Oct 25 2009, 02:48 PM) *
On July 8th, 2009 the Cassini Visual and Infrared Mapping Spectrometer (VIMS) successfully detected a specular reflection in the north-polar region of Titan. The signal is restricted to the VIMS channels at ~5 µm where most of the incident light reaches the surface without being scattered by aerosols in Titan’s atmosphere.


Gosh I hadn't realized the word was out yet. I guess if AGU abstracts are published then there's a good reason for the leakage . . .

- Jason
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ngunn
post Oct 26 2009, 02:33 PM
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Catching the lakeshine:

Radar 21st December '08 - VIMS 8th July '09 - Go ISS! wink.gif smile.gif
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Jason W Barnes
post Oct 26 2009, 02:46 PM
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QUOTE (ngunn @ Oct 26 2009, 07:33 AM) *
Catching the lakeshine:

Radar 21st December '08 - VIMS 8th July '09 - Go ISS! wink.gif smile.gif


Considering we only saw it at 5um, and not at 2.8, 2, 1.6, 1.3, or 1.1, I think that ISS is going to have a challenge finding it at 0.93um. wink.gif

- Jason
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ngunn
post Oct 26 2009, 03:04 PM
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Yeah, you caught the sun's direct reflection at a pretty oblique angle, right? A very spectacular result - I look forward to seeing the crucial image when it's published. I realise the haze makes that impossible for ISS but I'm still hoping (until I'm told otherwise) that they may be able to identify specularly reflected skylight near the Brewster angle.
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Jason W Barnes
post Oct 26 2009, 05:32 PM
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QUOTE (ngunn @ Oct 25 2009, 05:01 PM) *
The SAR of Ontario Lacus was long expected and advertised, but the VIMS Kraken Mare specular reflection was not mentioned in the July 8 Mission Description or in the 'Looking Ahead'. I wonder if it also was expected, or purely serendipitous?


I guess if those are the only two options, then it's "serendipitous". We have been looking for specular reflections all the time, but haven't seen any -- the reason of course is that the Sun hasn't been shining on the wet places (Ontario excepted). So while we look at the images and keep specular in mind, we haven't before designed a sequence around it. Now that we've found one and see how totally cool it is, though, and what great science can be done with it, we're looking for opportunities in the future to do a planned specular campaign. It all depends on the spacecraft geometry, though, so we pretty much just have to wait for the right time.

- Jason
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ngunn
post Oct 27 2009, 12:41 PM
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Thanks, Jason. Congrats to the team and good luck with future targeted lakeshine studies.
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