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Lakes in the limelight, the 2013 image bonanza continues
TheAnt
post Nov 16 2014, 12:55 AM
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QUOTE (ngunn @ Nov 15 2014, 11:16 PM) *
On the evidence of the recent re-observation of the Ligeia example (post 59) they do move, very slowly and mainly shorewards. That one also spread out over a wider area and faded somewhat after some months. I find it hard to imagine either waves or wrinkles hanging around in the same location for that long.


Waves seem to be a less likely alternative from what we know now.

That fading out and spreading points to the other plausible alternative as I see this right now, and that would be a collection of clumps of some lightweight organics behaving like the collections of woodpieces, plastic bottles and styrofoam one can find floating together on the ocean nowadays.
Those also move slowly toward the shore and are only sensitive to the wind to some degree, and only sometimes reach harbours and bays since currents easily can disperse them.

What I had written the above I realised it is not anything else but a small variation on the foam idea with the pieces just being less sticky. But I let it stand.
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marsbug
post Nov 16 2014, 09:35 PM
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QUOTE (TheAnt @ Nov 15 2014, 06:45 PM) *
I have given the hypothesis of marsbug some thought, and considering the possible chemistry of the lakes that could hold dissolved organics that indeed might bond into something of the kind.
An oily organic substance is also possible, it would also dampen waves, but would it be to heavy float?
Lastly we have the foam proposed by the scientists involved in these studies, yes it would float, yet if there's any wind it would move.
Regardless of those alternatives, I label the idea by marsbug a plausible alternative.


Just offering up a thought I had, thank you for devoting some thought to it!


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titanicrivers
post Nov 18 2014, 02:16 AM
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The excitement over new ‘magic islands’ in Kraken and sunglint from the large sea almost (but not quite) distracts one from an equally exciting bathymetry (white arrow) obtained during T104 and discussed in Photojournal PIA19046 http://photojournal.jpl.nasa.gov/catalog/PIA19046. Here are measurements of the depth of Kraken at the outlet of a “drowned” river valley or ria imaged previously during T 28 http://pirlwww.lpl.arizona.edu/~perry/RADAR/#T28. That one can analyze such earthly appearing but alien analogs from afar is mindboggling.

One might also wonder if the composition of the upper reaches of the drowned river bring a different mix of liquid hydrocarbons to the estuary akin to the fresh water-salt water mixing in many of earth’s drowned valleys. The figure below puts the drowned river valley in perspective with a broader view of SAR T28 and topographic data from PIA10353 (also in Photojournal) http://photojournal.jpl.nasa.gov/catalog/?IDNumber=pia10353 and compares it with the Susquehanna river ria known as the Chesapeake Bay on the east coast of the USA. In the figure K = Kraken, M = Mayda Insula and L = Ligeia. The Chesapeake Bay is roughly 300 km long from the Susquehanna River inlet (top red arrow) to the Atlantic Ocean outlet (A) photo credit NASA/Landsat https://www.google.com/url?sa=i&rct=j&a...416362873092336.
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rlorenz
post Nov 23 2014, 04:45 AM
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QUOTE (titanicrivers @ Nov 17 2014, 09:16 PM) *
One might also wonder if the composition of the upper reaches of the drowned river bring a different mix of liquid hydrocarbons to the estuary akin to the fresh water-salt water mixing in many of earth’s drowned valleys.


Very astute speculation. Entirely possible, both on the small scale you describe, and perhaps on the larger scale - it could be that the entire Ligeia-Kraken system has a methane/ethane variation akin to the salinity gradient between the sea of Azov/Black Sea/Mediterranean or Baltic/North Sea, where ethane (+propane etc.) are essentially analogs of salt (i.e. an involatile solute tracer) and the enhanced precipitation at high latitudes leads to 'fresher' composition there... See http://www.lpl.arizona.edu/~rlorenz/flushing.pdf

It may be that radar data (radiometry, and/or attenuation measurements in bottom-sounding altimetry) or bistatic radio reflection experiments can constrain the compositions somewhat. Possibly also near-IR spectroscopy from VIMS.
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ngunn
post Nov 23 2014, 11:31 AM
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Should we also expect a vertical 'salinity' gradient within the lakes, as we find in the Black Sea? Searching around I found liquid densities of 0.421 and 0.546 for methane and ethane respectively - quite a large difference. I note that in the Bosphorus there is a deep salty current flowing in and fresh surface water flowing out at one and the same time. Maybe something similar happens at the Throat of Kraken.
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Ron Hobbs
post Nov 23 2014, 03:35 PM
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QUOTE (titanicrivers @ Nov 17 2014, 06:16 PM) *
That one can analyze such earthly appearing but alien analogs from afar is mindboggling.


Yes! And that I can 'listen' in on this conversation is equally so. Thank you so much for that and for the links.

Ron
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Juramike
post Nov 23 2014, 04:59 PM
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Once again, Titan has the potential to be even more complicated than the simple Earth story. One of the fun possible "twists" in the story on Titan compared to Earth is that fluids percolating through the subsurface of Titan can exchange with clathrates. That would depend on the exact structure of the clathrates (structure I or structure II) and the kinetic rate of exchange (flow rate, contact time, initial mix, etc.) with the clathrates in the subsurface. So the hydrocarbon and nitrogen fluid mix going into the subsurface can be different than the fluid mix coming out. Think of it as having an ethane or methane sponge that sucks up one or two of the hydrocarbons.

Check out: Mousis et al., 2014: http://arxiv.org/pdf/1405.6588.pdf

Bottom line (!) is that you could have a propane-rich subsurface spring popping up under the surface of one of the lakes. But that would all depend on the kinetic rates, structures of the subsurface and the starting mix of the fluids.

So it has the potential to be a very, very complex system. As always, more laboratory work is needed. smile.gif

And as Ralph likes to point out during his presentations, most of the calculations are done assuming everything is at equilibrium. As we know from our terrestrial experiences, very few of us are ever at equilibrium. Last time I checked, my relative humidity was a loooooong ways away from 100% saturation (the equilibrium state). Using equilibrium calculatoins for Titan is a good start to see the idealized case, but the reality on (and under) the ground will be even more complicated.


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Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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rlorenz
post Nov 24 2014, 03:09 AM
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QUOTE (ngunn @ Nov 23 2014, 06:31 AM) *
Should we also expect a vertical 'salinity' gradient within the lakes, as we find in the Black Sea? Searching around I found liquid densities of 0.421 and 0.546 for methane and ethane respectively - quite a large difference. I note that in the Bosphorus there is a deep salty current flowing in and fresh surface water flowing out at one and the same time. Maybe something similar happens at the Throat of Kraken.


Indeed. Same thing happens at Gibraltar (as I noted in my Throat of Kraken paper). Stratification is something I'm looking into with Tetsuya Tokano. Stevenson and Potter back in the mid-80s suggested a seasonal CH4 layer might form on top of a denser C2H6 layer (but they thought it would happen in winter - it rather seems now instead it might be a summer rainfall thing). Transient layers of fresh water do form on Earth's seas (arctic freshwater pool, Amazon plume, etc.) - the question is how quickly things may get mixed up. Tokano in 2009 looked at thermal stratification. But with methane/ethane/nitrogen/etc the composition effects and temperature effects can trump each other - there's a phenomenon ('rollover') where this has happened in LNG storage tanks - am writing something up about this in a titan context.
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titanicrivers
post Feb 13 2015, 01:13 AM
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Antoine Lucas’ de-noising technique featured in today’s Photojournal article http://photojournal.jpl.nasa.gov/catalog/PIA19051 and http://saturn.jpl.nasa.gov/news/cassinifea...eature20150211/ provides an interesting perspective and relatively noise free view of the drowned river valley of T28. The small stream tributaries one might have anticipated are nicely shown in the de-noised view (included below).
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titanicrivers
post Feb 15 2015, 01:07 AM
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The ‘drowned’ river in the de-noised, despeckled perspective http://photojournal.jpl.nasa.gov/catalog/PIA19051 with topography from PIA10353 http://photojournal.jpl.nasa.gov/catalog/?IDNumber=pia10353 overlain is shown below. Titan’s rivers are said to show little in the way of erosive action http://newsoffice.mit.edu/2012/river-networks-on-titan-0720 but I wonder if the area circled might be a substantial valley cut into the icy uplands. A rough estimate based on the elevation scale shows a 400m difference between the river bed and adjacent upland over a relatively short distance of 5-10 km.
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marsbug
post Feb 15 2015, 12:35 PM
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Looking at the side by side comparison images in the press release, here, the despeckled images look much less like I was expecting - like they have giant seaweed draped ove the Titanian surface biggrin.gif biggrin.gif biggrin.gif Parts of it just look... too smooth!


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0101Morpheus
post Feb 15 2015, 03:16 PM
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Couldn't they do that with any object mapped by radar? Like, lets say, Venus?
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titanicrivers
post Aug 29 2015, 09:42 PM
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A nice article on Titan’s lakes and seas appears in the October 2015 issue of Astronomy magazine. http://www.astronomy.com/magazine/2015/08/...=NjIyNzQwMDg5S0. PIA 18432 http://photojournal.jpl.nasa.gov/catalog/PIA18432 is featured on the cover and on p. 25 of this publication. The author, Alexander G. Hayes, provides an authoritative summary of what is known about Titan’s seas including the composition, radio wave absorptivity and depth of the major bodies of liquid on Titan http://www.hou.usra.edu/meetings/lpsc2014/pdf/2341.pdf. SAR images of the “magic islands” in Ligeia Mare, a nice comparison of rounded surface ‘boulders’ on Titan and Earth and discussion about Titan’s lake distribution change with time are highlighted.
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HSchirmer
post Aug 29 2015, 11:18 PM
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QUOTE (rlorenz @ Nov 23 2014, 04:45 AM) *
QUOTE (titanicrivers @ Nov 17 2014, 09:16 PM)

One might also wonder if the composition of the upper reaches of the drowned river bring a different mix of liquid hydrocarbons to the estuary akin to the fresh water-salt water mixing in many of earth’s drowned valleys.

Very astute speculation. Entirely possible, both on the small scale you describe, and perhaps on the larger scale - it could be that the entire Ligeia-Kraken system has a methane/ethane variation akin to the salinity gradient between the sea of Azov/Black Sea/Mediterranean or Baltic/North Sea, where ethane (+propane etc.) are essentially analogs of salt (i.e. an involatile solute tracer) and the enhanced precipitation at high latitudes leads to 'fresher' composition there...


Neat ideas- there appears to be an impact crater in the Titan image, which reminds me that there is a large crater under Chesapeak bay.
That crater was found because of odd groundwater flow in that area, freshwater, regular sea water and brine.
One theory is that the heat from the chesapeak impact vaporized the water from deep aquifer seawater to create a concentrated brine.

Very interesting to think about what chemistry and fractionation you might get from an impact into hydrocarbon seas.
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Mongo
post Jan 15 2016, 02:08 AM
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Compositional Similarities and Distinctions between Titan's Evaporitic Terrains

QUOTE
We document the similarities in composition between the equatorial basins Tui Regio, Hotei Regio, and other 5-μm-bright materials, notably the north polar evaporites, by investigating the presence and extent of an absorption feature at 4.92 μm. In most observations, Woytchugga Lacuna, Ontario Lacus, MacKay Lacus, deposits near Fensal, some of the lakes and dry lake beds south of Ligeia, and the southern shores of Kraken Mare share the absorption feature at 4.92 \um observed in the spectra of Tui and Hotei. Besides Woytchugga and at Fensal, these 5-μm-bright deposits are geomorphologically-substantiated evaporites. Thus, the similarity in composition strengthens the hypothesis that Tui and Hotei once contained liquid. Other evaporite deposits, however, do not show the 4.92 \um absorption, notably Muggel Lacus and the shores of Ligeia Mare at the north pole. This difference in composition suggests that there are more than one kind of soluble material in Titan's lakes that can create evaporite and/or that the surface properties at the VIMS wavelength scale are not uniform between the different deposits (crystal size, abundance, etc). Our results indicate that the surface structure, composition, and formation history of Titan's evaporites may be at least as dynamic and complex as their Earth counterparts.


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