At first sight there appears to be a line of cloud in much the same place as before in this new image (on the far right just above Ligeia Lacus): http://saturn.jpl.nasa.gov/multimedia/imag...5/N00228346.jpg

Yep, there seems to be a cloud right between Muggel and Ligeia, alright.

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Yes, and no. The entry point was determined by a number of engineering factors (entry angle tolerable by heat shield defines a circle, given the delivery asymptote). Solar illumination for the descent spectral measurements, and communications geometry (including having the line of sight mostly east-west for doppler wind measurements) were also constraints. These determined a small entry region around 145W 20N.

This site was targeted by VIMS on the first Titan flyby (and hence had the first Nature paper written about it). The feature that happened to be at that spot, now named Tortola Facula, although I nicknamed it the 'cat poo', was possibly overinterpreted as a cryovolcanic construct - I think observations since do not lend much support to that interpretation.

When the Huygens mission had to be redesigned following the receiver design flaw discovered on the Earth flyby in 1999, the new delivery scenario actually relieved some of the communications constraints on the delivery point, and we actually had a choice of 2 sites (and now, circa 2002 IIRC, crude maps to think about) at 190W and 10 North or South. We actually discussed it and South won, because it was the border between near-IR (940nm) bright and dark stuff. 940nm data, even at this point, don't really discriminate photometrically between dunes and seas, and no-one really expected the former! (By this time the observation planning had moved to later in the tour, and the VIMS targeting of the old landing site remained unchanged..)

Anyway, had the probe landed in a liquid, it might well have capsized depending on the wind (the payload was indeed designed mostly with a liquid landing in mind, but the probe itself had no design requirements for any landing). The GCMS inlet was heated with the intent of volatilizing surface material, which indeed occurred in the damp regolith we landed in. So it might have been quite interesting chemistry-wise.

Obviously, we might well aim for the seas now, although they might in fact be of quite different composition. Ligeia looks to be rather methane-rich ('fresh') while Kraken may be more solute-rich (analogous to the Baltic and the North Sea, or the Black Sea and the Mediterranean) - see http://www.lpl.arizona.edu/~rlorenz/flushing_preprint.pdf
A sonar would probably work better in Ligeia, but from a chemistry standppoint Kraken might be the preferred choice. To understand the hydrological cycle you'd probably want a lander for each, or a vehicle that could somehow sample both......

Anyway, I take your point. If you want to survive a landing, a gullied streambed would likely not be the best choice. If we knew the surface, would we have aimed for the dunefields (as we did in the 2007 APL Titan Explorer Flagship Mission Study, before the seas had been mapped) ? Or the midlatitude blandlands? If we knew the seas were there, would we have targeted them - perhaps not - remember they were in winter darkness in 2005 !

Indeed where we ended up was information-rich - it certainly showed instantly that Titan was a hydrologically-shaped world.

Perhaps specifically the southern basin of Kraken given the drainage scheme you postulate there? I note that it lies partly outside Titan's arctic circle so would receive at least some sunlight even in midwinter. I don't know if the same can be said for the possibility of direct-to-earth communications

There it comes down to a 'how little data will you accept and how much risk of terrain obstruction' question. The usual story of contemporary planetary exploration - anything is possible, but how do you prove that there is no way, at all, ever, that it could possibly go wrong...

Arguably at the extreme south of Kraken (ditto at Ontario) the material is more likely to be muddy/viscous, which makes landing dynamics and material sampling harder to test/verify (again, chances are everything would be fine, just costs a lot to demonstrate..)

… and this paper in Icarus http://www.jpl.nasa.gov/news/news.php?release=2014-294 might help explain sea composition differences if some seas are much older and therefore alkanofers and clathrate composition changes and interactions can influence extant sea composition.

Below is NAC view (N00228357 from 256K km on 8-21-2014 CL1 CB3 filter) from the T104 flyby covering the Kraken (K) – Ligeia (L) estuary. The cloudy region (Cl) between Muggel (M) and Ligeia is well shown, the estuary (arrow) just barely visible. The image shows the ‘Looking Ahead’ ISS map (with a hint of radar) first and then the enhanced-cropped view of N00228357 fills in the right half of the scene.
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The connection between Ligeia and Kraken may involve several parallel channels (hence I referred to it in my flushing paper as the Ligeia-Kraken Labyrinth, LKL)

I'd say the Kraken inlet next one up from the labyrinth might be a better place for the label 'estuary'. (It was in this inlet that a radiometric change between T25 and T28 was observed, maybe suspended sediment?)

The 'Magic Island' returns: http://photojournal.jpl.nasa.gov/catalog/PIA18430

I love mysteries, especially when their circumstances mandate that even the most mundane explanation will be extraordinary.....

A mystery is always fun to poke the brain at. Considering the fact that ices will be heavier than the liquid on Titan, this might be the buildup of ice on a reef of ices right under the surface. The hypothesis that it might be foam is one I could have liked, but it is bright, which make that alternative less likely.

Try solid ice-foam. Closed cell ice foam on the lake bed would be buoyant in methane. Either it could be formed currently by being erupted from the seabed in some cryovolcanic process or it could be there already just waiting for some disturbance to dislodge it so it can float up.

Solid ice-foam is a good suggestion, and I'd really like to get the idea to float.

But the process would need to be just right to create foam bubbles of the right size and thickness to make all parts of this island buoyant.
Now that the total size is rather large, this mechanism creating the bubbles would also have to work evenly over a sizeable part of this feature.

So I am stuck in the icy reef, and the ice hypothesis here. =)

Here's my thinking. Radar bright means a polar material like ice. Methane-buoyant ice means closed cell foam, like pumice. On Earth, floating pumice disperses due to winds and currents, then eventually washes ashore or sinks as its cell structure breaks down. That seems to fit with what we're seeing.

How would a closed cell ice foam form? I don't know, but here we are on a world with a wide range of aqueous and organic materials. The occasional presence of some suitable surfactant when the material solidifies is not too much to ask.

Newly exposed shoals can I think be eliminated. The liquid level hasn't changed much if at all, and anything shallow would already have been visible whilst just below the surface. There was no hint of it before the 'island' first appeared.

(Note: porous materials, thought to be common on Titan, can be either permeable like sponge or impermeable like expanded polystyrene,)

More 'magic islands' - and more bathymetry - in Kraken Mare this time: http://photojournal.jpl.nasa.gov/catalog/PIA19047

(from the Cassini website) http://saturn.jpl.nasa.gov/news/cassinifea...eature20141110/

It's the Nautilus of captain Nemo!

I hope it's an unexpected an uniquely Titanian emergent property of the physical and chemical properties of the stuff in the lakes - something truly unique to Titans bizzare environment would be amazing!

It would be interesting to see if there are any surface temperature changes over time at these sites. However, and please correct me if I'm wrong, I don't think that there's any way to obtain data like that at a useful resolution for these features unless they are very pronounced changes.

It sets the mind racing, that's for sure. It reminds me of the uncomprehended phenomena, some benign and some dangerous, on Stanislaw Lem's imagined world Solaris.

The important thing here is the statistics of two. Just one is a remote possibility, but there are never just two of anything. Two in a relatively small sample of the liquid surface in both space and time means that these things pop up quite a lot. I'm left wondering about parts of the lakes and seas that have been imaged only once. Could a few of those other islands be 'magic' ones too? Do the radar images of the 'magic' ones differ in any way that would allow us to distinguish? I also wonder about the lake coastlines. Are there undetected inlets covered with rafts of flotsam disguising the outlines?

Luckily there's VIMS as well as SAR this time, so expect a good science harvest!

I have a thought that has been itching me all day, and I'd like to clear it out: Could these magic islands be tension wrinkles in a membrane that sits on top of the lake surface? If the lakes develop a fairly thick layer of something semi-solid, it might buckle and then relax as changing environmental conditions alter the overall tension. The specular reflections observed could be due to a thin liquid layer on the surface. It just struck me when my tea went cold that the patches of wrinkles on the skin looked a bit like the 'island'...

It has been said that some lakes or seas were almost as smooth as a mirror. As you say, why not a thin membrane over le liquid.

A new radar-bright feature about 50 km wide. Difficult to understand!

I see several hypotheses:
--> a detached chunk rising from the sea floor.
--> rising bubbles from hot springs
--> a new island via cryovolcanism
--> snow fall or fall of hydrocarbons or organics (some clouds have been seen over Ligeia Mare)

--> or perhaps, some submarine topography (close to the surface) can be discerned if the incidence angle from the radar mapper is low ( as deduced from the data of the Cassini Huygens website).
...
But the bright structures seem to evolve rapidly. Only plankton formations can change so quickly !

Here is a terrestrial 'magic island', no plankton required!
http://www.google.co.uk/imgres?imgurl=http...t=0&ndsp=12
I'm referring to the pumice raft not the new island there.

But I like the wrinkles suggestion for the degree of lateral thinking involved.

MOD NOTE: Let's please remember that rule 1.3 also doesn't permit discussion of plankton...

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.

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.

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

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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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.

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.

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

Ron

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.

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.

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.

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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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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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 Parts of it just look... too smooth!

Couldn't they do that with any object mapped by radar? Like, lets say, Venus?

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.

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.

Compositional Similarities and Distinctions between Titan's Evaporitic Terrains

Some of the best ISS overviews of the northern lakes are appearing now:
http://saturn-archive.jpl.nasa.gov/multime...5/N00263235.jpg

EDIT: This is from the Ciclops 'looking ahead:
"Late on July 26, ISS will acquire a series of cloud tracking observations covering Titan’s north polar region.

On July 27 Titan will be observed during a calibration observation of the polarizer filters on ISS."

I will be looking to see if the lakes look markedly different through the different polarizers.

This is a 'color' version using the CB3, MT1 and MT3 filters:

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Going for the MEX VMC look?

Looks very nice.

Thanks Jason! Yeah, I've been looking for a way to give the CB3 frames some color for a while now, and seemed to have hit upon a recipe that works:


Titan 2015-OCTOBER-02 by Ian Regan, on Flickr


Titan 2009-JUNE-25 by
Ian Regan, on Flickr

The latest view from August 3rd:

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And from the following day, August 4th:

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The study by Poggiali et al published describes radar studies which seem to show fluid filled valleys draining into Ligeia Mare. The continuous presence of fluid within these canyons in the absence of precipitation would thus seem to indicate a subsurface source of liquid methane?

2016-09-10 Titan by Ian Regan, on Flickr

Here's my version of Titan on 10 September
red, gr, bl and uv filter at right and 3 cb3 stack at left

In this view, with Sinlap crater in the middle, we can see: Kraken Mare, Lingeia Mare, Jingpo Lacus, Bolsena Lacus, Ledoga Lacus and Punga Mare.

The latest observation of Titan (from the 21st):

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