Printable Version of Topic

Posted by: belleraphon1 Dec 29 2007, 01:36 AM

All....

The Lakes and Seas of Titan: Observations From Cassini RADAR

http://saturn.jpl.nasa.gov/multimedia/products/pdfs/CHARM_20071127_Mitchell.pdf

http://saturn.jpl.nasa.gov/multimedia/products/wav/20071127_CHARM_Mitchell.wav

http://saturn.jpl.nasa.gov/multimedia/products/docs/20071127_CHARM_Mitchell_transcript_raw.doc

Perhaps due to the Holidays, this was not noted before...

Enjoy

Craig

p.s. what fill 12/20/07 SAR reveal?

http://saturn.jpl.nasa.gov/news/events/titan20071220/index.cfm

"Cassini successfully completed its most recent Titan flyby on Dec. 20, 2007, and data are currently being analyzed. During this flyby, the radar instrument studied Titan's "deep south." This will allow scientists to contrast this region against what they found in the lake regions of the north polar area. The spacecraft went as far south as 70 degrees. The radar imaged areas of the Tsegihi region it had not yet seen, and got some overlap in coverage. New ground was covered south of the dune fields of Belet. "

Posted by: nprev Dec 29 2007, 02:01 AM

Thanks, BP! Good stuff in there; obviously many more questions than answers at this point.

So, there's a new "cryo-ice" lab at JPL? Great idea; maybe we'll have a clue about how all this exotic stuff actually behaves.

Posted by: Juramike Dec 29 2007, 03:25 AM

Here's a wild speculation:

What if the karst-like terrain is due to the action of hydrocarbon solvents percolating through "rotten terrain" that is overlain by a deep blanket of precipitated organics?

So to get the caldera-like lakes you would need:
1) rotten terrain (old clathrate stuff at the surface?)
2) heavy solvent exposure (rainfall or subsurface percolation)
3) blanket of precipitated organics (brought down by rainfall)

So in this scenario, you'd only get karst-terrain in the polar/temperate regions in regions underlain by rotten terrain.
In the equatorial regions, which has a much, much smaller blanket of precipitated organics, there would be the "underpart" of the Titan karst terrain visible. So take the rotten terrain from equatorial regions, dump on precipitated organics, add sovent exposure and you'll get the caldera-like lakes seen in some parts of the north polar region.

[This scenario avoid the need for a geothermal hot spot that just happens to coincide with the polar lakes.]

-Mike

Posted by: belleraphon1 Dec 29 2007, 03:42 AM

Your welcome Nprev..

Juramike.... from p 35 of the transcipt

"If this is therefore karst, and if the depths of these lakes which we have in places mentioned a few hundred meters is indicative of a fitness of a non-waterized soluble layer, then we actually have an extensive and thick polar cap.

Now this isn’t like the polar cap on the Earth in that it’s not something that will face changing into liquid or melt. The liquids and the (unintelligible) in polar regions are actually quite different chemistries."

Your precipitated layer is the solid hydrocarbon polar cap.

Now... why does this only occur at the pole? Atmospheric circulation dumping more solid hydro precipitates at the pole as snow? Temperatures and humidity just right to allow methan/ethane/nitrogen precipitation in liquid phase?

Really neat picture..... really want that south pole SAR!!!

Craig

Posted by: belleraphon1 Dec 29 2007, 03:58 AM

Titan.... goo-ology in action

http://www.planetary.org/blog/article/00001085/

thanks to Emily for the link ... the Kargel paper is fascinating, and Karl Mitchell's presentation highlights how Titan is certainly the poster child for this.


Craig

Posted by: Juramike Dec 29 2007, 04:17 AM

So the polar caps are the "schizzle layer".

I would hazard that they are brought down by rainfall. The rain drops would have a thin shell of atmospheric organics on the outside as proposed by Ralph Lorenz in "The Life and Death of a Raindrop on Titan." Lotsa rain, lotsa schizzle. No rain, little schizzle.

So the polar/temperate rainstorms are bringing down the organics AND bringing down lots of hydrocarbon solvent that can act as the percolating fluid to make the lakes dissolve out.

Not all the stuff in the pit is going to dissolve. So you'll end up with a wet mess. In one sense it would look like a slushy puddle (except the solid and liquid will be different materials). In areas with lots of methane, it would have a covering of methane (with lower levels of undissolved emulsions and organics - these would likely be more dense than methane). In areas will lower amounts of methane, the area would be a dried out slushy puddle. (Or it may be pretty moist, with chunks of undissolved goop blobbing around).

Which could explain the appearance of lakes further away from the poles. They look dried since the material dropped out due to dissolution, but the amount of methane is not enough to cover the chunks it or keep it covered.

Soooo....if this is correct, then the dried out areas in regions with fractal lake patterns should be very, very different. In these cases, the lakes are in a hard non dissolvable substrate. Any organics washed in by rivers should deposit in thick undermethane deltas. I would thus predict (y'all heard it here first) that the slope bench of fractal lakes will be very wide, while the slope bench of caldera lakes will be relatively thin.

(Slope bench being defined as distance between highmethane mark and the flat bottom sediments).

[Now to check RADAR swaths to see if I'm Hero du Jour or Goat of the Day].

-Mike

Posted by: Webscientist Dec 29 2007, 11:18 AM

What a present for christmas, this paper from Mitchell, very well illustrated!
The findings upon the behavior of hydrocarbon molecules on Titan confirm that they are "natural lego" which can form very complex molecules. I still have in mind one of the latest news revealing complex hydrocarbon molecules in Titan's upper atmosphere ( a molecule of 10 000 atoms!).
So what occurs when the carbon atoms encounter (and interact with) a hydrocarbon solvent like what is probably found in those bodies of liquid(s). That's what I'm eager to know.

Posted by: Juramike Dec 29 2007, 02:56 PM

It probably resembles the non-halogenated organic waste container in a typical organic chemistry lab. The ratio of solvent, to goo, to gunk probably varies from lake to lake. The goo to gunk ratio might not vary much - it might depend more on relative solubilites of the components and the size of the "solventshed".

Another analogy might be the lower level of the tray after cleaning a chain (motorcycle, chainsaw, bicycle) or other motor part in gasoline. At some point there will be hydrocarbon solvent (gas), and gunk - some polymeric material that doesn't really dissolve in the gasoline, but gets loosened up enough to drop off the chain. The color is probably pretty close to Titanian lake sediments too (hint: not pretty).

-Mike

Posted by: nprev Dec 30 2007, 01:29 AM

Uh...yecchh!!!

Question: Do we see anything in the SARs that resemble completely filled in lakes from this crap? Seems as if this might be an analog to terrestrial sedimentary fills of similar lakes. Harkening back to Alaska again, I'd often see former lakes that had long since filled in & had young trees sprouting on them; they were pretty easy to identify in contrast to the surrounding terrain.

Posted by: Juramike Dec 30 2007, 03:46 AM

I think it will be hard to tell between something that was filled in, and something that is (temporarily) dried up. Especially since we don't know the properties of stuff when if dries up. Does it make a smooth coat? Or does it chunk up into radar brighter blobbies of gunk or goo? (picture dead jellyfish on a beach after a storm - yuk!)

Here is a picture of an ex-lake that has either dried out or has filled in. The ex-lake is outlined in blue, but there are other darkish shapes in the same area. The much darker shapes are possible lakes. This is from PIA01943 and is located roughly at [80N,357W]. It has a brighter RADAR signature, so it either has clumps of stuff on the surface from drying out, or stuff that plopped down from the atmosphere. Both would make the surface rougher and appear RADAR brighter than a smooth RADAR-dark surface.



Down near the lower edge of the outlined lake appears to be a cute little dune patch. These seem to be the polar/temperate style dunes, rather than the big humungous equatorial style dunes.

Since there are dunes on the lake bed, it indicates that the lake has either dried out and been that way for a while, or that the lake has filled in. Either way it has been dried out at least on the timescale of dune formation.


-Mike

Posted by: nprev Dec 30 2007, 05:31 AM

Ha!!!! Knew you'd be all over it, Mike; important observation re juxtaposition of dunes over a polar dark patch, congrats!!!

So it does seem possible that lakes eventually become filled with Titanian sedimentary/precipitory products, or to use the technical term I coined in my last post, 'crap'. Perhaps there's a bit of a race between drying up (seasonally?) and choking up...

Posted by: tty Dec 30 2007, 04:28 PM

Almost certainly true. That is what ultimately happens to all lakes here on Earth, and it is a rather fast process geologically speaking. Usually the lifetime of a lake can be measured in thousands or tens of thousands of years (that's why there are so many lakes up in the north woods and the northern prairies and almost none further south, up north the lake basins were scoured out by the ice only 15-20,000 years back). Only very deep lakes like Lake Baikal or Lake Ohrid last for a few million years.

Of course "geology" works much slower on Titan but I would expect lakes to ultimately fill in with gunk (or dune "sand") there too. New ones might be created by "karst" processes or tectonically.