Surface Chemistry of Titan Options

[Juramike]

The bulk of the liquid in the lakes on Titan is going to be a methane/ethane combination, but a lot of polymeric organic material is going to have been washed in from the terrain, as well as blown in from the dunes. (The lakes would be a dune trap). That means ice-silt and tholin-coated ice silt.

The higher-order organic polymers may act as a surfactant to coat the ice particles. I would hazard that the hydrophilic functionalities of the polymer subunits would side with the ice particle surface and the hydrophobic parts of the polymer would face the methane solvent. This would allow some really gnarly emulsions to set up.

A cross-section of a lake on Titan would look like a classic "nightmare extraction" sitting in a sep funnel in an organic chemistry laboratory. There would be a foamy goo or scum component floating on the surface, the methane/ethane layer as solvent possibly with low density organic shmeggums floating about, then a denser loose gelatinous organic polymer/solvent component full of organic yukkies (please excuse the med chem. technical jargon), then a more dense portion of organic polymer/organic solvent/water emulsion, and finally a water-ice silt bottom.

Water (ice) and organics are immiscible. But hexanes and acetonitrile (CH3CN) are also immiscible. By analogy, methane should also be immiscible with CH3CN (which would be a solid at Titan’s temperature, but a lower density component than ice). This should make for yet another fun emulsion possibility. [I’ve seen waaaaay too many ugly emulsions in sep funnels with “simple” organic components.]

With the complex organic chemistry at Titan, there is a very real possiblitiy of multiple layers of emulsions combined with an organic scum layer at the surface.

I’m not sure how any of this would affect specular reflections or even radar penetration. The surface would not look like the pretty foam of a bubble batch but more like the curd on overcooked pea soup.. Would certain layers reflect radar better than others? Can you get specular reflection when there are bubbles or “floaters” on the surface? What if the “floaters” are soft low density organics? How do organic emulsion blobs reflect radar?

The patterns we are seeing in the lower parts of the lakes may be channels in the goopy lower emulsion layers (think of the orange crud at the bottom of scummy ponds). I could imagine a scenario when higher density organic goo flows into the lakes and carves a path through the less dense emulsion. The real “bottoms” of the lakes may lie under meters of organic emulsion.

Lakes on Titan may resemble more of an open pit hazmat toxic waste dump (although I still like to think of it as “a pristine prebiotic environment”).


-Mike

[Stu]

Can't claim for a moment to have understood much of the science in that post jura, but with the references to "organic scum" and "overcooked pea soup curd" it's given me - possibly for the first time - a real and vivid mental picture of what a Titanian lake might look like, so thank you.

[ngunn]

Yes, a useful post, thanks. I had been wondering along these lines too. Seas of shimmering clear liquid are very enticing to imagine but probably wide of the mark. The scale of our ignorance just seems to expand the more we see . .

[stevesliva]

Titan's tar tarns revealed.

The real question I have (perhaps already addressed) is whether the liquid in the lakes solidifies with the changing of the seasons, or only evaporates. It's a difference in erosional analogies of rain eroding ice or rain eroding rock...

[nprev]

Yes indeed, a terrific post, Juramike. I suspected that we might be underestimating the chemical complexity of Titan's lakes; your post answered al lot of questions (or at least articulated some excellent hypotheses to explain many of Cassini's observations, or lack thereof in the case of specular reflections...)

It sort of looks like Earth; it sort of even feels like Earth in some weird ways...but it ain't Earth!!!

[lyford]

MMMMMmmm "creme brulee crust and scummy pea soup!"

[nprev]

Titan's tar tarns revealed.

The real question I have (perhaps already addressed) is whether the liquid in the lakes solidifies with the changing of the seasons, or only evaporates. .

Hmm...In fact, how much evaporation actually occurs? Given the "scum scenario" Juramike described, I wonder if the anticipated methane monsoons can actually occur from lake evaporation; seems like most of the CH4 should be bound or trapped in some way.

[edstrick]

"...Lakes on Titan may resemble more of an open pit hazmat toxic waste dump..."

Remind me to NOT join the Titan colony Polar Bear Club!

[remcook]

"[...] although I still like to think of it as “a pristine prebiotic environment”."

You've been writing too many proposals

[ustrax]

Great post juramike! Really visual and...smelly...

According to Lebreton's oppinion its not only the lakes but also the surface that "must be covered with thick layer of organic goo.
Something that may resemble a polluted area (an icy coast) on Earth after a black-wave.”
One thing that makes me scratch my head is what is the process that makes possible for that "gelatinous" stuff to carve channels?...

[ngunn]

I imagine that when fresh rain falls it is really very runny, with just a little suspended smust, looking a bit like well-diluted indian ink. Flowing across the surface it would get progressively dirtier and, especially in any rapids, foamy. I doubt if anyone is yet in a position to speculate on how long any such foam would persist, but I would expect both foam and sediment to decrease gradually after reaching the lake, leaving a dark emulsion. A coating continuous and persistent enough to seriously inhibit evaporation seems unlikely to me (I can't justify that - I suppose it could form a paint-like skin) but in any case there seems to be more than enough total lake area now to supply the proposed methane cycle. And with all that wet ground as well - -

It looks to me as if the narrow sinuous erosion channels continue into the deepest parts of some lakes, indicating that fairly runny stuff is present even in the later stages of drying out. This could be episodic (nocturnal?) new precipitation or a runny fraction may percolate out of the dirty deposits further upstream, even as they dry from the top down, rather as seawater can sometimes be seen trickling out of sandbanks at low tide.

Anyhow, clothes-peg for the nose definitely required, and NO SWIMMING.

[ustrax]

Thanks ngunn.

Here's an interesting pdf, I don't know if someone made reference to it already...

[ngunn]

Thanks Ustrax! That one's a real peach. Looks like the scientific literature is acquiring some interesting new vocabulary - and more may be required as the complexity of Titan unfolds. Still, they're not hard words to make up. Let's see now - spludge, flimp, thlupp, turj, frilth, glume, crusp, jellink, blooze . . .

And there's an obvious abbreviation for 'Polar goo'.

[ustrax]

Another question...
In a crop from this image it looks to me that we can distinguish the level the liquid filling the lake can reach.
For my untrained eye it looks like (sorry for the sketch's quality...) we can see the bottom of the lake and the line marking the maximum height of the filling.
If this is correct is it possible to calculate how deep can it be?

[ngunn]

OK this is difficult because I can't post annotated images but here goes. My guess is that the landward edge of your boxes does indeed mark the current shoreline. I'm counting your boxes from left to right 1 to 13. Now as regards the outer edge of the boxes - I think that from box 6 to box 11 your line follows a currently submerged drainage channel. At about box 12 the channel continues a bit to the right of your line, tracing a meandering course which continues all the way to the top of your crop, and beyond. This submerged channel, if that's what it is, cannot be deeper than a few 10s of metres (for 'clean' organic liquid). If the lake contains significant amounts of ice or other polar molecules in suspension then these features could be a whole lot shallower. That's my (tentative) view at the moment.