Titan's Lakes @ DPS 2008 Options

[volcanopele]

I hate to say this, try IE. Seems to work better there.

Just an advertisement for the talk I provided the most work for, Zibi Turtle's talk at 9:30am in the Titan Lower atmosphere session. I doubt you will be disappointed.

EDIT: That should be 11:30am EDT

Reason for edit: time wrong

[djellison]

Starting right now.

[Juramike]

"Pretty cool" was an understatement.

[ngunn]

The whole session was great. But with all that methane being convected and precipitated, large lakes with steep shorelines, extensive liquid-carved channels - why hasn't the VIMS team found anything deeper than a puddle?

[Juramike]

The whole session was great. But with all that methane being convected and precipitated, large lakes with steep shorelines, extensive liquid-carved channels - why hasn't the VIMS team found anything deeper than a puddle?

I wasn't exactly sure of the argument of calling the areas "playas" in one of the presentations. I think most of the absorbance curves for depth calculation were generated assuming the bottom albedo was "1.0" (perfect mirror). I kinda think that is highly unlikely.

In a later talk, Lawrence Soderblom's presentation seemed to imply that the 5 micron (2000 cm-1) albedo of Ontario Lacus was nearly zero (no scattering at all, no reflectance). The strong absorbance of ethane at 5 micron means that very little would be required to zero out the spectrum. (Slide 239)

So I think it was the 2.0 micron absorbance (or lack thereof) that was used to imply a shallow lake depth, since reflectance is pretty much unaltered at this wavelenght. (Slide 246).

But this assumes that the surrounding terrain (non-lake) is at the bottom of the lake. (The lake has minimal effect on the 2.0 micron absorbance, thus it's not real deep). If the lake material contains "stuff" (suspended? lying near the bottom?) that reflects 2.0 micron radiation pretty well then the depth analysis doesn't hold water (!).

[2.0 micron is a water absorbance band local minimum, so all it would take to get better reflectance than adjacent non-lake terrain would be some "less water-ice"-like material. So any organic "non-water-ice coated sediment" could do the trick.]

The questions at the end of the presentation did ask about suspended or floating sediment or materials. "You can't judge the depth of Cayuga (a very deep lake in the Finger Lakes region) by what I can see at the surface."

I think a fair statement is that the hydrocarbon absorbance (derived optical depth) from lake reflection is minimal. Not sure whether this could be solely due to shallow liquid depth.


[I also noted that the 5.01 reflectance image shown in Slide 245 correlated nicely with the putative Deep Black unit (which was proposed from the possibly artifact-ridden 2.8/2.7 ratio). "Noise shouldn't correlate" ]

-Mike

-Mike

[ngunn]

Yes, but the suspended material suggestion was countered with the question: what can stay afloat in liquid methane? (Not much.) Also someone made the point that fine material in suspension would be more transparent to IR than to visible light so it's that much more difficult to fool the IR with a 'false bottom' of suspended material.

In another presentation the case was made that the lake surfaces must be extremely flat, with no sign of wind waves, yet we know there are winds. Putting these two things together, I'm picturing a fluid more like black paint than petrol - difficult to make waves on and very opaque. The suspended material must be in particles small enough to be kept aloft by random thermal agitation, perhaps individual large molecules rather than 'grains'. Would that provide enough IR opacity? I haven't a clue! Perhaps you do.

Cue to admin: maybe we need moving to the Titan subforum.

[Juramike]

What can stay afloat in liquid methane? Well, something less dense than the liquid - maybe something with liquid and air. For example (my favorite), how about a chunk of clathrate with gas-filled micropores? ("Cryopumice"). Or some type of frothy, foamy organic material. (BTW, foaming can be a MAJOR problem in large scale chemical plants).

What can stay suspended in liquid methane is probably a much easier question. Heck, I'm not even convinced that the hydrocarbon lakes have a low density (or viscosity for that matter). With your paint analogy, there could be some organic goop suspended around in a yukky organic mess. The whole lake could be a big emulsion (which could also change evaporation rates).

The key is that there needs to be IR reflection, at least in the 2 micron area.

Now the other question is: if the lake liquid is so thin, how come RADAR isn't able to penetrate it? Or is RADAR hitting an absorbing(diffusing) subsurface layer as well? (AFAIK, RADAR hasn't yet gone over Ontario Lacus, I'm extrapolating from the northern lakes).

My picture of a Titan lake is now of a flat, black, hydrocarbon emulsion/suspension.

-Mike

[Yup, I agree, the last few posts should be put over to the Titan subforum, probably the "Titan's Lakes Revealed thread", starting from VP's post #12]

[volcanopele]

Moving Titan lakes talk here

[Jason W Barnes]

In a later talk, Lawrence Soderblom's presentation seemed to imply that the 5 micron (2000 cm-1) albedo of Ontario Lacus was nearly zero (no scattering at all, no reflectance). The strong absorbance of ethane at 5 micron means that very little would be required to zero out the spectrum. (Slide 239)
-Mike

That was actually Jason Soderblom. He's Larry's son and my replacement as VIMS postdoc in Arizona.

- Jason W. Barnes

PS -- Yes, yet a third Jason.

[volcanopele]

Can't even say VIMS Jason anymore.

[titanicrivers]

I didn't see a link posted for the DPS 2008 conference. Here is one that takes one to the schedule of presentations with links to the video stream and slides.
http://dps08.astro.cornell.edu/AAS_WebcastSchedule_2008.html

[ngunn]

My picture of a Titan lake is now of a flat, black, hydrocarbon emulsion/suspension.

Worth mentioning the likelihood that there may be huge differences between lakes, and between seasons (especially for the smaller ones). A recently recharged lake may be runnier and more transparent (or maybe not!!). A lake which drains into another (overground or subsurface) may be very different from one that is a 'dead end'. I think there are just too many variables and not enough observations yet for a comprehensive synthesis, and that's exactly why it's all so fascinating.

I'm a great fan of floating foams and pumice in some situations, but they don't seem to help with the present puzzle.

[belleraphon1]

I didn't see a link posted for the DPS 2008 conference. Here is one that takes one to the schedule of presentations with links to the video stream and slides.
http://dps08.astro.cornell.edu/AAS_WebcastSchedule_2008.html

I am not sure if this clarifies what you are asking, but click on the session 23 link for Sunday. This session has the presentations that are discussed in this forum.

See http://www.abstractsonline.com/viewer/viewSession.asp for a list of presentations. The relevant ones are the last four.

Titan ain't easy.... what fun!!!

Good Viewing!!!!!

Craig

[rdale]

I didn't see a link posted for the DPS 2008 conference.

http://www.unmannedspaceflight.com/index.p...mp;#entry128546

See http://www.abstractsonline.com/viewer/viewSession.asp for a list of presentations.

No such page...

[titanicrivers]

Try the link I used last night. http://dps08.astro.cornell.edu/AAS_WebcastSchedule_2008.html
Seems to work fine.