[X] My Assistant

[centsworth_II]

I know the problem - where does the neccessary heat come from to cause the evaporation?

Also, there's the question of whether an evaporation inhibiting layer exists on the surface.

[SFJCody]

I was thinking all those lakes, those hundreds of lakes, those thousands of lakes, are going to need names.

I favour the old Martian name (now defunct) of Mare Borealis for the big one.

[ustrax]

THis may sound completely non sense but from the last image it gives me the impression that even a larger lake, or sea will be created from other features that look like new proto-lakes being formed, eroding the top of the surrounding elevations...
At least that's what my better scientific weapon...intuition...tells so...

[ngunn]

Olvegg, I've another thought to add on the possible filling and drying out of quite large 'lakes' like (maybe) Mezzoramia. We may need to consider long term secular changes as well as seasonal ones. For example the quantity of methane in the system may vary quite a bit due to major outgassing episodes from cryovolcanos, unstable clathrate exposures etc. Then there could be global temperature fluctuations for these or other reasons. So an area like Mezzoramia or the great northern lakes just discovered could exist in a variety of states, from wet all year to dry all year with all degrees of seasonal filling and emptying in between. Ustrax, that fits in with your picture too, though I'm not sure what timescale you had in mind for those possible changes shown in your animation. We shall eventually need a way of dating these episodes, and it keeps running round my mind that radiocarbon may come in handy.

[ustrax]

though I'm not sure what timescale you had in mind for those possible changes shown in your animation. We shall eventually need a way of dating these episodes, and it keeps running round my mind that radiocarbon may come in handy.

ngunn, neither do I...
What I was trying to say is that in a near future the elevations will give place to a larger area covered by liquid, they are getting severely eroded, that process has started, you can see those proto-lakes at the top, and it looks to me that this is happening quite fast, the whiter material seems to erodes quite easily...but this is just an oppinion...

[JRehling]

The dichotomy to the two sides of the pole remind me (and others, obviously) of Minnesota vs. Western Kazakhstan. Maybe that is driven by topography like those two places? Minnesota is flat and glacier-scraped. Kazakhstan is mainly flat, but with a long gradient from west up to east.

Locally, they are both flat, but different kinds of flat. Maybe flatness is a sound expectation for northern Titan.

[Olvegg]

Olvegg, I've another thought to add on the possible filling and drying out of quite large 'lakes' like (maybe) Mezzoramia. We may need to consider long term secular changes as well as seasonal ones.

I agree with you. Secular changes may be responsible, in particular, for dried up caldera lakes, because Titan is losing methane in atmosphere and resupply from cryovolcanism is probably inadequate.
However, there is evident asymmetry in distribution of liquids between poles, and seasonal transportation seems to be the easiest explanation. All we need is to wait and watch

[Olvegg]

Comparison of RADAR and ISS images!
http://photojournal.jpl.nasa.gov/catalog/PIA08365

[Olvegg]

Citation from PIA06240: "The feature is named for Lake Ontario because its shape and length are similar, though the Titan feature is much wider. In actual surface area, the feature is roughly the size of Lake Victoria."
The area of Lake Victoria is 68 100 km2. But dimensions of Ontario Lacus are 200x80 km, which gives ~16 000 km2. What is wrong here?

[volcanopele]

Citation from PIA06240: "The feature is named for Lake Ontario because its shape and length are similar, though the Titan feature is much wider. In actual surface area, the feature is roughly the size of Lake Victoria."
The area of Lake Victoria is 68 100 km2. But dimensions of Ontario Lacus are 200x80 km, which gives ~16 000 km2. What is wrong here?

AHHHH!!! I just realized what happened.

[ngunn]

Comparison of RADAR and ISS images!

Thanks to the Cassini folks for this magnificent co-ordinated image product. It was a bit confusing reading separate press releases from the two instuments about giant lakes and larger and larger lakes, each without reference to the other to begin with. Now we have the definitive story on how it all fits together (not so very different from earlier posts here ). Larger and larger, AND LARGER, lakes! Even more exciting is the prospect of further visits to 'the beach' to watch the slowly ebbing tide; also perhaps reciprocal processes in the south, including active rivers?

[ngunn]

On the lake distribution again --
The largest lakes and lake-basin-like features in both hemispheres seem to be somewhat displaced from the actual north and south poles. I'm wondering if this indicates slight topographic highs centered on the poles and extending out to perhaps latitude 75 degrees. This could arise over time if the precipitation at the poles deposits a small solid component that remains where it falls in addition to the liquid that runs off into the lakes. Acetylene has been mentioned as a material that might behave in this way. Of course the polar crust would have to be rigid enough to support the overburden. The possibility of layered deposits that are (at least in principle) dateable might then arise.

[Juramike]

If you look at some of the lakes in Exploitcorporation's image that I modified (particularly the large one to the right of the circled area), their shorelines might be receding, leaving behind a grayish halo.

I found what appeared to be another "line of lakes" just to the west of the "Kissing Lakes" area in the T-18 radar swath. Looking further south and west down the line, down to lower latitudes towards the edge of the Land o' Lakes, there appear to be features that look like dried up lakes.

But shouldn't the dried up areas be radar-darker, from smooth sediments washed in?

Instead some of the lakes appear to be surrounded by a radar brighter gray halo, which would imply rougher terrain.

This would support a collapse caldera idea. (The bright stuff having been puffed out during the volcanic release)

Yet another possibility is that some of the gelatinous organic sludge ("goo") has been left behind as the lake receded and collapsed into little gross lumps along the littoral area. (Imagine frogs eggs at the edges of a drying pond - ick-o). Deeper in towards the lake bottom, the sediments or other organic yukkies have formed a smoother layer which would appear radar dark. Thus, it's chemical processes that explain the bright zones left behind as the lakes dry up. (But it doesn't explain how the lakes got there).

I played a bit with Powerpoint to try to show this interpretation in this one area.




It is very likely that many processes could form lake features on Titan. I'm just trying to put one interpretation forward that might explain some of the lakes with the brighter rings.

-Mike

[ngunn]

[quote name='Juramike' date='Mar 16 2007, 03:37 PM' post='86177']

But shouldn't the dried up areas be radar-darker, from smooth sediments washed in?

-Mike

Indeed I've been thinking that. The organic liquid doesn't seem to leave a dark residue on the surface. this would tend to indicate a lack of prsistent scum or paint-like skin on the drying liquid. Instead perhaps there are deposits of icy gravel along the beaches.

[Littlebit]

I found what appeared to be another "line of lakes" just to the west of the "Kissing Lakes" area in the T-18 radar swath. Looking further south and west down the line, down to lower latitudes towards the edge of the Land o' Lakes, there appear to be features that look like dried up lakes.

But shouldn't the dried up areas be radar-darker, from smooth sediments washed in?

Instead some of the lakes appear to be surrounded by a radar brighter gray halo, which would imply rougher terrain.

This would support a collapse caldera idea. (The bright stuff having been puffed out during the volcanic release)

Agreed The area surrounding the kissing lakes is certainly consistent with a caldera. I have seen radar images of the lava flows in southern Idaho, and they look very lake-like...except that they generally lack topographically driven tributaries.