Titan's black areas : a froozen sea ?

Hi,

I wonder why NASA didn't speak about the possibility that dark areas could
be large icy surfaces.
They speak either of dry surface or liquid. But IMHO there is another
explanation.

If I compare those images with aerial pictures of antarctic or any polar
coastline, the ice recently formed at sea displays a deep black color with a
very smooth surface compared to the old gray ice and bright reliefs.

So it is not impossible that the high and long white prominences we see in
the black area (prominences seem about 40-50m high and a few hundreds
meters slong) are reliefs plunged into a frozen see. As all these gas (N2,
Ch4, NH3, C2H6, etc) are transparent on earth, without analyse with the GCSM
we can not determine its nature.
This froozen sea can be constitued of methan if the temperature drop below
about -183°C, its fusion temp., ethan or even made of dirty ice like
clathrates (hydrates). Nitrogen is not impossible (they must have "riviers"
of nitrogen) if the temperature drop locally below -210°C. If there are
winters, why not.
That said, the most probable explanation is a dry terrain but the idea of a
froozen sea must not be rejected.

Remain to know exactly what are the fusion temperature of methan and ethan
on titan, under 1500 Hpa and -180°C.
NB. These possible lakes can not be of N2 because its fusion temp. is -190°C
on titan and can't thus freeze, excepting in deep gorges close to the
aquifere layer (a suggestion).

Thierry
http://www.astrosurf.com/lombry/titan-brumes.htm