[X] My Assistant

[ngunn]

The new 'looking ahead' with T39:
http://ciclops.org/view.php?id=4689

[Juramike]

The area just south of the Mezzoramia Basin has been referred to as "Dissected Terrain" in an LPS abstract discussing the T39 RADAR Swath. (Stofan et al. LPS XXXIX (2008) Abstact 1491. "Varied Geologic Terrains at Titan's South Pole: First Results from T39". Freely available here.) The dissected terrain has mesas with flat valley floors in several areas. From the Abstract: "The rounded heads of the valleys indicate that sapping along with rainfall, has contributed to the formation of the drainages." So it would seem that the infiltration rate (ability of ground to suck up rainfall) is different between the Mountainous Terrain and the Dissected Terrain. The Dissected Terrain apparently being more porous.

It was postulated by Stofan et al. that erosion of flat lying layers could explain the appearance of the Dissected Terrain. If there was a significantly harder flat-lying layer at the base of softer material, natural stream meander would cut broader valleys and make the broad mesas thin to ridges over time. (Glacial action (material?) was also invoked as an erosion agent).

I put together a putative erosion sequence with examples of the Dissected Terrain S of Mezzoramia Basin showing initial downcutting through the softer material (in orange), followed by widening of the hydrocarbon stream to expose the harder layer (in blue). (Darker orange is meant to show the slope faces).













It is interesting to note that the cliff faces become steeper over time, rather than broadening out - this would indicate that removal of sediments at the base by stream meander is more important than erosion and cutting back of the cliff face by alluvial fan formation. Erosion is at the base, not at the top or sides of the mesa. This fits the hypothesis that this material easily absorbs rainfall on the top and slope of the mesa.

Eventually sediments may fill the different stages of the erosion sequence and partially bury the valley floors.


(And if anyone has the technology to put together an animated gif of this sequence, I'll bet it'll come out pretty cool-o.)




Now the Big Question: Does Dissected Terrain = Rotten Terrain + high rainfall?


-Mike

[titanicrivers]

Is there SAR or other evidence of liquid in any of the streambeds on T39? Some of the short, radar dark channels may be methane springs and might be expected to have a steady supply of liquid from underground. I wonder if the meander coming in from the right side still has flow ...again its a bit radar dark. Also can we predict from the dissected terrain whether the rains come infrequently but fiercely as has been predicted from observations from ground based telescopes of Titan's S polar clouds? That huge cloudburst in Oct. 2004 must have moved some of that schizzle around a bit!


(Credit: H.G. Roe, Caltech)