[X] My Assistant

[RNeuhaus]

Interesting article.

http://www.newscientistspace.com/article/d...ng-craters.html

The scientists tought that Titan must have hundred impact craters but they found a few ones. Then the hypothesis of missing craters might be related to volcanoes, rain and settling soot - perhaps aided by an eggshell-thin crust.

Rodolfo

[Guest_Richard Trigaux_*]

A possible explanation to many more or less round isolated mountains would be diapirs. On top of the Titan crust, soot accumulates and it could bury craters, the author say. But if this surface layer is denser than deeper layers, an unstable situation appears, where the lighter layers bulges and rises in isolated blobs (diapirs) through the denser layer.

What could be the lighter layer?
-Ice? Ice is denser than common organics on Titan, and at its temperature it is rock hard. Only a carbon soot layer could be denser.
-methane mud? Mud diapirs exist on Earth, in alluvial zones where fine clays accumulate. Muddy layers pierce through surface layers. It is water-clay mud, but methane-ice or methane-solid organics may do the job on Titan.
-solid organics? Eventually methane washing could create a layer of solube organics in the depths of the crust. This layer would rise afterwards.

[ugordan]

Emily has written a very nice blog entry on The paper on T3 SAR swath. What got me intrigued is this little bit:

Also somewhat mysterious is the fact that the paper doesn't mention the altimetric data at all. The RADAR instrument gathers altimetric data on each end of nearly every SAR swath. The fact that it's not published here likely means that something is making it hard for them to make sense of the data. I am very curious about that story!

This reminds me of another writeup she made of a conversation with Ralph Lorenz in which she also inquired about radar altimetry:

Altimetry, I asked? The public hasn't been shown much altimetry data from the Cassini RADAR instrument yet. There is supposed to be a little burst of altimetry data on each end of the SAR images, so there should be data available; the fact that we haven't been shown it indicates that the RADAR team is not finding it as easy to calibrate their altimetric data as it is to produce the SAR images, which they seem to be able to spit out within hours or days of a flyby. Ralph laughed and said "There's a story developing but that's all I can tell you. The guys are basically doing things that we've got no right to get away with doing with SAR data but the results may be worth sticking our necks out for."

While both entries concern different SAR swaths, I'm really intrigued by this "coverup", wondering what they might be secretly cooking up?

[ngunn]

A possible explanation to many more or less round isolated mountains would be diapirs.

You'll find this suggestion from me near the bottom of Page 3 of the T13 thread, though I was referring to circular features in general, not only mountains. Volcanopele includes a brief comment on it in a post on Page 4.

[Guest_BruceMoomaw_*]

One LPSC paper mentions a thick, soft, runny layer ("mud") on Titan's surface as a possible explanation, concealing craters in the same way that craters on Earth's ocean floor are concealed by the ocean's surface. Really, it seems to me that there are so many possible explanations for the lack of craters -- since we now know that Titan's surface is modified both by wind and "hydrological" processes, and by a high level of volcanic and tectonic activity -- that it will be a long time before we know what the main cause is. And Cassini by itself probably won't be able to answer this question.