[X] My Assistant

[Juramike]

I made a list of 42 putative impact craters on Titan to try to estimate erosion rates of craterform features.

This list has the “typical” craterform features all characterized by an ISS or RADAR circular bright rim with either a RADAR or ISS dark central portion or a RADAR or ISS bright inner portion (dome or peak) and a darker inner circle. Several of these have been previously reported in the literature. Due to the extensive rim erosion, some of these are broken or incomplete circles.

These (broken)circular features have been classified into five groups depending on the level of erosion evident (from most pristine in appearance to the most used and abused):

- Fresh craters - with little to no erosion evident on the crater rim or debris apron.

- Recent craters – with some evidence of fluvial erosion on the rim, some crenellation being present.

- Eroded craters – with a single breach of the rim or with severe erosion of the rim wall.

- Multiple breached craters – with several complete breaks in the rim structure.

- Degraded craters – with collapse or removal of large sections of the rim structure with extensive invasion of new materials (e.g. dune sands).

Here is a map showing the approximate locations of these features on Titan:



-Mike

[titanicrivers]

I can't help but wonder about the contribution of subsurface erosional agents such as methane in the breakdown of crater walls, rock-ice islands and the older continents like Xanadu. Perhaps just calculating the rainfall over a region doesn't give a complete picture of the fluvial erosion at work on a region. For example the Huygens landing site looks pretty unimpressive from Cassini heights above the ground, the striking branching rivers (1) and what appears to be methane springs (2) don't show up, yet DISR images from Huygens (providing "ground truth") shows prime examples of sapping in the arid equatorial zone landing site.
Likewise on many of the focally eroded craters it appears dark erosional channels are arising from high up on the wall of the crater (3) rather than from surface run-off implying an erosional agent flows underground emerging as springs. The increased "whiff" of methane upon landing of Huygens, the abundance of CH4 on the spectral analysis of the air at ground level, the haze down to ground level seem to speak of methane just under the surface.
1) 2) 3)