[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

[remcook]

For those of you with access, this is now in press at Icarus, which seems pretty relevant to the discussion here.

"Fluvial Erosion and Post-erosional Processes on Titan

Ralf Jaumann et al."

There's not yet an abstract for public viewing, but there will be soon I suppose. It's rather long, so I won't quote it fully, but here are the main results:

" Thus the observed surface erosion fits with the methane convective storm models as well as with the rates needed to transport sediment."

and
"Only frequent storms with heavy rainfall or cryovolcanic induced melting can explain these [massive eroded area seen by VIMS at 7S, 30W, with changing spectral characteristics] erosional features."

[Juramike]

For those of you with access, this is now in press at Icarus, which seems pretty relevant to the discussion here. Jaumann et al. Icarus "Fluvial Erosion and Post-erosional Processes on Titan"

The area examined in the Jaumann et al. Icarus article was the hi-resolution VIMS imaging of the Pacman Bay Region of Bohai Sinus (I think it's more at about [-7S, 15W]). (ISS Image below - I couldn't find the hi-res VIMS pix on any publicly accessible site).



Through hi-res detailed VIMS spectral analysis, they characterized spectral sub-units of the VIMS dark blue ice sands unit.

They found that the fine spectral units they identified graded nicely away from the bright terrain. From the article: "Thus the systematic change of the spectral characteristics of Pacman Bay is most likely consistent with a fluvial origin of sediment, where material settles systematically dependent on the physical properties of the sediment load."

They eliminated glacial (which would dump stuff out jumbled moraine pile at the terminus) and aeolian processes.


And this gem caught my eye:
"[Dark blue ice-sand sub]Units #6, #7, and #8 are similar to areas identified at the Huygens landing site (Tomasko et al, 2005) and particularly the v-shaped structure of unit #6 may indicate some flow-velocity-dependant accumulation of materials."

Whoo-hoo! They found the "Spooky-Dude of Pacman Bay"
[Y'all gotta check out Figure 6b in the text]

Unfortunately, I have a sinking feeling that the Spooky Dude formation at the Huygens landing site might be too small to be resolved even in a hi-resolution VIMS image. So we may not be able to compare the two structures.

-Mike