[X] My Assistant

[Bill Harris]

Here are a series of false-color L257 Pancams of the current Oppy traverse stop. I'm still in the "arch the eyebrows and muttering 'fascinating' " mode so I don't have any words of wisdom right away. We can discuss over the next few day/sols before she moves on to the next miracle...

Cabo Frio: (order is #3, #1, #2 from left):

This post has been edited by Bill Harris: Nov 12 2006, 03:36 PM

[MarkL]

It appears to me that Victoria is a rare specimen among craters. I have yet to see a close analog to Victoria elsewhere, including on UMSF. If anyone can provide a link to an image of a similar cape and bay type rim with a large, relatively shallow bowl please post it. I don't see any similarity to the craters discussed earlier on this thread. I also have a tough time believing that wind and wind borne sand are the only factors in this type of selective (and radially symmetric) erosion. Why did the bays erode selectively ahead of the capes? And why is the pattern of bays and capes so neatly repeated along the circumference? I can't figure how wind could accomplish that. The reality may be more complex, perhaps involving radial fracturing and freeze-thaw cycling, perhaps in combination. Back on topic, the sedimentary record, now well laid out in cross section for us around Victoria in some gorgeous scarps (especially in the north east wall) should answer these questions.

[SteveM]

... I also have a tough time believing that wind and wind borne sand are the only factors in this type of selective (and radially symmetric) erosion. Why did the bays erode selectively ahead of the capes? And why is the pattern of bays and capes so neatly repeated along the circumference? I can't figure how wind could accomplish that. The reality may be more complex, perhaps involving radial fracturing and freeze-thaw cycling, perhaps in combination. Back on topic, the sedimentary record, now well laid out in cross section for us around Victoria in some gorgeous scarps (especially in the north east wall) should answer these questions.

Like Mark, I would expect asymmetry in any wind driven erosion, related in some way to the prevailing wind directions.

If I may toss another hypothesis into the pot to explain the lobate craters, it reminds me of some of the lobate hydrodynamic instabilities one sees in models of supernova explosions. Of course the physics, scale, and timescale are all totally different, but someone who knows more about the hydrodynamics of crater formation may have something to say.


Steve