This Hirise image shows pit craters in Alba Patera due to volcanic collapse:

Pit Craters on Alba Patera (PSP_005071_2150).
http://hirise.lpl.arizona.edu/PSP_005071_2150

Notice that part of the rims have a scalloped quality, similar to Victoria crater, though with Victoria this is more extreme and uniform.
Perhaps this is a diagnostic feature of volcanic collapse craters.
I had speculated that Victoria might be a volcanic collapse feature because of its scalloped rim here:

A volcanic crater in Meridiani, Mars.
03-October-2006, 06:01 PM
A volcanic crater in Meridiani, Mars.


Bob Clark

No matter how hard I try, they still look like bumps, not craters.

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It far more likely that "scallops" are a feature of how slopes evolve generally, regardles of how they formed.

Jon

Notice that Victoria crater has an ejection blanket surrounding it, and these two craters do not. I think that radically reduces the likelihood that it is volcanic collapse.

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Don't forget also that the rocks in and round Victoria have so far exibited none of the characteristics of proximal volcanic facies.

Jon

In the discussion I linked above I suggested some visual features were similar to columnar joints, a volcanic feature.
Let's see what the readings are on the rocks within the crater.


Bob Clark

Some times it does take alot of consentration to see those bumps as craters.

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Lots of rocks have presimatic jointing. They don't mean that a rock is volcanic.

On the other hand we do not see coherent volcanic rocks, graded bedding, bombs, dykes are anuthing else indicative of a proximal vent.

Jon

A key fact is that we do see something that looks like a dyke *inside* Victoria, as discussed in the link to that previous thread.
If they had decided to visit closer to Sputnik, which would have taken less than half a day to reach before they entered Victoria, they may very well have seen evidence of a vent.


Bob Clark