[X] My Assistant

[djellison]

I'm not really asking a question really - just posing an issue




Mars Pathfinder was about 2.2km from 'Big Crater' which was about 1.5km wide.

Now - Victoria is only half that size - but it says something about local topography that we cant see it from where we are now - about 3-4km from it.

Doug

[Pando]

I think it's likely that the climb in altitude is attributed to an ejecta blanket caused by the Victoria impact, in which case it's all just a bunch of rubble with no clear depositional layering, sort of what we saw around Endurance but in much grander scale.

Now, the cliffs inside Victoria may tell a nice story though, if they are reachable in any way

[dvandorn]

I think it's likely that the climb in altitude is attributed to an ejecta blanket caused by the Victoria impact, in which case it's all just a bunch of rubble with no clear depositional layering, sort of what we saw around Endurance but in much grander scale.

Now, the cliffs inside Victoria may tell a nice story though, if they are reachable in any way

I disagree that the rise ahead is Victoria ejecta. It's too widespread and doesn't appear to be situated right to simply be Victoria ejecta.

There is a crater roughly, what, four times the size of Victoria directly to the south of Erebus (the one I'm speaking of is very degraded, has a very dark duned plains floor, and probably looks a lot like Vostok in being eroded nearly to the ground). It, and a cluster of other craters similar in age and degradation (including Erebus at the northen border of the cluster) seem to sit along a ridge of somewhat higher elevation than the plains where we landed. It's possible that the rise in elevation we're looking at is an ejecta pile from that ancient crater cluster.

Also arguing against this rise being Victoria ejecta, in my opinion, is that Victoria seems to lie on a plateau of the same kind of very flat plains unit where we landed. The MOLA data shows that it's a little higher in altitude than the plains where we landed, but it looks very similar.

I'm guessing that the ejecta from the ancient crater cluster caused an initial landform rise, which was heavily modified by continuing epochal inundation by the brine sea we know was there. Once the sea receded for good, the relative roughness of the crater cluster terrain drove selective aeolian erosion patterns, which have resulted in the "etched" appearance we see today.

Finally, relating to the smoothness of the "plateau" on which Victoria is located -- if we postulate that the plains where we landed *and* the plateau on which Victoria is located were all formed by the slow wind erosion of a reasonably flat evaporite layer, and the etched terrain was formed by wind erosion of jumbled and water-modified ejecta blankets of a cluster of fairly large craters, then it stands to reason that Victoria was formed well after the altitude rise and the differentiation between flat plains and etched terrain had already developed. Otherwise, we'd have to dismiss ejecta roughening as the reason for the types of wind erosion we see in the etched terrain.

-the other Doug