Victoria Annulus, Discusions about Victoria's Apron Options

[RNeuhaus]

From today, Oppy will start to head toward the Victoria Crater which is about 500 meters away. The drive would take about one month (that is 15 soles of driven with an average of 33 meters/sol, the other 15 soles would be for other purposes or restrictive soles).

The surface around Victoria Annulus, I seems it won't be as smooth as the way between Eagle and Endurance craters but the surface would have no uniform or parallel wave of sand and dust in small size of ripple. See Phil's Victoria Annulus partial map, Tesheiner's one Victoria Crater picture

Otherwise, the surface might have ripples smaller and alike to the ones of El Dorado, on the skirt south side of Columbia Hill. Besides, the Anuulus has no outcrops except to around of few small mini-craters.

This is a change of morphology of surface around the Victoria Annulus. What does it explain about this developing kind of surface of sand? Its extension is just around the inside of Victoria's ray of ejection. That is coincidence. Around that has no bigger ripples as the outside of Annulus.

The explanation would be that around annulus has smoother rock or outcrop surface, no blocks which had not helped to build ripples by the winds. Other factor, I am not sure, is that the slope from the border of Annulus to crater is positive (going up by few meters), then this might be another factor not to build ripples. I have seen that anywhere in the desert that have a slopes does not have any ripples but only flat surface.

Any debate about why the Victoria Annulus does not look like ripples as the outside of Annulus.

Rodolfo

[dvandorn]

It's also very difficult to estimate the amount of material that was exhumed and deposited around Victoria. You would have to have a good topographic map of the contact between the ejecta blanket and its underlying layer. While this *might* be deduced from a seismic study of the neighborhood (the debris usually has more voids and more lower-density inter-boulder fill within its mass than the underlying pre-impact surface, and therefore has a different seismic signature), I don't think you could do much more than a WAG from the photo evidence.

I don't have the relative figures at hand (and it does vary by impact-target composition), but a certain amount of the target, and nearly all of the impactor, are usually vaporized at the moment of impact -- especially for a crater the size of Victoria. That vaporized material is sprayed in tiny droplets around the local area, and on planets with atmospheres, can be spread preferentially on the prevailing winds. *

As you reach the edge of the region in which the impactor and some of the target are both vaporized, heat and pressure are high enough to melt the rocks. This melt takes on the geochemical characteristics of *all* of the rock types that exist within the melt region of the impact event. It takes on the physical characteristics of igneous rock. This type of rock is typically called an impact melt.

Further out from the center of the blast, the temperatures and pressures decrease through the ranges at which some rock types melt, some are shattered into a fine dust, and others remain resistant to complete destruction. Those pieces which do not melt or shatter become clasts, embedded in a matrix of more easily melted rock. These are fine-clasted breccias -- the clasts in these breccias can be very tiny, indeed.

Even farther out, the impact melt and fine-grained breccias generated closer in to the blast are rapidly propelled through a portion of the target that is broken up, but not melted or pulverized. The still-liquid melts from closer in grab up these cooler rock pieces and make large-clast breccias. In many cases, the clasts in these breccias are pretty much pristine and unaltered examples of the rock that was originally swept up by the melt flow.

These are the kinds of things we ought to be seeing in Victoria's annulus as we traverse it. However, the fact that the Victoria area may well have had an active water table during or after the emplacement of the debris blanket muddies the waters (pardon the pun). The landscape has undergone massive aeolian erosion since the impact, and has possibly (but not definitively) undergone aqueous alteration since then, too. So the rocks will not necessarily resemble the examples we've seen of impact melts and breccias on Earth and the Moon.

* - In re the vaporized material -- it occurs to me that if there was any way to detect the extent of the deposition of vaporized elements from a given impact, we could back-model the atmospheric effects and set some limits on the nature of the atmosphere at the time of the impact. For instance, how thick it was...

-the other Doug