So, here's a nice little short-term thread, to let people get on the record with their wild speculations as to what we'll see when we get "up close and personal" with Vickie.

Some have mentioned seeing gully-like features in the walls, in the MOC images. I'll take this moment to disagree -- it looks to me like the talus slope (which makes up most of the exposed interior of the crater, that and the dune field) is streaked all along the interior, and that some streaks swirl a bit as they approach the upper rim. I think what we're seeing here is mass-wasting down the slopes of a non-homogenous surface. While the bulk composition of the surface layer that's slowly falling into Vickie is probably all pretty similar, there are obviously pockets of lighter and darker materials. Those pockets are sliding down into the crater, leaving a striated look as light deposits slide down adjacent to darker ones.

At this point, the wind circulation system within the crater kicks in, modifying the light and dark streaks -- especially near the upper rim around the capes and down into the bays.

I think the gully-like feature leading down from Duck Bay is probably nothing more than a mass-wastage slide of dark material down into the crater that has been swirled up a bit near where the winds howl in through Duck Bay.

Let's see, what other potentially embarrasing predictions can I make? I think that while the dark spots on the far rim's cape structures aren't entrances into deep caves, I'd bet that some of them are shallow "alcove" caves. Places where softer rock have been windblown out of the near-vertical rock face, leaving dimple-caves in the rock.

While these would be great places to repel down into and set up a sleeping bag for the night (the cliffs keep the big predators away, after all... ), I doubt a MER would ever be able to make its way into one...

-the other Doug

Cough.. cough...



I have to admit though, the image above is strictly an artistic representation, made in about 15 minute's time. I had no time to actually observe the high-res MSSS image to make it accurate enough...

But, I think you're right, Doug. The sandy slope appears to extend all the way up to the bays, and some of the outcrops stick out from that slope. Some of the sand streaks are dark, some are light, and I assume that is due to the different compositions of the rock above where it came from. We definitely won't be seeing the outcrops (cliffs) extending all the way to the bottom of the crater, and the current pancam views pretty much show about 80% of the cliffs already. The rest is just sand.

Amazing how many people elsewhere have fallen for it - hook, line and sinker

Doug

Heh, I know the MC forum had a few people feverishly trying to find it at exploratorium, but if you know other places also please let me know where

http://www.habitablezone.com/space/messages/439873.html

Doug

Actually, the graphic will not be that far from reality, I suspect. The sandy slopes below the main walls of Victoria, like at Endurance, are rather featureless till you hit the central dune/drift mass. THAT is gonna be really spectcular, with textures and colors as we saw at Endurance in a small scale and on el Dorado as Spirit stuck it's "toes" in the "water" and took a look.

Pando's visualization is very close to what we will see when Oppy gets to Victoria's rim. There will be that wonderful bluff (Burns Cliff x1000), talus and dunefield. Rather like the Mesas in the American desert southwest. I rather doubt we'll see in-place bedrock below the bluff, which is why it is important to examine the non-evaporite rocks on the ejecta apron; these should/may be from the lower units in the column.

"Buck Galaxy"? Not another nom-de-modem of Pando?

--Bill

I don't fully agree. I also think that Pando's not far from reality but what I expect to be different are the details. Some of us suggest that there's a field of boulders, some rocks felt down and stay hanging before the dune field, and some others observed/speculations. If true, that could make a big difference in the way Vicky is gona look. As I said in another post, Nature have most imagination than ourself. That's may be why we want to explore.

One of the tricks will be figuring out Vicky's age. If, as many suspect, there was a lot of groundwater (ground ice) still in the soil when Vicky formed, there would possibly have been gullies formed down the sides of the original Victoria crater, just as we've seen gullies in other Martian features in many places. However, the mass wastage process has probably destroyed them all, and in fact has probably also covered any other original evidence of age, with the possible exception of the upper portions of the cliffs that haven't yet collapsed.

I think we can forget about RATting any cliffs. If we can identify any debris as being specific to a particular layer or even a particular spot on a particular cliff, that's probably as good as it gets. But the cliffs will be unapproachable, just as Burns cliff was in Endurance.

There will be dimple caves; that seems to be part of the mass wastage process, since the lower layers seem more susceptible to wind erosion than the upper layers. Sitting under an overhang would definitely be high-risk, although probably not in the time-frame of Oppy's visit.

Vicky is not an exhumed crater. I went looking for photos of other exhumed craters on Mars; there's just no ressemblance.

I'm concerned that Vicky's interior may be mostly unnavigable, due to tallus. Check out this photo of tallus from Mt. Wilson: http://shallowsky.com/images/geology/wilson-landslide.jpg Not that this is entirely bad; we haven't really seen erosion on this scale anywhere along Oppy's or Sprit's paths.

When we get the ability to look closely at the exposed strata, we will see that for the 30 to 40 meters that Victoria lets us see, it is Epsom salts all the way down, with some variation in the content as we go down. At the lowest level we'll see, the blueberries will be 15 millimeters in diameter.

dvandorn asked for wild speculations. I thought I'd revive one from a few weeks ago. Someone speculated a while back that the margins of the bays were the original margins of the crater. For that to be the case, the capes, and associated overhangs would have to be accretionary features that formed after the impact. Can anyone come up with a scenario, which miight support that idea?

All I can think of would be drift sediments spilling over the sides of the crater and becoming indurated by some unknown process.

You asked for wild a crazy .....

I think we will see evidence of vertical shearing of strata in the promontories consistent with undermining of the original crater rim at some depth now concealed below talus and inblown sand.

One of the puzzles to me is the scalloped rim of Victoria, which is unique but not too unusual. Looking at Slinted's meridiani_themis image, we see several degraded craters to the northeast and southeast that have a very soft rounded rim and a central dunefield and one crater with a hint of scallops. Only one, Victoria, has the pronounced scallops but I interpret the soft rims on the other craters as a scalloped rim in a late stage of development. And you recall that the Payson outcrop area and the so-called "Payson Promontory" may be a highly eroded bay-and-cape at Erebus crater. And we may have seen immature forms of the scallops at Endurance crater with some of the cliffs standing out from the receding pre-bay areas. I'm wondering "why?", and presume that this relates to the mechanical and structural properties of the evaporite unit in this locale as well as Martian weathering processes.

As an aside, the next Rover mission ought to start in Big Crater and work it's way NW toward Victoria; that would be a wonderful traverse.

--Bill

Your thoughts on the scenario I suggested in post 315 of the 'Final Approach' thread would be most appreciated. If I'm talking rubbish I'd rather be told so at an early stage! (and in a nice friendly place like this)

Kind of bummed about the extensive dust obscuration of the slopes... ...sure hope that there's a few clean patches here and there, anyhow.