Victoria Annulus, Discusions about Victoria's Apron Options

[CosmicRocker]

Indian3000: That is very nice color, and thanks for giving us your "recipe."

Ant103: A parallel stereo pair is one in which the image for the left eye is on the left, and the image for the right eye is on the right...so your eyes are looking in parallel directions when viewing it. A cross-eyed pair is the the opposite, where the left image is on the right and the right image is on the left...so your eyes must be crossed to view the stereo pair.

Gray: Thanks. I am very curious about the ejecta. If they really are going to spend some quality time at Emma Dean, perhaps we'll see it and it's relationship to the soil below the wheels. Like Bill, I too am hoping for a closer look. It would be an anxious wait for us all, but I'm sure it will make it easier to understand what we see when finally at Victoria's rim.

[Bill Harris]

Here is an L257 Pancam of what I suppose to be the next IDD target, Cape Faraday. Note the blueberries imbedded in the rock along bedding planes. They are of the "large-size population" and dispell the notion that the large spherules are impact lapilli. They represent a new member of the size and morphological distribution of the hematite concretions. I suspect that these larger blueberries are from a lower horizon of the evaporite unit unheretofore exposed, and which was brought to the surface by the Victoria impact.

I'm looking forward to setting our CCDs on the reddish and purple-tinged and rough-textured rocks we see in Emma Dean. Victoria will still be there in a few Sols...

--Bill

[Stu]

Nice berries...

[CryptoEngineer]

JPL just released this (rather grainy) photo of a 30km crater on Titan.

The apron of ejecta surrounding it immediately reminded me of Victoria.

Perhaps these sharp-edged blankets are a common feature of craters
forming in saturated soils, within an atmosphere. (Of course, the
fluid on Titan is a hydrocarbon mix, and the atmosphere mostly
nitrogen).

Full post here.

[Marcel]

Nice berries...

Seems to me the closer we get to craters, the " berrieer" (more and more spherical) it gets.
Could craters and berries be related ?

[Pavel]

Seems to me the closer we get to craters, the " berrieer" (more and more spherical) it gets.
Could craters and berries be related ?

Apparently, the crater ejecta is eroded exposing the berries. The ejecta is fractured by the impact and thus easier to erode. Also, the dust is blown back to the crater, exposing the surface to the faster dust particles during the storms until there are enough berries on top of the rocks to protect them from further erosion.

[volcanopele]

Perhaps these sharp-edged blankets are a common feature of craters
forming in saturated soils, within an atmosphere. (Of course, the
fluid on Titan is a hydrocarbon mix, and the atmosphere mostly
nitrogen).

We've also seen such "pedestal" craters on Saturn's moon Dione, a world without an atmosphere or saturated near-surface.

[Bill Harris]

Here is an MI of part of the Cape Faraday rock from Sol 939. An interesting texture has been eroded onto the rock, which shows the evaporite in vertical cross-section and not the usual bedding plane section. I may be wrong, but there seems to be the light-toned evaporite dust adhering to one side of the blueberries. I don't know if this is on the downwind side of the spherules or has accumulated on the upwind. I'm not sure of the rover orientation (I think that the target rock is to the NE of Emma Dean), and the MI image is presented un-inverted so that it matches the Pancam planning image.

--Bill

[dvandorn]

The "Hershey's kiss" berries in this MI view are not only conical, the cones are slightly faceted. However, I still have a hard time believing that this is due to aeolian erosion.

My main objection to this being aeolian erosion is that, if these kisses are hematitic concretions that have been eroded out of evaporite from Victoria ejecta, they ought to have been emplaced on the surface (and thus exposed to winds) *after* some, if not most, of the blueberries out on the plains. All other things being equal, the berries on the plains, having been exposed to winds for a longer period of time, ought to display a greater degree of erosional faceting.

They don't. In fact, the blueberries seen in the soils out on the plains (and in both Eagle and Endurance, for that matter) were remarkably spherical. I don't remember seeing a single concretion, up until this last series of MIs in the Victoria ejecta, which displayed obvious ventifact forms. These are the very first examples of this type of morphology in the blueberries (if that's what they are) that I can recall.

Of course, the key to the above statement is "all other things being equal." If these are acutally hematitic concretions, they would seem to have eroded out of Victoria ejecta made up of concretion-bearing evaporite, correct? But evaporite emplaced this close to the rim of a crater this big must have been awfully shocked. What do berries which erode out of *highly shocked* evaporite look like? Maybe they look like Hershey's kisses...

One thing bothers me, though. We're only 120 meters away from the rim of a crater that was created in an enormous translation of kinetic energy into thermal energy. It was big enough to dig a crater that was, originally, probably at least a half a kilometer wide and several hundred meters deep.

I have a hard time imagining how the ejecta emplaced only a couple of hundred meters, at most, away from the edge of the hole made by this powerful explosion could have been so relatively unaltered that it would look even remotely like the evaporite we saw out on the plains. If, in fact, these berries are hematitic concretions which formed exactly the same way those out on the plains formed, and if they were originally formed in the target rock into which the Victoria impactor struck, why have so many of them survived seemingly intact (if mysteriously eroded into little cones)?

And if the "kisses" are the same size as the concretions we saw out on the plains, then what are the mostly spherical bodies which, except for size, closely resemble the mostly-spherical plains berries? Are these also concretions? If so, why are they fairly uniform in size but only a fraction the size of the plains concretions? And if the kisses and smaller, rounder bodies are both concretions, why do they both exist? We're not seeing spectrum of sizes, here, that would suggest the result of erosional or shock processes -- we're seeing a small population of kisses, and much larger population of fairly uniformly-sized smaller, rounded bodies. Such a neat division of populations suggests differences not in erosional processes, but in formative processes. And in composition. In other words, I think it makes more sense to assume that the kisses and the small spheres have different compositions and/or formation histories.

Ah, but if only one of these two populations is made up of hematitic concretions, which one is it? Perhaps there is a clue in this most recent MI image -- there is a feature in the dust "above" the rock face that looks rather like a worm. But this 'worm' is exactly the same size, in planform, as the small spheres. It resembles the small spheres in almost all respects, except that it is a drawn-out blob instead of a spherical blob.

Perhaps this would suggest that it is the small spheres that were once molten? I can visualize a spray of impact melt droplets solidifying into spheres in the very thin air as they flew out of the crater (not enough air pressure to compress them into teardrop shapes), and that while most of them fell as individual, rounded drops, some of them would hit each other in mid-air and form into, among other forms, chains of drops that ended up looking like tiny little worm-forms.

In other words, could the small spheres be the impact melt we've been looking for?

One last thing -- this all assumes that the annulus we see around Victoria is primarily the erosional remnants of her ejecta blanket. However, if Victoria is indeed a once-covered-over crater that has been (or is being) exhumed, then the soil we're looking at maybe doesn't incorporate much at all from the original ejecta. Maybe we're just looking at the erosional remnants of the materials that covered Victoria, and its actual ejecta blanket is still buried and inaccessible to our eyes? Of course, if that's the case, you would expect these soils to look exactly like any other patch of blueberry-paving in Meridiani, and it most definitely looks different from the plains soils. So I tend to discard the once-buried-now-exhumed crater theory. (Besides, it looks like a sharp, fresh crater -- most of the exhumed craters I've seen on Mars look far older and more eroded than this.)

Well, that's my two cents worth, anyway...

-the other Doug

[Pando]

Perhaps this would suggest that it is the small spheres that were once molten? I can visualize a spray of impact melt droplets solidifying into spheres in the very thin air as they flew out of the crater (not enough air pressure to compress them into teardrop shapes), and that while most of them fell as individual, rounded drops, some of them would hit each other in mid-air and form into, among other forms, chains of drops that ended up looking like tiny little worm-forms.

In other words, could the small spheres be the impact melt we've been looking for?

Interesting, but there is one piece of evidence that shoots this down. The perfectly spherical hematite spherules were found embedded between various layers of bedrock at Eagle and Endurance. This can't be explained by impact melt since the spherules were still in their original strata.

[Bill Harris]

This ejecta apron, and the blueberries in general, are quite a conundrum, no?

Even though there was a tremendous amount of energy transferred to the bedrock by the impactor and most of the bedrock was pulverized there were undoubtedly "quiet" nodes of lower energy where the shock wave cancelled itself out. This is a classic problem in designing a shot to fracture rock in mining. Therefore you will find pieces of less-fragmented bedrock. And an impact crater like Emma Dean can bring these fragments to the surface.

The hershey's kisses are a mystery. I have problems with the venifact (aeolian erosion) idea but it does offer a good explanation of observation that the facets have a similar orientation, as do the kisses with the point=up. Spherules emplaced by the impact would be random.

We saw blueberries embedded in bedding surfaces at Eagle and Endurance and a couple of examples of this in the Cape Faraday rock.

I saw the "w"-object and wanted to see stereo pairs before mentioning it. Too, too odd.

This stop may be a delay in reaching the photo-op at Victoria but there is good science to be gained here.

--Bill

[Guest_Oersted_*]

a crater that was, originally, probably at least a half a kilometer wide and several hundred meters deep.
-the other Doug

You don't mean that re: the depth, do you?

[Nirgal]

CAHVOR color projection L257

R = 80% L2 + 20% L7
G = 100% L5
B = 80% L7

[attachment=7412:attachment]

Very good job on the colorization from the uncalibrated stretched JPGs !
It almost looks like if it was one of the PDS-calibrated "true" color images
Also thanks for providing the formula (I'm surprised that a simple linear combination of the
filter channels already yields such "near-calibrated-looking" results since I once experimented with more complicated non-linear color mappings but with poorer results ...

[dvandorn]

Interesting, but there is one piece of evidence that shoots this down. The perfectly spherical hematite spherules were found embedded between various layers of bedrock at Eagle and Endurance. This can't be explained by impact melt since the spherules were still in their original strata.

Actually, I was suggesting that the smaller spherical objects we're seeing here in the annulus are *not* hematitic concretions, and thus are entirely different in morphology and composition from the blueberries we saw in Eagle, in Endurance and on the plains. In this hypothesis, of what we are seeing here in the soils of the annulus, only the bodies that have been modified into conical shapes would be concretions. The smaller spherical bodies, while they resemble mini-concretions, would be (I'm suggesting) impact melt droplets.

-the other Doug

[CosmicRocker]

I can see how some of the berries appear Hershey's kiss shaped, due to the brighter spot at top dead center, but I don't think they really are that shape. If the 3D images I posted were not convincing, then take a look at the shadows these things cast. The shadows should display a projection of the conical shape, if that is their true shape. Instead, the shadows display circular or eliptical shapes.

Look above to the false color pancam from sol 936 that Bill posted in message #92. It shows a good sampling of the spheroids in a wide range of sizes, and they all seem to be casting rounded shadows. They are all the same color and hue, suggesting that they are similar in composition, so it is hard for me to believe there is a sub-population of impact melt spheroids, even though I'd like to see some of those. I'm just not sure if much melt would even be created by an impact into rocks of this composition.

Looking at Emma Dean crater, we finally see just what one would expect if it was a hole punched into the ejecta blanket of Victoria...a jumble of lithologies, and nothing like Beagle and earlier craters. I am eager to move on to Victoria, as the rest of you are, but I really hope they move closer to this hole and take a closer look at it's walls. I'd really like to take a close look at a cross section through the ejecta. I'd also like to know if that is a piece of the Halfpipe formation right of center on the opposite side of Emma Dean. This is a pretty nice little crater. I wonder if Oppy will wander into it.