Fantastic colorization Nirgal!

Thanks Nirgal, I now have a life-size bit of Mars sitting next to my computer.
Click to view attachment

Very impressive Nirgal. What caught my eye was, just up from the lower left corner, is one of the larger grains with a smaller grain that appears to be embedded in it.

---lee

I noticed the same thing. They look like *very* small ventifacts. If so they must have been sitting there for a loooong time.

tty

I see 3 with holes in them - so it can't be a camera artifact. Did someone break their necklace here?

Um, where are we?

http://qt.exploratorium.edu/mars/opportuni...ZTP2560R3M1.JPG

I thought we were a long ways from anything but, small dunes.

That's from almost a month ago.

Greg, that image, for me, was immediately recognizable as the far wall of beagle from the approach...I'd know that big slab anywhere

We need a geologist to explain what the deal is with these "holy"rocks. What could be causing such perfect little holes? When I noticed just the one at the upper left, I assumed it was a camera artifact. I have to assume that we are looking at something that disolved out of the rock, or was created when the rock formed.
Any ideas? - Click to view attachmentSacramento Bob

The microcospic picture taken on scrapped track. It has no spherules but only fine grain -powder- and it is somewhat endurated.

http://marsrover.nasa.gov/gallery/all/1/m/...8ZP2936M2M1.JPG

Rodolfo

I see 2-3 ratted blueberries, plus 3 distinct horizontal layers. Looks like ratted evaporite to me.

It's soil pushed flat by the mossbauer.

Doug

I hate to keep obsessing about this bit of conchoidally fractured pebble, but Nirgal's superb colorization adds to its interest. A fractured face is visible, while we can just make out the margins of the downward face -- and this would seem to indicate a patina typical of the alluvial (!) chert gravels found in abundance in, among many other places, my home state of Louisiana. So one thesis is that, among the layers disturbed by the impact which created Victoria, is bed of alluvial gravel !?! There are of course other weathering processes which can create patinas, but it is interesting to note the relative freshness of the fractured surface.Click to view attachment

Gleenwsmith: The stone is the original comparing to the rest. It has good edges, a fractured stone after so many years, between thousand millions and millions years. Very strong stone which has withstanded the aeolian and hydro erosion . About the chemical erosion not like to the spherules which is the product of the chemical process ?

I have enclosed a picture. The surface has a very fine grain that leaves the wheels neatly well marked.

http://marsrovers.jpl.nasa.gov/gallery/all...8ZP2575L5M1.JPG

Rodolfo

Rodolfo, I am certainly agreeing with you if you are saying that the fractured stone is the result of different processes than those which resulted in the spherules. And nice picture indicating how spherules are sitting on top of a duricrust. . .

I keep wondering if the specific forms we see in the soil right now (the granule size ranges, the organization of the granules into three basic sizes and shapes, color and hardness) can tell us something about the conditions of the impact target at the time of the impact.

Does any of the soil material suggest that the impact target was wet or otherwised volatile-enriched? I'm assuming that at least some of the granules we see are pieces of impact melt, and I suspect the conical "drops" that some have labeled tecktitic are the most likely candidate for being impact melts. Does their shape and size, and the nearly ubiquitous hole in the center, suggest anything about volatiles content of the target? Or about its composition? Do we have to assume that their present shape and distribution is the result of erosional processes, or is there anything of their formation still evident in what we can see?

Unfortunately, the three granule types seem so thoroughly mixed that it will be impossible for Oppy to get a good specific composition of just one of the types... so we'll have to infer composition of the various types from the aggregate Mossbauer and APXS readings we get from it. But I think that, if we could answer some questions about the constituents of this soil, we'd have some further insight into the chemical and climatic history of the region.

-the other Doug

Finally, we got the makin's for L257 images of the current trench and skuff on the ejecta apron.

Doug, I haven't decided about volatiles in the impact target. We'll need to look into Emma Dean and specifically the evaporite chunks with the unusual texture and/or darker tone. Maybe we won't do a drive-by this time...


--Bill

I couldn't resist this comparison:

Click to view attachment

john s -- sweet!

That was freakin' brilliant! It is now my wallpaper. It makes me realize that before long we will have bootprints on Mars.

I'm not a geologist, but I minored in geology. Others have reported these holes. The best explanation I can find is that the concretions in many cases are associated with a network of dedos-like stalks. When the concretions are worn out of the rock, there is a tendency for these to snap off at the concretion, leaving a small indentation. We have noted the presence of these 'stalks' in several other locations, for example at the feature known as 'Pilbara' by Fram crater on the approach to Endurance. While wind erosion and chemical erosion certainly played a part in producing the stalks, there may be some evidence for a partial network of weakly indurated material within the matrix.

This MI image shows an example of such a stalk protruding from a spherule.

http://marsrovers.jpl.nasa.gov/gallery/all...00P2959M2M1.JPG

Please view the above as a half-baked suggestion rather than a fully baked hypothesis I'm just thinking aloud.

Bill Harris, I like your explanation of 'tektites' for at least some of the pebble-like fragments we have seen amongst the desert pavement. I'm not sure if that's a cut and dried explanation without more data, but it stands to reason that there must be 'tektites' present on Mars somewhere.

I've gone over all of the recent MIs and I can't find anything I'd call a tektite. If someone would post a picture identifying one of the suspected critters, I'd appreciate it.

Regarding that berry with the central hole, it's not the first one we've seen on this long trek. That one seems to be one of the occasional concretions that we've come across that has been cleaved in half and abraded. I would interpret the hole as the place where the concretion's center was more friable, so the material was easily eroded away. That is not an uncommon phenomenon in earthbound concretions. The one with the dimple might be the same thing as the first.

The third hole identified is in a clast (fragment) that doesn't resemble a concretion at all. There seems to be several sub-populations of fragments of different origins on the surface here. Among those that are not obviously concretions, some have noticeable porosity. But I must admit that the MI posted by SacramentoBob showing three different, tiny clasts with neat round holes is intriguing. ...just thinking out loud here... I wish I could tie them all together with a pretty pretty pink ribbon, but I can't.

I've also noticed a disproportionate number of concretions that have split in half.

If we accept that the concretions formed within the evaporite matrix as per the terrestrial analogy, I'd expect to find fine planar inclusions of evaporite within the concretion itself. We've discussed the possibility of changes in hydration states with diurnal temperature fluctuations. Intuitively, any such inclusions would tend to undergo a net increase in volume with an increase in hydration state and this would act as a wedge, exerting internal pressure on the 'berry' causing it to split in the plane of the original strata.

Do you think that's a credible mechanism?

"Tektites" or "impact lapilli" are the best name I can come up with. Unlike earthly tekties they are neither appear glassy nor aerodynamic (for the most part) and unlike earthly lapilli they are't volcanic. They are the basaltic basal unit melted by the impact, assuming a near-spherical shape in the thin atmosphere and falling onto the ejecta blanket. I think the observation of the larger-sized spherules in this locale is important. Look at the L257's taken at this stop, the larger spherules tend to have a color similar to the basaltic cobbles, while the smaller spherules have a slightly different color. I see we have new Pancams of this crater and the distinctive light-toned rocks, so perhaps this will not be a drive-by sighting. Although we'd like to get to the photo-ops at Victoria, we need to do some science at this stop. Understanding erosional-depositional processes on Mars is the key to understanding the geomorph.

I agree with the idea that the holes in the berries are related to the stalks we've seen. And I wonder if some of the berries are not hollow or have a "softer" internal composition (related to Aldebaran's "planar inclusions"). I'm thinking that we see more broken berries here because of the impact. When the evaporite was catastrophically fractured and pulverized by the impact some of the berries were broken along the fracture lines, whereas with slower weathering processes the evaporite matrix breaks around the berries.

By way of earthly analogy, take a look at the attached...

--Bill

Here are the latest color Pancams from the current stop, maybe these are next targets. Interesting rocks, we'll discuss later. I need to go fly...

--Bill

I don't know if I'd call them tektites, exactly, but I think the larger rounded bodies in these soils, which tend to have randrop or conical shapes, might well be droplets of impact melt. That would make them similar to tektites in origin and general configuration. But tektites are often formed in the initial blast, from materials near the surface, and are blown a considerable distance away from the impact site. These droplets, if they're impact melt, came from less than 200 meters away. So they were formed later in the impact process (and hence probably contain materials from deeper within the excavation), and were ejected far less energetically than the more far-flung ejecta.

-the other Doug

Doug: I don't have a problem with the term tektite. I've always assumed that any impact melt droplet that solidified into a glassy sphere or aerodynamically altered shape was essentially a tektite. I see a lot of spheres and a fair number of multiple sphere agglomerations, but I don't see anything that looks glassy, nor anything that looks aerodynamic. I can discount the importance of the things being glassy by assuming they have had time to devitrify or be recrystalized by some later alteration process, but I really don't see anything that can't be more simply explained by assuming that these spheres are simply the same concretions we have been seeing since day 1.

I think I have seen a very few that could be roughly described as conical, but those looked more like multiply-connected berries that were broken or eroded, or berries that were broken from eroded stalks of the evaporite cemented sandstone, like those we saw at Fram. I'd love to see something new, like evidence of an impact melt, but I am not convinced, yet.

I've looked at the L257s, but I really wish someone would post an image with an arrow or two. Damn, I see you have pre-emptivley eliminated two of the previous arguments made in my reply to Doug. Ok. I don't like using terms like "impact lapilli," since it seems to remove the historical connection between lapilli and volcanic processes. Also, these spherules have always appeared to have essentially no internal structure, as opposed to lapilli, which often display concentric rings of ash agglomeration internally.

Correct me if I am wrong, but the last thing we heard from SS regarding the cobbles was this August 2005 quote: "Oh, yeah, and the cobble we looked at with Opportunity isn't a meteorite, it's a martian rock... and one that's very different from anything we've ever seen before. Busy times... "

I've been wondering about the "basal basaltic unit" too. In this part of Meridiani we are supposed to be sitting on top of several hundred meters of "light colored sediment." Victoria surely didn't excavate basalt, unless there is a surprise inside, or unless the impactor was a secondary of external origin.

OK, then explain what we're seeing on the ejecta blanket. There have been several substantial or suble differences in the surface compared to the Meridiani plains. Your shot.

The "dark basaltic basal unit" is the holy grail tying the "oh yeah" cobbles to anything. It may not exist, but OTOH, since we have seen only a few meters of several hundred meters of "light colored sediment", we can't say that it doesn't. Your shot at the explanation...

--Bill

I think Bill might be on the right track. Look again at Nirgal's colorized image of the pebbles:

http://mitglied.lycos.de/user73289/misc/op...24pan_col_d.jpg

Many of the larger grains have a shape that looks like a Hershey's kiss. Some have suggested that they might be ventifacts. But it would take winds blowing equally from every direction to sculpt a grain that way. Unlikely IMO. Bill's suggestion that they may be formed by a melt/impact process makes more sense to me at this point.

One of the grains at the lower left-hand edge of Nirgal's image provides some tantalizing evidence for this idea. The grain is cut by the edge of the image, but you can see that there is a smaller grain (blueberry) contained it a larger grain. It looks as if part of the larger grain has wrapped around the smaller grain.

I'm envisioning a process like this: the meteor strikes the surface of Mars and in the process melts many of the silicate minerals in the crust (it could be a lower basalt or the basalt sands). Molten blobs fly through the air assuming a streamlined, rain-drop shape. The strike the surface while still partly molten. This flattens the bottom but they still retain a streamlined shape in the upper part.
If the grains fell, while partly molten on a surface which was already littered with the smaller blueberries. (A process Bill has already proposed). The under side of the "Hershey's kiss" grain would have the smaller blueberry imbedded in it. That partial view of a grain with the embedded blueberry might be evidence for this.

- gray

Yep. Please note that in the attached image, there are really four different size populations in the objects we see.

The finest particles are dust-sized, and are consistent with windblown dust particles or the aeolian erosional remnants of local larger bodies which have been worn down by local winds. These particles form the primary portion of the soil matrix at this site, and they resemble (a lot) the fine dust portion of the soil that we've been seeing all along.

The next largest size of body resemble, in size and general shape, the blueberries we've seen ever since Eagle. They seem to be more broken up -- some appear to have started out spherical but have been partially or completely shattered. But these look like the blueberries we've been seeing.

The next largest size of body we see are what Bill is calling tektitic. Most of them seem to have a conical shape, and while the linked image doesn't show this well, many of them have a small depression, pit or hole at the apex of the cone. One would be tempted to say, with a quick glance at the image, "Oh, yeah, those are blueberries." But if you compare their size (larger than the blueberries we've seen before) and their presence in the same soil with smaller bodies that far more closely resemble the blueberries we've seen before, you can see that these are different types of bodies. The conical (or teardrop) shapes seem unlikely to be ventifacts because of the very small size of the bodies and because they appear to have been evenly shaped into regular cones all along their circumference.

There is one larger sized body type in this image, as well -- a more rough-edged pebbly kind of stone that someone remarked (sorry, I don't remember who originally noted this) looks rather like chert or flint. These have multiple fracture planes that form their surfaces, and are significantly larger than either the blueberries or the tektitic droplets.

These four different types of bodies seem to be fairly well mixed in the soil here. But they are definitely all different in appearance, and I would imagine they are all different morphologically.

I'm about 80% convinced that the conical or teardrop shaped objects are some form of impact melt. I don't necessarily have an explanation for why they don't look glassy. I suspect it's a matter of either their initial composition or, more specifically, the volatiles content of the original melt that is responsible for this appearance.

-the other Doug

Thanks Gray and dvandorn for the image and the descriptions. I'm sorry it took me so long to catch on. At least now I know what you guys are talking about. When I first saw those MI's I thought it was curious that so many of the spherules seemed to have a dimple on the very top. It seemed odd to me that all of those spherules would be oriented in the same direction, but they do appear to have the approximate shape of a "Hershey's chocolate kiss" candy. That was a good analogy to use to describe the appearance for me.

After I understood that, I couldn't help but wonder why we didn't see at least a few of these things tipped over to better reveal that shape. I went back to the original MIs and noticed that several of them captured overlapping areas, thus providing some pretty nice stereoscopic image pairs of at least some of them. I made an anaglyph of the best pair I found, put it next to a similar MI anaglyph NASA/JPL created of some berries at Eagle crater for comparison. I know some of you prefer the side-by-side stereopairs, so I will try to post them as well, or in a following message if they both cannot fit below the forum limit. I think the second is a parallel image pair, so you may need to reverse them if you prefer to view them in crosseyed mode. I am using the excellent program StereoPhotoMaker that was recommended by another member here, and I think I haven't yet learned to force it to make a crossseyed pair.

I think these things we are seeing here appear pretty spherical in 3D, and quite similar to those we saw in Eagle crater. I'd like to hear what other people think, to make sure I am not deceiving myself.
Click to view attachment
Click to view attachment

That is what is puzzling about the larger "Hershey's Kiss" spherules. They seem to be oriented in mostly the same direction (point up) and from the very subtle shadows I have the impression they are faceted (ie, quasi-pyramidal more than conical). Therefore, I was initially thinking wind-created venifacts formed in-place instead of tectite-oid features falling and orienting by chance.

I dunno, let me look closer at the "faceted" issue. And after all, we are looking at a sample of a few spherules out of millions. And I'd like to get MB reading to see which spherules are basaltic and which are hematitic.

Any ideas about the rocks exposed in Emma Dean? I keep hoping for a closer look...

--Bill

If the "Hershey's Kiss" spherules are all pointing up, wouldn't that imply that the soil has never been mixed? Their shape is not so Hershey's Kiss like that they would sort to sit on their bottoms?

Perhaps they are blueberries that have been sitting on the surface so long, wind has eroded their ‘tops’ into that shape.

CAHVOR color projection L257

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

Click to view attachment

R = 100% L2
G = 100% L5
B = 100% L7

Click to view attachment

Wow! Delicious colors on the first pic Indian3000, I love it.

I made a crossed-eyes (or parallel what is the difference between this two?) animation from Sol 917 navcan pictures.

Cosmic


Good job on the anaglyphs of the pebbles. You're right, they do look more spherical thanI had originally thought. Now I'm scratching my head again. I still think the "impact tektite" explanation might work, but it's very conjectural.


Indian - good looking colors!

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.

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

Nice berries...

Click to view attachment

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.

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.

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

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

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

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.