Here is the closest tricolor sequence so far, an L257 Pancam of the dark outcrop at Mogollon Rim from Sol 657. This image is exaggerated 5x to show surface relief details. If the image is resized H=100% and V=20% the vertical exaggeration can be removed to give the natural appearance.

Interesting outcrop.

--Bill

The rock of Mogollon rim has two distinctive colors: clear and dark. What might influence the color of these rocks?

Perhaps, the line of two colors is determined by the heigth that the water had reached in past time?

The other hypothesis might be related to some kind of oxidation by any biological process.

Rodolfo

It looks to me like the horizontal rock is light and the sloped/vertical rock is dark... could this be a weathering effect? or a genuine effect of looking at fault surfaces as opposed to the cut-though version we see at our current pavement?

Structurally, this outcrop is on the Erebus crater rim, which may be upturned. Stratigraphically this seems to be down in the section and I have the feeling that the dark unit is below the Burns Formation (I'm getting away from calling it "the evaporite unit"). The dark unit seems to weather differently so it has a different physical appearance from the light-colored unit. I'm looking forward to getting close views of that Mogollon outcrop, as well as some chemistry (it will be great when we get our handlens and scratchplate back).

In the current Pancam images there a lot of interesting views of the adjacent bedrock. I've barely looked at them.

--Bill

Here you have a 7x3 pancam (L7) pano with the images from sol 657.

Click to view attachment (393k)

There are six additional columns planned for sol 658, so maybe it will end being a 360º view.

They seem quite interested in this feature - "Parks" A super-res set of observations came down, 17 pictures of it in total:

http://qt.exploratorium.edu/mars/opportuni...KCP2584L6M1.JPG

What is that ?

"What is that ? "

Looks like something in my cats' litterbox...nah...

It's probably another "something" that fell out of the sky, whether relatively short range ejecta (tens or a hundred or so km), ejecta from anywhere on the planet, low probability ejecta from a moon, or another meteorite... one that went "crunch" on impact but didn't have enough velocity to pulverize or vaporize and form a crater.

Whatever it is, it may have fallen on a sand sheet or drift and been lowered to it's current position.

What is odd for me is that the energy of the impact was enough to break the material but not enough to scatter the pieces.
Unless it was a friable material impacting at low velocity ?
And a low velocity impact should imply that this stuff was not coming from space (at least not with a direct trajectory) or from a far primary impact crater.

So perhaps an ejecta from a nearby crater ?

Anyway, I'm just guessing, I have absolutely no experience on this topic.

My preliminary take on Parks is that it is a piece of basaltic ejecta that is weathering in-place but is still a semi-coherent mass. I'm suspecting that the "dark cobble lag deposits" are similar but dis-aggregated and scattering.

It is interesting the way the bedrock in Tesheiner's L7 Pancam mosaic changes from neat slabs in the foreground to a fractured jumble of fragments in the background.

--Bill

Oh, it's called "Parks". I still call it the "Turkey".

And here are three color images of Mogollon and Payson taken on the travel in. The first was taken from the Erebus Highway, the next from the "Four Lane" exposure and the last from the current location at Olympia-Mogollon. 5x exaggerations, you can see them 'normal' by resizing H=100%, V=20%.

We'll get there eventually...

--Bill

I'm with youl on your interp, Bill. The dark unit is probably the source for the dark cobbles we've been seing. I don't know if there are any other references to the cobbles' compostion, but the Nov. 18 Mission Update described them as being "very basaltic".

I hate to sound Ultreya-ish about this outcrop, but I've been drooling (no, _lusting_) over this outcrop for a year now. It is bound to be an important piece of the Meridiani Layer Cake an is an important stop on the way to Victoria.

The 'very' in "very basaltic" is very important...

--Bill

I wouldn't worry about being "Ultreya-ish" unless you start imagining the outcrop conceals caverns, sinkholes, geysers, or whatever else it was he was claiming.

I think you're safe for now.

That's interesting. For some reason, I hadn't seen that Nov. 18th update mentioning the basaltic composition. I had only seen Steve Squyres' earlier note about the dark cobbles not being meteoritic.

Wouldn't you think that large, weathered boulder (rubble heap) nearby would be a target they'd want to investigate?

It sure is, and I can't wait to get up close and personal with it. There is definitely something different about that lower layer.


The nearby rocks are really intriguing, especially in false color. Parks (aka, Turkey) appears exceptionally dark in all the filters. That's not true of all the cobbles and pebbles lying about. The bedrock in this area has really captured my attention. I've found quite a few interesting features, several of which are apparent in one particular Pancam composite taken on Sol 657, which I have annotated and attached.

I have more questions than answers. Recently the bedrock has displayed contrasting color variations across short distances. In the false color images the rock color jumps from the typical cream colors to blues and grays across fractures and bedding planes. I can't help but wonder if some kind of local but pervasive mineralization is being displayed.

We have also been seeing some new features in the bedding. I haven't been able to pin them down, yet. I wonder if they are somewhat more irregular concretions, or a sedimentary structure. I can see some similarities to certain soft-sediment deformations, but sedimentary structures are so diverse, and there are so many I have never seen in person.

Rocks here are also showing something that resembles the rinds seen previously, but it has a different color. Other images show this stuff wrapping around fractures and onto bedding planes, and even merging into what appear to be irregular concretions.

Oh, and then there is the rock with the vertical fractures filled with some kind of mineralization. We've seen other examples recently, but this is the first I noticed that wasn't on the outside edge of one of the blocks.

This is an fantastic spot that Oppy is studying now. Good observations on your Sol 657 image: those color and textural changes have been noticable over the past few Sols in this area. There are a lot of interesting L257 images here, I'm just now starting to work on them.

I think the "new rind or mineralization along bedding" that you note is mineralization. On the attached image the rock at the right center is displaced from the bed to the left, both of which are overlain by the cream-colored rock in the upper right, and the bedding mineralization can be clearly seen. In addition to the subtle changes in color, there is also a notable rust-colored dust associated with the usual blueish "hematite dust" of the fractures.

Here we are, kneeling on this wonderful outcrop, can't find the handlens or scratch plate, and the carpal tunnel is acting up... ain't life wonderful.

--Bill

I agree this is a great area, so many textures, shapes and colours even without the IDD a lot could be learned from here. Is the mini TES still working OK.
The shape in the bottom left hand corner looks like a imprint in the dust/sand where a rock has been removed by some means or could oppy have made this mark.
Perhaps I'm seeing negative relief where there isn't any.


Reckless

Good catch! I was so befuddled by the weirdness in the center of the image that I don't notice that weirdness in the left corner.

Evidently someone at Cornell thinks this is notable, too, since there is a L257R2 sequence at the JPL site. Attached is an L257. I've got honey-do's to do, so I'll leave the stereo pair for later and/or for someone else.

This "depression" is only one weirdess I see; what are two (or more) others?

Hmmmm....

--Bill

It may because I am not a geologist, but most descriptions of unusual terrain features, with or without accompanying graphics, leave me quite confused.

Your excellent labeled graphic was a complete exception. I felt confident that I could actually see the features that you were talking about.

I also could see Bill Harris's depression. When it comes discovering weirdess, it is hard to know what is normal. However, for what it's worth, I think I see some unusual squiggles or "ripple lines" on the rock in the upper right of his [ Bill's ] graphic. They are on the top layer of the rock. They remind me of those marks that indicated flowing water back at Eagle Crater. However, they don't seem to be part of the layering?

Jack

I don't think anybody in their wildest dreams would have thought a couple of years ago (i.e. before the landings) that we'd be looking at such clear images of amazing rock formations like these. And that we can look "over the scientists' shoulders" as it were, downloading the latest images as they arrive from Mars.

Thank you NASA/JPL/Cornell!

Something I've been looking for (but have not seen clear evidence for lately) is the ripple marks as seen in Eagle Crater. Perhaps we need MI images to see those better, but the layering in these images looks pretty coarse, which would indicate a different sedimentation environment I suppose.

I wonder too if the undulations on the top right of Bill's first image are indications of ripples, or just the way it looks after the rock has worn away at a shallow angle across regular laminations?

Airbag

Bill,

the shape of the depression has changed between your two images !

Click to view attachment

Rakhir

And here I was thinking that nothing ever changed on Mars!

That changing pattern in the sand is very weird. The lighting is similar and although the viewing angle is slightly different but I can't see any way to explain the transformation from one clearly defined subsidance\imprint pattern to the other.

Explanations anyone?

Nice catch Rakhir! I don't think this was changing lighting conditions either. Wind perhaps?

The full initial shape of the "depression" can be seen in this Sol 652 pancam
The shape change was observed after 9 Sols, in Sol 661, so there is plenty of time inbetween for wind, rover motion shaking the outcrop, or whatever...

I suspect settling of fine dust by shaking will be the answer but the outline and bottom of the depression seem a bit too neat (in both senses of the word)

Reckless

The bunnies did it.

It looked fairly solid in the raw images but it looks more like a pile in the images at Cornell's pancam image site
http://marswatch.astro.cornell.edu/pancam_..._1_True_RAD.jpg

Bingo, Rakhir. One of the strangest things I've seen. We know that things do change on Mars, but to see it happen in the timeframe while observing is unusual. We've seen bunnies and sand move, and now dust settle.

The "third" odd thing I saw was red-blue color fringing on the right and left rock shadows on the Sol 661 image, whereas there was none evident on the upper and lower rock shadows. But the may be a non-issue since there was some 2.4 minutes between the exposures, so it's possible that fringing was likely. Fringing suggests movement, either of the shadows or the subject, and this (perceived) uneven fringing set off an alarm in the back of my head.

Attached is a grayscale montage of this slump area to play with. Enjoy!

--Bill

So who says it's boring just sitting in the same place then?

How do you like the fact that just as Opportunity finds an interesting outcrop and the sand is performing shapeshifting feats the IDD fails? It's possible that the IDD itself brushed the shapeshifting sand, but I'd still love to see some MIs of that outcrop.. Let us all use our combined mental powers and will the IDD to work. Joint of the stream, flowing freely.. let ye be seized NO MORE!

Maybe the attempted motions of the IDD transferred some mild vibrations to the ground?

Congratulations to Reckless for noticing this event. It completely escaped my attention. My apologies for the length of this post, but that is now beyond my control.

These transient events don't come often, but the collective eyes in this forum have managed to document several. I've scanned back through recent images, and based on my squinting at the area in the front hazcams, it apears that the noted change took place between sol 651 and 654. I am guessing that Opportunity's approach to this outcrop supplied the required vibrations to initiate the slumping which was captured in the sol 652 pancams. The rectangular outline of the earliest view of the slump intrigues me. I can only suspect that was caused by a certain amount of cohesion in the near-surface grains...a weak cust, so to speak.

I could detect no movement of the rover after its initial approach on sol 651, other than that of the cameras on the mast. Perhaps that was enough to trigger the further slumping seen in the sol 661 pancams, perhaps it was the wind, but it might have just been inevitable, once the initial disturbance occurred.

I think I see evidence of the slumped sediments which flowed downward through the small gap between the rock blocks, and created a mini alluvial fan (alluvial fan) below, so to speak. Some of the pancams displayed a slight contrast boundary between the darker "alluvial fan" and the undisturbed sediment below. That boundary seems to have expanded between the sol 652 pancams, and those from 661.

I have created an animated gif image to illustrate this. Please ignore the irrelevant defects in this animation, as I am still learning how to make these things. I have inserted some arrows pointing to the contrast boundary I described, so it would be obvious that this feature had expanded. The rock blocks appear to move in spite of my best attempts to align them. I think that is only an artifact, created by the different viewing angles of the tilted rover.

I noticed that 'alluvial fan' slump outflow feature after I posted the montage above. I'll revise it later today, FWIW.

Good comments and animation, CR.

This tells us things about dust movement. At first I was puzzled by the initial 'horizontal' upper boundary of the depression as it was replaced by the later curved one. I was thinking that a mass of dust slumped, leaving the surface intact but moving a volume of dust at depth. But what I think has happened is that we are looking at movement of a coherent crust of dust overlying another coherent crust that was undisturbed. From the presence of the 'alluvial fan' it seems that the dust is thixiotropic in that as a crust it is fairly coherent but when disturbed it flows readily.

You'll recall that we saw similar dust movement at Methusaleh (??) on Husband Hill. Image attached.

--Bill

Good Gif Cosmicrocker
It couldn't show the movement more clearly.
I assume the darker colour of the fan is due to dust at the surface being fresher and that it will fade in time.

Reckless

For those who want to play with it, here is another version of the montage, with almost-perfectly-aligned images from Sols 652 and 661. These images are simply cut and rotated from the source files and haven't been tweaked otherwise. Have fun!

--Bill


edit: Updated the image to one with better registration: sol_661_slump3.jpg

In the earlier image of the slumped area, isn't there a large chunk of still-cohering crust broken off (from the top?), with a rough trapezoidal shape, still lying in the middle of the slumped area? In the later image it disappears -- either disintegrated or covered up.

The sand depression might be caused due to the sudden drift of sand in the crack below between the two rocks. This sudden drift of sand might be caused by the some vibration caused by the rover motion.

Rodolfo

Good animation.

The dark sand, below of depression seems not be growing but it remains the same size. The pictures changes and it looks like it is growing because of the angle of view but if I put a very close attention on that shadow for its size, I realize that its size remains about the same. The depression only has growth toward the upper of picture or below of the rock. That is due to the crack is above of the depression so the sand has slumpped toward that direction.

Rodolfo

Since we're going to be here for a while, here is a Pancam that I processed this weekend. Note the weathering, especially on the rock in the upper left.

And an Oppy self-portrait.

And another view of the surroundings. This _is_ an odd place...

--Bill

Because the layered slabs are so fragile, they could crack one and then push other half aside with a wheel. I dont know what purpose that would serve but it would be neat..