Very nice! Other rocks might be sedimentary but this looks like a vesicular basalt.

Here is a circular view of the sol 135 location. Much of the distant horizon is hidden by the local topography as we dip down into a hollow.

Phil

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Partial Panorama Mastcam-Z Right Sol 136.

Small adjustments made (contrast, saturation, sharp...)

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Full resolution https://flic.kr/p/2mafXG3

We are still missing two part-frames from the sol 136 Navcam panorama but this shows what we have now in circular form.

Phil

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And sol 137 - another 36 or so m south on very rugged terrain bur heading for easier surfaces.

Phil

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Sol 136 panorama is now complete so here is a finished version of a circular view of it.

Phil

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To emphasize Phil's earlier observation I created a simple chart using exported geojson data, plotting the elevation changes on completion of each drive. Quite a dip
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Sol 00134MR

In a rock garden on sol 136 (Mastcam-Z left eye filter 0 RGB colors enhanced by PCA)

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Sol 139 SuperCam RMI (context not yet available)

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I see that the current location is where the published drive plan showed the stop at the Crater Floor Fractured Rough unit, where the first sampling might take place. Of course, it might take place on the way back after a look at Seitah South and the ridges, rather than right now. Still, a good reason to take a close look at the rocks.

Phil

Investigating the Crater Floor - Fractured Rough unit (mentioned by Phil in the last post)

Front Left Hazard Avoidance Camera (Hazcam) image acquired shortly after sunset on sol 138 (note the lack of shadows)

Plus 2 images from the PIXL micro context imager (MCI) acquired several hours after local sunset. The scale are for the PIXL images are not known at this time.
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Given the drop into a more eroded area there is the possibility that these are sedimentary deposits.

A multispectral rock from sol 135
1) Mastcam-Z raw image
2) Filter 0 visible RGB colors contrast enhanced
3) Left eye filters 0 to 6 multispectral channels PCA transformed
4) Color anaglyph
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Kodiak in stereo. Mastcam-Z sol 135 for left eye, sol 128 for right eye.
There seem to be some "balconies" at the cliff above the scree slope on the left.

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Sol 140 SuperCam

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Slightly enlarged and enhanced sol 139 Navcam context image fot the sol 139 SuperCam RMI

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A picturesque collection of rocks from sol 136

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. . . and in stereo

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The rock just left of center has an interesting change in texture.

The possibility is that the smoother section was buried as the rest eroded.

I am going check other rover sites but...
it seems like every-other large/midsize rock that Percy images in Jezero ... is 'cracked in half' or has a very flat face somewhere on it (when it cracked and separated?)

• Is it a cratering thing (more craters here than Gale)?
• A billion years of daily cold/warm cycles?
• The rock makeup and types?
• Just me?

I'll check back in a few weeks on this ...

To speak from a basis of great generality, every large rock that we see had to arrive, somehow, in the location where we now see it, and in most [every?!?] case in this location of the Jezero floor that involved motion horizontally and downward. These rocks did not grow up from below and they did not form in place. Many are ejecta from craters elsewhere on Mars. Some were part of the earlier, larger delta and tumbled down slopes that no longer exist proximal to the rocks. These rocks fell, often at high velocity. And that's going to lead to some cracking.

The last major event in Jezero would have been the formation of the mafic capping unit on the crater floor. This must have occurred after the delta had eroded back as it embays delta remnants. The rocks we have seen to date seem to be the eroded remnants of this effusive lava. Because of its mineral composition basalt weathers reasonably rapidly and when the mafic floor was deposited Mars would still have been a reasonably dynamic environment. So the basalt deposit has suffered significant erosion, progressively broken down due to tensile cracking and spalling caused by the large temperature variations. Some of the flat surface you refer to will be ventifacts formed by wind blown sand.

Ventifacts (windkanters) and cracked rocks from sol 137

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Sol 137 SuperCam RMI with Mastcam-Z context
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Context, context-in-context, and context anaglyph for sol 139 SuperCam RMI

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Looks like a possible contact science operation (abrading) could be imminent?
Sol 143: Front Right Hazard Avoidance Camera (Hazcam)
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Sample collection core drill with abrasion bit fitted.?

A news conference next week will discuss science to date and plans for sampling.

Phil

https://mars.nasa.gov/news/8990/nasa-to-bri...nce-mars-rover/

First light in Jezero (raw sol 144 R-Hazcam)
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That was taken before 4am LMST. And this shot was taken at almost 8pm LMST on the same sol:
https://mars.nasa.gov/mars2020-raw-images/p...0_01_295J01.png
I don't recall the twilight glow being so visible for over 2 hours before sunrise/after sunset. The sun would be approaching very roughly 30 degrees below the horizon at those times, and on Earth it would be utterly dark by the time the sun's 20 degrees below the horizon. That's an indication of how dusty the air is there, I guess.

Here is a color-enhanced version (hi serpens!) of the picturesque rock collection of sol 136.
Mastcam-Z left eye filter 0 RGB values transformed with principal components analysis.
The lightest parts of the orange dusty rock surfaces may have a slight greenish tint. This is due to highlight clipping in the red channel of the raw images, it is not a spectral property of the dust.

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Definitely picturesque, but also a nice example of how on a water challenged Mars, what was once a solid outcrop broke down over time through tensile cracking and spalling.

A rock pile from Sol 138 in PCA-transformed colors, its anaglyph, and a magnified Mastcam-Z context image for the SuperCam image of Sol 140.

Are there two different rock types, or is it just the texture that is different?
In the upper part of the pile, the rocks are compact and solid and have fairly sharp edges and straight cracks.
The rocks in the lower part and in the foreground have pores and vesicles, a rounder shape, and seem less resistant to weathering.
Interestingly, the SuperCam may have photographed a rock with the layer boundary between the two types.

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The rocks in the foreground do seem to have a lot of vesicles giving a foamy appearance. It seems that the lava embayed Seitah so this area would have been close to the edge of the lava flow(s). The encroaching lava could have interacted with the hydrated sediment/rocks of the crater floor and edge of Seitah, causing gas release and a ‘frothing’ effect on the first lava to arrive. So lower sections of the capping unit would have lots of holes while the upper, possibly later deposits would be more solid. So yes, you could well be correct that the supercam has targeted a contact. On the other hand the process could have been quite different and others may have more logical suggestions.

Meanwhile, multispectral raw images from the same site, taken on Sol 139, have been published. Here is a multispectral PCA image from Mastcam-Z right eye, filters 0 (RGB, visible light) and 1 to 6 (infrared).
In this image, there is no noticeable color difference between the upper solid rocks and the lower vesicular rocks.
A small rock fragment with a smooth surface (in the white circle) shows a significantly different spectral reflectance, but it was probably moved to this location from elsewhere.
The same PCA procedure using only the infrared channels was not satisfactory. The result is a colored mess of flatfield inhomogeneities, pixel shift between the spectral channels, and image noise.

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On SOL 144 -- Navcam took images of the same area 15 HOURS apart (4:30 AM and 7:15 PM -- 15+hours difference)
The repeatability of the camera aiming is amazing (the camera head on the mast was busy all day)
The slight camera offset can be seen on the 'funky target' over the right wheel (is there a name for those things?)
The image is of the 'pavers' - a potential drill site? -- or did we move already?
GIF
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Not amazing. The process is digital and operates using stepper motors. It is just commanded to go to a certain value of "clicks" in x, y and z. Think of an industrial assembly line robotic arm programmed to cut, weld or drill a succession of parts on an assembly line. Same principle.

--Bill

The 'slight camera offset' could be associated with a load applied by the arm to the drill support posts for an upcoming abrading operation.

I believe the 'funky target' on the steering actuator is called a 'Fiducial Marker', but I cant recall seeing it in an official release.

Sol 146 SuperCam RMI with sol 143 Mastcam-Z context

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Sol 145 SuperCam RMI with context

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Sol 144 SuperCam RMI (or in this case RTI = Remote Tele-Imager) with multiple context.
Presumably an attempt to spot some layered outcrops on top of the crater wall which can be seen in the HiRISE photos to the south-west from the rover at Lon=77.284° Lat=18.286°.

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Edit: Added link to the HiRISE map. There, the coordinates of the mouse pointer are displayed in the lower right corner.

On the Sol145 Supercam one thing that amazes me is the almost vitreous luster of the wind-polished surface of the basalt. Eons of abrasion with micron-sized particles is indeed a powerful process!

--Bill

A rock pile from sol 135 with enhanced colors. Most interesting is the layered outcrop above the center of the image.
If this outcrop is composed of the same basaltic material as the other rocks, I wonder if lava can be deposited in such thin layers.
Is it possible that these layers are more likely deposits of volcanic ash from multiple eruptions of a volcano?

Another observation: the material (dust, sand, weathered remains?) on top of this small ridge is more orange-red than the granular and dusty material in the surrounding area.
This can also be observed on other similar elevations (e.g. here, here, and here).

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First use of the rock abrading tool seen in Hazcam images from sol 417
Here's a before and after GIF (145 / 147) and the frames
To my old eyes it appears as though the bit has just been pressed into the rock (possibly hammered?) without rotating the tool, but I guess better images will follow soon.
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EDIT
Here's a pair of crops from NavCam's tiled mosaics from 145 / 147 posted on Twitter . these provide a comparison of the abrading bit captured before and after its first use.

Effusive lava flows are really cool tau. As the surface of the flow cools, depending on the velocity of the flow the surface can be convoluted (folded, coiled, ropy), blocky or broken up. Beneath the surface the flow is more coherent. It is this lower part of a flow where gas bubbles or vesicles form. Reaction with the sedimentary lake bed would have produced a lot of gas and this would seem to indicate that the basalt with a foamy aspect previously discussed formed towards the bottom of the flow near the old lake bed. As far as the colour difference is concerned, just a guess but there would be some eroded basalt particles mixed in the lower levels.

Interesting what different appearance basalt can have.
Here in a Mastcam-Z image of Sol 145 are some typical examples of the solid type ventifacts that look like shark dorsal fins, and of the vesicular type that look like sponges.
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The second SuperCam RMI series from sol 146 . . .

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. . . and its Mastcam-Z context

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An unusual undulating erosional form of a rock from sol 139 (anaglyph and cross-eyed stereo pair).
Faintly visible is also a wave-shaped feature in the lower part of the rock.

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