Gigapan - PERSEVERANCE 423-N
© NASA/JPL-Caltech/MSSS/ASU/NeV-T

Panorama taken with Navcam Left (my first attempt to this tricky dataset!) on sol 422 at 14:12 LMST.

Sorry, no clue. The colors are somewhat arbitrary, because the results of the principal components analysis depent on the overall image content and some manual adjustments.
Irrespective of this, radiometrically calibrated multispectral image data are required for mineral determination.
An idea of the calibration and processing pipeline is given by this paper, this paper, and this document.
With radiometrically calibrated data and mineral spectra libraries, it might be possible, see the "Mineralogy" chapter and Fig. 3 in this paper.
The rover has further instruments for elemental and mineral analysis (SuperCam, SHERLOC).

I think with PCA, all that you can safely say about two highly contrasting colors is that there is a difference between two things, but there's no definite information about the nature of that difference, and it could easily be some combination of illumination, texture, composition or possibly other things, in any unknown combination.

For example, when you see the color patterns where oil or gasoline and water are on wet pavement, the color differences have absolutely nothing to do with compositional differences.

An image of snow and ice might show considerable variation in color even though every bit of solid present is pure H2O.

Moreover, with the PCA, the contrasts seen across one part of the image are further altered by what happens to be present in other parts of the image.

We may easily be looking at one more or less constant composition of the rocks in these photos with different history of weathering, burial, dust cover, etc.

Gigapan - PERSEVERANCE 422-N
© NASA/JPL-Caltech/MSSS/ASU/NeV-T

Very good, Tau. My sense suggests to me that the finely-bedded bluish rocks are silt- or mudstones. Fine particle sizes that remained in suspension and settled away from the early delta. The purplish rocks are a different mineralogy and are somtimes associated with the siltstone units, which may well.be cyclic. Some purplish rocks appear to be coarse grained and may represent rocks that have tumbled down from higher in the section, or may represent cataclysmic flows in the streams or may represent turbidites from the delta. The mineralogical difference may be the result of intense chemical weathering of volcanic rocks in wet basins of the upland that were breached during intense rainfall events and entered the streams as a slug.

--Bill

If you are right that the deposition was fallout in the lake prior to delta formation Bill then couldn't the banded layers reflect variations in oxygenation conditions within the lake? Assuming an abiotic influence, say periodic changes in cloud or ash cover affecting levels of UV at the surface and potentially shallow water.

Thank you, StargazeInWonder, I couldn't explain it better.
Another example with relation to Mars:
A solid piece of crystalline hematite (like the famous "blueberries") is steel gray and may appear blue after PCA transformation.
Hematite powder is red (used as pigment Red ochre).
The nature of the difference here is the different particle size, the mineral is the same.

I had the same impression due to the smooth surfaces and thin layering.
I hesitated to write it down until we get more details (high resolution images, mineral analyses).

I'll mention again - might want to check the "Newark Basin Coring Project" out of Rutgers-
They were able to correlate orbital orientation to rainfall, correlated to lake depth, such that blueshales are deep-water anoxic,
redshales are shallow water-playa exposed and oxidized.

Some terrestrial basins have tell-tale enrichment of rare-earth elements from the deepest lakestands, I'd be quite curious to see if any of those compounds turn up, or are detectable.

Meanwhile- What's that? Everyone's looking at the silt layers, what's with the 'worm castings?"

A SuperCam image of this little pile would be interesting,
and a SuperCam image of the bumpy surface of this purple rock in the foreground of the sol 423 Mastcam-Z image below.

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Here comes a sol 424 SuperCam RMI mosaic of the presumed siltstone/mudstone with sol 423 Mastcam-Z context.
The graininess in the bluish-gray parts of the SuperCam image is most likely image noise.
Possible mineral grains are too small to be visible. If there are grains, their diameter should be less than 0.15 mm assuming that at least 3 pixels are necessary to resolve a grain.
The vertical sequence of laser shots in the center of the SuperCam mosaic indicates that a chemical-mineralogical analysis is in progress.

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Gigapan - PERSEVERANCE 424
© NASA/JPL-Caltech/MSSS/ASU/NeV-T

I'm not willing to stick my neck out on that just yet!! Aeolian weathering can create the strangest shapes!!

--Bill

Absolutely. In (polluted) terrestrial waters you can have low dissolved oxygen due to BOD (Biological Oxygen Demand) and COD (Chemical Oxygen Demand). The chemistry of the water can scavenge oxygen. And still water in the bottom of a basin or Cup ( ) can certainly produce anoxic zones.

--Bill

Sol 424 SuperCam RMI mosaic no. 2 with Mastcam-Z context and sol 422 Navcam context

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Sol 425 SuperCam RMI mosaic with sol 423 Mastcam-Z context and sol 422 Navcam context

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Interesting shapes- they remind me a bit of the raindrop casts you find in some eastern USA Triassic red shales.

Anyone heard any guesses on what size raindrops on Mars would grow to?

I know Ralph Lorenz has 'previous' on this matter!

In brief - it appears to depend on the atmospheric pressure.

Andy

We have had some really nice panoramas posted by Damia and Thomas recently, certainly much better than I could manage. I have been playing with circular versions of them so here are some examples.

Damia, sol 419:

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Thomas, sol 422:

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and the same with some contrast enhancement and other processing:

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And we just had another drive, this time to the east, looking like we will approach an interesting outcrop north of where we are now.

Phil

Just reporting in from the MEPAG meeting. Ken Farley reports that the rover will now move back to the Three Forks area and up into Hawksbill Gap. It will survey outcrops on the way up, then sample them on the way down. At the end of 2022 it will be back at Three Forks and that may be the site of the first sample cache, because it is so flat and benign for operation of the later sample collection missions. Then Perseverance will climb onto the delta top for more sampling. It is possible that the cache will be closer to the crater Belva on the delta top, some time in 2023, but there is a desire to get a good cache safely deployed fairly soon. Later the rover moves to the main channel of the delta and finally up onto the crater rim in about 2024. A second cache would be further southwest after more sampling.

Phil

This is Damia's panorama for sol 419 (as posted above) but with enhanced contrast and adjusted colour. Changing contrast messes up the colour, which is why I make changes to it. I know it's not realistic.

I have not worked on the latest panorama, hoping someone else will do it first.

Phil

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Sol 425 RMastcam-Z (34mm):
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sol 426, a circular panorama with lots of aeolian bedforms AKA drifty-like ripply-like objects.

Phil

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More of those lovely aeolian bedforms (See Phil's post) this time after the drive on sol 428 (site 24-1970)
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Sol 428 Navcam panoramic. Look at this very nice place !

Very interesting. Rather than strata these layers have the appearance of striations given the uniformity of the mineralogy and almost invisible grains and a colour which seems to match that of other igneous rock in the region. It seems very unlikely that distinct layers deposited in different periods would appear so uniform and cohesive with uniformly microscopic grain size and exhibit such stable fractures. Admittedly the orientation seems wrong but could be the result of a kinetic event. Glaciation or rock glaciation might explain the unusual erosion evident in the geography of the delta front.

Here's an example:

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The mineralogy of many rocks here is most likely not homogeneous.
There are color variations (bluish/purple) parallel to the layers. They are particularly well visible in multispectral images like this one in post #48.
I would exclude a glacial influence on the shape of the rocks here.

Here come some more multispectral images. The next three were taken around SuperCam RMI investigations.

Sol 425 no. 1 Mastcam-Z left eye filter 0 raw image and filters 1 to 6 multispectral principal components

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Sol 425 no. 2 Mastcam-Z left eye filter 0 raw image and filters 1 to 6 multispectral principal components

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Sol 425 no. 3 Mastcam-Z left eye filter 0 raw image and filters 1 to 6 multispectral principal components

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Sol 425 no. 4 Mastcam-Z left eye filters 1 to 6 multispectral principal components.
Links to filter 0 raw images: left and right part

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Gigapan - PERSEVERANCE 425
© NASA/JPL-Caltech/MSSS/ASU/NeV-T

Sol 427 panorama in circular form. I thought this area would be difficult to cross but it seems not. I only used the upper tier of tiles in the multi-tile image to save time.

Phil

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And this is Damia's very nice panorama from sol 428 in circular form, with a closeup of the area around the rover. Still lots of terrain relief distortion in this. Thanks for a timely panorama, Damia.

Phil

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Gigapan - PERSEVERANCE 425-N
© NASA/JPL-Caltech/MSSS/ASU/NeV-T

Two SuperCam RMI mosaics from sol 428 with Navcam context image

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A drive on Sol 432 takes the rover to site 24-2770
Trimmed this roughly assembled / processed end-of-drive tiled L-NavCam to remove a little image drop out.
JSON drive data not yet available.
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Now the map is updated - a good drive out of the ripple area and out into the plains of Three Forks. According to the MEPAG presentation we will head for the bacon buffet now.

Phil

Which map is updated, Phil? The last Route Map uodate ia 3May22.

I was referring to the JPL map:

https://mars.nasa.gov/mars2020/mission/where-is-the-rover/

It is updated after every drive, usually within half a day.

Phil

Has Perseverance taken RIMFAX scans since it was at South Séítah? A scan around sol 419-422 could help determine whether the crater-floor volcanic unit onlaps or underlies the sedimentary beds of the delta.

Edit: Two possibilities:

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RIMFAX is used on almost every drive. A place as significant as this will certainly be probed by RIMFAX, but it may be quite a while before we get to hear about the results.

Phil

Sol 425 SuperCam Remote Micro-Imager mosaic with Mastcam-Z context and sol 422 Navcam context
Here is a link to a multispectral image of the Mastcam-Z context

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Do we know what slope angles will Percy have to drive climbing up the delta?

A circular panorama for sol 432, coming back into the Three Forks area.

Phil

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After the short drive on Sol 434
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Here is a map of slope angles derived from a digital terrain model with a horizontal resolution of 1 m. Local small-scale slope angles may be greater than shown on the map.
Thick elevation contour lines every 10 m, thin lines every meter.
The steepest slope Curiosity has climbed so far in Gale crater was about 31 degrees to my knowledge, most probably on solid ground.
I wouldn't try this with Perseverance on a scree slope.

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Don't forget Perseverance's wheels have twice as many treads as Curiosity's wheels, so that could mean less slippage when traversing slopes ?

Sol 433 circular panorama. A good landing strip for the sample return lander!

Phil

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Given tau's very nice topo map, it looks like Perseverance can reach some delta layers by climbing a slope no steeper than 6° in the direction of motion. That doesn't account for the need to negotiate some dunes in the early going, which is also tricky. But it looks like nothing harder than what Curiosity has already done.

This is the description of future activities shown by Ken Farley at MEPAG (public information, will be online shortly). We are at point 4 now.

Phil

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