South from the landing site, sols 72-237, Starting the science traverse Options

[serpens]

2 mm is around the maximum size of volcanic ash particles but the vast majority are much smaller. It is almost certain that there will be some volcanic ash present in Jezero sedimentary rocks but the majority would be in the matrix. To give an example of size the image below is volcanic ash from the Mt St Helens eruption. The width of the view is 4mm.

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[HSchirmer]

2 mm is around the maximum size of volcanic ash particles but the vast majority are much smaller. It is almost certain that there will be some volcanic ash present in Jezero sedimentary rocks but the majority would be in the matrix. To give an example of size the image below is volcanic ash from the Mt St Helens eruption. The width of the view is 4mm.

How do we guess the size of ash particles on Mars?
I know they calculated that raindrops could be about 1/8th larger on Mars-
https://www.sciencedirect.com/science/artic...6005?via%3Dihub

[Andreas Plesch]

Looking up and down core hole #2 on sol 198, from three, cross-faded Watson images:



click to play (wait a bit).

[Andreas Plesch]

And an animation of another Watson series of focus down the core hole, of 16 images:

[Andreas Plesch]

Core hole #3 so 198 Watson animation 1:

[Andreas Plesch]

Core hole #3 Watson animation #2:

[serpens]

How do we guess the size of ash particles on Mars?
I know they calculated that raindrops could be about 1/8th larger on Mars-

How about we just agree the definition of volcanic ash (<2mm) holds. The size distribution in the range will vary, after all it does between volcanoes on Earth but the real question is what would have been the size of particles deposited in Jezero or the watershed as a function of distance from the as yet unidentified source. Unfortunately there are three unknown variables for that calculation; atmospheric density and viscosity as well as the nature of prevailing winds. Larger particles preferentially fall out close to the source and it would be reasonable to assume that ash deposited in our area of interest would be fine.

[Bill Harris]

And it may not be ash emplaced from airfall. It could be ash from a pyroclastics flow, or from fluvial transportation or from from erosion from an ash deposit.
In the animations of the coreholes I see reddish-tan streaks, which imply weathering of minerals under wet conditions, which is consistent with with their description of the findings.

--Bill

[charborob]

Sol 211 LMastcam-Z:

[tau]

1) Stereoscopic grain-size measurement yields a prevailing diameter of 1.2 to 1.8 mm for the visible grains in this sol 206 Mastcam-Z image
2) Multispectral false color image, sol 208 Mastcam-Z left eye filters 0 to 6, principal components
3) Multispectral false color image, sol 208 Mastcam-Z right eye filters 0 to 6, principal components
4) Context image, sol 206 Front Left Hazard Avoidance Camera A

The source of the coarse grains seems to be weathering of rocks like the one in the center of image 1 and at the lower left corner of 2 and 3.
Some of the flake-like rock fragments show a thin layering.

[dburt]

And it may not be ash emplaced from airfall. It could be ash from a pyroclastics flow, or from fluvial transportation or from from erosion from an ash deposit....

Agree. And just to be complete, it could also consist of impactoclastic particulate matter (flow or fall), from cratering uphill. This might be difficult to distinguish from volcanic material, given that it also would be composed of it.
dburt

[Bill Harris]

And impactoclastic, also (nicer term than base-surge). And remember, weathering, erosion and transportation are so slow compared to terrestrial processes. We have no idea of the age of this surface.

--Bill

[tau]

Sol 211 SuperCam RMI with Mastcam-Z context and sol 210 Navcam context.
SuperCam image now with improved self-made flatfield correction, based on eight SuperCam images from sol 206, where the zenith of the Martian sky was captured.
Color correction is not possible without further calibration, so the colors of the rock here are somewhat arbitrary.
The blue color in the Navcam image is only set as a marker.

n

[serpens]

The olivine rich deposit in the watershed is believed to be a result of deep excavation by the Isidis impact. As it overlays some of the megabreccia it may be base surge, impact related melt flows, fallout which could include ash size particles or a combination of these. The deposits in Jezero appear to have been deposited in the crater from early inflow and the delta material overlays the olivine rich deposits. Seitah is olivine rich and potentially has been eroded to the olivine deposit level subsequent to embayment by the mafic floor. If so the latest sample would represent the earlier deposits in a closed system before the formation of the delta.

[tau]

Sol 213 SuperCam RMI with sol 211 Mastcam-Z context and sol 210 Navcam context