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South from the landing site, sols 72-xxx, Starting the science traverse
serpens
post Sep 24 2021, 01:20 AM
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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
post Sep 24 2021, 01:29 AM
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QUOTE (serpens @ Sep 24 2021, 02:20 AM) *
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
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Andreas Plesch
post Sep 24 2021, 02:44 AM
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Looking up and down core hole #2 on sol 198, from three, cross-faded Watson images:

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click to play (wait a bit).


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Andreas Plesch
post Sep 24 2021, 02:55 AM
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And an animation of another Watson series of focus down the core hole, of 16 images:

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Andreas Plesch
post Sep 24 2021, 02:58 AM
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Core hole #3 so 198 Watson animation 1:

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Andreas Plesch
post Sep 24 2021, 02:59 AM
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Core hole #3 Watson animation #2:

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serpens
post Sep 24 2021, 04:05 AM
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QUOTE (HSchirmer @ Sep 24 2021, 01:29 AM) *
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.
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Bill Harris
post Sep 24 2021, 11:44 AM
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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.

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charborob
post Sep 24 2021, 12:42 PM
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Sol 211 LMastcam-Z:
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tau
post Sep 24 2021, 01:22 PM
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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.

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dburt
post Sep 24 2021, 06:07 PM
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QUOTE (Bill Harris @ Sep 24 2021, 04:44 AM) *
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.
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Bill Harris
post Sep 24 2021, 11:05 PM
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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


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tau
post Yesterday, 08:52 PM
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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.

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