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The Top of Vera Rubin Ridge Part 2, Site 67-, sol 1944-, 24 Jan 2018-
post Nov 12 2018, 03:23 PM
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QUOTE (HSchirmer @ Nov 12 2018, 04:13 PM) *
IIRC, the drill is designed to efficiently chip and remove rock, not grind it into fine dust.

The CheMin instrument requires powdered samples:
The sample introduced into the funnel consists of <= 65 mm^3 of powdered material with a grain size of <150 Ám.

The drill is designed to deliver samples with a sufficient portion of the required range of grain sizes.

But you might be right, that some kind of silt stone with hematite as siltgrain-sized clusts instead of matrix material could be conceivable. (Although I'm unaware of an according example)
So, let's see, whether MAHLI can give us a hint towards the grain size of the drilled rock.
The remaining question would then be, whether hematite grains small enough to escape MAHLI's resolution can still be light grey instead of dark red.
(APXS can't distinguish unambiguously between hematite-bearing silicate rock and clay minerals of high iron abundance like nontronite, but CheMin can.)
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post Nov 12 2018, 04:02 PM
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Sol 2224 FrontHazcam Drilling Animation.

Jan van Driel

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post Nov 12 2018, 04:14 PM
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QUOTE (Gerald @ Nov 12 2018, 12:33 PM) *
I've compared the color of the drill tailings in Paul's Sol 2224 MR image with early drill tailings taken by MAHLI
Apart from different cameras as you pointed out, tau can also have a large effect on the uncalibrated colours, as we've seen recently with the dust storm. Higher tau gives relatively more scattered light from the sky, and hence redder colours. Even at fixed tau the elevation of the sun will effect the colours.
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post Nov 12 2018, 09:58 PM
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If hematite formation was a late event (during the net erosion rather than deposition period) then different permeability of the rock or buffering effects of variable mineralogy could result in patchy oxidation to the ferric state. At low pH the reaction is very slow and and as a very rough rule of thumb a pH rise of 1 requires 100 times more oxygen availability.

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Phil Stooke
post Yesterday, 08:02 PM
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This is Jan's panorama for sol 2222 in circular format.


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... because the Solar System ain't gonna map itself.
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