Some quick analysis:
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Not the cleanest, neatest abrasion, as we see from the broken outline from 10 to 12 o’clock, but at least this stuff didn’t fracture badly, like the one further downhill that we made just last week (#38), or two other ones we made on this side of the crater rim (#36 and #33). Surprisingly, we successfully sampled the latter two, so #39 may be a candidate for drilling as well.
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The target rock seems reasonably hard (note that the chisel marks - those lines radiating outward from the centre - are well-preserved and easily visible), which is not always the case: see #32, which crumbled into dust every time we tried to sample the stuff.
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Those small, dark grains (toward the edge, between 1 and 2 o’clock) - pretty interesting; nothing quite like them has been found in any other target we’ve abraded on the rim so far. As a (very) general rule, darker minerals are often igneous (volcanic). Not saying that’s the case here, but they sure stand out in this buff/tan-coloured material.
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This crater rim/hillside really is an amazing place. The other patches I’ve linked to were taken just hundreds of metres away. We’ve made about 8 of these abrasion patches now over this one stretch of crater rim (roughly half a kilometre long), and we’ve sampled multiple times, more than in any other section. The geologic diversity packed tightly together in adjacent layers - featuring stuff like crater impact debris beside solid but heavily soaked minerals - is seriously wild!
Zooming out from the patch:
What are the purposes of this experiment?
We do these abrasions on the rocks before we start analyzing them in detail with the science instruments.
The geologists prefer not to analyze the raw, eroded outer surfaces of rocks - they tend to be covered in dust and sand, and they’ve been eaten away by the wind, or even (over long timescales) the minor amounts of humidity in the Martian atmosphere. By grinding away the outer surface, the fresh, unaltered interior of the rock is exposed.
The instruments then let you learn what minerals and other materials are in the rock, hopefully allowing us to ID what we’re looking at. If the instruments turn up interesting results, the science team may decide to take a sample of the rock for eventual return to Earth.
Hope this helps. Feel free to ask if I wasn’t clear about something.
Very cool. That makes sense, the outer surface may be some mixture of particles from many places but the interior would give a better indication of what the composition is deeper into the crust. Are there instruments capable of determine the age of the samples?
Not onboard the rover, no - which is one of the reasons many hardcore types are obsessed with sample return, in spite of the cost and extreme technical difficulty.
A number of age estimates for stuff in this area (the Jezero crater itself, the old mudstone down in the river delta we sampled last year, and so on) put them at easily 3.5 billion years plus - possibly older. That means the samples Perseverance already has in hand could be just as old as, or even older than, the most ancient sedimentary rock we’ve found on Earth. I get chills thinking about it.
