SpecialSetOfSieves

For more details on this latest sample (which has not yet been sealed away), the mission has posted an informative blog as well, but Mars Guy brings the neat animations and the narrative, as always.

Some quick analysis:

• Well, let's see... this one isn't fractured like half the patches we've made on this outer rim of Jezero (e.g. #39, #36), has a neat circular outline, and seems to have reached a decent depth. Seems like a clean abrasion to me. So that means it would be difficult to sample, right? 😆

• The target rock seems to have been chosen in part because it forms small resistant "nubs" (that is, it forms little ridges; the stuff hasn't been eroded down to near-perfect smoothness, like some other outcrops that gave the sampling system a lot of trouble). The chisel marks on this patch - the lines radiating from the center - aren't very distinct like past ones (e.g. #30, which features some harder volcanic minerals), so it is probably average in terms of hardness.

• Just look at all those dark spots, dramatically sprinkled through the dark tan body of this rock! Patch #39 had dark grains too, but they were much smaller, much more rounded; the science team thinks those are spherules embedded in the rock up there. Not so down here. If you zoom in, you can see that the dark material seems to be made of clumps of different, smaller grains, rather than just being one kind of mineral. It looks like we've got a grab bag of different things going on here, which is always exciting! In fact, this one doesn't really resemble any of the prior 39 patches. And that only makes this one more interesting, because...

• Percy is near the bottom of the outer rim, just above the local floor of the Nili Plateau, which features some of the oldest known rocks on Mars - and could be dramatically different from what Percy or any other rover has explored so far. Yes, we know Mars was wet, we know there was a much different climate billions of years ago - but when did that begin? We just might be in the right place to begin finding out...

For those unaware, Perseverance and Curiosity are both armed, like the good patriotic American rovers they are - equipped with lasers which have a definite scientific function, but which also (let's be honest) serve to dissuade any Martian critters they come across from getting too close...

Let's hope Sheriff Percy doesn't need to use it.

Original image with caption (MastCam, sol 1495)

Some quick analysis:

• 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.

• 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.

• 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.

• 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!

See also this post for a discussion of the published paper Mars Guy is discussing in the video.

This image is a close-up of the tailings (fine debris) left behind after Percy drilled for the latest successful sampling operation. The sharp contrast in colours seems to reveal a change found with increasing depth of drilling - the nearby abrasion patch, which is much shallower than the coring hole, mainly produced tailings of the duller, darker-toned kind seen surrounding the coring hole, as can be seen in this image comparing the two.

The row of small neat holes on the lighter-toned tailings (upper right) was created by the rover's LIBS laser (the "death-ray" originally made famous by Curiosity), which is used when we want to know what kinds of elements (e.g. iron, magnesium, calcium) the target is made of. This laser analysis was done about four sols after the core sample was originally taken, just before the rover drove off to its next field site.

What will the elemental analysis tell us? For one thing, the science team will know quickly if the change in colours is caused by a sharp difference in composition, that is, if the rock is made of fundamentally different stuff as you drill deeper down. If that is the case, it would show that this old bedrock we're driving over has more than one tale to tell about alteration, with different processes operating over just a few vertical centimetres near the surface. We already know from samples taken higher up the hill that this old crater rim has seen significant water activity... and yet earlier core samples didn't produce these multi-coloured tailings, so something different was happening at this exact spot.

If the lighter-toned tailings have the same basic elemental make-up as the duller stuff, we still learn a lot - it means something other than a change in building blocks is responsible for that notable difference in colour. It's worth noting that the ~35 prior drilling operations on this mission haven't produced more than one shade of tailings... except in the case of the super-intriguing sample #25, from the Neretva Vallis channel. I expect we'll be hearing a lot more about #25 in the next year or two - but as for the bedrock seen above in the latest one, #28, the scientists are pretty intrigued, given that they tried to get a second sample of this stuff, even before this latest laser analysis. Stay tuned!

EDITED to add context about earlier drilling operations.

In which Sample #28 and abrasion patch #36 are discussed.

Source image

My favourite trailside Martian snack. A particular delight to anyone who misses Opportunity's long traverse in Meridiani Planum, home of the world-famous blueberries.