SpecialSetOfSieves

Well well, this one is certainly different from the last few around the rim interior! This stuff doesn't seem like a good candidate for coring, given the evident weakness/crumbliness.

When looking at some of the LED-lit night-time imagery of this new one, I was immediately reminded of the sandstone/conglomerate-type rocks we analyzed down on the delta fan (Ouzel Falls and Thunderbolt Peak), but those were evidently more "solid" in bulk, despite their "messy", pebbly appearance (or so I considered them at the time!)

The friability of this latest one is pretty unprecedented - we've definitely seen prior examples of targeted rock breaking under the abrasion bit, but in a much cleaner way (Malgosa Crest, taken on the edge of Neretva Vallis, was the last one to do this, but that one has distinct vugs, and was definitely a harder material; Elkwallow Gap, from the delta front/"bacon strip" region, was surprisingly weak, but broke clean in two - and that only after digging into the rock a fair distance, it seems).

I find it particularly interesting that the points where the rock is most brittle/cracked align very neatly with darkest material in the patch... and there is quite a bit more to see here besides. This mission is just so much fun. Happy terrestrial New Year!

What are we hoping to learn from the abrasion patches?

A great deal.

• What is the overall elemental chemistry of the rock/target? (identifying iron, carbon, sulfur, magnesium, oxygen etc. etc.)
• How are the elements in the rock put together? (in other words, the minerals formed by those elements)
• Are there organic molecules present? (If so, not necessarily signs of biology, but are always worth learning more about)
• The "texture" of the rock (is it made of loosely bound material like pebbles and sand, or large close-packed solid mineral grains, or something else entirely?)
• What is the rock like inside? (Sometimes different from the outside! Percy has found dissolved salts and mineral veins in some rock interiors, which were not even hinted at from analysis of the outer surface)

The above is not a complete list. The dust and weathering rinds Paul Hammond mentions (the undisturbed outer surface of the rock), in general, prevent you from answering these questions in the same detail, or at all. By answering the first two questions above, you get a good idea of how the rock formed and what it contains (e.g. is this volcanic rock - like from a lava flow - or something laid down in calm water, or something else entirely)?

Generally speaking, if the mission decides to abrade a hole in some rock, it's a sign that the geologists find the stuff interesting, or at least need to identify what's at that spot to make sense of the immediately surrounding landscape.

I'm still working on a series of posts explaining all this in more detail - with neat pictures - but it's going to take a while yet (we've made more than 30 of these holes, and they've shown us quite a few different things from start to finish!) Questions are welcome!

Sampling here wouldn't surprise me, given the mission's pace of late, although there's a lot more outcrop to study just downhill, which makes me wonder if they're going to be careful and selective. If the long-term plan really is to drive Percy back to the crater floor some time from now, they don't need to be quite so cautious about preserving tubes as they have been, you'd think...

Close-up, sol 1360, taken in the early afternoon

Close-up, sol 1360, taken in the evening (illuminated by LED)

This stuff doesn't superficially resemble any of the prior patches closely; this should be fun to dig into!

EDIT: fixed broken link

Why wouldn't there be avalanches on Mars? It's a rocky planet, and gravity doesn't function any differently there. Same goes for Earth's Moon. Satellites orbiting Mars have managed to catch them in progress, and that I believe was even before the InSight lander proved there are fairly strong groundquakes, which would trigger even more. And this is a planet known for its deep canyons...

Hmm. Well, infrared (from the Sun) and other sources of heat definitely eat away at ice, but that's more of a thing near the south pole, where the CO2 ice goes away every spring. Rocks have been known to crack due to repeated heating and cooling, yes, so you've got the first part of erosion, the breaking part. Moving/transporting broken fragments is another matter, though.

Cosmic rays do cause damage to rocks, but on a much finer scale than the cracking referred to above - you're not going to get big chunks of the rock to break off as a result. Meteorites and Lunar samples definitely show tiny streaks ("cosmic ray tracks") when viewed under the microscope, and I'm sure fresh Mars samples will show them as well, but it's not the kind of thing a rover (or human) would see in the field.

a day of on duststorm days?

Ha, I wish it was just a day.

Adding to what Paul Hammond wrote, Perseverance, the rover itself, has not been forced to stop yet for bad visibility. The storms have never gotten that bad here in Jezero since this mission started 2+ Martian years ago, and we haven't seen a really bad "global" storm since that 2018 one. Unfortunately, even smaller Martian storms can lift the dust so damned high in the atmosphere that it takes weeks or even months to fall out, and the winter season is known to be dusty, so... we're stuck with this scenery-killing haze for a while.

Right, the layering/bedding. I see why you'd define those as grooves. Generally speaking, for sedimentary rocks (which these are), some layers "stand out" because they're more resistant, and some get eroded more easily, making little ridges, which creates the contrast you're seeing.

I've never thought of them as soothing before - but yes, the more rounded ones remind me of underwater sand ripples you'd see in a river or large body of water, which is pretty calming, isn't it? And since there was so much water in Gale Crater, once upon a time...

EDITED TO ADD: On Earth the "stair-step" pattern that comes to mind for that is shale, but there are plenty of examples!

Paul, let me thank you again for all that you do to keep this community going. I know this question is kind of detailed, but I'd be happy if you could steer me even a little here.

I have some confused impressions about Ingenuity's last several flights. I seem to remember the flight team (or someone at JPL) mentioning that the drone's navigation software was having trouble orienting itself above mega-ripples and ripple fields, like the one occupying the Neretva channel, though Ginny had crossed plenty of ripple fields elsewhere in Jezero. If those fields were that disorienting, why was the team determined to fly the drone along that terrain, rather than directly across? (You can see that in flights 68-70, they didn't take the short way across the ripples, as they did in flights 36-40!) Some stretches of the Neretva channel do have steep sides, admittedly, especially as one moves in the upstream direction. I can imagine that they wanted Ginny to avoid that sloping terrain - well and good; why not follow the edge of the upper fan, then, alongside the channel, as Percy did? I do remember that the terrain was very blocky, and that it was slow going for the rover, but Ginny had navigated such terrain before itself, simply keeping up with the rover. They could have flown Ginny across the same relatively narrow and unrippled reach of Neretva that the rover took on the way to Bright Angel.

For me, the irony of Ingenuity's loss is that it did not occur in flying over all the variegated terrain of the crater floor - confusing even to geologists - or the steep cliffs of the delta front, or the weird surface of the upper fan... but in a ripple field. On a vertical hop, no less, when no lateral motion was planned. Geoscience me thinks, probably naïvely, that moderately-sized ripple fields like the one in Neretva are among the most organized and benign terrains the landscape offers in this part of Mars. They're not featureless like the smooth slopes of the crater rim - ripple crests are readily identifiable in Ginny NavCam images as sequential, distinct and curvilinear, forming high-contrast boundaries in most, if not all, cases. So you... land between them, where slopes are gentlest (and the drone didn't even seem to need the flattest slopes available!) I'm not a coder or engineer by any means, and I'm not trying to say that any of this is easy, but... if ripple fields are disorienting to the point where you must fly over them high and fast, shouldn't we have avoided them as much as possible?

I'm not sure what you mean by "erosion patterns". Are you referring to the layers (parallel and mostly curving lines) in some of the boulders?

Worth noting that we've traversed about 3.5 km and climbed 400 m since the beginning of the "Crater Rim" campaign, c. sol 1245. This rover really has traveled.

After 8 years of ascending the mountain, this is what it's come to. As this episode documents very nicely, the rover's brush tool has been working perfectly all this time... until now. After stumbling over all that raw sulfur and being forced to backtrack over all this rocky terrain - he's faulty, malfunctioning. Kept babbling on about his mission.

To quote Mars Guy:

that post, spinning at a few hundred RPM, appears to have been jammed into the rock, which was soft enough to result in a shallow hole. Now the remaining question is, after hundreds of uses without jamming the post - what went wrong this time?

These astro-droids are getting quite out of hand. Even I can't understand their logic at times.