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…

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.

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?

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.

Moderators, would it be possible to add a pinned post or two, with some resources to give people an overview of what Percy has done so far? The mission website outlines things to an extent, but I’d be happy to add some explanatory material. I’m thinking, to give one example, of a post that shows all the abrasion patches Percy has made to date. IRL I get a lot of blank reactions when I try to show people photos of geological materials on a screen, or comments like, “It’s just a rock. So what?” Seeing all of the holes/patches in a montage would be very illuminating, however.

If a pinned post isn’t the best way, I’ll go ahead with making a new post each time we get suitable images from a new patch, but it might be difficult to find in a search. I look forward to your feedback.

I’m already committing the cardinal sin of discussing redox states on social media, Paul, so forgive me for adding this note:

With all the groundwater that seemingly flowed within the rocks of this region, oxygen needn’t have been present at the time of deposition. Alteration/diagenesis seems to be pretty damned important here. (Further aside - non-geologists are always shocked to learn that oxygen is part of so many minerals and rocks to begin with. Maybe it’s easier to talk about free oxygen, the kind that isn’t already attached to the iron or magnesium of whatever…)

Not necessarily. Here comes another episode of Wide World of Iron Minerals…

The mineral that Prof. Ruff refers to - hematite - contains ferric iron, as opposed to the other kind, ferrous iron. The difference between the two is simple - ferric iron is missing 3 electrons, whereas ferrous is only missing 2. Some process has to strip the ferrous iron of that extra electron - it requires noticeably more energy to make ferric than ferrous. Mars has plenty of the ferrous kind, like you find in the rocks on the Jezero crater floor; it’s what you’d generally expect to find in the planet’s hard rock. So you want to pay attention when you get the ferric kind - especially when you find it in the “soft rock”, like Percy is exploring now. One way of making ferric is exposing it to free atmospheric oxygen and moisture, as on modern Earth, producing various “oxidized” minerals, which some casually call “rust”. But there are other ways for oxygen to do the job, as well - say, when it’s dissolved in groundwater. And this Neretva Vallis site evidently had plenty of groundwater. The oxygen content of that groundwater, however, is kind of a big question.

Thing of it is, hematite can also be produced without water and oxygen, purely by volcanic action, too. So hematite has a lot to say either way, it’s one of those minerals to watch.

The phenomenon of iron minerals on Mars has been a big deal, and will continue to be. Opportunity’s landing site was chosen because the variety of hematite that satellites detected there was unusual, and that led to the discovery of sandstone laid down by massive amounts of water - the first sedimentary rock ever discovered off Earth. Without that discovery, I’m not sure that Percy gets sent to Mars. And I haven’t even started to talk about other sources of ferric iron, like you find in the dust, or all the weird stuff that happens when sulfur and iron get together and have a baby…

EDITED to talk about hard and soft rocks. Don’t giggle, we’re geologists.

The thermal cycling hypothesis for erosion has been advanced for Mars since the 1960s - before we had landed even a single mission on the surface - but personally, I’m not convinced. The effect should be ubiquitous and would apply to every clast/rock a rover can see, but just about any landscape shot shows that there are plenty of rocks without the network of cracks you’d expect. Paul Hammond is correct in pointing out that rocks preferentially fracture along planes of weakness (the direction/face where a mineral is naturally weakest), and the composition of the rocks should have a lot to do with it, but I still think that the process would be a lot further along after billions of years.

The potholes you see (…feel) in places with sub-zero winters show us exactly how good freezing/thawing water is at breaking and flaking hard surfaces, so Mars Guy isn’t wrong to point that out first in the video.

I know that the mission releases the proper calibrated images here, but only some months later, so neumast’s reply is the correct one for now.

Thanks for your detailed reply, Paul. It would definitely be worth compiling a set of NavCam images like the ones we’re talking about here. A casual review came up with this recent one, and Sol 1093 has another, so there should be a few.

Just to clarify, the very specific framing of the NavCam tile above is something I don’t remember seeing much since we landed. There are a few elements that make the shot perfect, like the ratio of rover suspension/wheels to surface, the shadows, alignment of the rover and so on. The sense of depth created by seeing parts of the rover at different heights from the camera is really important here. I realize that I’m getting into the weeds and thinking like a photographer and not a rover planner. I’m just trying to point out that this specific framing here is both informative and artistic - maybe even iconic - in a way that other regularly-planned shots don’t quite match.

I’ll see if I can compile a list in the next week or so.

I don’t want to be pedantic here in saying this: Mars experiences dust storms, rather than sand storms. That is a significant difference, because dust is light enough to stay aloft for much longer than sand, which has noticeable effects on climate. Today’s Martian atmosphere cannot loft sand very far. Keep in mind that sand storms would be much more effective at eroding rocks like the one Percy is investigating now - and doing damage to things like rovers and solar panels.

Imagery from today (sol 1084) shows that visibility is not great - parts of the Jezero rim are hazy or invisible - but it’s far from the worst we’ve seen on the planet (I’m thinking of what Opportunity saw in the great storm of '07). I would actually expect Ingenuity to survive this.

Potato-shaped??? I’d like to see Mars Guy’s figure after a few billion years…

Please. Some respect here for these two well-accreted ellipsoids with a few extra tera-tons. If you people want to swipe left on something, you can go straight to the Belt with all those charisma-free rubble piles and old boulder-faces. Sure, they’ve got the organic matter and the metals, but we’ll see who you come running back to when you remember who’s been lighting up every romantic Martian evening for all these eons…

Perseverance is deep within the ongoing Margin Unit campaign, where orbital signatures of carbonate minerals appear strongest.

Perseverance is approaching a small, ~50-m-wide impact crater that has created a natural cross-section of rock layers of the Margin unit, potentially providing new views of deeper bedrock. The team is eagerly awaiting images of the interior of this small crater, which could reveal information about the emplacement of the upper Margin Unit.

Based on orbital satellite images, rock layers near the Jezero Crater Rim are thought to be among the oldest rocks that could be explored by a rover on Mars. Therefore, the light-toned rock layers pictured here could represent much older strata than has yet been explored by Perseverance – possibly dating back to the Noachian (approximately 3.7 – 4.1 billion years ago). Exploration of these terrains could provide unprecedented insight into the climate and environmental habitability during earlier and possibly wetter periods in Mars’ history.