That seeming volcanic cone is quite distinct and intriguing. I recall there was perhaps a flyby of this area in one of Sean's videos in the last year or so. I suspect most of the faint linear features are likely sand dunes, with the larger arcuate feature seen perfectly intersecting through several craters looks like the trail vacuumed clean by a dust devil, it would be interesting to see if older imagery of the same area reveals seasonal differences in this and similar such features in the image. I'm curious if the cone, and perhaps also the similar chaotically eroded conic plateau just below to the left of it in this image that the arc leads to, may post-date delta formation.

[edit] Here I think is the view of that hill from Perseverance R mastcamZ, added in the left view for a parallel stereo to get sense of intervening terrain placement, the pancamZ segment is at far righthand of second teir in EliBonara's panorama linked in serpens' post below
Click to view attachment

The cones are the product of aeolian erosion. There are a number of similar in EliBonora's treatment of the panorama on the Perseverance Lands In Jezero Crater thread post #425 with the link to the image in her flickr album being https://www.flickr.com/photos/lunexit/50995739733/

I'm not convinced of that due to the extensive apron of material at the base that has not eroded. Where would the rest of the surrounding material have gone?



Sand cones, yes I get that. But this has a prominent rocky base with no nearby continuation. Appears to just have popped up in the landscape.If it was a volcanic cone it would be a pretty small one. Would be amazing to see it up close. Atomoid, I think you are right The image above is the top of this volkini (mini volcano) I think. Once Percy gets closer to the apron to its north to look over the dune field to the west, it will see the base which is well below Percy's current viewpoint.

Looking at the landing images the original proposed track would have depended on landing in the flat area that is now between Percy and the edge of the delta front. Now there are a lot of whipped cream dunes and tricky terrain to traverse to move further southwest.

On the other hand, the path to the north looks pretty smooth and clear. The rightmost of the nearby crater twins (Twin E) offers a look at what the lower unit in this region consists of. The heat shield is very nearby that crater and would be a useful target for the materials engineers to get a look at. Then there is a wide open plain to the northwest of that crater leading towards the little volcano and the Jaw Bay I mentioned earlier. Between Percy and Twin E, there is a small outcrop as well that would be a useful first closeup look at the stratigraphy. I tried to find it in the panoramas but had difficulty. It s a very small prominence visible to the northwest of Percy on the way to Twin E.

The path to the south looks similarly rough. So my vote is they start moving northward. I am thinking they will want to avoid dune fields at first and prefer flat open areas to test drive on. Once down in the plain at the foot of the delta, the driving should be easy and fast so any particular point will be quite accessible. Getting up on the delta will be quite an interesting exercise though.

The canyon at lower left in the picture in post #50 is interesting. A long dark valley, then a small crater, then what looks like the continuation of the valley. It reminds me of the pit chains that looks like partially open lava tubes. This one could have been carved by water except it looks black like the lava ones.

Wouldn't that be one crazy vista? Imagine looking up at that dark vertical face from Percy's vantage point at the edge of the dune field by the foot. There is so much here. Caves? Strata in abundance. Toothy dunes arrayed radially. A half pipe at the crest.

How tall is this according to the DEM? 50m?

A portion of a possible traverse that would examine some really interesting features:

Click to view attachment

Points along the way are labeled:

1. First contact along the delta face.
2. Base of cliff below a major channel deposit.
3. Isolated remnant of delta. The images from the rover indicate a spectacular vertical outcrop, possibly displaying sedimentary structures of various kinds.
4. Possibly traversable section of sediments, which may include lake beds.
5. Very nice outcrop of possible lake deposits.
6. Another butte to explore on the way up to the delta's surface.
7. Strata outcrop along the entire way to the top.

Stop 5 up close:

Click to view attachment

This is just utterly amazing.

Would also like to examine some of these up close:

Click to view attachment

I'm guessing clastic dikes with alternately expanding and subsiding material.

Excellent work -
That large image size is giving my eye-crossing muscles a bit of a workout though...

One trick for anybody learning to see cross-eyed is to place you palm vertically in front of your nose.
(Something I learned from viewing molecular bio papers that showed cross-eyed protein structures)

Could also be good old normal jointing / faulting and later mineralization.
The Isidris region may have had a 2 kilometer elevation drop due to slow crustal deformation from the weight of Tharsis plateau & the Isidris gravity anomaly/deposition.
When you try and stretch rocks, they break into joints at fairly regular intervals, based on the material strength, so that MAY be a clue to whether the basement stone is weak mudstone or much stronger basalt/granite.

Looks like a lot of sand traps to me...

A stated difference between Curiosity and Perseverance is that the former's mission is to explore the diversity of features - i.e., drive to and examine as many interesting features as possible. Percy's mission is to collect a full set of Jezero samples (~15) within one Martian year. In presentations, managers have said that there will be less time exploring interesting features.

...That large image size is giving my eye-crossing muscles a bit of a workout though...[/quote]

that was just a parellel view, though thats more comfortable to the eye muscles (you just fool your eyes to splay as if to look into the distance past the image) it limits the image width to the distance between your eyes as dependent upon the viewing screen size (unless you fiddle with the zoom of your browser window to compensate). Below is the crosseye version, i left it much larger since its a far easier feat to cross than to splay the eyes..
Click to view attachment

Like Hawaii?

vjkane, Perseverance has four primary mission objectives which contribute to the key science goals of NASA's total Mars exploration program. The program goals are:
Determine if Mars Ever Supported Life.
Understand the Processes and History of Climate on Mars.
Understand the Origin and Evolution of Mars.
Prepare for Human Exploration.

Primary mission objectives are:
Explore an astrobiologically relevant ancient environment on Mars to decipher its geological processes and history, including the assessment of past habitability.
Assess the biosignature preservation potential and search for potential biosignatures.
Demonstrate significant technical progress towards the future return of scientifically selected, well-documented samples to Earth.
Provide an opportunity for contributed Human Exploration and Operations Mission Directorate or Space Technology Program participation.

The first two primary objectives are not incompatible with sample collection and caching and the samples would be harvested from 'interesting features' with solid geological/geochemical indications. But I suspect that a baseline path is being prepared based on the touchdown location and that they will want to move off the mafic floor unit as fast as possible, possibly collecting an igneous sample along the way.

Serpens, you are right that exploration is compatible with all those goals. But while Curiosity has taken years to get to where it has, Percy is supposed to make the Jezero crater rim in about one Martian year. That just leaves less time to smell the flowers or zap the rocks.

And then if I remember right, about another Martian year to reach the Midway area, about another year to collect samples there, and then the MSR lander is scheduled to arrive.

I thought the revised schedule was for launch of the retrieval mission in 2028 with the return of the samples in 2033?

A review team suggested planning to delay the launch but nasa is still going with 2026. Between you and me I’d bet on 2028, but 2026 has 2028 as a backup. There’s no backup to 2028.

One of the papers I read (can't find it now) implied that speed is not about finishing before the retrieval mission arrives, but placing enough caches down in case something catastrophic happens years down the road, rendering any samples still inside Perseverance irretrievable. The fetch rover's job is difficult enough as is; no need to make it harder.

The current plan is to double collect in Jezero. Half the collection is left on the rim in case Percy has a catastrophic failure on the way to Midway. Ideally, Percy collects new samples in Midway to supplement those retained from Jezero.

There doesn't seem to be a consensus yet on how to deal with samples carried from Jezero or collected in Midway. If they are retained by Percy and it has a catastrophic failure, the fetch rover can't remove them from Percy. If Percy deposits all of them in a cache at Midway and the fetch rover fails, Percy can't pick them up to deliver them to the MAV.

I was under the impression once Percy drops the tubes on the ground it cannot pick them back up.

One solution to this would be to fill about 3/4 (~24) of the sample tubes on the way up to the rim. At the top of the rim, drop ~16 of them, representing the whole trek up the delta, on the ground, and keep ~8 that also represent the trek up the delta. Then pick up ~8 more on the crater rim, and when that is complete, drop all ~16 in one spot.

That leaves you with ~16 representing the delta in one place and ~16 representing both the delta and the crater rim in another place. The return can choose which group of 16 to retrieve. If there were any failure in the return, there's another group of ~16 for a second try. If Perseverance failed after reaching the crater rim, there would be the first set of ~16 for a first and only retrieval attempt.

Let me introduce you to 1998 Jeremy Clarkson... https://youtu.be/X7USYfgvIkU?t=28

Phil Stooke at NASAspaceflight.com posted links to presentations from a recent sampling strategy workshop. Extremely interesting with lots of details on the notional traverses, notional sampling plan, and notional caching strategy

Link to Phil's post

First set of slides

Second set of slides

Third set of slides

These slides are from those presentations and represent a notional sampling strategy.

Thanks for the full background, Van.

It was this pair of adjacent statements from the first set of slides: "Perseverance is likely to create two depots, only one of which will likely be returned. - notionally, one in Jezero Crater and one somewhere on Nili Planum. The Science Team believes that the only way to have the complete collection in a second depot is to 'double sample' critical (all?) samples prior to first depot deployment."

…that I was summarizing with my comment in terms of ~16s and ~8s.

Thanks, these slides provide a good summary of what I take is the current understanding of the crater and surroundings in terms of geology, traversability, and relevance to mission goals. It was the first time for me to delve a bit deeper into these planning steps. I have to say, it was surprising to me how much emphasis there is on getting out of the crater even given that it is clearly stated that the delta and the crater lake basin are the primary target. Why not really focus on that primary target ? I understand that the more diverse geology outside of the crater (Nili Planum) is tempting and that it could be explored but the criteria for not leaving the crater is either serious rover dysfunction or extremely exciting discoveries on the way (what ? a fossil ?). That leaves room for only one traversal up and along the delta. In effect, it gives the delta and crater interior the same weight as Nili Planum which does not sit quite right. So I think it will be important to make this one delta traverse count perhaps by attempting to cover all sides of the (remaining) delta. One could even argue one should stay in the delta until there is a sense of exciting discoveries, and only then leave, rather than leaving by default.

Another impression I had that there is rather high confidence that it is possible to plan a detailed traverse based on current remote sensing data. My very limited experience looking in detail at HiRISE imagery around the landing site (and even EDL imagery) and comparing it with rover imaging on the ground would make me much less confident to do such planning much in advance. The rover is only 3m or so, eg. a few pixels in these images. In other words, it will be critical to use on the ground imagery as it becomes available, with a willingness to revise existing plans freely. This seems perhaps obvious but with all the planning investment there may be a degree of inertia.

Considering this, I think there should be a lot of, almost exclusive emphasis on getting to and sampling the sediments about which we can know with a high degree of confidence that (a lot of) water was present. Apart from the potential for life, their composition is an indirect sample of the watershed area (at the time) which often leads to strong conclusions about geologic evolution. Imagine finding a conglomerate bed. The clasts could be dated.

I share the subjective feeling that Andreas indicates, that the relative emphasis on the pre-lake materials may seem a bit surprising, but I think that what gives it relevance is the extremely compressed nature of martian history, where the time since the lake ceased to exist until now is extremely long compared to the time from the origin of the primordial martian crust to the creation of (and even end of) the lake. Given the model of an early warmer, wetter Mars that ceased to exist a long time ago, the formation of the crust and the crater is part of the same timeframe as the lake, and if we're interested in the evolution of the martian environment in which the lake formed, it would be very unfortunate to get an excellent characterization of the middle of the lake era but miss the opportunity to characterize the start of it, as represented in materials only ~1 km away.

I suspect that as with Curiosity there will be significant deviations from the planned path over time. There are also unknown variables to consider such as Rover health and the potential for a schedule delay with respect to the retrieval mission, as was the case for Curiosity and the Exomars program. A healthy Perseverance and a forecast 2 year schedule delay could well give rise to some competitive discussion on science targets. As Robert Burns penned, The best laid schemes o’ Mice an’ Men Gang aft agley.

From presentations I watched several years ago, the focus was always to get a good sample of Jezero from the crater floor to rim in the primary mission lasting one Martian year. Any extended mission is gravy.

A couple of thoughts on why to leave. The Great Cosmic God smiled on us and the top two places to sample Mars (as selected through a series of workshops bringing in much of the Mars science community) happen to be within driving distance. As I recall, Jezero won the vote of the workshop participants, but not by much. Not only does Midway likely contain a geologic record of key events, several of the proposed sampling sites could be locations of significant astrobiological interest. The science community *really* wants sample from both areas.

As for planning the traverse, I have experience with similar products to what I expect the mission planners have. From stereo HiRISE imaging, they likely have a highly accurate 1 m (or slightly better) digital terrain model. They also can tell a great deal about the likely surface of each location from both direct photo interpretation and from texture analysis of variance among adjacent pixels. They have been using these products to plan Curiosity's traverse for years now.

Thanks for the background. Concerning the planning products, of course they are very valuable for considering all options. I was just impressed how every twist and turn was shown on some of planning maps. Now, the map presented today seems to go out of the crater on another route, eg. straight through the main inlet, for now.

Looking at the slides, I did start to think that there are probably strong factions in the community for both the Delta and also Midland. In that case the planning discussion material makes more sense. Thinking ahead it is somewhat problematic that the expected lifetime (1-2 years) of the mission is so conservative, in light of the success of previous missions. It will be impossible to argue to go back into the crater once the rover left it.

Everyone hopes and probably expects that Percy will have a long life and will sample both Jezero and Midway. However, rovers/spacecraft do break, and any operations past the first Martian year also require that NASA approve an extended mission and that is funded. So the managers and science team want to make sure that the base mission requirements are met in that first year.

I found the timeline for Jezro in the press package links very interesting
- especially when overlaid with the Arabia and Dueteronilus shoreline information. - rough ages gleaned from -

(would be VERY interested to hear other ranges of dating)

So, here\'s a guesstimate of adding the Martian oceans to the mix-

1) 4BY and the Martian northern ocean has a stable border at the Arabia shoreline.
2) 3.95 BY and Isidris impact creates a shallow bay, future location of Jezro is underwater.
3) 3.95 & 3.85 BY and regional olivine- carbonates form, (possibly in a shallow bay?)
4) 3.75 BY and Jezro valley drainage system established, (when was the crater-forming impact?) If Jezro was an shallow ocean crater like the Chesapeake Bay crater,

it could have dominated the surface drainage networks and the local groundwater / saltwater aquifer boundary.
5) 3.7-3.6(?) BY and Tharsis volcanism deforms crust and raises Jezro crater and Isidris bay ~2km.
6) Concurrent with Tharsis, the northern ocean retreats and stabilizes at the Dueteronilus shoreline, leaving Isidris Bay as Lake Isidris.
7) Mafic crater floor emplaced, could be during or after Lake Isidris dries up.

I’m not sure the emphasis is on the pre-lake deposits as much as it is in the initial, earliest lake deposits that are directly above them. The lowest, most distal lacustrine clinothem facies (toesets) will be the finest grained and most likely to concentrate less dense organic material. If a location can be found that is beyond the limit of coarse grained (sand?) deposition, that records only the distal parts of several clinothem cycles, several toeset samples could be acquired. Otherwise, sampling will have to concentrate on the lower parts of the coarsening/thickening-upward successions, which unfortunately get mantled by recent eolian deposits and talus.

Good information, tdemko.

In this case, it seems like getting as much of the timeline as possible is a priority, and that no one best sample could possibly give us the information we're looking for. Whatever warm, wet epoch Mars had, it was relatively short, and what we hope for is the ability to see how it evolved. The final chapter of the book might be the most interesting, but the whole story will be very interesting.

Should I just change the name of this thread to "The Great Percy Debate", subtitled "Why UMSF Admins Drink So Much"...?

EDIT: Created a dedicated thread for the name discussion. 7 posts moved.

Onward.

I assume that this has been addressed in erudite analyses although I haven't been able to locate any, but with respect to the source of the MFU how confident are we that the anomalously high mountain with the crater on top, in the South just outside the rim (opposite the delta) is not the remnant of a volcano and caldera. The presence of such would raise the probability of flows from weak points in the crater floor and the presence of dikes.

Not sure if the question about experimental basin fills was in this thread, but here is a nice animation by Zoltan Sylvester of the Jurassic Tank/XES experiment in 2002:

https://twitter.com/zzsylvester/status/1368688046435106826

Note the clinothems, their timing, and stacking patterns, especially in relation to the water/base level in in the experiment.

Here is a nice paper describing the facilities, their capabilities, and some more visualizations of results.

https://www.researchgate.net/publication/24...al_Stratigraphy

I used to do this for a living, so, if there is interest, I can provide more information on physical and numerical modeling of deltas.

The source of the sediments in the delta

The (main?) inlet through the crater wall into the crater basin is well preserved. It is possible to trace back the main stream flowing into the basin about 100 miles to the west which is further than I thought:




Esri has a nice ctx mosaic map at https://arcg.is/1Wumea to zoom into.

It is possible that evidence of flow further upstream was eroded but there are only very faint indications for that.

From a terrestrial perspective it is curious that there are no obvious tributaries, indicating perhaps a locally or regionally arid area. But in the potential catchment area upstream there is also a lack of a network collecting from a larger source. Does that hint at very episodic but large volume flow ? Completely speculating, the periglacial in advance of glaciation margins is often arid. Is glaciation being considered physically at all consistent with atmospheric and aquatic conditions at the time ?

Here is a rough elevation profile from the basin floor to the catchment area:



The relief is more than 2km today which is about a 1.5% slope on average, and perhaps enough of a change to get into a glacial climate in the highlands.

Another first order observation is the linearity of the west to east flow direction, with larger scale meandering superimposed. That would require a consistent but small slope across the 100 mile stretch, and limited time for flow to avoid generating a more equilibrated profile. In deed, the profile today is still at a pretty constant slope but a careful measurement along the base of the stream may be needed.

Sediments in the delta would seem to need to be sourced from rather close to the course of the stream. Let's take a look at the geologic map.

Last but not least, there is also a (secondary?) inlet at the northern rim of Jezero which can be traced into the more mountainous region south of Hargraves crater which seems like a more promising area for catching and collecting precipitation. It looks like it is possible to map more of a network of streams and potential crater lakes there. Around that second inlet there may be sediments as well (edit: closer inspection does not look promising), and their composition may contrast with those from the delta given the differences in their expected provenance. Nevermind, the second, northern inlet is not a mission target, other areas do seem more promising.

The "crustal deformation" paper upthread mentions an mass-concentration under Isidris basin, which could be upwellings of denser crust.

With both respect and gratitude for the expertise of the terrestrial geologists, would the different geophysical properties on Mars adjust some of the parameters in a predictable way. E.g., at 0.38g, would the slower flow downslope flow of rivers at a given slope change the morphology in predictable ways?

Andreas, despite erosion there are obvious remnants of tributaries to the main river. The image below is taken from https://www.sciencedirect.com/science/artic...03206331200044X

There are sedimentologists specializing in landscape evolution and numerical modeling, see for example https://agupubs.onlinelibrary.wiley.com/doi...1002/jgrf.20031 . Consequently, there are a large number of models, based on diffusion or advection concepts. Unfortunately, I am not such a modeler and do not have that insight. My inclination would be to treat lower gravity similar to a change in slope both acting on the erosional effect at the river base in similar ways. Slope is just one parameter besides flow rate, sediment load or potentially tectonic uplift or subsidence.

With that in mind I would expect that 0.38g would require a much steeper slope for a stream to develop similar erosional characteristics, other parameters being equal (which would be difficult to establish). The 2km relief over 100km intuitively feels rather steep and it should be possible to find longitudinal river profiles of similar length, for a direct comparison. A main difference is that the profile does not look like a textbook river profile on earth which has a steep initial gradient, an intermediate section, and a very gentle final gradient before entering a base line (a lake or ocean) which is considered an equilibrium profile where erosion at the source and aggradation at the sink are in balance.

I suspect that there have been attempts to understand such profiles on Mars, after the idea of an early wet history was getting (more?) widely accepted.

Looking more closely along the stream, there are what could be rather short tributaries, and perhaps drainage from the Hargraves crater region to the north.

Proposing a secondary inlet at the northern crater rim clearly requires some interpretation since it would be not very well preserved. I do think there are markers of channeling and meandering further upstream which seem to connect to it.

[edit] ah Thanks serpens, yes that is what I see as well. It is just not much of a system of tributaries.

Nice recent papers on the subject:

https://pubs.geoscienceworld.org/gsa/geolog...J8C5xSG4mS7RX60

https://www.sciencedirect.com/science/artic...019103520305716

Summary: Yes, we should expect differences, but they may be subtle. Morphodynamic comparisons of Martian and terrestrial channels, both fluvial and submarine, show the same geometric relationships. Bedforms may form at different shear stress - grain size conditions and there will be differences in bedload versus suspended load transport. The Amy and Dorrell paper does predict that the upper reaches of graded suspended load rivers in less than earth gravity will have gentler slopes, as Andreas observed in his long profile.

I find myself agreeing with much of what the abstract says:

https://doi.org/10.1016/j.pss.2012.02.003

But I would be less certain about not having cycles of deposition, and erosion, or perhaps completely drying out the Lake. We already saw at least two cycles of progradation and regression on top of each other, with the benefit of ground views. The sudden end of the Lake, leaving the proximal part of the delta largely intact and unincised is just the final act of potentially millions of years of depositional history, as the authors suggest.

Do we have any insight as to why the small deltaic remnants exist at such a distance from the main delta front? Did they move somehow from where they were emplaced? What could cause the significant and remarkably complete (scoured clean down to the top of the underlying unit) erosion of the delta material and what saved these remnants which are presumably analogues of the main delta. Could they have been islands in the lake?

The interesting one (to me) to the north looks much like a volcano from above with no clear evidence of stratification. There are some concentric dust rings that might relate to strata but it’s hard to be sure. Getting a close look at that might yield some useful information about the delta and the erosional processes that have sculpted the front.

Likely chance and the vagaries of the wind over billions of years.

Remember the entire area may have dropped 2 km and tilted during the millions of years of Tharsis volcanism.
Then is probably tilted again during the Isidris basin volcanism.

During the era of the Arabia Ocean Jezro could have been a coastal crater partially below sea level.
Tharsis volcanism would have dropped Jezro up to 2 km below the Arabia Ocean sea level (if that ocean was still there).
During the later era of the Deuteronilus Ocean, Jezro could have been an inland lake feeding into a great lake in Isidris.

While the catchment as it stands can be reasonably constrained, as HSchirmer alludes to the area has been subject to tectonic activity, cratering and erosion that makes the accurate assessment of the ancient drainage area and tributary flows challenging to say the least. While there are traces of the tributaries much has been erased. As I understand it the mineralogy of the Northern and Southern deltas vary, reflecting the mineralogy of the two separate catchment areas. All in all it is a pretty impressive drainage area which I suspect would have hosted an extensive tributary network.

Undoubtedly, there has been substantial vertical tectonics (with some extensional rifting) as there is so much geologic time available. Nevertheless, today the crater floor is essentially horizontal and the main stream bed is well preserved, up to a 100 miles back. So the base assumption would be that first order tributaries would be preserved to a similar degree. I agree that together the Northern and Southern deltas were supplied from a large catchment. Since the main stream to me looks relatively starved to the west and south, perhaps at times there was major supply from the north.

A follow up point - when tectonics tilts an entire river drainage network on 50, 200, 500, 1,000 km scale, you get paradoxes:
Example is the geology / biodiversity paradox for the US east coast: 500 MY old fish populations in 200 MY old rivers.

The main US coastal rivers: Hudson, Delaware, Susquehanna, Potomac, Cape Fear, Congaree & Savannah all run east from the Allegheny mountains to the Atlantic ocean. The Atlantic ocean opened up ~200 million years ago when Pangea broke up.
However, 500 MY old fossils of the same fish species that are in the river now indicates the rivers are over 500 million years old. At first glance would requires the east coast rivers to run UP HILL towards the central "Himalayan plateau" of Pangea.

The solution is that the river tributaries are older than the river & ocean they currently drain to, the large main stems have reversed course.
All the large east coast rivers USED to be small header tributaries that drained west to the proto-Mississippi.
Once the Atlantic opened, they had a steeper gradient heading east, which allowed quick erosion to gorges, which cut back to the west and captured more and more feeder rivers and streams, which accelerated erosion...
https://www.researchgate.net/figure/River-n..._fig1_327653964

Conversely, as the old western-draining network lost tributaries, reduced flow leads to silting up, which slows flow, dropping even more sediment: you get a series of lakes & wetlands, rising water levels, and eventually the water level over-tops the watershed divide and begins flowing east to the Atlantic instead of west to the Mississippi.

Repeat that process a few times for Jezro, add in 2 possible ocean shorelines, and you've got an idea of the scope of the question!