If you're trying to figure out what's going on in some mastcam view of the foreground, remember that there's normally good coverage of the foreground with navcam, normally on the sol they arrived at the site. So in this navcam view you can see the ground covered in the M100 view you linked to, and you can see by the tracks that indeed they did drive over those rocks:
http://mars.jpl.nasa.gov/msl-raw-images/pr...NCAM00354M_.JPG

The presence of conglomerate in some spots does indicate fluvial clastics similar to your Tennessee example. Better yet, the strata at Gale are probably cyclical (like the Pennsylvanian beds in TN), so there could be several repeating sequences of fluvial conglomerate/sandstone, lacustrine beds, and possibly eolian sandstone.

A number of sedimentary sequences appear to outcrop in the lower slopes of Mount Sharp (though I'm not sure how close those are on the stratigraphic column with the rocks examined up close by the rover).

Yep, I see same thing right in the middle, those things are strange indeed.

The Mars sunset was just on The Weather Channel .

Magnificent view on sol 981:
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My take on the 7x2 L-MastCam mosaic (processed version)

Full size (8053 x 2643) LINK

Plus the latest USGS MSL Mission Update from Ken Herkenhoff - Sol 983: More sand traps

Left Mastcam (M-34) Sol 981.



Click image for full resolution.

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The complete Mastcam L panoramic view on Sol 952.

Jan van Driel

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The Mastcam L view on Sol 969.

Jan van Driel

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and part of it taken on Sol 976.

Jan van Driel

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yup, Zelenyikot's funny ventifact from sol978 was snapped on sol976 as well, hence a crude wider-baseline crosseye is derived.. ..couldnt resist the other interesting sol976 scenery coming down
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My take on the sol 975 R-MastCam mosaic of the outcrop at the base of Mt Shields.

Clicking image will open the 1024x435 pixel version, Full size is 15235 x 6471 pixels!

Quick and Dirty NavCam mosaic using the 11 available R-NavCam images from sol 983 LINK, may help to confirm the post drive location until the rest of the set comes in.

Sol 983 Navcam R view.

Jan van Driel

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experimental MARDI anaglyph sol739 just came down just for the heck of it
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USGS Mission Update Sol 984: Slippery Sand, by Ken Herkenhoff: LINK
Slippery Sand causing more issues

Sol 894 Partial End of Drive R-NavCam (6 frames) LINK
We can see where the rover backed out of the sand before going forward again... Looks like the rover is on an incline?

Yes - here's a hazcam view to show how we moved. You can see more of the tracks.

Phil

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PS this traction issue is something that really has to be fixed for 2020!

Nice detective work again Phil, I wonder what the slope angle of that section of the north wall is
Fully agreed re traction issues for 2020. For MSL, maybe they can modify the drive software, so when it detects too much wheel slip, it then backs out and providing it has enough traction, it then tries a pre-loaded alternate route... (just thinking out loud)

It's really weird because traction is one thing they tested extensively on sand dunes with Scarecrow (see e.g. this blog and this JPL video). Clearly there is something we don't yet understand about how the physical properties of Martian dunes are different from Earth dunes.

The Navcam L view on Sol 984.

Jan van Driel

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At first I was thinking that fine dust in the atmosphere would imply small grained sand dunes on Mars, then I read that the grain size of Martian dunes is typically about twice that on Earth. So I guess it wouldn't be due to a fine grained sand dune.

Alien aeolianologists (if there is such a thing) are always telling us not to call these things dunes - they are drifts or ripples, and I think they are dusty or silty rather than sandy. The real dunes are the big dark things between us and the mountain. So it may be that the wheels don't do well on these very fine sediments but would actually cope quite well on the big dunes.

Phil

I really hope that there is such a thing and that one of them will drop in to give us a proper account of the distinction in physical terms. The 'drifts' resemble dunes in shape and in their tendency to form periodic patterns. They are undoubtedly formed in a very similar way by surface modulated wind transport of grains. The grains are smaller, the necessary winds lighter, and they may be more slippery. Does that warrant a terminology barrier worth poilcing?

I would have thought that it would be pretty difficult to emulate the absolute dessication and armouring of Marian dunes/ripples as well as the particle compression due to the reduced gravity? So test results from Scarecrow would be indicative rather than absolute. Personally I think the design and slippage detection methodology is pretty good and sometimes when facing the unknown you just have to suck it and see and then adapt your operational approach. The bottom line seems to be stay away from dunes.

Ngunn, the transition between ripples and dunes is generally accepted as being a height of 0.075 metres. On Mars it is probably best to just think of ripples as small dunes - the distinction doesn't really seem all that important.

On this wikipedia page (Deposition Section) there is some distinction made between aeolian ripples and dunes, in the layout of larger vs smaller particles from ridge to trough:

http://en.wikipedia.org/wiki/Aeolian_processes#Deposition

Of what I've seen of the preliminary 2020 rover design, the wheels will move forth and back during driving to overcome this issue, looks funny, a bit like crawling, but seems to work significantly better than the more rigid MSL design.

They will stay away from the migrating dunes, at least, since otherwise the rover would run into the risk to be covered by the dune, in case of immobility for some period of time.

Considering the incredibly slow pace of geological change & aeolian surface processes on Mars I don't think that being overwhelmed by dunes is at all a risk.

As Spirit's demise showed, the problem with dunes is that there's no reliable way to gauge the depth of them prior to entering them. As Opportunity's struggle in Purgatory Dune showed, the mechanical properties of a given dune are also not readily obvious at a distance.

So, yeah: Avoiding them whenever possible seems eminently prudent.

Source for this?

That's been a short video during a talk of someone who should know. I didn't try to find a weblink to the video.
Since the talk has been accessible for the public, the information should have been unclassified.

---

The mean migration rate of the dunes is estimated to 66 cm / Earth year in this paper.
The migration shouldn't be uniform, but may be accelerated during storms.
Take the scenario of a halt of a few weeks in the migration direction of the dune, coincident with a dust storm.

Thanks for the link to the paper. Note that it specifically concerns the dark dune field that was near MSL's landing site, which of course was studiously avoided for the reasons I previously described & is no longer a factor in MSL's traverse. That 66 cm/yr rate estimate is for a very localized area.

Re 2020 mission relevant design features, if you have a publicly accessible link for this data please post it in the appropriate topic. If you're not absolutely sure it's been publicly released, please don't refer to it.

USGS Mission Update Sol 985: High Tilt, by Ken Herkenhoff: LINK

"Highest tilt of the mission" made me a little nervous but I was reading some Spirit mission history today (PDF), and it's worth remembering the kinds of slip and tilt the MERs have dealt with in the past, e.g.
Curiosity should be able to handle much more difficult conditions than she's had to face before.

(I would like to see less slip on these sand drifts, though.)

Sol 984 : ChemCam observations of a nearby rock called "Una" to test the newly-installed ChemCam auto-focus software

Full size (3116 x 1139) LINK

Left Navcam Sol 984



Click image for full resolution.

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The thing making me feel a little uncomfortable is less the slope taken allone, but the very soft-appearing ground, leading to a possible risk to sink in at the downslope side.
It's certainly a good decision to first analyse the current state.

The left mast camera mosaic from sol 984 (adjusted colours)

Full size (5996 x 1710) LINK

I spent two hours last night googling around, and fast forwarded through the few Mars 2020 telecons on YouTube but was unable to find anything on this topic. If it is in public domain, could you give a little more of a hint?

On a separate note, I did find an interesting video of Honeybee's development of the drilling, sample acquisition, and caching system:
http://www.unmannedspaceflight.com/index.php?showtopic=8016

Have we seen duricrust type features here in Gale? Perhaps it is drier here and the particles don't stick together as well as we expect, leading to slippage.

A view of the drifts/ripples from Sol984 as an anaglyph



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The FHaz view from Sol985


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I tried to track back the source, but failed to find the video. The closest similarity is to the wheel walking approach I've linked to in the ExoMars thread.
I can't rule out confusion between the two rovers somewhere in the communication pipe, probably my fault.

I just came across this MSL update. Interesting to understand a bit more how the route's planning takes place.
Here is a link to the text and a direct one to the video: Curiosity Rover Report: Rover Road Trip

Fernando

USGS Mission Update Sol986: Finding a Path, by Ryan Anderson LINK

986 post drive R-NavCam, used just 4 frames for a quick stitch, some data drop out in this batch, but looks like we are back on leveler ground
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If they can make the Logan run more power too them. pia19398-main_mcam04234rs24b_annotated

Further tests with the ChemCam's new software (early images, more to come?) on target called Yellowjacket...

This is a reprojection of Dig's panorama from sol 984, to circular form:

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And here's the path plotted on the panorama PaulH51 just linked to:

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Here is the complete Navcam NL B panoramic view on Sol 983.

Jan van Driel

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