Trek to Mount Sharp - Kimberley

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hortonheardawho







PostPosted: March 17, 2014 12:32 AM 

Sol 0572 panorama about 100 meters from the Kimberley area:

NRB_448279299EDR_F0300484NCAM00299M_a_p-3

with location link.

Time for a new topic.

hortonheardawho


Posts: xxx

Reply: 1



PostPosted: March 17, 2014 12:33 AM 

The previous topic was Trek to Mount Sharp

The sol 0567 gigapan is here.

newboy


Posts: 1

Reply: 2



PostPosted: March 17, 2014 6:22 PM 

Hort, Re 'Trek to Mount Sharp' and Kye's 'mystery' in 611, I think this image of yours shows a mystery for me.

What is that shallow trench that looks like a gouge mark in the centre of the image?

My only explanation is the funny cracks we saw filled with sand many times at Meridiani, due to slab settlement, but here there is no sign of underlying slabs.

So who dragged their toe across the ground? (Actually there appears to be more than one).

Kevin


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PostPosted: March 18, 2014 11:50 AM 

Well the black rectangle in this picture certainly blocks out the most interesting rock which looks like a fossil of a Lizard.

[link]

Kye Goodwin


Posts: 1166

Reply: 4



PostPosted: March 18, 2014 1:59 PM 

newboy, re your 612, in the older Trek To Mount Sharp Thread (see Horton's reply 1). You wrote, "Sand is blown around the outcrop under 'high' winds. This is unstable as 'high' winds do not persist. So in the absence of 'high' wind, the slopes are unstable, and slip. That's it for me." There's not a lot of detail there. What I read is more like, "Come on, we all know it has to be wind, so any old throwaway wind theory will do." Why would high winds preferentially load the upper slopes? What removes the accumulating material from the lower slopes? Why does nothing like what you describe happen on Earth? How would high winds hold slopes up? I don't know what you mean by "blown around the outcrop" but if you are implying curved paths for airborne sand particles, that's very unlikely on Mars because of the thin atmosphere.

I went through my collected soil disturbance library for Gale last night. The way these soil disturbances are associated with rock is so reliable that its got my Who-detectors going CLANG HONK TWEET! An aeolian theory of slope-steepening based on the interference of the rock outcrop in the wind-stream, is an obvious possibility to consider, but it just doesn't seem like such an agency could be DETERMINISTIC enough to produce the extremely consistent association. It would be hard for anyone to assess this last statement without spending a lot of time in the library looking at all the examples. These slopes seem to point in all different directions, from my initial look at this, so the action of prevailing winds in a single storm doesn't fit very well. There could be some directional bias but I don't have the resources to do this analysis.

Here's an example I find interesting:

Its small, between the center of the image and the lower left corner. Its a typical slide and has an appropriately scaled-down overhanging rock outcrop at its origin. This location is close to the many disturbances at Cooperstown but not on the same slopes.

Here's another interesting one because the slope it is on doesn't seem steep enough to slide (center left), but the position relative to rock is normal:

Here's another interesting one because of the very dark material that's been uncovered;

There's a big slide with it's origin just right of center in the image running down and to the left. Its full length is about one third of the width of the image. Toward the top there's a very dark area that's hard for me to interpret. Maybe its just a rock fissure. Anyone? This would maybe not be worth noting but there's a second smaller slide in the image as well, below center and left in the image, further away across the slope. It shows a very dark area more clearly.

I could go on posting images for a long time. There's lots of interesting variety. I've got about 100 images in my Gale slope-disturbance collection. Some are duplicates but many show more than one disturbance.

hortonheardawho


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PostPosted: March 18, 2014 7:12 PM 

Sol 0572 panorama of Kimberley rock outcrop:

From Sol 574 Update On Curiosity From USGS Scientist Ken Herkenhoff:

a drive of about 40 meters is planned toward an interesting outcrop that may be the target of contact science.

As a rock guy ( or a life guy ) where would you direct Curiosity? I would want to peek under the ledges.

RJS


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Reply: 6



PostPosted: March 18, 2014 7:46 PM 


Re #5, I agree Horton. Under the ledges; but ones that have had the least exposure to the sun (if you are a life guy that is).

Paul Scott Anderson


Posts: 53

Reply: 7



PostPosted: March 18, 2014 10:39 PM 

Kye, what do you make of the dark patches on the sand below the outcrop in this new image from sol 574?

Paul Scott Anderson


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Reply: 8



PostPosted: March 18, 2014 10:40 PM 

Kye, what do you make of the dark patches below the outcrop in this new image from sol 574?

Paul Scott Anderson


Posts: 53

Reply: 9



PostPosted: March 18, 2014 10:43 PM 

Kye - what do you make of the dark patches on the sand below the outcrop in this new image from sol 574?

hortonheardawho


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PostPosted: March 18, 2014 10:43 PM 

Sol 0574 panorama of Kimberley area rock outcrop:

with 3D links, including this one:

Notice the nice thick rock shadowed overhangs. Notice the very large number of dark dust avalanches nearby. Notice the long shallow depression crossing the trench in front of the outcrop.

Wow, I think Kimberley will be a fun place.

Kye Goodwin


Posts: 1166

Reply: 11



PostPosted: March 18, 2014 10:43 PM 

I count 8 fresh little slope "failures" in this image:

The sands of Gale CHURN with recent activity.

Kye Goodwin


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Reply: 12



PostPosted: March 18, 2014 11:03 PM 

Hey, Three of us posted simultaneously. Paul, re your 7, Good to hear from you . I'm pretty excited about all the activity as you can tell. At this point I'd rather just get more people to notice it than try to explain it, that is, notice it and not dismiss it as trivial, which it cannot be.

Do you understand my argument about the need to explain this? If one wants to explain this as wind-powered activity then the slides have to be explained basically as slip-faces, but these can't be slip faces like the ones on dunes, because without dune movement across the landscape the whole process of steepening and sliding would soon come to an end as the sheltered slope would become too gentle to fail.

I don't think that this is a wind powered process. My best guess at the moment is that this is Martian life. Wow! The universe probably teams with life. Joy to All Sentient Beings. All That Groks is God.

newboy


Posts: 1

Reply: 13



PostPosted: March 19, 2014 10:24 AM 

Kye, this is 'wind-blown sand 101'. To give you a quick image from Earth, have a look at this photo on Flickr:

A light sand, all of similar grain size, has blown across a pebbly beach. Some of the sand gets trapped/entrained around the pebbles.

If it is not wind blown, how do you explain a sorted fine grained sediment concentrate located in semi-sheltered positions?

A perfectly well understood process, not controversial, easily duplicated in a wind tunnel.

I do think it is exciting to think about the timescales. Those lovely little slides in Hort's 8 above, same thinking. Sand blown onto/under the ledge and then gradually collapses. But what is the timescale?

So what is your problem with this simple process?

hortonheardawho


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Reply: 14



PostPosted: March 19, 2014 10:48 AM 

Kimberley area 3D map:

I couldn't find false color 3D images of this area - so I made one.

I see at least four distinct horizons.

A download and view with StereoPhoto Maker is a must.

Kye Goodwin


Posts: 1166

Reply: 15



PostPosted: March 20, 2014 1:22 AM 

newboy, re your 11, I'm having trouble following your argument. The only disturbance I see in that image is the human footprints. Shouldn't there be sand slides in the image to make it relevant?

It is probably not impossible for me to imagine a sequence of events on Earth by which wind could cause repeated small avalanches in the same place, but I'm having a hard time thinking of any way that seems plausible. How about this: Sand blows into a boulder field from one direction until steep little slopes form in some protected places and some of these slopes slide. Then stronger winds, not carrying sand from elsewhere, blow into the boulder field from new directions removing all the sand, even from the protected places. Then sand blows into the boulder field again and the cycle repeats. This works just as well without the rocks, when you think of it, because dunes form spontaneously, with or without boulders in the vicinity and the protected slopes among rocks that would accumulate sand and eventually slide would probably look a lot like dune slip-faces with overly steep sand crests. They could have a rock crest if the observer comes along at the right time or the process stops in time, before the rock is buried.

That last paragraph might be a complete waste of time, but I include it to show that I am TRYING to take the aeolian explanation seriously.

Here's the Mastcam of that lovely area we saw with Navcam yesterday:

Here's another further down the line of outcrops:

In the second image, lower right, there's a dark slope with avalanching below a rock as usual. Will this slope elongate as more sand slides down? Will it widen and eventually fill all the space under the rock?

I think that these little slides, over time, create the slopes that support them. The question immediately arises, where does the sand come from? I think that it is coming out of the ground at the top of the slope, perhaps along the interface of rock and soil. Maybe the sand is all being created from rock before it emerges, but given all the slide activity that seems to me to make the Gale erosion rate way too fast. Maybe most of the sand is being circulated and a little is always being created.

Kye Goodwin


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Reply: 16



PostPosted: March 20, 2014 4:02 AM 

Whatever is the effect of wind on sand in this landscape it should show some consistency across the scene. I'm looking again at the second image in my reply 13. That one active dark slope, lower right, occupies a position relative to the adjacent rock that is rare in the image. There are several rocks with similar orientation and with similar spaces underneath to trap windblown sand, but that active slope is unique in the image in the way it fills the space under "it's" rock. Aeolian sand delivery should show more consistency, a pattern generalized across the crater floor, something like one end and one side of every rock piled with sand. The localized deposit of sand supports the hypothesis of a localized sand source.

Dishman


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Reply: 17



PostPosted: March 20, 2014 6:28 AM 

I am wondering if these stratified "rocks" are the remnants of microbial mats that tend to form over wet sediments as they dry out?

Kevin


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PostPosted: March 20, 2014 7:01 AM 

These "sand avalanches" are interesting as they seem to have occurred at the same time and they look quite fresh. But what has caused these to happen? One could say it is an overload of sand building up and so it becomes top heavy and it slips downward or is it that there has been a disturbance?
Curiosity weighs a good half a ton on Mars did it disturb these slabs on the way here?

[link]

RJS


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PostPosted: March 20, 2014 8:56 AM 


Kevin (and Kye), re Reply 16. The weight of the rover may have caused these recent slips. However there is clear evidence that there is older slips as well. I agree with Kye, that the slips we are seeing almost always come from near or underneath rocks; rarely do we see them on or near sand dunes.

In this photo there are several small crested dunes and none appear to have slips that I can see.

hortonheardawho


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Reply: 20



PostPosted: March 20, 2014 2:10 PM 

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