Journey to Mt Sharp - Part 3A: In-situ science at the Kimberley, Sol 596 [Apr 10,'14] to 633 [May 18, '14] Options

[fredk]

I'm neither a chemist nor a geologist, but I think we've seen hexagonal-ish structures elsewhere around here - here's an example:

Maybe these have the same origin, but are seen at different stages of erosion?

[CosmicRocker]

Apparently there was some misunderstanding regarding my previous post, and I apologize if I offended anyone. I have edited the post to make it clear that the f-word I was referring to was "festoon."

[jvandriel]

The Mastcam L images taken on Sol 631 and Sol 632 stitched together
in a 360 degree panoramic view.

Jan van Driel

[neo56]

I stitched together the 367 MastCam 100mm pictures taken on sols 617, 618 and 619. The huge resulting mosaic is 41657 x 13062 pixels, too big to load on the web!
I reduced it to 25000 x 7750 pixels to put it on Gigapan, then to 11900 x 3700 pixels to put it on FlickR:


Enjoy

[atomoid]

a couple m100/m34 pair crosseyes of interesting features from 631 including the 'dragon-scales' hexagons fredk referenced (is that ledge at lower right sticking its tongue, er, 'slide'-ing its tongue out at Curiosity?)

[neo56]

Panorama of the southernmost outcrop of The Kimberley, taken on sol 631, is now complete:


Higher resolution version available on Gigapan.

[James Sorenson]

I'm not a geologist either, but seems to me that the material that filled the fractures and formed the veins are the harder material leaving the rest of the bedrock around to erode down around them because it's softer material. Like we have seen in the past.

[neo56]

Another outcrop in the southern part of the Kimberley imaged with MastCam 100mm on sol 631:

[neo56]

My take on the panorama of sols 631-632 taken with MC34 as Curiosity left the Kimberley:

[serpens]

Apparently there was some misunderstanding regarding my previous post..........

You gotta be joking??? Actually that is a reminder that regardless of smarts, people tend to fixate on their first interpretation and fail to consider alternatives. This has particular relevance to Curiosity as we admire spectacular image treatments and overlook just how limited Curiosity really is. Towards the right of Neo56's panorama there are erosional features that at first glance had me thinking ripple interference patterns. Probably something completely different, but one cannot just wander over for a closer look. Ditto the dragon scales that are probably mud cracks but why such a small, isolated incident? Could this be something else? It is also difficult to get ones mind around just how benign the erosional environment that shaped the current surface is, or the extraordinarily long timescale.

[CosmicRocker]

Thanks, serpens, for the moral support. While you apparently understood what I was saying in that posting, you must have been one of the very few. I had hoped to make the post interesting by doing exactly as you described, hinting at the first interpretation, but then expecting the regulars here to remember all the discussions we've had in the past about that other f-word (festoons).

I actually might have pulled it off if more people than just you and I knew what I was talking about.

By the way, I see the intriguing features you noted in neo56's pano that resemble interference ripples. They certainly could be, but the fact that they are aligned vertically across multiple beds suggests to me that they may be related to the pervasive fracture box work structures we often see here.

[Gerald]

This has hexagonal veins through it http://www.midnightplanets.com/web/MSL/ima...54E01_DXXX.html

Sorry for being late, but that's an excitingly perfect hexagonal shrinkage pattern.
Either due to cooling like for e.g. basalt or due to desiccation (mud cracks), in a very homogenious way.
My first guess would be desiccation, since the rock looks sedimentary; in this case the settings wouldn't have been subaqueous, but instead a wet drying surface exposed to the atmosphere.
That's in contrast to the more syneresis-like pattern (typical for subaqueous shrinkage of mud under low external mechanical forces) of the veins observed at YB.
(based on my limited knowledge about physical processes)

[serpens]

Looks like a sand/rounded to sub rounded granular gravel deposition with non orthogonal fracture fill. I'm not sure I would call this perfect hexagon patterns. While desiccation shrinkage seems most likely it is not the only possible cause and as evidenced clearly from CosmicRocker's experience above, you have to consider all alternatives. For example thermal contraction is a possibility and can cause this effect in dry, salt cemented desert sands on Earth. There is also the possibility of chemical reaction or mineral phase change which have a volume reduction effect. Cracks like this happen pretty quickly and in the case of chemical/mineral phase change do not necessarily reflect a sub aerial process. Image interpretation is extremely limited and we don't even know the nature of the fracture fill and the cement.

[Gerald]

... you have to consider all alternatives...

That's agreed, to some reasonable degree (as far as unitarity is applicable to geology). One (fringe) option I've been considering were tafoni, which later have been flooded by the sediment, as an explanation not using shrinkage. But it's less likely that most of the walls get that same thin, without some of them degrading further.
Horizontal placement of the honeycombs would be by chance, too.

Another kind of shrinkage fracture patterns occurred at Meridiani Planum.

[CosmicRocker]

The thing that I find most intriguing about these pretty hexagons is the fact that many of them appear to be double-walled, and a few might have multiple generations of walls, though these have a thicker, obscuring layer of dust and are more difficult to see. I don't think I've ever seen shrinkage cracks with these characteristics. It seems to imply multiple, well defined episodes of contraction.