I combined this oh-so-unreal color composite using images from sol 20 using filter L2 as red, L5 as green, and L7 as blue. This makes both red and blue a little extreme, see my pancam post, but hey, what the heck it's a very interesting spot and I used it as a tutorial on channel combining.

There are some very interesting things here, to this geologist's eye.

This image ought the help with my notes:

1.What is this? Non-spherical concretion with a diffusion halo?

2. Well, that's odd, catching the light just right, ain't it? Or are there some other compositions of spheroids?

3. An igneous petrology student would call this the top view of a columnar joint. Would they be wrong? If we see more of this it would indicate at least part of the outcrop cooled from extrusive igneous material. Or they could be joints caused by impact. I know, we don't see the vertical expression of columnar joints elsewhere in the outcrop, but we may not be seeing the side view of this particular rock unit.

4. Contact: a plane between two rock types. Is it a impact fault ? Obviously the rocks on either side are at two different orientations. I believe we are seeing the top of layers in the upper left of the image and a side view of the layers to the lower right. This is a difference of almost 90 degrees. My guess is that the outcrop blocks are at many different angles due to the impact in the crater. Although, it could be an different rock type or different morphology of the same rock type. Volcanic flows often have layered and massive phases in the same outcrop. Check out the purple hue along the contact.

5. Okay, here it gets weird. Look at the texture of the layers, the pinching and swelling. I really want a microscopic view of this baby. What would cause this? Irregular compaction during welding of volcanic material? It sure looks like a sedimentary structure to me. Dare I say a side view of ripple marks? But (water) sediments don't jive with the possible columnar jointing. I am certain there are other possibilities.

There is another structure this reminds me of, but do I speak the word without getting flamed as an anomalist? Okay look this up: stromatolite. I'm not saying that's what it is, stromatolites typically have much more rounded forms, but I've met many that didn't. It'd be carbonate, though, pretty much rules that out. Besides, were it stromatolites, ancient life on Mars would be proven. I repeat: I am not saying or implying that this is a stromatolite, it just kinda looks like one.

6. Note this blocky rock that seems to have similar composition to the spheres. This rock can clearly be seen from the first panoramic photos (at the far left of the outcrop), and there are more of them around.

OTHER:

NASA has still not released any data on the outcrop that I can find (and I've been downloading lots of .pdf's) so I'm still considering sulfates, sulfides, etc.

"There is nothing so humbling as an outcrop." Pettijohn