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[nprev]

Good observation, Richard.  I have been looking so carefully at the bedding in vertical sections that I didn't even notice that bedding plane staring me in the face.  It's an important view, but I need to stare back at it for a while.

Very interesting "squiggly" forms on the base rock at about 7o'clock from the flat rock in this shot. Limestone, just maybe?

[CosmicRocker]

wwwwwooooooooowwwwww!  It works. And I didn't even have to enter a MySQL query!  I don't even have to know what a MySQL query IS!
I have god-like POWER!!!
HeHe, just wait till that bully kicks sand on me next time. 
The name is Bond...James Bond.

OK, so who was it who bestowed the secret, "god-like POWER" on Shaka? You may live to regret it.

On a more serious note, I've been meaning to dig up an image for dvandorn ever since he first mentioned the "G" word a while back. The dropstone discussion reminded me I hadn't done that. I think it was shortly after Spirit left the summit when she took some pancams on sol 642. When I saw this one, my first thought was "moraine." I have some problems imagining significant glacial transport in Gusev crater, but that view from near the summit still makes me wonder.
http://marsrovers.jpl.nasa.gov/gallery/all...8P2390R1M1.HTML

It took me a while to find a decent earthly analogy, but imagine this scene after removing all of the ice.
http://www.wonko.info/blackandwhite/new/moraine.jpg

Regarding the "dropstone," such a thing would be amazing, but it sure would be nice to see that feature with one of the narrower-angle cameras. They are taking MIs so near it, maybe we can hope. I'm not sure it would be visible to the Nav/Pan cams. It's not obvious that the dark clast is actually embedded in that layer. It could be a fortuitous arrangement of a piece of float on an anomalous area. If you follow those lower layers laterally, they do display a lot of lateral thickening, thinning, and bending.

[Guest_Myran_*]

nprev said: Limestone, just maybe?

I would be extremely suprised if we found any limestone, remember the theory of acidic water on Mars? It based on two thing mots importanly the sulphur salts found and the second as a way explaining the absence of limestone. With sulphuric acid lakes and oceans, no limestone would ever form. Well that's at least one theory, but fact remains, we've sent several detectors to search from orbit but found none.

[Bill Harris]

Conversely, if limestone, CaCO3, did form and acidic conditions later developed, it would form gypsum, CaSO4 and CO2. The components don't disappear, they get rearranged...

--Bill

[SteveM]

I was just looking at this image from the Exploratorium and was struck by the clear fractures running across the strata. In several cases you can clearly see the matches between the left and right halves of the fracture.

Does anyone have any hypotheses about the kinds of processes that could have produced these fractures without widely dipersing the fragments?

[Guest_Richard Trigaux_*]

I would be extremely suprised if we found any limestone, remember the theory of acidic water on Mars? It based on two thing mots importanly the sulphur salts found and the second as a way explaining the absence of limestone. With sulphuric acid lakes and oceans, no limestone would ever form. Well that's at least one theory, but fact remains, we've sent several detectors to search from orbit but found none.

hmmmmm...
I don't think that sulphuric acid by itself forbad limestone to form.

Acids, sulphuric or carbonic, are bound to reacts with iron, calcium, sodium, etc... to form sulphates or carbonates.

If sulphuric acid or carbonic acid (the later in the form of carbon dioxyd) accumulated, it is because they did not found anything to react with.

In clear, there was not enough calcium to form limestone, the very few calcium available was "used" to form gypsum (sulphuric acid being stronger than carbonic acid).

And why only very few calcium? likely because the marsian crust is not differentiated, formed only of basalt, with very few turn-over by mantellic convection (no plate tectonics). Certainly there is as much calcium on Mars than on Earth, but on Earth the calcium dispersed into the mantle was brough to the surface by a massive mantellic convection, and it accumulated into differentiated rocks such as granites (the core of the continents) and was thus made available on the surface by an erosion which groung million more times rocks than on Mars. Even carbonatite lava can form directly from very differentiated magmas.

The same would apply on Venus, and it allowed carbon dioxyd to accumulate on the surface without being fixed in the form of limestone (until the greenhouse effect arouse the temperature so high that now it is impossible to form limestone).

[Shaka]

I was just looking at this image from the Exploratorium and was struck by the clear fractures running across the strata.  In several cases you can clearly see the matches between the left and right halves of the fracture.

Does anyone have any hypotheses about the kinds of processes that could have produced these fractures without widely dipersing the fragments?

Hypthesis #1: As surrounding support material (crater wall? outer extent of broad strata?) is removed, rigid strata of HP sag and fracture.

Hypothesis #2: Shock waves from impacts in surrounding area fracture HP strata.

Hypothesis #3: Other local tectonic stresses (e.g. implacement of plains lavas) fracture HP strata.

Hypothesis #4: Combine the forces of Hypotheses 1-3 in any desired combination.

Name your poison.
and I'm not even a geologist.

[imipak]

I was just looking at this image from the Exploratorium and was struck by the clear fractures running across the strata.  In several cases you can clearly see the matches between the left and right halves of the fracture.

Does anyone have any hypotheses about the kinds of processes that could have produced these fractures without widely dipersing the fragments?

I wondered about the effects of thermal cycling over such long periods of time. Presumably such processes would only be felt on the exposed surfaces, though, so it can't account for such deep fractures. (Sun exposure could heat the surface, but most of the heat would be rapidly conducted away into the cold body of the rock; the steepest temperature gradient would then be in the outmost layer of an exposed rock.)

What about impact shockwaves? Bedrock that was far enough from the site of the impact not to be thrown up / out as part of the ejecta blanket could still be jolted enough to shatter, like a jigsaw puzzle when a heavy book is dropped on the table. But then, my usually reliably wrong intuition says that rocks would split along the bedding planes , rather than perpendicularly. Unless the impact was almost vertically overhead, perhaps? Hmm, that would fit the theory of HP being the exposed base of an impact crater after all the surrounding material's eroded away.

The only other thing that occurs to me is gravity. As the lower (softer?) layers are eroded faster that the upper layers, small overhangs develop; eventually the weight fractures the parent rock and a chunk drops off (or just detaches slightly, with it's slide downhill slowed by windblown sand deposits?) It's interesting to note that in the really specacularly eroded blocks, although almost every layer seems to have eroded at a slightly different rate from the adjoining layers, there are no overhangs longer than, perhaps a couple of cm. (It looks that way to my untrained eye, but after confusing sand and rock the other day, I've now learned to mistrust almost everything I think I see in the images, including scale )

[CosmicRocker]

Everything we've seen on Mars is so busted up, it's really not suprising to find more. I think the answer is "all of the above," and then some. Faults, fractures, and joints are pretty ubiquitous in rocks on Earth. They seem to be even more common on Mars, but we need to remember that the Martian rocks we are seeing are mostly as old as the oldest (and quite rare) rocks still preserved on Earth. Current temperature min/max ranges on Mars are also much greater than on earth, and we don't know much about how those ranges may have changed over time. The paucity of water to aid in the healing of wounds probably also plays a role. These rocks almost certainly have experienced noticeable vibrations from numerous nearby impact events as well.

I'm not sure which particular fracture Steve had in mind when he posted his question, but I think it would be a difficult one to answer conclusively.

The really cool thing about the MER missions has been the way they have forced all geoscientists and geo-enthusiasts to reconsider previous conceptions. Even when new imagery is slow to come down, there is yet so much to to think about from "sols old" imagery!

[Guest_Sunspot_*]

Damn .. exploratorium must be down, no pics from either rover.

[djellison]

Nothing at the JPL site either - probably something broken at JPL - I'm sure they'll fix it ASAP

Doug

[Guest_Sunspot_*]

Some of yesterdays pics from Spirit are on the ground according the the tracking website but not on exploratorium yet.... also, no pics have arrived today (sol 730) from Opportunity, maybe an early morning pass? ....somethings up.

[SteveM]

As I read the Spirit listing, as of a few minutes ago, there have only been 5 MI full frames downloaded since SOL 749. Everything else is only down as thumbnails.

2. What EDRs do we have on the ground from sol 749, 750, 751, 752?
Actual number of EDRs by sequence number and image type:

Sol Seq.Ver ETH ESF EDN EFF ERP Tot Description
--- -------- --- --- --- --- --- ---- -----------
749 p1121.03 2 0 0 0 0 2 front_haz_idd_apxs_doc_512x512x1_bpp_high
...
750 p2936.02 1 0 0 1 0 2 mi_cover_open_minloss2_LUT3_pri44
750 p2936.02 1 0 0 1 0 2 mi_cover_open_minloss2_LUT3_pri44
750 p2936.02 0 0 0 0 0 0 mi_cover_open_minloss2_LUT3_pri44
750 p2936.02 1 0 0 1 0 2 mi_cover_open_minloss2_LUT3_pri44
750 p2936.02 1 0 0 1 0 2 mi_cover_open_minloss2_LUT3_pri44
750 p2936.02 1 0 0 1 0 2 mi_cover_open_minloss2_LUT3_pri44
...
Total 239 0 0 5 0 244

[Guest_Sunspot_*]

An Odyssey relay problem perhaps?

[alan]

Minites, mossbauer, apxs may be using all the bandwidth.