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JohnD
2004-May-25, 09:37 AM
All,
The latest pic from Opportunity, of the area outside the rim of Endurance, shows a 'pavement'.
See http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20040524a/site_B115_navcam_180_cyl_L-B118R1_br.jpg

Wide thin plates of rock apparently once a flat, smooth expanse now lifted and cracked into 'paving slabs'. The Mars Rover site offers no discussion or comment but is this not evidence of sedimentary rock? Ie water? The crater is surely too small for the impact to have produced enough heat to fuse sand into glass.
John

Bewildered
2004-May-25, 04:37 PM
I see a pavement too but I see the same thin crust structure inside the crater walls.

It looks like the crater was originally smaller but the sides have collapsed because of erosion under the crust.

Surely only water running into the crater or seeping out of the side walls can do this? Its the deepest place for miles so it would be the last place where water was most recently present.

Tacitus
2004-May-25, 08:16 PM
Most likely the bedrock was broken up into "slabs" by the impact that made the crater. The whole immediate vicinity has been deformed.

MAL
2004-May-25, 08:22 PM
OMG!! It tiles from a martian bathroom floor!!

Sorry, couldn't help myself. Very interesting though. Looks like dried out cow ponds from back on the farm I grew up on. Nothing special about it. Ummm... except all the water it took to make it.

ToSeek
2004-May-25, 09:07 PM
The MER home page (http://marsrovers.jpl.nasa.gov/home/index.html) has an anaglyph of the scene.

Bewildered
2004-May-25, 10:18 PM
Most likely the bedrock was broken up into "slabs" by the impact that made the crater. The whole immediate vicinity has been deformed.

Surely the impact must predate the water since large amounts of impact debris would be ejected but this is simply not there. It must be underneath the crust and the occasional rocks seen at the surface are the remnants of later impacts on the surface from miles away.

JonClarke
2004-May-26, 11:30 AM
The impact that formed Endurance crater is a lot younger than the water laid sediments that contain the concretions. The crater walls clearly show that the sediments are the host rock and have been extensively fractured, faulted and deformed.

The slabby fracture of the sediments may be due to the impact, but are quite likely due to the natural weathering of the rock, which would probably enhance any prexisting fractures anyway. This sort of slabby outcrop is quite common in flat lying sediments.

As to the surface crusts, I agree that water is probably a key feature in their formation. But you don't need much. A slight dew or frost on rare occasions would be enough to mobilise the surface salts in the soil and make them crystalise into a hard crust. This crust will follow the surface, irrestective of whether it is flat or on the crater walls. This is a common process in saline environments on earth.

Jon

ToSeek
2004-May-26, 01:30 PM
The image some here have dubbed Opportunity's own face (http://marsrovers.jpl.nasa.gov/gallery/all/1/n/110/1N137952920EFF2513P1950L0M1.HTML) seems to suggest a crusty surface in that area - looks as if Opportunity broke a piece off that settled down again.

slinted
2004-May-26, 08:07 PM
The image some here have dubbed Opportunity's own face (http://marsrovers.jpl.nasa.gov/gallery/all/1/n/110/1N137952920EFF2513P1950L0M1.HTML) seems to suggest a crusty surface in that area - looks as if Opportunity broke a piece off that settled down again.


This has already happened at least twice in relatively quick succession. Once from the image you posted, which was a wheel stutter intended to disturb the soil, and once apparantly on a drive. The science group studying surface (soil) features must be having a field day with this stuff.
(please excuse the uncalibrated, very blue, colors):
First surface cracking:
http://www.lyle.org/~markoff/processed/1P137948744EFF2403P2584L257M1.JPG
Second surface cracking:
http://www.lyle.org/~markoff/processed/1P138036835EFF2513P2587L234567M1.JPG