Mars on Earth, or is it the other way around?:
The little hoodoo formations in the upper right of the image, posted by r lewis in reply #8, resemble certain sandstone formations on Earth.
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shows the Fiery Furnace in Arches National Park in Utah (everyone should visit this park at least once).
In Utah, wind and water erosion have worked on and widened joints in the rock. On Mars, wind is likely the only participant, at least in this case.
Yes, we rock guys are muttering. Forget RATS, I want some of those for a paperweight and bookends. 
The gray strips running down the surface of Burns Cliff are just plain weird. They appear as if they were painted on the layers without disturbing them. I would've guessed that they're chemical alteration along hair-line fractures, but the features that are fractures are either filled with similarly colored material or lack any staining at all.
Can't wait until it's time for a close-up.
