We do not know the lateral, nor regional extent of the Opportunity Outcrop. Not until we see what is in other craters, or what is under the surficial deposits of the area outside the crater. That big crater has got some really interesting vertical layering that shows an apparently deeper view of the stratigraphy..I have to tell you, it is one of those difficult field choices,,,"do I stay or do I go now"....

Well there is "white", and then there is "white". A high albedo is a partially diagnostic test. Careful - one white rock does not all white rocks make.

If there are brines acting to mobilize various elements within a groundwater system, yes, the highland would be depleted in soluble minerals/elements. However, a regional (not global) or local hydrodynamic system is far more likely. And, brines become far more concentrated down hill.

Yeah, quite the irony!

Which paper o' Nicks? Must have missed that post? Was that before I wandered in here?

Anyway...the hematite does have something to do with it, I'm not sure what role it is playing here, but brines carry lots o' metals, if we go with this model. Ya know, while I'm talking metals...we've not heard 'bout the magnet device at all on this trip. That one of the first things you do with a rock is hit it with the magnet, if you got one. But we've heard nothing 'bout the magnetics, perhaps with the new RATing.

'Bout the hematite and location. Small variations in pressure-temperature-pH-Eh-etc differentiate metals into zones within a depositional system. Nick is right 'bout the "lag deposit" business. Who knows how much rock may have weathered away to create the sphereoid filled soil we see today. We could guess by calculating the number of spheroids in a given thickness and compare it to the density of spheres within the soil and thickness of the soil. I'm sure someone will. I'm not at all surprised by a greater concentration of hematite in the fairly undisturbed soils outside the crater. How much soil got blasted out upon impact? Where did that soil go? How much filled back in with those infamous Mars winds bringing olivine from everywhere?

By the way, olivine in these soils really argues against water directly under the soil. It is sooooo unstable in water. These are old deposits. How old, I don't know, but I don't think these layers are actively being deposited, or even recently, but a long stinking time ago,

So right about the getting good data to characterize spectra for future Observations.

Enjoyed the post dtb, made me think and go off on this train of thought thing. As a reward for reading this whole damn post, a present: the view from Pikes Peak, a view I've enjoyed, in person, more than 200 times.