[X] My Assistant

[Stu]

Couple of blasts from the past...

Gypsum vein imaged on Sol 3049...



...and 456 colour view from Sol 3070...

[belleraphon1]

Turtle with a top hat?

Naw... Triceratops..... whose a nice tricie... pats rock

[Bill Harris]

New MIs of the eroded massive rock with the bluish resistant areas. This may be the most beautiful MI of all.

http://qt.exploratorium.edu/mars/opportuni...00P2906M2M1.JPG

The resistant areas are particularly interesting.

--Bill

[udolein]

result of Sol 3076 brush on Whitewater Lake (must be taken upside down !):


Link to Image

brush movies:
PanCam
HazCam

Cheers, Udo

[PDP8E]

here is my take on a rock (is there a name?) that was taken on Sol 3070 (L456)


edit: 'wolverine?'

[marsophile]

... a rock (is there a name?) that was taken on Sol 3070 (L456)

Isn't that Kirkland (the Fin rock), where the previous MI was done? (The one that is getting all the attention.)

[Tesheiner]

Kirkwood.

[Stu]

Slightly "artier" view of Whitewater Lake's recent brushing...

[serpens]

Is this a discrete location where they identified clay on Cape York? Authigenic clay cementing?

[Bill Harris]

Serpens, this area is "close" to where the phyllosilicates were ID'd. The sensor resolution was fairly coarse and I take any location with grains of salt.

By thinking "authigenic clays", that is a term that covers a lot of territory. Authigenic implies to me that the mineral was formed in-situ by precipitation, recrystallization or metamorphosis. One mechanism could be impact-induced low-temperature hydrothermal activity. We need to see if there are the proper puzzle-pieces to put that picture together. The scenario I favor is that the light-toned material of Whitewater represents an ancient soil horizon where the clays were formed authigenically by weathering of volcanics or impactites which is overlain by the coarse blue-toned "surprise spherules" (of unknown affinity) of Kirkwood, which are impact-related. And they are not even related to the Endeavour impact as they represented the surface or subsurface at the time of the Endeavour impact.

One paper I'd like to read is:

TERRESTRIAL PERSPECTIVE ON AUTHIGENIC CLAY MINERAL PRODUCTION IN ANCIENT MARTIAN LAKES
Thomas F. Bristow, and Ralph E. Milliken

http://ccm.geoscienceworld.org/content/59/4/339

and I'm trying to pull strings to get a copy.

At least, this is how the puzzled-pieces are stacking up for me now. As we get more info in, and if my chicken starts to look like it has duck-feet, I'll revise my views...

--Bill

[CosmicRocker]

I don't know, but it may be a bit premature to be talking about authigenic clay minerals at this point. Once we find and identify the clays, and see them in context, an authigenic origin might make sense.

I've been sort of eyeballing the published CRISM phyllosilicate overlay with respect to Eduardo's route map to estimate Opportunity's location relative to the anomalies. Serpens' question encouraged me to do a quick and dirty overlay of the CRISM anomalies on Tesheiner's route map. This overlay could be off by a few meters here or there, but it will give people an idea of where this interesting outcrop is relative to where CRISM's lower resolution imagery says it should get interesting.

The paper that the CRISM map came from was titled, "Phyllosilicates and sulfates at Endeavour Crater, Meridiani Planum, Mars." The image caption said (in part), "Distribution of Fe/Mg-phyllosilicates (red) and polyhydrated sulfates (cyan) in CRISM spectral parameter maps."


edit: I used the only CRISM phyllosilicate map of the area I am aware of. If anyone knows of a better one that's publicly available, please speak up.

[serpens]

That's the best CRISM map I have seen Cosmic. But if the map is accurate it does beg the question as to why Oppy zigged to avoid the clay bearing area? The ground in that area looks pretty driveable in Navcam so perhaps as Bill implies the clay location isn't all that clearcut.

Bill, the reason I mentioned authigenic is Whitewater seems to be reasonably well cemented mudstone/siltstone and I would have thought a product of CY erosion would be the most likely provenance. The APXS will give a few indications I trust. Those spherical (clasts? concretions? nodules?) in the Whitewater MI are also different.

But if you would indulge me, Steve's description of the spherule layer made me think immediately of my favourite Larsen coffee mug:

[CosmicRocker]

I don't think she zigged to avoid anything. They simply saw some outcrops they couldn't resist.

[Bill Harris]

Tom, very good overlay of the Route Map and CRISM map. I've been meaning to do that forever.

"Authigenic" in that the clays were produced relatively nearby, as opposed to allogenic where the clays were created in another area and then transported to this site via aeolian or even fluvial processes. We are on the same page, although in different paragraphs.

One puzzle piece that I've had sitting off to the side since the traverse leg along Shoemaker Ridge was the set of orthogonal, light-toned lineations that coincide with the strongest CRISM clay signature. Oppy was closest on Sol-2742-2746, and as you recall, I informally named that area "Secular City". Given that we have since discovered the Homestake-type veins which are low-temperature hydrothermal, this spot should be on our to-do list.

--Bill

[ngunn]

Whitewater represents an ancient soil horizon [ ] which is overlain by the coarse blue-toned "surprise spherules" (of unknown affinity) of Kirkwood

Isn't Whitewater above Kirkwood in the section (or am I hopelesly confused)?