[X] My Assistant

[CosmicRocker]

... The fluids that created the ubiquitous hematite spherules in the sulphate units must have also diagenetically altered the units at and below the unconformity.

That really is a great point. Looking at the rocks around Opportunity now, we have seen several apparently different rock types that all seem to have spherules in them. That would fit nicely with your hypothesis. I hope we have more than one MI target around here.

That was three days ago. So are we still missing the R5s? I thought we'd have this nailed by now.

Yeah, so did I. For some reason all of the sol 3063 Milnet images are apparently stuck somewhere in the pipeline, and to make matters worse, all of the subsequent image sets do not include the R5 filter. Instead of running an "Rall" sequence (meaning R1-2-3-4-5-6-7), recent sets have been R1-2-4-6-7. I just noticed that we should get a full right filter set on sol 3067 (pancam_Kirkwood_PreRatBrush_L234567Rall). I think that will be an important set to keep an eye on.

In the mean time, I have spent the evening studying the calculated IR false color image algorithm that I have been using to identify hematite. After comparing the right filter band-passes to some hematite IR reflectance spectra, it appears that the R4 filter should work as well, if not better than the R5, so I think I can work with the recent image sets. I'm working on some outcrop images and will hopefully be able to post something tomorrow.

[kungpostyle]

The Planetary Society monthly report is up:

September Report

[Stu]

Wow...



And look at the bottom of this one... shiny veins..?

[Burmese]

I think Oppy is going to be considerably delayed hitting that 37k mark. Whether those turn out to be blueberries or not, these structures are very different from anything we've encountered before, and I'm sure the team will be spending a good stretch of time here applying the rovers' reduced toolset to try and figure out what this is and how it came to be.

[charborob]

Wow...

A 3D look:

[fredk]

Love those crazy web-like bright veins.

Here's an L7/R1 anaglyph:

[Bill Harris]

After comparing the right filter band-passes to some hematite IR reflectance spectra, it appears that the R4 filter should work as well, if not better than the R5, so I think I can work with the recent image sets. I'm working on some outcrop images and will hopefully be able to post something tomorrow.

Please do! I worked with the "IR ratio image technique" for a while, but got sidetracked and still use my "TLAR" method.

--Bill

[dburt]

I am betting this is not hematite simply because these are hollow spherules; and all of the broken hematite spherules we have seen in the past have been solid.

For comparison the first is a photo taken this afternoon of some hollow spherules, type devitrification lithophysae, from Cerro El Lobo, Tepetate, San Luis Potosi, Mexico, from a broken hand specimen I collected in 1985 (cf. my earlier posts 182 and 207). This is a topaz rhyolite (the light is glinting off a small topaz crystal in the large lithophysa to the left), much richer in water and fluorine than anything expected on Mars, and the groundmass has completely devitrified (following formation of the lithophysae). The typical onion skin texture is evident.

The second photo from this afternoon is shows more typical devitrification spherulites, from a weathered specimen collected last March by my colleague in the Superstition Mountains east of Phoenix, Arizona. The spherulites, especially broken ones in the lower center, clearly show the radiating microcrystalline texture that is typical. The groundmass is a somewhat perlitic (gray hydrated) obsidian, not devitrified. The spherulites, unlike the lithophysae, are resistant and weather or break out of the rock.

Hope these photos prove instructive; I was a little dissatisfied by what I found on the web (although Gladstoner's in 206 isn't bad). In both photos, note the extreme variation in size over a small area (also typical of concretions, but not Mars blueberries). In any case, the MI Mosaics of Stu in post 173 seem to show a rather large variation in size over a small area, also suggesting (together with the unusually close packing) that these might something other than the typical blueberries.

[CosmicRocker]

Sorry it has taken so long, but I generated 15 of these images covering much of the outcrop, and that took a long time. I was hoping I could stitch them all together, but that is not working, so I'll post it in pieces.

These are false color composites using right filter images and ratios of the images. Although some of you may not believe the uncalibrated, raw jpeg images can be used to do anything consistent, this algorithm has very consistently identified hematite on Meridiani Planum. I have looked at hundreds of these images and in all of them hematite appears as a bright, canary yellow color. I suppose that some other mineral that has a similar IR reflectance spectrum to hematite's might also appear yellow with this technique, but I don't think we have seen any such minerals on Meridiani.

As you can see, there appears to be a lot of hematite around here.

As I look at this I wonder if it may be similar to something we've seen once before. If you look closely at the left side of this pano and also the bottom right you can see ares where a bluish rock appears to be behind an encrusting layer of hematite. Do you remember seeing something similar on a target called Chocolate Hills?

[Eutectic]

Although I have yet to find the MI images I *think* I remember of fractured blueberries, this hematite concretion picture on the left from 2004 (!) is consistent with the harder rind/softer interior spherules we're seeing presently in the right frame.

[Bill Harris]

Thanks, Tom. Now we "know" what color this puzzle piece is. Chocolate Hills, if I recall correctly, was decided to be a fracture fill.

--Bill

[CosmicRocker]

Yes, Chocolate Hills was a fracture fill, but it was a fill composed largely of closely packed, hematite concretions of various sizes, held together by an intergranular cement of hematite. All of these rocks do not look like Chocolate Hills, but some parts of them do.

That first pano I posted was just left of where the rover is doing IDD work. The following picture is just to the right.

[centsworth_II]

I don't know about Opportunity previously seeing hollow hematite concretions, but here is a figure showing some solid-looking fragments along with experimentally grown "blueberries".

Edit: I just noticed that the Meridiani blueberries are measured in mm while the lab-grown berries are in um. So the lab berries are in reality about one thousandth the size of the real blueberries.


http://www.sciencedirect.com/science/artic...032063312000736

[Bill Harris]

CR: very good. On your IR ratio images, do you know what shows as the cyan color? The magenta is shadowed areas.

Centsworth: Not a problem. Every Blueberry started out as a um-sized seed. It is telling that the lab-grown variety fracture te same way as the Meridiani BBs.

--Bill

[centsworth_II]

I found a paper describing the methods that produced the synthetic sphereules in my last post. Also more comparisons with fractured Meridiani concretions.

"Comparison of morphology of whole and broken spherules.... Fracture surface textures in both sets of spherules are consistent with a spherulitic (radial) growth."

http://ia600607.us.archive.org/30/items/na...20080012477.pdf


In my ignorance, I find it hard to imagine the radial-structured spherules described above becoming hollow with an outer shell. But I found another paper, quoted below, which describes a possible rind formation process for hematite concretions. I don't know if it's an either/or situation or if both processes can be at work.

"....Field observations and numerical simulations indicate that spherical iron oxide concretions can form in a variety of host-rock conditions..... Laboratory tests indicate that chemical gradients between the inside and the outside of these spheres cause diffusion of Fe ions toward the outer perimeter of the amorphous sphere, forming a rind. The rind then grows inwards due to diffusion within the sphere, and may produce 'onion layering'. Continued diffusion, dehydration, or changing temperature are a few of the factors that may further affect the secondary internal structure-forming processes...."
http://archive.li.suu.edu/docs/ms130/AR/chan7.pdf