Matijevic Hill first survey, Sol 3057 - 3152 Options

[dvandorn]

I'm not yet convinced that the blueberries are embedded into the rocks of this outcrop. They could just be scattered on top of these rocks, either as a lag deposit from previously overlying layers of concretion-bearing rocks that have since been eroded away, or lifted there by aeons of impacts that have redistributed such melt-resistant fragments liberally throughout the area.

A good MI campaign ought to shed more light on whether or not these outcrops have embedded concretions, or just have concretions draped over them.

-the other Doug

[Floyd]

I'm a microbiologist--so what do I know--but to my eye, these don't look like blueberries-not round, not shiny, and the ones that have fallen out look more rounded-cubic or random bits than spherical. The sick green-grey (even with Stu playing with colours) doesn't look like the blueberries we have seen before. I'll go with VikingMars and guess dry eroding clay.

Here is a link to a nice image of eroding clay. With no rain and millions of years of wind erosion, I think we could get what we see in front of Opportunity.

[Tesheiner]

Here is today's mosaic in L2 filter.

[nprev]

Floyd, I agree with you re the berries. First thing I thought was "those sure are tiny & funny-looking blueberries..."

Becoming cautiously excited.

[PaulM]

Interesting how well those tilted back layers match the red lines in this diagram from a paper by James Wray (interview linked in post 101) et al.

...phyllosilicate-bearing layers (red lines) exposed in Endeavour rim."

From the text:
...layers within the western rim dip away from the crater interior, as expected if the beds predate Endeavour crater and were back-tilted by the impact."
...The Alpha Particle X-Ray Spectrometer could determine major and minor element chemistry, and the Pancam and Microscopic Imager could document grain sizes, shapes, and possible sedimentary textures (e.g., cross-bedding or laminations too fine to resolve from orbit)..."

This paper suggest that the strata that Oppy is currently investigating predates the formation of Endeavour Crater.

I understand that the majority of the group of craters of which Endeavour is one are thought to date from the late bombardment. I think that Endeavour is a good candidate for a crater formed during the late bombardment because it is so eroded.

It is therefore possible that the strata that Oppy is currently investigating predates the late bombardment. If the clays formed during the deposition of this strata then this clay might also predate the late bombardment and might therefore be more than 4 billion years old. If this was true then this clay might predate the Gale crater clays by several hundreds of millions of years.

However, I understand that the prefered theory for the origin of these clays is that they formed due to weathering in crevaces after the formation of Endeavour crater and so might be contemporaneous with those of Gale crater.

[Don1]

I'm no geologist, but I'm going with a greenstone/green schist/chlorite schist with embedded garnets. The rock looks finely layered, so maybe it is a schist. The little pebbles could be embedded garnets which have eroded out of the rock. Chlorite is a group of phyllosilicate minerals, some of which contain iron and magnesium. Chlorite could be the source of the Fe/Mg rich phyllosilicates seen in the spectra.

Green schist is a metamorphic rock formed from basalt. Some of the oldest rocks on earth are green schist.

Image here

[ngunn]

Well I'm even less of a geologist than you obviously are but I really like your suggestion. I'd love those things to be garnets - my favourite mineral. However, don't you need huge tectonic movements to produce highly metamorphosed rocks like schist? In favour of the idea: at least schists are hard enough to produce upstanding outcrops, whereas I'd be surprised if eroding clay beds would be.

I expect these rocks to be the progenitors of the clays but not the clays themselves. My reason? A little farther on there is a crater formed into Cape York which CRISM shows to be surrounded by clays (weathered ejecta?) although the interior of the crater appears relatively clay-free.

The Gale crater clays likely have a completely different story to tell. It's an old, old world.

[Stu]

A couple more sections added...

[Zeke4ther]

I think you have the colour balance better here Stu. You can really tell that we have something special here.

[PDP8E]

Here is one of those sub mosaic images of the current formation that OPPY is looking at.
The filters used for this shot are the far infrared, far UV, and plain old green... so my hat is off to Stu for pushing them into something that looks more 'real'. I went with crispness

[Bill Harris]

This paper suggest that the strata that Oppy is currently investigating predates the formation of Endeavour Crater.

{SNIP}

Bingo, Paul.

I've been looking at this outcrop line with interest since leaving the Whim Creek stop. Although we've seen distant views of this zone, my initial impression is that brown-toned layered rocks represent a weathered clastic unit unconformably overlying a basaltic impactite that is pre-Endeavour. This unit was, literally, the paleo-surface of a wetter, warmer Mars. We've had glimpses of it in passing below the basal Burns Formation during the last leg of the pre-Cape York part of the traverse.

Here is a enhanced HiRISE image of this part of Cape York. The area of interest is the light-toned (ie, reddish in the RED-filtered HiRISE image) areas near the center of the image (ESP_024015_1775_RED).

http://i142.photobucket.com/albums/r91/wil...maker_bench.jpg

You can match up the route of the traverse using Tesheiner's Route Maps.

Closer PanCams and MIs are going to be interesting.

--Bill

[CosmicRocker]

Bill: I think the clastic unit underlying the basal Burns formation but overlying the Endeavour ejecta is being unofficially called the Deadwood formation after the target of that name from around sol 2770 or so (near Homestake). It's not exactly what you are talking about, but close. It was discussed in a recent paper that I can't put my fingers on at the moment, but I will try to find it for you.

ngunn: I think I would have to agree with you regarding garnet schist. As much as I'd love to see it, I don't think Mars has been tectonically active enough to have generated much in the way of schist or gneiss.

Right now I find myself agreeing with centsworthII. They look like blueberries to me, though they are on the ragged edge of resolution in these images. Whatever they are, they are embedded in the rock and not just loose granules lying on top. They are resistant to erosion and they are at the head of some mini-yardangs on the surface of the rock, as we have frequently seen with the blueberries out on Meridiani Planum.

We should be able to determine if they are hematite concretions in short order. There is an image set coming from sol 3063 with a full set of right filters...
pancam_Milnet_L234567Rall...
If Milnet is an image of a part of this outcrop, as I suspect it will be, a quick IR ratio image should identify any hematite that may be present.

[walfy]

i tried to stitch a group of these frames together for a 3D, made a headache for the eyes instead! Spectacular outcrop here. The overhanging rock near the top has a nice white vein in it. The rock near the bottom also has such a vein. Perhaps it rolled off eons ago.



And a thanks for the great color panos of these rocks already posted! Really nice work.

[walfy]

Thick blueberry froth!

[serpens]

I expect these rocks to be the progenitors of the clays but not the clays themselves. My reason? A little farther on there is a crater formed into Cape York which CRISM shows to be surrounded by clays (weathered ejecta?) although the interior of the crater appears relatively clay-free.

The

I expect you are right about the rocks being a precursor although that impact possibly excavated a clay bearing layer which is exposed as ejecta while the crater bowl has infilled? No matter how I torture the L257 the clasts seem to have the same response as the matrix so it seems unlikely they are the same hematite concretions as found in the sulphate sandstone. It would be outstanding if this turns out to be pre Endeavour impact materiel and MIs should be real interesting. This ageing rover has stolen the limelight yet again.