Hum,
i was only using the `broken gabbros or breccias` phrase as a catch all statement to indicate that it could be some sort of igneous or broken up sedimentary (including volcanic ash) rock.
Either way it is clearly different to the deeper banded layers.
It may even possibly be the eroded impact impact ejecta blanket.

__________________
`Irony` actually does mean `metal like`...

Thank you! The possibilities are endless. Based on the high resolution imagery I suggest it is a massive, albeit fractured sandstone.

Jon

Saw this image of Beacon Hill in Victoria crater on MarkCarey.com/mars:



The roundish boulders remind me of pillow lava, which occurs during underwater eruptions or when lava flows into water:


Columbia River Basalt Stratigraphy in Oregon.
http://or.water.usgs.gov/projs_dir/crbg/flowbottom.html

Note also the similarity of the striations in the boulders in the Beacon Hill image to the striations in this pillow lava:


LAVA AND WATER.
http://www.geology.sdsu.edu/how_volc...ava_water.html


Bob Clark

Opportunity Sol 968
Zoom view of Beacon Hill

Attached Images

OPPsol698B.jpg (92.9 KB, 13 views)

__________________
`Irony` actually does mean `metal like`...

This 3-D image on Unmannedspaceflight.com shows what could be columnar joints, though degraded, in the right center of the image:

Duck Bay, Scouting the rim.

http://www.unmannedspaceflight.com/i...naglyph&st=379

Compare to the columnar joints here:

Figure 1. Columnar joints in the Traveler Rhyolite. Regularly spaced joints like these developed as the ash flow cooled slowly, causing it to contract. These are seen in a longitudinal view showing the length of the columns to be about a meter. On the upper surface, the columns are nearly hexagonal (like a honeycomb) in cross section.

http://www.maine.gov/doc/nrimc/mgs/e...es/may00-1.htm

And this shows columnar joints in association with pillow lava:

Columbia River Gorge

http://c3po.barnesos.net/homepage/lp...mbiaGorge.html

The possibilility of finding columnar joints and pillow lava on Mars was examined in this report:

THE FORMATION OF COLUMNAR JOINTS ON EARTH AND MARS.
M.P. Milazzo, L.P. Keszthelyi, A.S. McEwen, and W. Jaeger, Lunar and Planetary Lab., University of Arizona, Tucson, AZ. ****@pirlmail.lpl.arizona.edu
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/2120.pdf


Bob Clark

The columnar features are specifically the vertical structures visible in this attached image. The similarity to columnar joints is made stronger when viewed with 3-D glasses.


Bob Clark

Attached Images

columnar.JPG (9.4 KB, 9 views)

Here is an image of pillow lava of a more flattened appearance that may
be a closer match to that seen in the Beacon Hill image:


"Pillow basalt (upper half of photo) indicate that some lava flows
advanced into water. The light colored layer is lake sediments. The
presence of lake sediments indicate a reasonable pause between the
eruption that formed hyaloclastite and the emplacement of the pillow
lava. The reddish-layered deposit in front of the volcanologist is
hyaloclastite, a type of pyroclastic rock that from when lava and water
interact."
http://volcano.und.edu/vwdocs/volc_i...ia/monaro.html

This also shows a thin, white sedimentary layer below the pillow lava.
This may be analogous to some of the thin white layers seen in Victoria
crater:


Re: A volcanic dike in Victoria crater?
http://uplink.space.com/showthreaded...&Number=594101

and


Victoria's Stratigraphy.
http://www.unmannedspaceflight.com/i...66&#entry72366

Hyaloclastite is also seen in association with the pillow lava and the
sedimentary layer. Perhaps mini-TES or APXS spectra could be taken to
determine if the rock in these outcrops in Victoria crater match that
of hyaloclastite.


Bob Clark

If it is A sedimentary layer, that implies the rock surrounding it is something ELSE.
Such as igneous for example.


Bob Clark

Take a look at all the highest resolution Cape Verde HIRISE images on this page to get a better idea of this feature:

NASA'S Mars Rover and Orbiter Team Examines Victoria Crater.
06-Oct-2006
http://marsrovers.nasa.gov/gallery/p...20061006a.html

There is a roundish feature there, but looking at all highest resolution images, this roundish "depression" is very subdued, if it is even a depression.
But in the 3-D image from the rover there looks to be a deep hole and this hole looks more linear than round. I think what the 3-D image is showing is the gap between the two dark ridges that lie in the roundish feature in the HIRISE images.
This linear gap would not be caused by an impact.

Post Volcanic Structures.
Fissures

http://www.geol.umd.edu/~jmerck/gals...e/volcano.html


Bob Clark

This shows a simulated view from NASA of Opportunity at the Cabo Frio
promontory which would require the rover to go past the Sputnik
"crater".
Perhaps this suggests an intention of moving the rover in that
direction?

LINK TO IMAGE


Opportunity on 'Cabo Frio' (Simulated).
"This image superimposes an artist's concept of the Mars Exploration
Rover Opportunity atop the 'Cabo Frio' promontory on the rim of
'Victoria Crater' in the Meridiani Planum region of Mars. It is done to
give a sense of scale. The underlying image was taken by Opportunity's
panoramic camera during the rover's 952nd Martian day, or sol (Sept.
28, 2006)."
http://marsrovers.nasa.gov/gallery/p...20061019a.html


Bob Clark

Bob, these images are very cool, but they're starting to get a bit large. Could you please not hotlink to images like that? It makes it very hard for people to read the board.

I edited your last post to simply link to the image instead of loading it. It's not against the rules to hotlink to images from NASA or other sites where bandwidth is not an issue, but it's not a good idea to do so.

__________________
Phil Plait
The Bad Astronomer
http://www.badastronomy.com
badastro@badastronomy.com

Understood.


Bob Clark

Thanks. It was a bit much to swallow -- bandwidthwise. Even with a high-speed connection, I prefer to choose when to use it. Thumbnails are our friends.

I gotta ask how perhaps-predictive you think a scale-model rover effect impressed on a Cabo Frio is, when they did the same thing for Cape Verde?

Don't you suppose that their intentions really are more along the lines of studying the Cape Verde panorama they get after conjuction, and moving around the rim in the direction that appears more profitable?

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That sounds reasonable. Given the outcrops at Capo Verde, both I think would be profitable.


Bob Clark

Sounds (Squyres Update, November 3) like they've decide to proceed clockwise, away from Sputnik Crater for now.

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