Rocks And Radent Light, beautiful stratified rocks at Erebus Options

[CosmicRocker]

There's little doubt in my mind that that is the image Steve Squyres was talking about. I was just about to post it in the Erebus topic, but thought I'd check here to see if anyone had beaten me to it.

When that image first showed up the other day my jaw dropped. It's spectacular.

[Bill Harris]

I've been following the series of low-incidence lighting images for a couple of weeks. This technique can bring out fine textural detail on the surface.

--Bill

[Anoolios]

There is festoon bedding all over the place in that image, and I agree that its absolutely spectacular. It looks remarkably like patterns that can be obtained in a "wet sandbox" setup with a pump for water and wet sand.

I cannot imagine an explaination for these features other than flowing water.

[Bill Harris]

For general information, here is an overview of sedimantary structures/bedding:

http://www.uwgb.edu/dutchs/PETROLGY/Leaverite-SedFeat.HTM

--Bill

[CosmicRocker]

I think that really was the nicest collection of sedimentary structure images I have come across on the web. Thanks for that. Those who might want to learn a bit about geology might want to review that page.

I thought it was funny that this section of his web site was devoted to leaverites

[CosmicRocker]

Then, there is this confirmation of the sighting.

http://marsrovers.jpl.nasa.gov/gallery/pre.../20060106a.html

[Bill Harris]

I got a chuckle out of 'leaverites' once I remembered what they were; it's been decades since I've heard that term.

Hopefully we'll get some use out of those fine sed structure reference images here and AT THE MOGOLLON RIM (hint,hint) _and_ over at the Inner Basin (which is really starting to get interesting).

Another thing I noticed in that confirmation mosaic at the JPL site: just below center there appears to be a small post-depositional slump in the sediments. Or so I think; it looks a _lot_ like something I've seen locally.

A crop and close-up from the JPL image is attached.

--Bill

[sranderson]

I am somewhat concerned that what is being called festoon crossbedding is merely differential erosion of flat layers that have no festoon "smiles" intrinsically.

The image evidence presented so far at Erebus is of rocks with an erosional exposed surface that is nearly coincident with the plane of the layers themselves. This makes it hard to tell whether or not the layers have real peaks and valleys or if they are more eroded in a pattern that makes it look like it has peaks and valleys.

I have seen numerous RAT grinds with the rotating axis perpendicular to the layer plane, but few if any that are parallel to the layers (to grind against the edge of the layers). If we could find a festoon-candidate outcrop with a good straight up-and-down side exposed, then we could put the RAT directly against the edges of the layers and grind off any erosional effects.

Then we could definitively say whether or not there are festoons -- unless the layers are so homogeneous that the grinding operation erases the character of the layers themselves.

Scott

[alan]

Closer look next week

The real news, though, is that it looks like we're finally about ready to move the rover again. I can't give you a definite date, but I'd say that sometime next week is very likely. Our first move, of course, is going to be to get into position to get some nice MI mosaics on the festoons. The rock we're going after first is one called Overgaard.

http://athena1.cornell.edu/news/mubss/

[Bill Harris]

I am somewhat concerned that what is being called....

Me too. Looking _at_ an eroded bedding surface is somewhat iffy. What I was hoping was that Oppy would look at some of the vertical joint planes exposed at this current outcrop. Or/and/also at the Mogollon Rim area 80 meters away.

<chant>
Move Move Move
</chant>

--Bill

[Airbag]

I'm glad it is not just me then - I've wondered that right from the first such sightings in Eagle Crater. I've been tempted to make a model using layers of cardboard to see if I could simulate features that look like festooning, but have not had the time so far...

Airbag

[sranderson]

I'm glad it is not just me then - I've wondered that right from the first such sightings in Eagle Crater.  I've been tempted to make a model using layers of cardboard to see if I could simulate features that look like festooning, but have not had the time so far...

Airbag

Here are two photos of a layered rock I have. The first one is looking directly at a surface that is fairly parallel to the layers. I can make myself believe I see ripples here.

The second one is from the side -- and it shows that all the layers are flat and parallel to each other with no ripples.

[Reckless]

I can see that laminations can weather to look like cross bedding etc. but I find it hard to believe the the team at JPL would not take into account the strike and dip of the bedding plains before anouncing festoon bedding, but maybe I expect too much of the guys working by remote control in a very difficult invironment.

Reckless

[elakdawalla]

A key question is whether you can see one set of layers terminating against another layer. You will not see that kind of geometry no matter how you slice a parallel-layered rock. Look at those pictures and see if you can see "T" shapes where one layer dead ends into another, and you know that something came along and cut one set of layers before depositing another, which happens all the time in these shallow-water ripple deposition environments.

--Emily

[Reckless]

I Think I see "T"s

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