On the Road Again - Again

The On the road again topic is getting kind'a big - so I will start a volume 2...

Sol 1870 ( Apr 28, 2009 ) R12 4x1 pan after 12 meter move from sol 1868 postion:

Going back a few sols now I think we saw a clear confirmation of the theory that the ripple banding represents the exposure of layers that extend through interior of the ripples:

Here's a navcam context image. The same area is below center but this image doesn't show the banding very clearly:

We've seen banding only on the east slopes of the ripples until now. These images show banding on a north-facing slope that has been created by an impact and two dark bands appear to be continuous, wrapping around from the east slope to show on the north-facing crater wall. If the banding were created by some sort of surficial process acting on the east (probably windward) slopes then it would just be too much of a coincidence that the same process would build up matching bands on the north slope.

I'm getting pretty convinced. This also means that some of the "cross-ripples" are actually "cross notches" because they show the banding on all their surfaces and should not if they are composed of material that has been overlaid on the big ripples.

er, this is part of a false-color panorama posted a week ago:

sol 1873 ( May 1, 2009 ) looking SE:

ready to finally turn eastward?

As one of the most visited threads I will use this to announce the live streaming from the open house at JPL from 19:00 UTC.

http://www.ustream.tv/channel/nasajpl

--Mizar

Sol 1870 pan and reply 3,etc.,
Interesting how the extensive cracking and shattering of bedrock(?) did not displace the resulting fragments. They all still largely fit together like pieces of a puzzle. This suggests that a great uniform overlying weight contained the shattering energy to a horizontal plain. Or that a more passive, incremental process is involved, such as erosion, dessication and freeze/thaw cycles.
James

James; I think the passive, incremental process is the more likely.

Yes Ben, that seems likely. However, to speculate a little further, it's possible this terrain was modified by glacial action. It's not too much of a stretch to imagine an ice sheet riding over the apparently thin, fragile 'bedrock' flattening and cracking it. Arguably such glaciers may still be present on other areas of Mars.
James

To me this looks like dessication cracking of sedimentary rock with some thermal influence. Dessication causes shrinkage creating cracks and the segments contract and expand under the extreme temperature range on Mars. Fragments and dust fall into the cracks so that the segment can't expand and close the gaps, causing the 'flagstone. effect. A similar process to that which caused the patterned ground at the Phoenix site.

Not sure why you say the bedrock is thin. Victoria crater shows it to be many meters thick and satellite imagery suggests hundreds of meters. Perhaps you are referring to the ejecta that has moved on occasion when the Rover ran over it?

Sol 1873 ( May 1, 2009 ) R0 10x1 ( 360 panorama ):

Haven't done one of these in a while...

Because none of the cameras on the mast rotates through the camera nodal point, seamless panoramas can not be created. In particular, close features will have a noticable displacements as the camera rotates.

Notice that the rover parts do not match in the overlaps.

It would have been so easy to design a camera mount to accomplish this... I see that the same mistake was made with MSL...

Bummer.

sol 1874 ( May 2, 2009 ) bedrock outcrop L257 ( false color ) 3x2 panorama:

There is a second 6x1 outcrop panorama - but not all of the data has been downloaded.

If anyone is interested I can post a "white balanced" version.

Re 8:
Granted, the total thickness of this exposure may be considerable. However, it's uncertain how deep these cracks go - at least away from the immediate vicinity of craters et al. It seems improbable that the effects of dessication would reach very far below ground level. The cracking we see out on the open plains may be confined to a rather shallow, fragile surface layer(s).
James

Here's the first big crater in a ripple that we saw:

Way back then I didn't accept that this was an impact crater but that was before HiRise which has revealed a great many more (hundreds?) of circular depressions in ripples in the Victoria area alone. I didn't notice it at the time, but like the crater imaged on sol 1854 (my reply 1, Horton's reply 2), this crater shows faint banding in the far crater wall that matches that on the ripple's east face.

The latest Planetary Society update includes an interpretation of the banding in the Sol 1854 crater. I'm uncharacteristically mainstream:

[link]

I have added to the sol 1873 380 degree panorama a number of image note links to L257 panoramas.

Here's a quote from the latest Planetary Society Update:

"When these big ripples formed, they required lots and lots of blowing fine sand to drive the coarser particles in creep mode," explained Robert Sullivan of Cornell. "The coarser particles, such as the blueberries, probably weren't blown directly by the wind in saltation, because they were probably too big and too heavy for that. But smaller grains that are much more easily driven by the winds could have bashed them along. We don't know if fine basaltic sand was the main driving material for these large ripples, but it's a handy candidate to point to now, because small quantities are present currently. This type of sand may have been much more abundant at the time the larger ripples were on the move. The hematite concretions that are all around this area are very hard and difficult for the wind to move, so once you form these ripples, it's kind of hard to keep them moving unless you maintain a large supply of basaltic sand handy, ready to be driven by the wind."

The rover team interpretation of the ripples hasn't changed despite the increasing evidence that they are very old. Their view: The ripples are no longer active, but when they were active they changed just the way that granule ripples change on Earth. Its interesting that the reason cited above for the current inactivity is not that the climate has changed but rather that the sand supply has somehow been exhausted, and without saltating sand the granule-sized particles cannot be pushed along in creep or reptation mode. How can there be a shortage of sand when the great majority of the volume of the ripples is made up of particles smaller than granules? Though MI evidence of ripple particle size is not extensive, it seems from the available evidence of the physical properties of the ripple soil that most of the volume is made up of particles finer than sand - particles that, should they ever move in the wind, would be suspended and not contribute to saltation or reptation of the granules. On Earth granule ripples are composed of a mixture of granules and sand - the very sand that pushed the granules along and became incorporated into the ripples during the process that moved the granules. Why then are the Meridiani ripples made up of a mixture of granules and dust?

Maybe Robert Sullivan is not saying that the ripples are short of sand-sized particles but only that the sand is mostly protected by a granule armor that keeps it from ever being mobilized. But, if that were the case, why don't we see something like "blow-outs" where the impact craters have disturbed the protective granule lag and opened the ripples to erosion? I think that the Meridiani ripples have very little in common with Earth's granule ripples, which they superficially resemble.

sol 1877 ( May 5, 2009 ) science stop:

Oppy has moved a few meters to the edge of the outcrop in reply 10.

Looks like a science weekend.

sol 1872 ( Apr 30, 2009 ) hazcam montage:

Since Oppy may be here a while I thought I would try something different. This is a close 360 companion to the 360 degree panorama of reply 9.

I wonder why stop here?

My hope is that the very distinct, um, fine red dust - yeah, that's it - fine red dust - between several slabs of bedrock is the science target. I don't think the crack "mud" has been examined in detail yet...

More likely just another data point in the bedrock composition graph on the way to Endeavour.

sol 1877 ( May 5, 2009 ) closeup of science target:?

A full filter exam only???

This is an "impossible" combination of 2 L234567 and R1234 images into a panorama. This was doable because the area is "mostly" flat.

There is a curious and subtle "bluish" rind on the rock.

sol 1879 MI montage of cobbles:

There were 24 images in the MI sequence before the APXS exam, so there should be more - someday.

Interesting thing about those cobbles... the contrast between the obviously eroded rounded specimens and the more angular, relatively recently fractured fragments. The process of change continues, however slowly.
Is that 'bluish rind' caused by blueberries squeezing out from the apparent rock layers?
James

sol 1879 ( May 7, 2009 ) colorized EDF ( Extended Depth of Field ) MI created from 4 affine registered MIs:

The color was derived from this pancam image.

See image comments for some processing comments.