On the Road Again - volume 8 - Page 15

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Posts: 344

Reply: 281

PostPosted: May 27, 2011 11:54 PM 

I meant Stu's anaglyph. To other matters...

This sure looks like a sinking slab.


Posts: 73

Reply: 282

PostPosted: May 28, 2011 6:53 AM 

Sinking, no, it is an illusion. It is the same washing process. The berries and surface material have been moved away and outside by a fluvial substance. Water, most likely.

John Henry Dough

Posts: xxx

Reply: 283

PostPosted: May 28, 2011 9:06 AM 

Posts: xxx

Reply: 248

PostPosted: May 24, 2011 6:31 PM

And another bottom right,
These seem to be originating from beneath?
,,,,,,as I was saying a few days ago,,,,,hmmmm

John Henry Dough

Posts: xxx

Reply: 284

PostPosted: May 28, 2011 9:53 AM 

second try,,

Posted: May 24, 2011 6:31 PM

And another bottom right,
These seem to be originating from beneath?
Not to be rude,,,but as I was saying,,,
HM-HM,,COUGH,,,What about that ELEPHANT in the room,,,no,,,just kidding,,,four million years old?

John Henry Dough

Posts: xxx

Reply: 285

PostPosted: May 28, 2011 9:56 AM 

sorry double post perhaps a moderator might correct,,,again sorry,,,it showed up after I posted,,,
next time hit REFRESH before complaining,
now it is a triple post about nothing!


Posts: 3465

Reply: 286

PostPosted: May 28, 2011 10:04 AM 

sol 2589 ( May 7, 2011 ) 3D saturated false color of micro-channels:

with location links.

A couple of things to notice:

The bluest ( cleanest? ) berries are next to the reddest ( dustiest? ) micro-channel areas.

There is a micro-drift crossing the end of the micro-channel on the right which implies a wind from the right. The dust fields to the left of the channels supports that wind direction.

To my untrained eye it appears that dust ( light - moved by wind ) and berries ( heavy - moved by gravity ) are falling into the channels - which means their creation is an ongoing process - perhaps thermal expansion / contraction along rock boundaries? perhaps a seepage of a gas ( H2O? ) around the sides of the rocks that has collected under the rocks?

Finally, note that the bluest berries are next to both sides of the micro-channels.


Posts: 344

Reply: 287

PostPosted: May 28, 2011 12:28 PM 

Horton, your 286 is magnificent! There is no doubt in my mind that water once flowed along that micro-channel. When it happened may be open to question.

More micro-channels?

Note the "grooves" in the rocks. Fossil micro-channels?


Posts: 73

Reply: 288

PostPosted: May 28, 2011 12:38 PM 

Od to the elephant man.

Well I be danged. Frost under rocks! Who (pun intended) would have thunk it.

Its build-up and melting, would create micro-pressure centers and along with the extreme thermal swings present us with these features.

This image should help with the explanation.

Everyone back on the bus.


Posts: 5

Reply: 289

PostPosted: May 28, 2011 1:36 PM 

Serpens; Are you going to reply to the recent comments on the desication cracks or just wait here with me for the next bus? Laughing


Posts: 3465

Reply: 290

PostPosted: May 28, 2011 3:48 PM 

Catching up...

Mercury program craters:

with links.

It is now 10:45 LST of sol 2610 and no MI or APXS observations yet planned.

Perhaps the plan is to clear up the flash memory first? There are still a number of L1 pans and calibration target sequences not yet downlinked.

The last sunset is mostly down:

er, Ben why the crack about cracks?

Do you believe the Meridiani cracks are completely understood and are beneath comment? I am really puzzled by the remarks of reply 289.

I figure that if I can work my %*$*ing tail off providing you rock guys with some decent images then you can at least pretend you are actually interested and provide a serious rock guy explanation of the images.

Perhaps you can stop laughing long enough to explain to poor deluded sots such as myself why the darkest berries collect around the brightest dust in the micro-channels?


Posts: xxx

Reply: 291

PostPosted: May 28, 2011 6:26 PM 

Hi Ben. This has been covered so many times before but OK, let’s have a look at 286. Key features are the ubiquitous dessication cracking of the old sediments with a thick lag that has terminated nay aeolian erosion. There is indeed a small ripple at the end of the right hand but to me this implies wind from around 7 o’clock. Looks to be heavier ‘bluish implying basaltic’ dust. False colour is misleading at times but the channel fill appears to be atmospheric dust. The cleaner berries are on the steeper dips to the cracks and shooting wildly from the hip it seems that the ripple has caused a localised low pressure in the lee enabling the atmospheric dust to settle on and cover the berries. That would explain why the berries on the left, flatter side of the crack are covered in reddish dust and is a further indication of the wind coming from the bottom of the image. The lag has trapped some atmospheric dust while the berries on the steeper edges of the cracks are more exposed to direct wind and are clearer. In particular the berries on one side of the crack running left to right and facing the wind. Some berries have undoubtedly fallen into cracks in the past but the crack, being in topographical lows are now full of dust. With no erosion due to lag protection no new berries are being eroded out.
Hortonheardawho, I think you know that your images are appreciated. but also try and understand that at times it is also very frustrating for ‘rock guys’ to put a great deal of effort into providing responses to some of the points raised only to have the explanations ignored and the same tired arguments raised a few weeks later. Calling these cracks channels or micro-channels probably provides some kind of subconscious reinforcement of the concept that they are caused by water. They are dessication cracks.


Posts: xxx

Reply: 292

PostPosted: May 28, 2011 6:32 PM 



Posts: 3465

Reply: 293

PostPosted: May 28, 2011 10:33 PM 

Serpens, thanks for your detailed analysis and (mud)pot-shots from the hips.

Dessication crack == mudcrack == structure formed when wet sediment drys and contracts.

Wet sediment dried. Wet sediment. Wet. We then are fundamentally in agreement. Yay!

To paraphrase a famous joke "we now know, madam, what you are - we're just haggling over the timeline."

The timeline for the drying out is somewhere between a few billion and a few hundreds of years.

If the final drying out and cracking was billions of years ago over a very short time ( a few sols? ) then the standard Meridiani model implies that the cracks were buried 10s of meters deep for a few billion years and then exhumed by the wind "recently" to this critical layer. OK, is possible. Maybe.

But then after grinding down several 10s of meters of NOT cracked overburden - the wind then cleaned out the cracks to several cm - and then the wind filled the cracks with fresh fine wind-blown soil - in a "just so" manner that collected and polished the overburden "lag" ( berries ) on the very edge of the cracks.

I think that is not likely. Nope. Can't afford the price.

I think that a 100,000 year timeline is a better price for the winds fine services in this matter.


Posts: 73

Reply: 294

PostPosted: May 28, 2011 10:41 PM 

Serpens wrote:
“Some berries have undoubtedly fallen into cracks in the past but the crack, being in topographical lows are now full of dust.”

If the topographical low areas were all full of dust, as they should be, we would not be going over this again.


Posts: 344

Reply: 295

PostPosted: May 28, 2011 11:24 PM 

The standard model of Meridiani is that there were cycles of wetting and drying before more extensive drying set in. Even under this scenario, one might expect to find trenches that began as desiccation cracks but were subsequently modified by flowing water, and later filled partially with dust. I think it is clear that some water still flowed even after the berry layer formed, perhaps a long time ago.


Posts: 5

Reply: 296

PostPosted: May 28, 2011 11:45 PM 

Thanks Serpens, I couldn't have said it better.
However, I would like to add a few other comments about what we see at Meridiani.
Other than some of the craters, the elements associated with the Meridiani surface are the result of the latest events during this cold-dry period of Mars History.
The drying up of a wet Meridiani which caused the dessication cracks, was around 3 billion years ago.
These cracks may have penetrated a few meters and the mud then lithified without further deposition.
There is no indication that erosion started immediately and could have begun after an extended hiatus.
This period of erosion has not removed the soft,original surface to a depth below the cracks .
Therefore, it was probably very short and ceased with the accumulation of a sand ripple covering added to the armoring effect of spherules released from the preceeding erosion.
This was followed by another long period of relative inactivity leading up to the present.
Processes that appear recent could be several thousand years old but those minor ones may be weeks to a few years old and can best be simply explained by wind and gravity.

Suggested timeframe:

MM Years Activity
30 Playa dried up and cracks formed.

1500 Period of inactivity.

50 Erosion of Meridiani beds etc.

1400 Period of inactivity

20 Current activity


Posts: 5

Reply: 297

PostPosted: May 29, 2011 12:03 AM 

Barsoomer; I have a couple of comments about your 295.
Berries were deposited as lag from preceding erosion of Meridiani beds (after the playa dried up)
There is no current evidence that erosion of the soft Meridiani beds and formation of sand ripples was anything other than wind.
Surface water moves down-slope in tributary systems (except for flood sheet-flows) of which we haven't seen either.


Posts: 5

Reply: 298

PostPosted: May 29, 2011 12:09 AM 

Barsoomer; Forgot to comment on your 287.
Your micro-channels are parallel to the bedding planes and most likely caused by differential erosion of softer layers. Smile


Posts: 344

Reply: 299

PostPosted: May 29, 2011 12:09 AM 

> Surface water moves ... in tributary systems....

Not if there is a pre-existing network of desiccation cracks to channel the water flow. A natural drainage system.


Posts: 5

Reply: 300

PostPosted: May 29, 2011 12:31 AM 

Hort; Forgot to thank you for the Skylab crater images.
Looks like one may have penetrated to that "dark rock" found at SM.

Doesn't appear to be much shallower so I wonder if we are still going down section ?

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