On the Road Again - volume 5 - Page 2

Previous 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 ... 29 Next
Author Message
LWS


Posts: 3062

Reply: 21



PostPosted: February 8, 2010 1:44 PM 

Ben; You said "Millions of years of weathering and erosion has provided what must be billions of tons of dust from the soft material and yet there is no evidence of it on the current surface."

That is one of the things that don't compute with me. Of course you may be right, It might have been blown away by aeons of wind.

But the evidence from Hort's latest images don't appear to support it. That blue, very fine, deposit "exudate" around rocks has'nt moved for sometime if one accepts NASA/JPL's aging of the crater and the fact that droppings from the rock crevice overlays it in the image we were discussing yesterday.

Despite the desert pavement effect which is very poorly understood even re. earth's geology, your billions of tons of dust should have covered the berry lag. Also a proper study of the berries will show that they are not as hard as we have been led to believe with cracked ones, ones with pieces somehow removed by oppy movements, pale ones, ones grounded into dust, etc should have ensured that they themselves should have degraded over the billions of years they are presumed to have existed. They should not be there in such numbers if they were formed several billion years ago and have not been replenished since then.

Winston

Barsoomer


Posts: 344

Reply: 22



PostPosted: February 8, 2010 4:59 PM 

Some new pancams. Note the smaller irregular piles that look a little like "horse droppings" and seem to be studded with large numbers of fresh-looking blueberries.

serpens


Posts: 169

Reply: 23



PostPosted: February 8, 2010 5:57 PM 

Bill and Ben. Outstanding! In combination, the best explanation of Meridiani weathering I have seen posted anywhere. I think that the key to understanding the Meridiani landscape is just how fine the particles are. The kinetic energy is minimal despite the high velocity of Martian winds because of the negligible mass. There is none of the stinging energy we might experience from saltating sand on a beach in a late afternoon sea breeze.

The debris in Hortonheardawho’s look into the shadows (those 3d images are marvellous) could have been (thermally) flaked from the disrupted layer on the edge of the upper slope of the right hand rock. I don’t think that the stalks are intrinsic to the berries else most of the berries in the lag would have stalk remnants. I like Bens harder strata idea. But that is not to say that some will not have a hematite based appendage. One of the first Rat images at Eagle seemed to show such.

LWS. I think Squires estimated about 2 meters erosion at Meridiani this deflation cycle. Some dust is in the dunes and ripples. Billions of tons have gone into buried craters and more yet has probably been trapped in the polar layering. Some berries have definitely deteriorated as you say, primarily through thermal effects. But if the eolian erosion struggles with the salt cemented rock it is understandable that it has little if any effect on a hematite cemented berry. I don’t think there is any mystery surrounding this.

Ben


Posts: 2270

Reply: 24



PostPosted: February 8, 2010 6:00 PM 

Winston; Thats my point, the billions of yds of fine, dust should have covered everything but it is gone WHERE??

I think massive dust storms that could transport the fine dust but didn't have the capacity to move the heavier fe dust, transported it away to areas where we see thick dust accumulations.

You have seen giant dust clouds from space that carry dust east out of China and west out of the Sahara!!

Kye Goodwin


Posts: 1166

Reply: 25



PostPosted: February 8, 2010 7:07 PM 

I've been contemplating this article again that places the last significant change to the big ripples between 100 and 300 thousand years ago:

http://www.lpi.usra.edu/meetings/lpsc2010/pdf/2373.pdf

The Beagle Crater impact post-dates the last big ripple movements because it has rays crosscutting the big ripples and no North-South oriented ripples have formed on the ejecta blanket. However, Beagle shows plenty of erosion of the ejecta at least in places:

I think that at least 10 cm of material must have been eroded in the available 300 thousand years to create that smooth surface from a pile of breccia. Maybe half a meter of "planing off" would be necessary. This seems too fast, but we've never had any reliable evidence to even "ballpark" erosion rates. This seems even faster when we consider that the erosion took place in a time when the big ripples did not move for lack of sufficient wind speeds. Presumably (following that paper again) even without winds sufficient to mobilize the granule-armoured ripples there is enough sand saltating to plane rocks down to match the surfaces of the big ripples. Funny thing tough, there are smaller cross-ripples on Beagle's ejecta and sometimes rocks seem to be planed down to match the smaller, more recent and presumably unarmoured cross ripples as well:

Aren't the particles that make up the smaller cross-ripples supposed to be the very same particles that are saltating around the plains scouring down the bright rock? How can particles both form the ripples that are protecting the rocks and participate in the movement of the ripples that are protecting the rocks? I think that the cross-ripples are just about as active as the big ripples, whatever that activity is, and so far Mars science has made very little progress in explaining either.

Bill Harris


Posts: 72

Reply: 26



PostPosted: February 8, 2010 7:33 PM 

Ben said:

"Because these thin planar layers vary in hardness is what allows the formation of the berry stems, parallel along the hard layers . Sort of like wind-tails."

Good points, Ben.

Look at one of today's Pancams. Although this is the initial view of the other side of the Chocolate Hills boulder, I think I see a great difference in the degree of weathering from one side to another. Anisotropic weathering??

This is a good stop.

--Bill

LWS


Posts: 3062

Reply: 27



PostPosted: February 8, 2010 8:02 PM 

Barsoomer

I've done some RGB composites of the releases today that illustrates fairly clearly your point about fresh looking berries in the irregular piles.

One of the earlier images also seems to show a depression from which a rock was probably dislodged at impact. The depression looks extremely fresh. It is not an oppy created trench. Talking about trenches, the Hazcams seem to be suggesting that Oppy is making a few today or within the last few days and is overturning quite a few small rocks. Several of them seem to be shallow.

I suspect that further examination of the treasure trove of images from conception will establish that the crater is indeed very young and that eolian erosion has so far had little effect on the exposure of berries on the rocks or the sculpting of the ejecta around the crater.

Here are some of the images:

The youthful berries in irregular piles

The area from which one of the crater annnulus rocks has been dislodged and a candidate rock that might have been dislodged


Crop of area from which rock was dislodged. There are no oppy tracks in that area as viewed from the Navcam and Hazcam images.


Anaglyph of area from which rock was dislodged.

Winston


LWS


Posts: 3062

Reply: 28



PostPosted: February 8, 2010 8:40 PM 

Bill; re. your #26 "this is a good stop". I totally agree. I also hope it will be a long stop.

Winston

LWS


Posts: 3062

Reply: 29



PostPosted: February 8, 2010 11:26 PM 

Bill, Barsoomer and others

Looks like my preliminary identification of a depression in the images above as a place where a rock was dislodged by the impact and ended up elsewhere is wrong. One of today's NavCam images shows the depression much better than the earlier images and it now looks like a small overturned dislodged pavement rock showing the undersurface of the rock and the hole left by its displacement.

Here is an anaglyph of the area with the depression and dislodged rock in the upper right of the image.

The depression might be even more interesting than I expected since it seems to show a number of "outgrowths" that were presumably underneath the rock before it was disturbed. There are no Oppy tracks near the area so the nature of the disturbance is not obvious.

Winston

Ben


Posts: 2270

Reply: 30



PostPosted: February 9, 2010 12:40 AM 

Winston; My interpretation of the dislodged rock is that it is a piece of the rock behind it that has been detached by weathering and fallen to its present location. Subsequent weathering has resulted in further exposure of spherules.

Your image also indicates the rubble between the two larger rocks may have come from the weathering break-up of a smaller rock located at the top of the void between
the two.
Some remnants still appear to be lodged and hanging in the upper part of the void.

I tend to agree that aeolian erosion does not appear to have had a great impact on the ejecta and I think weathering has been the major factor.

We don't know when the current wind regime developed but I agree this crater is younger than that.

Observing the multitude of land forms I have seen on Mars leads me to believe surface forming processes are very slow and this crater could be many thousands of years old.

Due to the lack of vegetation and water cover plus the abundance of exposed outcrops we have a better picture
of the surface of Mars than we do of earth.

During the time we have been viewing Mars the Earth has sufferedcatastrophic ,floods, landslides,earthquakes tsunamis, volcanic eruptions, melting glaciers, meteor impacts, and much more.

Compare this to Mars where we have seen a few landslides , melting ice, and meteor impacts and it shows the relative dynamics of the two planets

LWS


Posts: 3062

Reply: 31



PostPosted: February 9, 2010 7:58 AM 

Hi Ben

I think you are right about the rock. Thanks

Winston

LWS


Posts: 3062

Reply: 32



PostPosted: February 9, 2010 8:54 AM 

Ben; I think you are right about the rock. below is the latest image of the surface of the target rock. The berry areas are very interesting (to me)


Original size here

Winston

hortonheardawho


Posts: 3465

Reply: 33



PostPosted: February 9, 2010 9:26 AM 

3D saturated false color detail of "porcupine rock":

OK, if the wind is responsible for carving the delicate network of berries on stems on theis rock then where is the wind borne "polishing dust" carried by the same wind???

Oh yeah, it conveniently blew away after eroding the rock.

Riiiight.

T_D


Posts: 7

Reply: 34



PostPosted: February 9, 2010 10:04 AM 

Hey, please remind me what you guys think the "berries and the stems" are?

LWS


Posts: 3062

Reply: 35



PostPosted: February 9, 2010 10:37 AM 

T_D;

As I understand it, the mainstream view is that the berries are concretions that were all formed in a shallow lake under reducing conditions a few billion years ago. The stems are merely wind tails caused by the removal of the relatively soft sand encasing the berries after the berries became indurated in layers of mud forming the softish rock we see at craters edges and on the pavement rocks outside and between the craters.

My own view is that, while there may be some berries and tails that fit this description, there are some that don't. There are too many observations that suggest that the accepted model of the berries may not be correct. Judging by some of the images so far at this concepcion stop, there are likely to be many more questions asked in the weeks ahead.

Winston

James


Posts: 3

Reply: 36



PostPosted: February 9, 2010 11:56 AM 

Ben your reply 13,
With all the water coming and going, no mention is made of the role of water-ice in shaping Meridiani. Surely at several times these waters froze on-site, and their effects then became glacial. Even catastrophic water-withdrawal would most likely have been tiggered by glacial processes, if Earthly comparisons hold true. Effects of ice may also be apparent in the larger rock cracking - a possible result of freezing ground-water.
Nadine Barlow of the Northern Arizona University, writes: "Thus, current evidence suggests the formation and movement of ice has been the dominant geologic process for most of martian history..." (Sky&Telescope, 2006, p.56).
The cyclic, changing tilt of Mars' axis means that these episodes of freeze/thaw may be far from over. Rather than a single period billions of years ago, the planet may undergo local or widespread interglacial periods over a time span of millions of years
Just a few thoughts from the frozen north.

Ben


Posts: 2270

Reply: 37



PostPosted: February 9, 2010 12:04 PM 

Hort; Good point. I think weathering is also a factor in the break down of these rocks.
A dust storm every century that blew thru and removed less than a mm off the surface could gently "erode" a substantial amount. Smile

Barsoomer


Posts: 344

Reply: 38



PostPosted: February 9, 2010 12:53 PM 

Horton's 3D version of Porcupine Rock is very interesting. The delicate nature of the stems compared to the berries would seem to argue against them being some kind of erosional artifact, whether wind tails or due to thermal weathering. Moreover, the berries and stems appear to be attached to some kind of lattice superstructure.

If it is erosion, why should Porcupine Rock be almost completely denuded while the other rocks retain most of their "filling"?

By the way, is Porcupine Rock a piece of the main rock above it that has fallen off? (A "chip off the old block" if you will excuse the expression Wink )

LWS


Posts: 3062

Reply: 39



PostPosted: February 9, 2010 12:58 PM 

Ben; What is stopping the net deposition of dust carried on these storms and other more normal winds at meridiani planum? Why should the winds be always taking up dust from this area and depositing it elsewhere?

There have been explanations for what has been claimed to be dust being deposited in rat holes that were imaged sometime after the ratting process. There have been numerous old tracks seen to have become infilled a few months after there were formed. There has been dust deposited on the lander itself with some on the solar panels removed by the mysterious cleaning events. In other words, there is ample evidence on the ground that some dust is deposited on meridiani. There does not appear to be any evidence of huge amounts being wafted away on the winds to other areas of mars.

I think the wind rationale for sculpting of berry stalks still needs some evidence. It has not been served well by NASA which imaged some wind tails firmly cemented on some rocks and set it up to appear as if they were typical stems. As far as I know there have been no MI's published which showed in situ stems on berries (i.e. the numerous berries seen in Pancam images with organic looking stems - not wind tails- have never been imaged)

Anyhow, there is significant richness of stemmed berries on chocolate hills and concepcion in general. There should be no dearth of berry and stem targets. Hope they will take some. In my view, this is a more responsible task than rushing to Endevour crater to repeat the same old geo experiments.

Winston

Kye Goodwin


Posts: 1166

Reply: 40



PostPosted: February 9, 2010 2:25 PM 

T_D, re your 34, Thanks for asking. I don't think you will find much agreement or much certainty in a survey of this blog's contributors.

I have to offer one change to LWS's account of the mainstream theory of the origin of the berries: I think that they are hypothesized to have formed in a deep, locally uniform, water-saturated aquifer rather than a shallow lake. The absence of clustering in the berry distributions, especially the lack of evidence for local concentrations of spherules at a particular depth, makes the shallow lake idea problematic. The shallow lake idea comes into the mainstream theory earlier, at a time when the sediments were being deposited.

I'm inclined to think that the berry stems are created by erosion of the bright layered rock. I don't think that we know how erosion works at Meridiani but scour by saltating sand doesn't fit with what we see in my opinion. When we see stems longer than a berry diameter pointing in different directions in close proximity, saltation scour just doesn't seem delicate enough or precise enough to do the job. Here's another example from Fram Crater:

On the other hand, the frequent rough local coordination of the stem directions suggests that air movements are probably involved in the erosion process in some way.

There are plenty of possibilities besides sand scour for contributions to erosion at Meridiani. Scour by suspended particles is possible, as serpens seems to be suggesting in reply 23. There is wicked daily heating and cooling at Meridiani, up to a range of 100 degrees C. The "rock" would probably fall apart in a gentle rain being roughly half soluble salts. There is no rain, but there are traces of water as frost renewed daily. The rock is presently hydrated with a water content of about 5%. I think that repeated microscopic dissolution and precipitation of the soluble minerals in the surface of the rock could be part of the process of erosion.

How any of these influences might preferentially preserve the berry stems I can barely guess, but I'll speculate that whatever the protective mechanism it somehow increases for a time as the berry stem lengthens.

serpens, reply 23,

Previous 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 ... 29 Next


Join the conversation:















Very Happy Smile Sad Surprised
Shocked Confused Cool Laughing
Mad Razz Embarassed Crying or Very Sad
Evil or Very Mad Twisted Evil Rolling Eyes Wink
Powered by MTSmileys