Back At Larry's Lookout Options

[aldo12xu]

Yes, I also agree that it's a hardened layer of duricrust that was disturbed in some way by the rover. Duritcrust was previously observed at Opportunity, Pathfinder and Viking landing sites.

http://marsrovers.jpl.nasa.gov/gallery/all...03P2584L7M1.JPG

This paper describes the process involved and you can also read a summary on my site under the "Duricrust" heading.

http://www.lpi.usra.edu/meetings/lpsc2004/pdf/2188.pdf

Cheers,
Aldo.

[Bob Shaw]

The paper on the duricrust posits some very credible processes, and when one considers the Viking 2 images of hoar frost at the landing site then a ready source of water is apparant.

I'm reminded of the 'mineralisation' process which occurs in sandstone used for buildings (a big chunk of Glasgow, where I live, is built of Old Red Sandstone from the north-west of Scotland) and which often preserves 400 MYO bedding planes etc in the facades of houses. I wonder whether the aeon-long formation of duricrust would eventually give us rocks comparable to terrestrial sandstone, or whether it would always remain rather more friable and delicate? The exhumation of buried features we see from orbital imagery suggests that there are episodes of harder/softer rock deposition, which may be linked to relative abundance of water (eg a nice big impact could create a briefly wet Mars with well mineralised rocks, with a gradual return to the fairy-cake stuff as time wears on).

Ah, the ghost of Tommy Gold beckons!

[dilo]

Here's a pancam mosaic of four of the images posted by Mhoward. I'm waiting for the other frames with missing data to update, hopefully.
Very intriguing this feature.
Cheers
Nico
awalkonmars new Spirit sol 489

Nico, missing (right) portion in the next Sol:

Regards.

[CosmicRocker]

...
Ah, the ghost of Tommy Gold beckons!

Shiver me timbers! Are you suggesting we'll eventually be drilling impact sites on Mars to harvest hydrocarbons?

[CosmicRocker]

Sorry this is long, but I found myself on a roll...

It definitely seems to be a "crusty unit," but going so far as to call it a "duricrust" seems unwarranted. I really haven't yet seen anything I'd call a true duricrust on Mars. I really prefer the "weakly cemented by salts" hypothesis. Water ice is a second choice for me.

There were a few images from around sol 110 taken near Endurance that keep popping up as examples of duricrust, but taken in the context of the surroundings, they appear to me to be soil/dust covered slabs of fractured bedrock that were disturbed by Oppy's wheels.

Purported examples of duricrust:
http://marsrovers.jpl.nasa.gov/gallery/all...03P2584L7M1.JPG
http://www.lyle.org/~markoff/pds/234567/1P...87L234567C1.JPG

Context images showing the dust/soil covered plates of broken-up bedrock surrounding Endurance crater:
http://marsrovers.jpl.nasa.gov/gallery/all...3P2366L7M1.HTML
http://marsrovers.jpl.nasa.gov/gallery/all...3P2366L7M1.HTML
http://www.lyle.org/~markoff/pds/257/1P137...P2361L257C1.JPG
These are some that have been partially exhumed:
http://www.lyle.org/~markoff/pds/257/1P138...P2295L257C1.JPG
http://www.lyle.org/~markoff/pds/257/1P138...P2295L257C1.JPG

[Bob Shaw]

The 'Tommy Gold' reference was more in regard to his ability to think out of the box - a bit like Fred Hoyle. A lot of their ideas didn't pan out, but they were always interesting!

And as for the cosmic origins for hydrocarbons hypothesis, well it seems unlikely at first glance but...

[dvandorn]

It definitely seems to be a "crusty unit," but going so far as to call it a "duricrust" seems unwarranted.  I really haven't yet seen anything I'd call a true duricrust on Mars.  I really prefer the "weakly cemented by salts" hypothesis.  Water ice is a second choice for me.

"Duricrust" is a term that was applied to some Viking soils back in the 1970s, to describe the cohesive properties of the upper few mm of some of the soils. As far as I've ever been able to tell, it's used in a descriptive, not a diagnostic, manner -- it describes the cohesive qualities of some top layers of Martian soils. It doesn't pre-suppose a reason for the cohesiveness, i.e., it doesn't assume that the duricrust is created by a permafrost layer or anything like that. (So the idea of an absolute "true duricrust" doesn't really enter the discussion, I don't think.)

In fact, the conclusion of the original Viking team was that the duricrust is likely a weakly cemented unit resulting from evaporation of salts from groundwater. Since no evidence of current groundwater was returned, they didn't state that assumption as certain, but I know it was the preferred theory for the observed phenomenon.

-the other Doug

[dvandorn]

The 'Tommy Gold' reference was more in regard to his ability to think out of the box - a bit like Fred Hoyle. A lot of their ideas didn't pan out, but they were always interesting!

Tommy Gold's problem wasn't that he thought outside of the box (which claim I question just a bit) -- it was that, in the face of overwhelming evidence that his theory was invalid, he not only stuck to it, he got louder and more shrill about it right up to the point where men actually walked on the Moon.

Face it -- after two successful Luna and five successful Surveyor landings proved that the lunar regolith was sturdy enough to support all sorts of weight, the man was still strongly (and publicly) pressuring NASA to include a set of large weights with brightly colored flags attached that were to be shot out in front of the LM as it descended, to make *absolutely sure* that the surrface below wasn't a meters-deep quagmire of lunar quicksand.

"Thinking outside the box" is no excuse for vociferously hanging on to theories that have been discredited.

-the other Doug

[Bob Shaw]

But a flag-draped LM would have been *entertaining* at the very least!

[CosmicRocker]

"Duricrust" is a term that was applied to some Viking soils back in the 1970s, to describe the cohesive properties of the upper few mm of some of the soils.  As far as I've ever been able to tell, it's used in a descriptive, not a diagnostic, manner -- it describes the cohesive qualities of some top layers of Martian soils.  It doesn't pre-suppose a reason for the cohesiveness, i.e., it doesn't assume that the duricrust is created by a permafrost layer or anything like that.  (So the idea of an absolute "true duricrust" doesn't really enter the discussion, I don't think.)

In fact, the conclusion of the original Viking team was that the duricrust is likely a weakly cemented unit resulting from evaporation of salts from groundwater.  Since no evidence of current groundwater was returned, they didn't state that assumption as certain, but I know it was the preferred theory for the observed phenomenon.

-the other Doug

I know that the term had been used for similarly caked soils observed by a Viking misssion, and even by many other scientists studying other parts of Mars over the years. All I am saying is, it that it's a misuse of the term. Duricrust is a useful geologic term which has a much longer history than that of the space program. While the definition is fairly broad and open to some interpretation, it has always implied an indurated, strongly to moderately cemented soil or regolithic material. Ie, it is literally as hard as a rock, and therefore has the ability to control the later geomorphic evolution of the landscape. Laterites, bauxites,ferricretes, silcretes, even caliches are classic duricrusts.

Apparently most of us agree that whatever we call it, this looks like some kind of a salt-caked crust. I don't want to debate semantics. It's just that I hate definition-creep, especially when it erodes the value of a time-worn and useful term.

[edstrick]

Tommy Gold and Fred Hoyle were similar "theory testing impaired"

They were wrong a lot of the time. They had tremendous abilities to sort through and select and interpret evidence in support of their theories and ignore evidence that blew their theories out of the water entirely. Much of the science they did in their later years bordered on or went over the border into crackpottery.

But when they were right, they were spectacularly right. Their theories were always worth listening to, and thinking about, even when you were 99.9% sure they were totally off--the--wall wrong

[CosmicRocker]

When I saw this front hazcam today I initially thought we would see MIs of the crust, but it's clear they are looking at the rock above.

http://qt.exploratorium.edu/mars/spirit/fo...EEP1131L0M1.JPG

Here is a mosaic of the MIs from today.


The clasts in this rock seem to me to be more angular than some of the other outcrops we've been seeing as we came up the hill. Looking at the pancams from Larry's outcrop I am wondering if I am seeing some evidence of graded bedding. Does anyone else see that?

Finally, back to the crust. It appears to me that this image captured evidence of some other, partially eroded, crusty dust in the upper right.
http://qt.exploratorium.edu/mars/spirit/pa...EEP2535L7M1.JPG

[Bubbinski]

Seeing some of the microscopic images from Spirit last night reminded me a little bit of the images Oppy took at El Capitan and other outcrops in Eagle Crater. Is this going to turn into press conference material??

[mhoward]

Seeing some of the microscopic images from Spirit last night reminded me a little bit of the images Oppy took at El Capitan and other outcrops in Eagle Crater.  Is this going to turn into press conference material??

I had the same question. And there seem to be lower levels of outcrop available to look at if they're feeling lucky... I can't wait to see what those look like.

[Guest_Sunspot_*]

I had exactly the same thought when I saw these latest MI pics. One in particular stood out:

http://qt.exploratorium.edu/mars/spirit/mi...EEP2957M2M1.JPG

Look towards the right of the image, say about 80% of the way towards the right edge, and just over half way down. It looks like a "blueberry" encased in rock.