Checking Out The Rind Options

[mhoward]

Bunch of MI's of the "rind" (mentioned in Steve Squyres' latest mission update), I believe, starting with this one:

http://nasa.exploratorium.edu/mars/opportu...DIP2956M2M1.JPG

Forward hazcam:

http://nasa.exploratorium.edu/mars/opportu...DIP1110L0M1.JPG

[mhoward]

The area being checked out is to the left of this image:

[mike]

I wager that Mars has had a more interesting history than anyone has necessarily imagined thus far.. Perhaps it was Earth, just a few billion years earlier and terminated before it had space-faring beasties. Then again, maybe it had space-faring beasties, and all their Earth-sent probes have since been obliterated. Earth would have been rather uninteresting compared to Mars back then.

How about this, Earth was going along pretty well, then whatever gave us the Moon hit Earth, and voila, set us back a few hundred million years or so. Mars on the other hand keeps cranking, and hey, Deimos and Phobos aren't huge, but neither is Mars, so surely they would induce some sort of decent tidal effects (thought to be important to the formation of life on Earth, by me if no one else). But then, the sun cools down, Mars' lower gravity isn't enough, and it all disappears, or freezes onto the surface, or both, and next comes Earth.

As the sun cools down further (before going red giant..), I imagine Earth's climate will change quite noticeably and Venus will cool down etc. etc. etc.

And if I'm wrong about the current ideas of star formation (perhaps stars start cold and get hotter and hotter until they go red giant, eh?), then guess what, THEY'RE ALL WRONG. But in that case I'll couch my bets and just say that Venus was once Earth and Mars will be Earth soon enough. Except that we don't have any probes on Venus (yet) so I don't find that as exciting right now.

Once we find those ancient Martian tools a few feet beneath the surface, you'll all know I was right.

[RedSky]

As the sun cools down further (before going red giant..), I imagine Earth's climate will change quite noticeably and Venus will cool down etc. etc. etc.

Actually, I think the current thinking on main sequence stellar evolution is that the sun is expected to increase slowly... but continuously, in luminosity over the next few billion years. In fact, the earth would probably become uninhabitable due to this effect long before the sun reaches the red giant stage. (I think it has to do with the fact that the hydrogen "burning" keeps progressing out in a layer from the center... which becomes too helium-rich for efficient nuclear fusion).

[Guest_Sunspot_*]

I'm assuming this area has had the RAT Brush applied to it?

http://qt.exploratorium.edu/mars/opportuni...DIP2936M2M1.JPG

Very unusual.

[um3k]

I'm assuming this area has had the RAT Brush applied to it?

http://qt.exploratorium.edu/mars/opportuni...DIP2936M2M1.JPG

Very unusual.

Oh wonderful, more fossils.

(That smilie would work better if it weren't...er...smiling.)

[atomoid]

I'm assuming this area has had the RAT Brush applied to it?
http://qt.exploratorium.edu/mars/opportuni...DIP2936M2M1.JPG
Very unusual.

yep, its a rat-brushed version of this same spot thats in shadow here
...rat HOLE coming soon?

Should we assume that the "mysterious rind" was created by moist contact between the bedrock and the overlying (or blowing) basaltic sands (or dusts)?

[Bill Harris]

We're starting to see some interesting things there.

From Sol-556 (the same time as MHoward's FHazcam shots), we have a Pancam shot off to the side of this outcrop we're on:

http://qt.exploratorium.edu/mars/opportuni...DIP2584L7M1.JPG

A couple of observations: the weathering rind is dark, with a similar value as the sand. You can see an area just left of center where the crust is wind-eroding down to the underlying evaporite. And notice the HUGE blueberries on the left side and below center. They must be in the 10-12mm range!

This is what I suppose: a thin blueberry-sand covering is over the evaporite bedrock and protects it from aeolian erosion. But this covering is thin enough that the bedrock is heated by the Sun and can pick up some water from surface condensation. This is a good setup for chemical weathering; heat and water, and the weathering crust is protected from erosion and can continue to "cook" for a long time. The thin sand shifts and we are observing a freshly-exposed weathering surface.

I think this is why we saw that dark ejecta and the dark floor at the heatshield impact bonk. My thoughts were that was a weathering surface and I was disappointed that we didn't look closer then; hopefully, we will now. It will be interesting to know the minerology of the weathering crust.


--Bill

[abalone]

Where have all the blueberries go, seems to be only one in the middle? I assume this is a grind of the rind.

Attached thumbnail(s)

 

[slinted]

Here's a falsecolor view on the double RAT action (RAT and brush?, RAT and RAT?) on the rind and nearby outcrop. I believe the 'berry-less' MI's are of the bottommost hole.

[CosmicRocker]

Excellent image, slinted. This is getting interesting. My apologies for the length, but please bear with me...

Recent comments from the team said the rind is more red than the interior. Slinted's image clearly shows the red color in the RAT cuttings and a lighter interior. In chemical weathering and other secondary geochemical rock altering processes observed on earth, oxidized and hydrated forms of iron are often the cause of red colors. If such iron minerals have been concentrated in the rind, did the iron arrive there after being leached from the interior? Or could it have migrated from a previous covering of iron rich sediment.

Some have noticed that parts of the rind near vertical fractures bear a strong resemblance to the interesting structures seen at Razorback in Endurance crater. It is difficult to imagine a process that could create such rinds that did not require water to facilitate the migration of ions.

Consider also that rocks on the other side of the planet also have displayed an outer rind and a soft interior. (Breadbox et al. come to mind) It has been hypothesized by others that this is a phenomenon called "case hardening." It has been observed in rocks on earth and involves leaching, migration and redeposition of ions. I have seen it caused in several different geochemical environments, and in different kinds of rocks. I now wish I had paid more attention to them at the time, or at least colected samples of them.

Having said that, it seems curious that similar processes that are not common on earth were observed by two, somewhat randomly placed rovers on opposite sides of Mars. Could this be evidence of a global phenomenon?

[stevo]

Having said that, it seems curious that similar processes that are not common on earth were observed by two, somewhat randomly placed rovers on opposite sides of Mars.  Could this be evidence of a global phenomenon?

We probably shouldn't draw too many conclusions from two just two sites, but my guess is that the effects of weathering on different places on Mars probably is very similar because nothing much really happens on the surface of Mars, relative to Earth. It's very dry, very cold, and in most cases, the rocks have just been sitting there being gently sandblasted, perhaps occasionally moistened, for a very, very long time.

[David]

In the news conference, Steve Squyres has said that the rind is similar in composition to the underlying rock, but has elevated amounts of Na and Cl. He allowed that yes, it might be because of a final precipitation of NaCl onto the rock. But he was guarded enough that you can take it with a grain of salt.

[stevo]

In the news conference, Steve Squyres has said that the rind is similar in composition to the underlying rock, but has elevated amounts of Na and Cl.  He allowed that yes, it might be because of a final precipitation of NaCl onto the rock.  But he was guarded enough that you can take it with a grain of salt. 

Very good So, is the percolation of groundwater up from below and evaporation at the surface an option, or does this really point towards precipitation onto the rock from a "shallow, salty sea" ?

[Bob Shaw]

We probably shouldn't draw too many conclusions from two just two sites, but my guess is that the effects of weathering on different places on Mars probably is very similar because nothing much really happens on the surface of Mars, relative to Earth.  It's very dry, very cold, and in most cases, the rocks have just been sitting there being gently sandblasted, perhaps occasionally moistened, for a very, very long time.

Stevo:

That was firmly my view, too, until seeing the debris blowing into the RAT hole recently, and the weathering at the top of Husband Hill (not to mention discussions about, well, dampness...)! I always veered towards the slow, dry and cold variety of weathering, but might now be prepared to reconsider... ...perhaps things can be a bit more dramatic than we thought.

Bob Shaw