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MSL at Rocknest, First scoop samples - sols 57-101
john_s
post Oct 31 2012, 02:37 PM
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QUOTE (dvandorn @ Oct 30 2012, 09:40 PM) *
So, there's a significant feldspar content in the ubiquitous Martian dust, eh? It will be interesting to see if we find source rock that is anorthositic, or source rock that is granitic.


Note that feldspar is also an important component of basalt, so that's probably the most likely source rock, consistent with what the team says. Feldspar has a wide range of compositions (e.g., anorthosite feldspar is much poorer in sodium and richer in calcium than granite feldspar), and Curiosity can probably tell what kind of feldspar we have here- were any more specifics given at the briefing? Or are there any XRD experts out there who can read that diffraction pattern :-) ?

John
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dvandorn
post Oct 31 2012, 04:38 PM
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I hear you, John. I guess I ought to have stated my thought by saying I wonder if the source is plagioclase or alkali feldspar? The former is found both as laths within basalt (at least it is on Earth and on the Moon), and as purely anorthositic rock. Alkali feldspar is water-altered and is found (again, at least on Earth) in granitic rock.

However, as I noted in a response to Phil a while back, when you find plagioclase in basalt it is usually in the form of little, almost feathery intrusions in the basalt called laths. As I understand it, this is due to a plagioclase component in the lava melt which cannot mix with the pyroxene and/or olivine components of the lava, and it just solidifies in place in the same distribution found in the original melt, as the strings, strands and thin layers of the lighter, more aluminous plagioclase floated and were moved about as the original melt convected, moved and flowed. (I think of it as freezing a glass of water very quickly after trying to stir in a liquid that won't mix with the water; the non-miscible liquid will form flow structures within the water, which are then frozen into the ice.)

While these laths are not always highly identifiable in macroscopic images, they're usually fairly easily seen when you look with any reasonable magnification. I know I've looked for this kind of lath structure in the various basalts we've seen over the course of 36 years of Martian surface exploration, and I've not seen anything I can definitely say is a lath structure that would say for certain that Martian basalts have a significant feldspathic content.

I'm not saying it isn't there, I'm just saying that I've not seen it. Of course, it may be I wouldn't recognize a lath structure in situ -- I normally see it best in thin-section slides, after all. And, of course, I've not seen the basalt elemental abundance results of all of the MER sensors, at least not directly. So, I certainly can't be sure. I'd just be interested in seeing whether or not MSL finds a significant feldspathic component in the intact basalts it studies.

-the other Doug


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Phil Stooke
post Oct 31 2012, 04:38 PM
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And just to add names to John's feldspar types, anorthosite feldspar is plagioclase, granite feldspar is mainly orthoclase (though granite contains both feldspars). Plagioclase is white - it make the lunar highlands brighter than the maria. Orthoclase is pinkish, often giving granite a pinkish tint (granite with little orthoclase is really granodiorite).

Phil



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dvandorn
post Oct 31 2012, 04:45 PM
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Exactly, Phil -- what I just called alkali feldspar is the pinkish stuff you find in granites. Of course, on Earth these are formed as a result of subduction, with various rock types including plagioclase being altered under high heat and pressure in the presence of water after the crust has been subducted and then re-exposed by tectonic processes. It would be quite revealing if we were to find significant orthoclase-type feldspar or full-on granitic rocks on Mars, as that would tend to indicate a period of subduction and re-exposure sometime in Mars' past.

-the other Doug


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fredk
post Oct 31 2012, 05:24 PM
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A new stereo mahli view of Burwash. Taken from a bit farther away than my previous anaglyph (so lower resolution), but with better lighting:
Attached Image

Attached Image

Is that a rounded pebble sitting in a groove near centre top?

And check out what's coming down the pipeline...
http://mars.jpl.nasa.gov/msl-raw-images/ms...0010I1_DXXX.jpg
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walfy
post Oct 31 2012, 05:43 PM
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A new one of "Burwash":

Attached Image


(Oops! Just noticed fredk got to it already!)
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ronald
post Oct 31 2012, 05:55 PM
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Some "Et-then" and since my take on "Burwash" was done allready - I'll post it too smile.gif
Attached Image
Attached Image

Cant wait for the new MAHLI sequence blink.gif
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ElkGroveDan
post Oct 31 2012, 06:02 PM
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QUOTE (fredk @ Oct 31 2012, 10:24 AM) *
A new stereo mahli view of Burwash.


Those paper-thin eroded features are breathtaking.
Attached thumbnail(s)
Attached Image
 


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walfy
post Oct 31 2012, 06:56 PM
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QUOTE (ronald @ Oct 31 2012, 09:55 AM) *
my take on "Burwash"...


Very nice to have the wheel tracks in the shot to see just how small these rocks are! My brain keeps telling me they're much larger. Maybe the rover should've brought along a Swiss army knife to place in each shot. tongue.gif
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stewjack
post Oct 31 2012, 07:50 PM
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Just a casual observation. However; I haven't noticed any rounded pebbles lately. I haven't been specifically looking for them, but I noticed them right after landing without being told about them. Since we are down slope there are probably some, but they don't seem to be as common. Even if my observation finds agreement: Since we have been stationary for such a long time, I suspect that it is to early to call it a characteristic of the new terrain of Glenelg. If someone has already mentioned this I apologize for missing it.



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Explorer1
post Oct 31 2012, 09:19 PM
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Telecon Friday morning, on atmospheric studies. What many have been waiting for:

http://www.jpl.nasa.gov/news/news.php?release=2012-343
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elakdawalla
post Oct 31 2012, 11:15 PM
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I've gotten behind on MSL so spent today getting up to speed. My sol-by-sol timeline is now up-to-date. I noticed two time-series of Navcams taken late in the day on sols 75 and 77. Anybody know what these were for? Dust devil searches? I tried animating one set but didn't see anything different from frame to frame except cosmic ray hits.


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fredk
post Nov 1 2012, 04:02 AM
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I guess you mean the series ending with these two frames:
http://mars.jpl.nasa.gov/msl-raw-images/pr...NCAM00530M_.JPG
http://mars.jpl.nasa.gov/msl-raw-images/pr...NCAM00524M_.JPG
(They were taken early afternoon, not late in the day.) They've been doing series like this for a while. My original guess was DD searches. But Spirit used to crop the DD navcams on the horizon before sending them back to earth at full resolution. So maybe they're also interested in looking for the effects of wind gusts in the foreground?
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jhagen
post Nov 1 2012, 08:26 AM
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First post...
I don't know how to link to the full size image yet, but here is a 500px wide anaglyph version of the sol 82 MAHLI stereo with shadows removed.

Attached Image

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jmknapp
post Nov 1 2012, 10:53 AM
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QUOTE (jhagen @ Nov 1 2012, 03:26 AM) *
First post...


Nice 3D on that one. I didn't realize how small that rock is until this image came down:

http://mars.jpl.nasa.gov/msl-raw-images/ms...0048E2_DXXX.jpg

So, what, just a few inches across?


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