MSL at Rocknest, First scoop samples - sols 57-101 |
MSL at Rocknest, First scoop samples - sols 57-101 |
Oct 31 2012, 02:37 PM
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#344
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Member Group: Members Posts: 699 Joined: 3-December 04 From: Boulder, Colorado, USA Member No.: 117 |
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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Oct 31 2012, 04:38 PM
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#345
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
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 -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Oct 31 2012, 04:38 PM
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#346
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Solar System Cartographer Group: Members Posts: 10153 Joined: 5-April 05 From: Canada Member No.: 227 |
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 -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Oct 31 2012, 04:45 PM
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#347
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
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 -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Oct 31 2012, 05:24 PM
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#348
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Senior Member Group: Members Posts: 4246 Joined: 17-January 05 Member No.: 152 |
A new stereo mahli view of Burwash. Taken from a bit farther away than my previous anaglyph (so lower resolution), but with better lighting:
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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Oct 31 2012, 05:43 PM
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#349
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Member Group: Members Posts: 404 Joined: 5-January 10 Member No.: 5161 |
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Oct 31 2012, 05:55 PM
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#350
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Member Group: Members Posts: 154 Joined: 19-September 12 Member No.: 6658 |
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Oct 31 2012, 06:02 PM
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#351
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
A new stereo mahli view of Burwash. Those paper-thin eroded features are breathtaking. -------------------- If Occam had heard my theory, things would be very different now.
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Oct 31 2012, 06:56 PM
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#352
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Member Group: Members Posts: 404 Joined: 5-January 10 Member No.: 5161 |
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Oct 31 2012, 07:50 PM
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#353
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Member Group: Members Posts: 252 Joined: 5-May 05 From: Mississippi (USA) Member No.: 379 |
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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Oct 31 2012, 09:19 PM
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#354
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Senior Member Group: Members Posts: 2082 Joined: 13-February 10 From: Ontario Member No.: 5221 |
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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Oct 31 2012, 11:15 PM
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#355
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
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.
-------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Nov 1 2012, 04:02 AM
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#356
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Senior Member Group: Members Posts: 4246 Joined: 17-January 05 Member No.: 152 |
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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Nov 1 2012, 08:26 AM
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#357
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Newbie Group: Members Posts: 14 Joined: 7-August 12 From: California Member No.: 6489 |
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Nov 1 2012, 10:53 AM
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#358
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Senior Member Group: Members Posts: 1465 Joined: 9-February 04 From: Columbus OH USA Member No.: 13 |
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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