Cape York - The "Lakelands", Starting sol 2703 |
Cape York - The "Lakelands", Starting sol 2703 |
Sep 20 2011, 08:40 PM
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#121
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Junior Member Group: Members Posts: 98 Joined: 17-July 11 From: Pasadena, CA Member No.: 6066 |
Is there enough control in the arm and enough brush left to sweep out the grind debris? I remember that the brush bristles were a bit "cattywumpus". We are thinking about doing that sometime soon. There was considerable debate among the SOWG whether or not the extra rubbage in there would contaminate the exposed core of the rock. We've got ground in the loop to look at some things tomorrow and may try another brush+APXS. Soonest we can count on boogeying on out of the Chesterlake area is... Friday? We'll be hitting nominal sols soon and it'll be day in day out for two weeks. -m |
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Sep 20 2011, 10:09 PM
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#122
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The Poet Dude Group: Moderator Posts: 5551 Joined: 15-March 04 From: Kendal, Cumbria, UK Member No.: 60 |
Interesting responses! But that's why it would be interesting to collect RAT images throughout the mission to see how the holes have varied in appearance. Anyone? (I don't have time right now) Phil This page might be useful for you, Phil... http://marswatch.astro.cornell.edu/pancam_...ges/merges.html -------------------- |
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Sep 20 2011, 10:57 PM
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#123
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Solar System Cartographer Group: Members Posts: 10131 Joined: 5-April 05 From: Canada Member No.: 227 |
... and even more useful for the person who makes the comparison image! Actually I think straight pancam images would be easier to use for this.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke 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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Sep 20 2011, 11:00 PM
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#124
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The Poet Dude Group: Moderator Posts: 5551 Joined: 15-March 04 From: Kendal, Cumbria, UK Member No.: 60 |
Ok, just thought it was worth a look for you. I'll have a delve into the archives tomorrow.
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Sep 21 2011, 12:12 AM
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#125
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Solar System Cartographer Group: Members Posts: 10131 Joined: 5-April 05 From: Canada Member No.: 227 |
It's a great site, Stu! I just don't have time to look at this question right now - up to my ears in Itokawa problems.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke 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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Sep 21 2011, 02:55 AM
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#126
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Senior Member Group: Members Posts: 2997 Joined: 30-October 04 Member No.: 105 |
QUOTE considerable debate among the SOWG whether or not the extra rubbage in there would contaminate the exposed core of the rock Brushing may not make a difference-- look at the surface of the pre-RAT IDD site and it looks really sand-blasted clean. Brushing off the cuttings would be critical if the surface were weathered or dust-covered. Though it would be nice to see what the clean, grinded surface looks like.AFAIK, the next known important site is in the area of the CRISM phyllosilicate signature around that summit crater ~300m NE. And, of course, important sights seen along the way... --Bill -------------------- |
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Sep 21 2011, 03:54 AM
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#127
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Junior Member Group: Members Posts: 54 Joined: 10-August 11 Member No.: 6119 |
A composite pancam/microscope image of the recent RAT hole in 'Chester Lake'
pancam L456 sol 2721 microscope sol 2719 (jvandriel's image from here) |
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Sep 21 2011, 05:13 AM
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#128
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Senior Member Group: Members Posts: 2228 Joined: 1-December 04 From: Marble Falls, Texas, USA Member No.: 116 |
Could they be obsidian in a perlite matrix? That's certainly a possibility, Fran. I didn't think of that, but I suppose it could be obsidian in perlite. I don't have a lot of experience with volcanic glasses, but the few times I saw such rocks in the field, the obsidian inclusions were typically rounded and not angular like these. That's an interesting suggestion that I will have to consider. I have to wonder, though, would we expect to see glasses in rocks that are so old, or would they have devitrified after all this time, perhaps leading to the formation of clay minerals? -------------------- ...Tom
I'm not a Space Fan, I'm a Space Exploration Enthusiast. |
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Sep 21 2011, 02:05 PM
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#129
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Senior Member Group: Members Posts: 2997 Joined: 30-October 04 Member No.: 105 |
I'm not familiar with that mineral, but AFAIK perlite is a volcanic glass (obsidian) that is hydrated and when heated, it expands producing a light weight, light-colored material. From the few pictures I've found it looks like a medium-greyish rock with a pearly luster. The diagnostic feature is that it expands greatly when heated.
What have we seen here that looks like perlite? And how was it identified? It would be good to find a perlite since that would imply an impact melt that was hydrated because it was created from a wet parent material. Enquiring minds need to know... --Bill -------------------- |
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Sep 21 2011, 04:53 PM
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#130
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Member Group: Members Posts: 214 Joined: 30-December 05 Member No.: 628 |
"Perlite" (I assume it's the same stuff) is a soil conditioner commonly used in hydroponic gardening. It's very soft - you can grind it between your fingers, and I think even under today's martian environmental conditions, exposed perlite would have long since eroded away from just the rarefied effects of the wind. I suppose there might be deposits of it buried underground dating from the noachian era, but very unlikely that it could be mined with just a RAT. (I'm no geologist - please let me know if this is a completely different substance I am thinking of.)
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Sep 21 2011, 08:22 PM
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#131
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
A break from mineralogy: the cyclops is crying.
http://qt.exploratorium.edu/mars/opportuni...19P2285L2M2.JPG The crater seems to collect and 'focus' the downslope streak. |
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Sep 21 2011, 09:19 PM
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#132
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Solar System Cartographer Group: Members Posts: 10131 Joined: 5-April 05 From: Canada Member No.: 227 |
Great view!
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke 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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Sep 21 2011, 09:24 PM
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#133
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Senior Member Group: Members Posts: 2997 Joined: 30-October 04 Member No.: 105 |
Ah is a gee-ologist but 40 years outta school. "Perlite", as far as I can tell, is a manmade product created by heating a hydrated obsidian to some 1600*F where the volcanic glass softens and the entrained water causes it to"foam up" and expand. And as far as I can tell, hydrated obsidian, the mineral, is also (and possibly informally) called "perlite". I don't think that the manmade commercial soil additive occurs in natural deposits anywhere. However, I wonder if the "hydrated obsidian" could refer to an impact melt created from a water-saturated source material. With certain temperatures/pressures/timeframes I can see this as "possible".
Over time, a glass can weather or degrade from a "glassy" form to a "crystalline" form, a process called "devitrification". In obsidian samples, this is seen as "snowflake obsidian". It could devitrify into a smectite or a clay mineral, but I've seen no suggestions at Salisbury1 of devitrification of the impact melt. And, picking nits, obsidian is a siliceous rhyolytic glass which is not compatible with the mafic (silica-poor) basalts we see in this region of Mars, so we're looking for glass of basaltic composition, such as a tachylite. Why get worked up this much about a volcanic glass? It may well be the best way to do a comparative study of the creation and weathering of impact melt (impact glass) on Mars. --Bill -------------------- |
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Sep 22 2011, 01:52 AM
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#134
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Member Group: Members Posts: 107 Joined: 29-January 09 Member No.: 4589 |
Here's an L2/5/7 composite from sol 2718, part of the 'big pan'. There are some subtlety fascinating variations in colour coming through.
-------------------- Protein structures and Mars fun - http://www.flickr.com/photos/nick960/
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Sep 22 2011, 04:48 AM
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#135
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Senior Member Group: Members Posts: 2228 Joined: 1-December 04 From: Marble Falls, Texas, USA Member No.: 116 |
... Over time, a glass can weather or degrade from a "glassy" form to a "crystalline" form, a process called "devitrification". In obsidian samples, this is seen as "snowflake obsidian". It could devitrify into a smectite or a clay mineral, but I've seen no suggestions at Salisbury1 of devitrification of the impact melt. ... At this point, even though it appears likely, we really don't know if we are seeing impact melts or not. But the point I was trying to make regarding devitrification was that after about 4 billion years any volcanic glass that may have existed should have had ample time to devitrify. Have you ever seen a Precambrian glass? ... And, picking nits, obsidian is a siliceous rhyolytic glass which is not compatible with the mafic (silica-poor) basalts we see in this region of Mars, so we're looking for glass of basaltic composition, such as a tachylite. ... I understand that we are expecting to see basaltic rocks here, but we don't "know" that all of the rocks here are mafic. Some silicic volcanics would probably be a very exciting discovery on Mars, but I was simply acknowledging Fran's observation that the current science target does resemble an outcrop of obsidian in a perlite matrix. We have to remember that we are among the first geologists from our planet to have had the opportunity to explore the rocks of another. We should expect to be surprised as often as we find things that are familiar. N.B: The perlite used in hydroponics and soil conditioning may be derived from the rock known as perlite, but it is not the same thing. -------------------- ...Tom
I'm not a Space Fan, I'm a Space Exploration Enthusiast. |
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