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MSL - SAM and CHEMIN, Discussion of the science/results from these instruments
mcaplinger
post Nov 23 2012, 04:09 PM
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QUOTE (MrNatural @ Nov 23 2012, 08:08 AM) *
Can we discuss SAM's stereochemistry capabilities? I believe that SAM can sort out chirality, but I have seen very little written about this.

First, ask in the SAM/Chemin thread. Second, read the SAM instrument paper. Third, do a simple google search for "sam msl chirality" and then you will be prepared enough to ask questions.


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elakdawalla
post Nov 23 2012, 05:18 PM
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Actually they're only free through Nov 30 -- one more week. Get 'em while they're hot.


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marsophile
post Nov 23 2012, 07:24 PM
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QUOTE (marsophile @ Nov 22 2012, 08:54 PM) *
... or something like it.


Thanks very much for those links, especially this one:

http://link.springer.com/article/10.1007/s...z/fulltext.html

This image from the above link illustrates what I was trying to recall:

Attached Image


There are chemical solvents that can separate possible organics from the sample before heating, and also there is initial heating at a lower temperature.
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Don1
post Nov 24 2012, 04:49 AM
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SAM has a number of different modes of operation. The most common mode is going to be evolved gas analysis. On heating minerals like carbonates, sulfates and perchlorates will decompose, yielding gases like CO2, SO2, Cl2 and HCl. Water trapped in the crystal structure of minerals will also be driven off. SAM has a lot of capability to measure the isotope ratios for CO2 and H2O. If those isotope ratios differ from those of gases in the present Martian atmosphere, that will be an interesting result. The isotope ratios of Martian atmospheric gases have changed over time due to the loss of atmosphere to space. The isotope ratios of carbon and oxygen in carbonate minerals would be the same as that of the atmosphere at the time of their formation.

What about organics? If both organics and perchlorate are present in the soil SAM would see chlorohydrocarbons. If the soil at this site is different from the rest of Mars, then organics might be present without perchlorate. In that case SAM would detect the breakdown products of the organics. Detection of organics would certainly qualify as earthshattering, but the Martian surface is known to be a hostile environment for them.

If organics are suspected, I would expect a second run of SAM, this time in the wet chemistry or derivatization mode. Only 9 of the 74 sample cups contain the wet chemistry reagent. This reagent can remove perchlorates, which enables the organics in the sample to be directly detected.

Given the speed at which things move on SAM, they probably haven't gotten around to doing wet chemistry yet. If they are in a hurry to do a second run on the same sample, that would point to organics.
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Spin0
post Nov 26 2012, 10:28 AM
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From AGU's 2012 Fall Meeting scientific program:
MONDAY, DECEMBER 03, 2012

Session: U13A
Results From Mars Science Laboratory Mission Four Months After Landing
1:40 PM - 3:40 PM

U13A-01. The Mars Science Laboratory Mission: Early Results from Gale Crater Landing Site (Invited)
John P. Grotzinger; Dave Blake; Joy A. Crisp; Kenneth S. Edgett; Ralf Gellert; Javier Gomez-Elvira; Donald M. Hassler; Paul R. Mahaffy; Michael C. Malin; Michael A. Meyer; Igor Mitrofanov; Ashwin R. Vasavada; Roger C. Wiens

U13A-02. Overview of the Atmosphere and Environment within Gale Crater on Mars (Invited)
Ashwin R. Vasavada; John P. Grotzinger; Joy A. Crisp; Javier Gomez-Elvira; Paul R. Mahaffy; Christopher R. Webster

U13A-03. First results from the CheMin, DAN and SAM instruments on Mars Science Laboratory (Invited)
David F. Blake; Paul R. Mahaffy; Igor Mitrofanov

U13A-04. The Radiation Environment on the Martian Surface and during MSL’s Cruise to Mars (Invited)
Donald M. Hassler; Cary Zeitlin; R F. Wimmer-Schweingruber

U13A-05. Chemical Composition of Rocks and Soils at Gale Crater, Mars (Invited)
Roger C. Wiens; Ralf Gellert; Sylvestre Maurice


Unfortunately the session is not on Video On-Demand Lectures and Sessions list. huh.gif
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elakdawalla
post Nov 26 2012, 05:43 PM
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Provided there's wi-fi or cellular signal, I'll be live-tweeting it!


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vjkane
post Nov 26 2012, 06:54 PM
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QUOTE (elakdawalla @ Nov 26 2012, 09:43 AM) *
Provided there's wi-fi or cellular signal, I'll be live-tweeting it!

Thank you for being there, Emily! This is the first year in several I won't make AGU (conflicting conference), and I already have anticipatory withdrawal symptoms.


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Holder of the Tw...
post Nov 26 2012, 07:08 PM
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QUOTE (Don1 @ Nov 23 2012, 10:49 PM) *
On heating minerals like ... perchlorates will decompose, yielding gases like ... Cl2 and HCl.


You sure about this? I was under the impression that mineral perchlorates (calcium and magnesium) would normally decompose by heating into the chloride salt and oxygen. There might be some HCl from the calcium perchlorate if it is the tetrahydrate, but I wouldn't expect to see Cl2 at all. Maybe I'm wrong.

Update: Right about the O2, wrong about the Cl2. See discussion below. The reaction Mg(ClO4)2 -> MgCl2 + 4O2 does occur as part of the mix, and occurs at a higher rate under earth atmospheric pressure as opposed to a vacuum. The other decomposition reaction branch (which produces chlorine) is 2Mg(ClO4)2 -> 2MgO + 2Cl2 + 7O2.
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serpens
post Nov 27 2012, 04:40 AM
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I would suspect that the end products (and intermediate stage products) would depend on the makeup of the total sample and associated hydration states. For say pure Mg perchlorate the end product would (I think) be MgO, Cl2 and O2. If Ca perchlorate is present and depending on hydration state then HCl should be a stage product which would react to give CaCL2 and CO2. But I stand to be corrected.
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Don1
post Nov 27 2012, 05:50 AM
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QUOTE (Holder of the Two Leashes @ Nov 26 2012, 11:08 AM) *
You sure about this? I was under the impression that mineral perchlorates (calcium and magnesium) would normally decompose by heating into the chloride salt and oxygen. There might be some HCl from the calcium perchlorate if it is the tetrahydrate, but I wouldn't expect to see Cl2 at all. Maybe I'm wrong.



I'm not sure about the Cl2. Sounds like you know more about this than I do!
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mcaplinger
post Nov 27 2012, 06:21 AM
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http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2008.pdf and various other abstracts coming up with a google search for "sam msl perchlorate" may be of interest.

QUOTE
The parent salts of the perchlorate on Mars are unknown, but geochemical models using WCL data support the possible dominance of Mg-perchlorate salts. Mg(ClO4)2•6H2O is the stable phase at ambient martian conditions, and breaks down at lower temperatures than carbonates giving off Cl2 and HCl gas. Devlin and Herley report two exotherms at 410-478°C and 473-533°C which correspond to the decomposition of Mg(ClO4)2. They support a two-stage process:
(1) 2Mg(ClO4)2 = [MgO•Mg(ClO4)2] + Cl2 + 3.5O2
(2) [MgO•Mg(ClO4)2] = 2MgO + Cl2 + 3.5O2
If the chlorine gas produced reacts with moisture in the system or if the magnesium perchlorate has not fully dehydrated, then HCl gas can form and react with a carbonate phase to evolve CO2:
(3) CaCO3 + 2HCl = CaCl2 + CO2 + H2O


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belleraphon1
post Nov 27 2012, 01:01 PM
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AGU Press Conference Schedule:
http://fallmeeting.agu.org/2012/important-...edia-advisory-4

There is a Curiosity briefing (the first one) December 3 at 9:00 am PT.
Mars Rover Curiosity's Investigations in Gale Crater
Monday, 3 December 9:00 a.m.

NASA's newest Mars rover, Curiosity, has been investigating past and modern environmental conditions in Mars' equatorial Gale Crater since August. This briefing will offer findings from examining the composition and textures of targets touched by the rover's robotic arm. Curiosity is the car-size rover of NASA's Mars Science Laboratory mission. At the time of the AGU Fall Meeting, it will be four months into a two-year prime mission.
Watch live here: I don't you need to be registered???
http://live.projectionnet.com/agupress/fm2012.aspx

Edited to remove copy/paste formatting.
ADMIN NOTE: All, please either edit these down or only post a link to the original.
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serpens
post Nov 27 2012, 11:18 PM
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QUOTE (mcaplinger @ Nov 27 2012, 06:21 AM) *
http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2008.pdf and various other abstracts coming up with a google search for "sam msl perchlorate" may be of interest.

Thanks for the link and as expected I stand corrected on the Ca perchlorate decomposition products. The sheer volume of information on the web is daunting but I couldn't find anything on analysis of mixed samples reflecting candidate martian perchlorates/soil compositions? I seem to remember that the thermal stablility of a mix of perchlorates is lower than that of the pure components and the initial endothermic reaction in the figure 1 Wicked Witch sample seems closer to that for Ca perchlorate. Curiosity's investigative capability is remarkable and I can't wait for the next LPSC.
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Lucas
post Nov 28 2012, 04:57 PM
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Well, this is interesting... apparently all the hype was simply due to a misunderstanding by the NPR reporter who was interviewing Dr. Grotzinger!

http://www.slate.com/blogs/the_slatest/201...out_entire.html

A tweet by Curiosity (screenshot attached) was meant to reduce the expectations and clarify Dr. Grotzinger's remarks, but apparently it wasn't noticed and the story went viral.

Sigh...

--Lucas

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fredk
post Nov 28 2012, 07:28 PM
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It certainly does look like bad reporting, at least in part. Remember that the word "earthshaking" was used in the original npr story. However, it was not directly quoted to Grotzinger. Now that word has been quietly changed to "remarkable".
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