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MSL - SAM and CHEMIN, Discussion of the science/results from these instruments
stone
post Mar 17 2015, 09:59 PM
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Looks like a few new results have been presented at LPSC. It looks like that the Cumberland sample was sitting in the MTBSTFA vapour from the leaking derivatization oven and now they found something.
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TheAnt
post Mar 25 2015, 05:27 PM
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Nitrates detected by SAM in sediments. LTU webpage.
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Gerald
post Aug 10 2015, 03:22 PM
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I've read the link of the previous post, after doing the following analysis. So I'm sharing the nitrate conclusion, but with these new high NO values I'm sceptical about impacts as the main cause of nitrates for the new targets. Here my largely independent deduction:

An attempt to understand the SAM "Solid sample pyrolysis with GCMS" of "Mojave 2" on Sol 887. Particularly the high abundance of nitric oxide (NO) made me ponder:

QUOTE
"SPECIES","ABUNDANCE" (mole)
"1,3-bis(1,1-dimethylethyl)-1,1,3,3-tetramethyldisiloxane",2.00E-10
"tert-butyldimethylsilanol",8.00E-10
"tert-butyldimethylfluorosilane",7.00E-10
"2,2,2-trifluoro-N-methyl-acetamide",6.30E-09
"CH3Cl",8.20E-09
"CH2Cl2",6.00E-10
"HCl",1.47E-03
"H2O",5.70E-05
"CO2",2.70E-06
"SO2",3.03E-05
"O2",3.50E-06
"NO",1.24E-04
"H2S",2.88E-04


(The "Telegraph Peak" analysis of Sol 928 shows high NO, as well.)

Nitric oxide points towards the presence of nitrites, formed from nitrate minerals by heating and release of oxygen. Ammonium-bearing minerals, like ammoniojarosite, appear less likely, since they should evolve some ammonia, at least, instead of NO.

KNO3 (between 550C and 750C) as well as NaNO3 (between 500C und 750C) form a quasi-equilibrium with the according nitites in the presence of oxygen:
CODE
2 NaNO3 <--> 2 NaNO2 + O2


Nitric oxide is known to form from NaNO3 together with FeSO4 and H2SO4:
CODE
2 NaNO2 + 2 FeSO4 + 3 H2SO4 --> Fe2(SO4)3 + 2 NaHSO4 + 2 H2O + 2 NO


This kind of reaction may prevent the release of N2 or NO2 after the removal or reaction of O2 with other compounds during the pyrolysis.
The presence of other iron compounds might catalyse the decomposition of nitrites, as well.

NaNO3 is invisible to CheMin:
"As a result of the transmission geometry and the presence of a Mylar or Kapton window between the sample and the detector, CheMin will only detect elements with an atomic number greater than 12 (Mg) in the periodic table."
Hence NaNO3 is the more likely nitrate candidate. A high abundance of (crystalline) KNO3 is ruled out.

H2O and SO2 evolved during the SAM analysis.
This is to be expected from the presence of jarosite as found by CheMin.
H2O and SO2, together with some of the released O2, may provide the H2SO4 for the above release of NO from NaNO2.

cmb_476051894min08850450000ch00113p1.csv
("The abundance of clay minerals was estimated ... at ~5 +/- 3 weight% of the total sample mass. In addition to the crystalline phases, a broad rise in background ... indicate that ~28 +/- 15 weight% of this sample consists of X-ray amorphous material.")
("column 2 lists the mineral abundances in weight percent")

MINERAL,PERCENT,ERROR
[NaAlSi3O8 to CaAl2Si2O8, Albite-Anorthite Series (Plagioclase feldspar)] PLAGIOCLASE,55.1,4.5
[(Ca,Na)(Mg,Fe++,Al,Fe+++,Ti)[(Si,Al)2O6]] AUGITE,2.6,0.6
[(Mg,Fe++,Ca)(Mg,Fe2+)Si2O6] PIGEONITE,12.7,2.6
[Mg2SiO4, Fosterite (Olivine group); Fe++2SiO4, Fayalite (Olivine group)] FE-FORSTERITE,2.0,1.3
[Fe++Fe+++2O4, Magnetite] MAGNETITE,6.8,1.0
[SiO2, Quartz] QUARTZ,1.5,0.6
[Fe2O3, Hematite] HEMATITE,7.4,1.1
[Fe++TiO3, Ilmenite] ILMENITE,0.9,0.4
[KFe+++3(SO4)2(OH)6, Jarosite] JAROSITE,6.8,0.8
[Ca2Ca3(PO4)3F, Apatite] APATITE,4.2,1.2

The observed HCl might have been provided by amorphous Cl-akaganeite (considered e.g. here).

The evolving H2S needs to be explained.
HCl or even H2O, reacts with sulfides to H2S.
Iron sulfides are among the more stable sulfides. Candidate iron sulfides would be nanocrystalline ("amorphous") FeS, or mackinawite, precursor precipitates for e.g. pyrite.

CheMin may not be able to identify "amorphous" FeS.
Besides reacting with acids to H2S, FeS could have been a precursor for amorphous Cl-akaganeite, jarosite (observed by CheMin), and the (amorphous) FeSO4 needed for the NO synthesis.

Traces of carbonates or organics may have provided the carbon for the evolving CO2, where organics appear more likely than carbonates in the acidic context.

Nitrate minerals may have formed photochemically from atmospheric nitrogen and soil minerals, possibly in the presence of catalysts.

Since FeS, as well as jarosite aren't very stable in a wet environment, my first idea for the formation of "Mojave 2" and "Telegraph Peak" would be a short-lived "salt lake" with nitrates and sulfates as "salts", the nitrates having undergone some transport and concentration. Akaganeite, jarosite, iron(II) sulfates may have formed mostly in-situ from "amorphous" FeS precipitated in the short-lived lake. For this, the lake should have beared H2S, e.g. from volcanism, and Fe ions from chemical weathering.
A longer-lived ("salty") lake or ocean would have needed a mechanism to seal the sediments before they could alter further. Therefore this latter option looks less plausible.
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Gerald
post Dec 4 2015, 06:33 PM
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Chemin reduced data (file cmb_479423416min09230450450ch00113p1.csv (Telegraph Peak drill sample) in this PDS directory says

QUOTE
MINERAL,PERCENT,ERROR
PLAGIOCLASE,38,3.5
K-FELDSPAR,5.9,1.1
AUGITE,2.1,0.5
PIGEONITE,7,1.3
ENSTATITE,2.8,1.1
MAGNETITE,10.9,0.7
QUARTZ,1.2,0.3
CRISTOBALITE,8.7,0.7
OPAL-CT,14.5,3
HEMATITE,1.6,0.5
ILMENITE,0.9,0.4
ANHYDRITE,0.5,0.2
BASSANITE,0.5,0.3
JAROSITE,2.4,0.5
APATITE,3,0.5


Interesting are Cristobalite and Opal-CT, together about 23% of the crystalline phase.
Together with quartz, it's more than 24% SiO2 of the crystalline phase.

The sample contained about 1/3 of x-ray amorphous material:
QUOTE
In addition to the crystalline phases, a broad rise in background is present and has been modeled using the program FULLPAT to indicate that ~34 +/- 12 weight% of this sample consists of X-ray amorphous material.
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Gerald
post Aug 2 2016, 12:29 PM
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The scoop sample analysis (cmb_507241145min12360521162ch00113p1) of "Namib Dune" (Gobabeb dune sample) revealed a high abundance of olivine:
QUOTE
...This table contains mineral abundances and analytical errors ... for the Gobabeb dune scoop sample...
In addition to the crystalline phases, a broad rise in background ... indicate that ~34 +/- 18 weight% of this sample consists of X-ray amorphous material...

QUOTE
MINERAL,PERCENT,ERROR
PLAGIOCLASE,35.8,1.8
OLIVINE,28,1.5
AUGITE,20.2,1.7
PIGEONITE,10.9,1.9
MAGNETITE,2.8,0.6
ANHYDRITE,1,0.3
QUARTZ,0.7,0.4
HEMATITE,0.5,0.3


Olivine is rather resistant to physical weathering, but weathers rapidly in the presence of liquid water.
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TheAnt
post Aug 7 2016, 09:14 AM
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Light coloured veins seen in the bedrock in images from Yellowknife Bay have turned out to be sulphates (as was already suspected).
More interestingly is that they might have formed as a lakebed dried out.
The sulphate material were probably gypsum according to a study done at the University of Leicester.
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Don1
post Aug 27 2016, 07:39 AM
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From the GSA meeting abstracts:

"THE INVESTIGATION OF CHLORATE AND PERCHLORATE/SAPONITE MIXTURES AS A POSSIBLE SOURCE OF OXYGEN AND CHLORINE DETECTED BY THE SAMPLE ANALYSIS AT MARS (SAM) INSTRUMENT IN GALE CRATER, MARS"

" ... Previous SAM analog laboratory analyses found that most pure perchlorates and chlorates release O2 and HCl at different temperatures than those observed in the SAM data. Subsequent studies examined the effects of perchlorate and chlorate mixtures with Gale Crater analog iron phases, which are known to catalyze oxychlorine decomposition...... Overall, mixtures of perchlorates or chlorates with saponite provide the first explanation for the high temperature HCl releases in addition to the oxygen releases observed in Gale Crater materials.''

My comment: chlorates are ClO3 and are closely related to perchlorates which are ClO4.


"STRATIGRAPHIC DEPENDENCE OF CHLORINE ISOTOPE VALUES IN GALE CRATER"
"Previous work revealed δ37Cl values in Gale crater that are exceptionally light and more variable than any other measured material in the solar system (Farley et al., 2016), observations tentatively attributed to the unusual behavior of Cl isotopes in oxychlorine compounds.....new data reveal a statistically significant correlation between stratigraphic height and δ37Cl....a monotonic relationship between elevation and δ37Cl is observed."

My comment: This is weird. They have no idea why this is happening.

"OFF-PLANET GEOCHRONOLOGY: ONGOING RESULTS OF RADIOMETRIC AND COSMOGENIC DATING ON MARS"
"...Our first dating attempt was undertaken on the Cumberland mudstone (Farley et al., 2013), yielding a K-Ar age of 4.21 0.35 (1σ) Ga, in good agreement with crater-density estimates of the age of the mudstone's likely source terranes of 3.5 to 4.1 Ga. A much younger (<2 Ga) and non-repeatable K-Ar age was obtained on the Windjana sandstone. We attribute this result to incomplete thermal extraction of 40Ar from the very Ar retentive phase sanidine..."
"The team is presently readying to deploy a two-step heating protocol that is designed to obtain a K-Ar date on jarosite in a mudstone called Mojave. "

My comment: It seems they have been having some trouble with their rock dating technique, which is probably why we haven't heard much about it in recent years. However there is another sample in the works, which aims to tell when Mars was making the sulfur mineral jarosite.

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marsophile
post Dec 17 2016, 12:53 AM
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https://agu.confex.com/agu/fm16/meetingapp.cgi/Paper/143915

I've been wondering about the "spike" of methane. I recall that after Curiosity landed, it released a large amount of methane that it had apparently carried with it from Florida on Earth.

Is it possible that the later spike was due to passing through an area where the cloud of methane that was released had partially persisted? How rapidly would the released cloud have dispersed to the very low normal background levels?
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