MSL - SAM and CHEMIN, Discussion of the science/results from these instruments Options

[Gerald]

That's a good point!

So this is only allowed to happen within a quartz cup.
The challenge is then the appropriate heating of the tubes (made of nickel).
Similar precautions have to be taken during "designed" sample analyses.

[Don1]

I'm not very keen on any scenario which accumulates hydrochloric acid inside SAM. The samples are small and wouldn't produce much, but we need this instrument to last a long time.

For a future mission, I assume that a Raman spectrometer would be able to detect organics even in the presence of perchlorate. That is a totally different instrument from SAM, and doesn't depend on heating anything. I believe it gives a lot less information on the types of organic compounds present than SAM, but as a touch science instrument it would be much quicker to use.

[Gerald]

Thinking about how to design SAM experiments helps to better appreciate the job the SAM team is doing day by day. I can only leave the cost/benefit assessments and decisions to them.

The Raman approach (GORILA) has been proposed for the 2020 mission, see Mars 2020 Science Definition Team Final Report - Appendices, p.169.

[marsophile]

A couple more questions about potential instrument interactions.

If SAM could add water (not HCL) to a solid sample, would this possibly encourage the growth of additional crystals from the amorphous component that might be detected by CHEMIN?

After a pyrolyzed solid sample from SAM has been dumped, would it be feasible or useful to do an APXS analysis of the residue?

[Gerald]

I've been thinking at the same idea. H2O could turn some amorphous phases to crystals, or enrich minerals.
But unfortunately SAM samples cannot be dumped, but remain in the cups "forever". Only gas can be released to the environment (probably).
Would be nice to get the contents of cups somehow to CheMin or APXS. I'm not aware of such an option.

[Gerald]

Before we think about teaching SAM new tricks I think we should remember that there are a number of tricks that SAM was supposed to know which we have yet to see performed. For instance SAM hasn't done the O2 combustion experiment ...

Sol 557 - 559 Update:

... the SAM instrument has been doing overnight combustion experiments that require lots of power. The last one of these is planned early in the morning of Sol 558...

Now I'm curious, whether these experiments allowed to distinguish between carbonates and organics. If more CO2 has been released at lower temperatures at an excess of O2, this could indicate the presence of organic compounds.

[vikingmars]

Thanks so much Emily about the nice article found this morning in "Science" magazine ("Search for @@@@ Clears Another Hurdle") you "co-authored" with Richard Kerr and which summarizes very well the latest discoveries made by SAM about organic compounds.
Dixit :
"Caroline Freissinet and Daniel Glavin of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a score of fellow SAM team members reported that the latest results are persuasive. The new findings offer “compelling” evidence that some of the carbon-containing compounds SAM recently detected such as chlorinated methane, ethane, and propane came from organic matter in ancient martian rock, not from earthly contamination, Freissinet said. And Glavin said that other results are “a good indication” that some of the chlorobenzene is martian as well. Or as one of his slides pointedly put it: “The detection of reduced organic compounds in Martian near-surface samples is a signifi cant step.”
The implications for "@@@@" are interesting and because this is a forbidden topic on this Forum, I hope that you will give us more insights inside your nice blog in the TPS website...

Thanks so much in advance Emily !
VM (also supporting your much-appreciated work as Charter Member of TPS)

[serpens]

More than a touch of overkill there I think. The possible detection of organic material by SAM has nothing to do with astrobiology and the lack of accumulated organic material from infall has always been a bit of a head scratcher. To segregate from discussion elements of the SAM results which could have a significant effect on the interpretation of the depositional environment seems a little silly. I think forum members are well aware that organics simply refers to material containing carbon and hydrogen atoms and the moderators responsibility is to ensure that posts don't drift off topic. Just my five cents worth.

[diane]

More than a touch of overkill there I think. The possible detection of organic material by SAM has nothing to do with astrobiology and the lack of accumulated organic material from infall has always been a bit of a head scratcher. To segregate from discussion elements of the SAM results which could have a significant effect on the interpretation of the depositional environment seems a little silly.

Agreed. Organic chemistry is the chemistry of carbon. Biochemistry is the chemistry of things that crawl. As I understand it, Curiosity doesn't have sufficient instrumentation to cross that line. As long as we stay on chemistry, we should be fine.

[elakdawalla]

In his talk Glavin repeatedly referred to this work by Steve Benner that suggested benzenecarboxylates would be likely compounds left on Mars from the oxidation of meteoric organics, and that benzenecarboxylates were a possible precursor to the chlorobenzenes that SAM has detected.

[stone]

Benners work is one of the corner stones for all the people search for organics on Mars, but his carboxylic acids are a suggestion, there might be other compounds which are more stable. I know of no real good study on the survival rates and decomposition pathways of organic compounds so the real sink for organics is unknown. Benner suggested the aromatic carboxylic acids but he favored the mellitic acid which is not a good starting point to get to chlorobenzene. The to get from C6(COOH)6 to C6H5Cl needs at least 5H which are not available in the perchlorate mixture. The most likely way is oxidative chlorination of an C-H bond or an addition elimination reaction of a C-H bond, but for this you need a benzene or another not to oxidized aromatic compound.

The reactions in the gas phase during pyrolysis with oxygen and chlorine present make it hard to get the chemistry right and get the precursor molecule of the chlorobenzene right. Benzoic acid works fine, phenylalanine also works fine and the resulting compounds are always chlorobenzene and nothing else in the detection threshold. Ming did some experiments and could not find anything with melitic acid, so lets wait for Kimberley and Aeolis mons for better and richer samples.
[url="http://adsabs.harvard.edu/abs/2009LPI....40.2241M"]

[Don1]

These abstracts from LPSC give an update on the search for organics:
Chlorobenzene / Glavin

Chlorinated hydrocarbons / Freissinet

They are detecting chlorobenzene (6 carbon ring with a chlorine attached), chloropropanes (3 carbon chain with chlorine(s) attached) and chlorobutanes ( 4 carbon chain with chlorine(s) attached) which they think come from a martian source.

They see this in the Cumberland sample, but not in John Klein or Rocknest. These species are not produced when the contaminant MTBSTFA is reacted with perchlorate in the lab.

This result seems to me to be very tentative so it will be interesting to see if it survives peer review. Is the chemistry of these samples really well enough understood for MTBSTFA to be confidently ruled out as a precursor?

[stone]

Is the chemistry of these samples really well enough understood for MTBSTFA to be confidently ruled out as a precursor?

No, nobody ever did this before the SAM team started with putting MTBSTFA together with perchlorates. Here on earth every analytical chemist would wash away the perchlorates before starting to do derivatization. The problems you create if you don't if are so obvious. Most of the time you try to get ride of all inorganic salts and the inorganic matrix before you try to do experiments with the organic.

In N-(tert.-butyldimethylsilyl)- N-methyl-trifluoroacetamide the largest hydrocarbon fragment in the compound is the tert.-butyl group with 4 carbons while the next smaller fragment is the acetamide fragment which is only two carbons.

To get the two compounds chloropropanes (3 carbon chain with chlorine attached) and chlorobutanes ( 4 carbon chain with chlorine attached) might be possible from the tert.-butyl group but this reaction is not that straight forward because you have to lose one methyl group or you have to rearrange the chain.

The chlorobenzene is a little bit more complicated. Benzene is a standard pyrolysis product of many organic rich materials especially those not very volatile ones. To get it from the MTBSTFA is not absolute impossible, but unlikely. The clorination of the benzene is working very well with perchlorates so if you have a organic in the ground which releases benzene at higher temperatures you will end with considerable amounts of chlorobenzene.

The only place to get more information is the SAM testbed at Goddard and this is working all the time to get the the relevant experiments done.

[Gerald]

Ken Herkenhoff pointed to two papers about ongoing analysis of the SAM results.
The SAM team has added evidence for the Martian origin of the mostly chlorinated hydrocarbons by testing a couple of possible origins within the SAM instrument. But they didn't find a quantitatively convincing scenario for the latter.

The precursor compounds aren't pinned down yet.
One series of experiments tested, whether alanine (one of the most simple amino acids) of Martian origin could contribute to SAM's observation of volatiles.

[Gerald]

CheMin results of the Windjana drill sample, truncated and merged from the PDS files cmb_452848863min06240311330ch00111p1.*:

Mineral identifications, abundances and analytical errors for crystalline phases, other than clay minerals:

MINERAL,PERCENT,ERROR (estimated 2-sigma analytical errors)
PLAGIOCLASE,5.6,1.4
K-FELDSPAR,21.1,3.5
FORSTERITE,5.2,1.4
AUGITE,29,3.3
PIGEONITE,16.7,3.1
ENSTATITE,1,0.9
MAGNETITE,13.8,1.3
ANHYDRITE,1.4,1.1
BASSANITE,0.2,0.2
QUARTZ,0.2,0.2
HEMATITE,0.9,0.8
AKAGANEITE,2.5,1.2
PYRRHOTITE,1.3,0.8
ILMENITE,1.1,0.7

The mineral reported as K-feldspar is fit equally well as either sanidine or orthoclase.

The abundance of clay minerals was estimated ... at ~8.2 +/- 4 weight% of the total sample mass.

In addition to the crystalline phases ... ~20 +/- 11 weight% of this sample consists of X-ray amorphous material.