The dent in the O2 peak when the CO2 is released seam reasonable.

The amount of CO2 and O2 is not really deducible from the plots. It gives only the MS detector count numbers. The ionization ratio is very different for the small molecules. A little bit of oxygen can give you a large peak while the same amount (number) of CO2 gives you a weak signal. I have no clue about the ionization ratio of both species.

Yeah the 4th sample looks kosher. I was thinking along the lines of an error in labelling in the first plot identified by Emily as a press release image.

On EGU 2013, Monday, 08 April 2013, Press Conference 1, "Latest results from the Curiosity Mars Rover", John Grotzinger told:

see video stream, 03:50-04:00.

Here are some quotes from AGU 2013 abstracts on SAM:

Re organic compounds detected by SAM
"[Mars samples] afforded a number of chlorohydrocarbons including chloromethane, dichloromethane, trichloromethane, a chloromethylpropene, and chlorobenzene (1, 2). Some proportion of these compounds can be traced to instrument background from organic materials within the chromatographic columns, hydrocarbon traps and wet chemistry capability of SAM... (MTBSTFA) and dimethylformamide, compounds carried in SAM for chemical derivatization can react with gases released from the sediments to yield the C1 and C4 chlorohydrocarbons. However, we continue to explore the possibility that a portion of the C1 chlorohydrocarbons are derived from organic carbon compounds on Mars."

For completeness, here is a link to Emily's October 15th blog post concerning the SAM results presented at DPS 2013:
DPS 2013: Confusing Curiosity SAM results

My opinion is that SAM's organic detection capability is broken and probably won't get fixed unless the rover gets away from the perchlorates. All the organics being detected can be explained as the product of leaking MTBSTFA reagent reacting with Martian perchlorates. There seems to be little hope of a robust, convincing result on the Yellowknife Bay samples.

There is also this. Prior to launch the derivatization capability of the wet chemistry cells was touted as providing the solution to the problem of detecting organics in environments that contained perchlorate. However, the following abstract hints at a possible problem with samples that contain hydrated minerals:
"To enable a more accurate interpretation of the in situ derivatization GC-MS results that will be obtained by SAM, the lab experiments were performed as close as possible to the SAM flight instrument experimental conditions. Our first derivatization experiments display promising results, the laboratory system permitting an extraction and detection of several proteinogenic amino acids and carboxylic acids from Martian analog materials. Preliminary results show a lack of derivatized organic molecules in hydrated solid samples however, where the MTBSTFA reagent possibly reacts preferentially with the water from hydrated minerals (Stalport et al. 2012)."

Stalport et al. 2012 is online here. From the abstract "... However, the rapid reaction of MTBSTFA with water in several analog materials that contained high abundances of hydrated minerals, and the possible deactivation of derivatized compounds by iron oxides,...proved to be highly problematic for the direct extraction of organics using MTBSTFA".

For years, scientists have been talking about searching for Martian clays and the hope that they would offer a good environment for preserving organic compounds. If the wet chemistry capability on SAM doesn't work with clay minerals, then why wasn't that discovered a long time ago?

The wet chemistry was never intended to be of any use for trace levels of organics. Only 7 ovens are with derivatisation and the rest of ca 60 are only pyrolyis. Derrivatization is the silver bullet for amino acids. A. Buch should have some publications on that topic. If you have a normal Mars sample with trace levels you would never use one of the derivatization capsules. The pyrolysis is not a best method, but the best what you ever brought to Mars. The method will be used until pyrolysis would show you elevated levels of organics with some nitriles and some nitrogen compounds you know are amino acid derivates. The same sample would be filled into a derivatization oven and heated to 250°C to make a reaction. Then the whole stuff will be trapped in the hydrocarbon trap and then through the chiral column of the GC. With the MS to detect you can seperate most of the amino acids into ther enantiomeres and with a little luck you have an ee (enantiomeric excess). Case proven! Life on Mars.

This is the story I wait for.

The GC-MS onboard the Exomars rover for the 2018 launch still includes derivatization capsules, after the disturbing news from SAM.

MSL09 was developed in the time before the perchlorate was discovered in 2008. The way NASA is managing instruments, a strong change in the instrument was no longer possible at that time. So they had to life with the derivatization they had at that time. Not really true because they implemented the TMAH, which was nor baslined at that point. The clay minerals are a problem anyway. They are like a sandwich with the good stuff between the two layers, but it is hard to get the good stuff out from there. Some studies by P. Ehrenfreund showed that extraction techniques give bad yields and from my experience with pyrolysis of clay samples it is the same. Clays are a good thing to have because they preserve the organics in the layers, but they also hide them in a way.

Here on earth nearly nobody uses derivatization directly on soil. There are some strange humic acid researchers doing derivatization, but they try to dry the sample well and they need a lot of time to get things right. Here on earth you do extraction with acid and solvent and do the derivatization without the disturbing, interfering and reacting inorganic material. The SAM team did inovative and good things, but they were hit by this leak in one of the derivatization capsules.

The latest SAM results are complicated, so I'll just comment on the CO2 releases and the chances for organics.

The team makes a good case that the carbon in the CO2 comes from a Martian source. There is 50 times more CO2 than can be explained by combustion of the leaking reagents MTBSTFA/DMF. One possibility is that hydrochloric acid released from decomposing perchlorates is catalysing the decomposition of a Martian carbonate. The other possibility is that oxygen released from decomposing perchlorates is combusting a Martian organic.

If the CO2 is coming from an organic then there is a lot of organic here, maybe in the parts per thousand range. SAM can detect organics at an abundance as little as 1 part per billion (ppb), and organics have been detected in Martian meteorites at an abundance of 100 ppb.

The only organic molecules directly detected by SAM are some simple chlorinated hydrocarbons. The abundance of these declines when special measures are taken to drive the leaking reagents MTBSTFA/DMF out of the system.

When organic minerals like coal combust on earth, they typically produce a range of pollutants like nitrogen and sulfur oxides and unburned hydrocarbons in addition to CO2 and water. Both nitric and sulfur oxides are detected by SAM, but no organics other than chlorinated hydrocarbons are being seen.

The team seems to think that any martian organics are likely to be heavily degraded by the combination of radiation and perchlorates. The hope for the future seems to be on finding an environment that is better for preservation.

This is probably naive, but is there some way to trap the hydrochloric acid and then add it to an unheated sample? That might serve to identify carbonate if it is there.

I think there is a cold trap in the instrument which is used for concentrating organics, but there is no way to put anything back into the sample chamber.

The trap is filled with Tenax an organic material which is a good sorbent for organic material at low temperatures. HCl is not the best material for being adsorbed there. The tubing schematic is complicated I have too look it up again, but reintroducing material was never planed.

The total absence of any non-chlorinated hydrocarbons gives the impression that the overall principle of pyrolysis-GC-MS might be not the proper way to do the search for organics on mars. I feel very sorry for the SAM team that the perchlorates seem to be everywhere.

There is also a noble gas trap. But my knowledge is too limited to decide, whether they can/should be used (by skipping the scrubber) to trap HCl gas or liquid hydrochloric acid. Traps can be heated to release the contents. It's at least an interesting idea.
Emily's post will be a good introduction to SAM.

The fragile 1/16th tubing and the valves are not made to withstand HCl for several years at elevated temperatures needed for the gas flow. I hope they do not get any corrosion.

The perchlorate distribution may be patchy. John Klein and Cumberland were drilled in the same type of rock and they are only 3m apart. And yet the O2 abundance at Cumberland was nearly 8 times greater than at John Klein. There are other differences as well. The John Klein release had 2 peaks, and it started at lower temperatures than Cumberland, so there may be another oxygen source besides perchlorate.

Whatever is releasing the oxygen is not evenly distributed, so I'm hopeful that at some point the rover will get away from it.

Sam results

The perchlorates are very water soluble. So lets assume that they are there for billions of years. The water amount varies due to the change in obliquity. Additionally the rocks at the surface are weted and dried every day. With this cycle the perchlorate moves by Capillary effects. If the perchlorates are concentrated at the surface of the rock, because the internal salt concentration forces the perchlorate to the outside, the wind will erode the material away and you have a rock with low perchlorate concentration. If the rock is more like an ion exchanger and likes the perchlorate ions inside the concentration in that rock type might be high.

The problem is always that you need to find a juice rock with low perchlorate concentration. A juice rock with high perchlorate concentrations will give you CO2 and other unspecific molecules.

The worst thing for me is that the most interesting molecules are the ones which are oxidized much faster than the aromatic compounds. C-N bonds and C-O bonds weaken the structure for oxidation. So a sugar with C6H12O6 compared to cyclohexane C6H12 and benzene C6H6 will be the first molecule to end up as CO2. But this molecule would indicate a biochemistry while the other molecules do only indicate that there is organic material present.

So far I've only fringe ideas to overcome that obstacle, meaning to synthesize the necessary reagents like water or HCl from Martian soil. That's either extraordinarily difficult or not possible with SAM.
If it's possible to synthesize some water by dry destillation of a "large" sample or by accumulating some water by repeated experiments, and this water could be delivered back to a small sample, one could try to leach out perchlorates together with polar organic compouds. By heating, polar and non-polar compounds should burn up / evaporate in a different way from an untreated sample, showing the presence of polar organic compounds.
But I actually doubt, that this can be performed. Mainly because I suspect, that transporting trapped substances back to the ovens isn't foreseen.
Next question: Can ovens be kept under pressure to enable water to condense?

So, at the end, I think, they'll try a wet cup, if there is sufficient evidence for the presence of organics.

To get enough water for leaching seems unlikely.

There was a good idea and already some hardware development for the Urey instrument.
Subcritical water extraction followed by a sublimation step to get ride of the salts. (pre Phoenix so no perclorates)

http://www.geology.wisc.edu/astrobiology/d...ace_Sci_Rev.pdf
----Urey: Mars Organic and Oxidant Detector
http://astrobiology.berkeley.edu/PDFs_arti...reyAstrobio.pdf
---The Urey Instrument: An Advanced In Situ Organic and Oxidant Detector for Mars Exploration

The instrument was a good idea and would have been a good start for sample preparatuion. The Micro-Capillary Electrophoresis is not the best method I can think of but the extraction would benefit any Mars mission.

If you have another brilliant idea the MOMA pyrolysis GC-MS team is always searching for the perfect method to get rid of the perchlorates.