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

[Astro0]

ADMIN NOTE: Hi All, a new topic for the discussion of the science from the SAM and Chemin instruments.
There has been a very important amendment to Rule 1.3 which is explained here.
Please remember Rule 1.3 at all times when discussing matters in this section.

[Don1]

I think we're looking at a work in progress with the SAM results. They don't really have publication grade scientific results but they do have some very interesting data and hypotheses.

The most interesting is the detection of the chlorinated hydrocarbons, which are mostly chloromethanes. These showed up in Viking results on Mars, but were not seen in pre-flight tests of the Viking instrument. Chloromethanes are good solvents and cleaning agents. For instance CCl4 is used for dry cleaning. The Viking results were written off as contamination of the sample handling system by cleaning agents.

After the discovery of perchlorates, Chris McKay pointed out that a perchlorate containing soil would convert any organics it contained into chloromethanes on heating. He suggested that Viking did indeed detect Martian organics, but that the data was misinterpreted because the presence of perchlorate in the soil was unknown at the time.

I think the detection of chloromethanes by SAM puts a big question mark over the interpretations of Viking data, including the Viking conclusion that the Mars soil did not contain organics. The non-detection of organics by Viking was a very important result that drove the interpretation of some of the odd data produced by the other experiments.

However, SAM still has contamination issues of their own to sort out, including evidence that the rover is shedding plastic on the soil and hints that there might be a leak of organic reagent inside the instrument. People are also suggesting ways to make chloromethanes from purely inorganic reagents like CO2, water and perchlorate. So at this point there are viable hypotheses that explain the data without needing Martian organics. Only time will tell which is correct.

[serpens]

The most interesting is the detection of the chlorinated hydrocarbons, which are mostly chloromethanes. These showed up in Viking results on Mars, but were not seen in pre-flight tests of the Viking instrument.

As identified in the thesis linked by marsophile in post #44, (page 197) these chlorinated molecules were revealed in tests conducted on the spare flight instrument using the entire system. They would not have been seen in the pre flight oven checks or the flight blank tests and would only have contaminated a real run. Could additional chlorinated species have been produced as well as the contaminants? Certainly, and the SAM result indicates that maybe perhaps this could be so, but I think I want to see a heap more test results before drawing an conclusions or comparison to Viking results.

Re organic, none of us have problems with understanding homonyms in context , identical words with different meanings such as peer, rose, engaged etc. Lets all get over it.