It appears Viking found organics after all! My head is spinning.

Here is a link to the abstract: http://www.agu.org/pubs/crossref/2010/2010JE003599.shtml

And here is a link to a detailed abstract for Europlanet 2009 (some of the same authors) that shows thermolysis results of soils from the Atacama desert:
http://meetingorganizer.copernicus.org/EPS.../EPSC2009-2.pdf

The authors did their theoretical calculations based on methane release and subsequent oxidation.
The "smoking gun"* is the detection of cholorohydrocarbons.



(*Bonus ironic trivia: Carbon tetrachloride (CCl4) was widely used as a fire extinguisher)

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This whole business was discussed in three subsequent publications:

Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars

Comment on “Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars” by Rafael Navarro-González et al

Reply to comment by Biemann and Bada on “Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars”

In the end the SAM data made it clear that the chloromethanes can be produced by pyrolysis of organic material and perchlorates on Mars.
The origin of the organic molecules (Martian or terrestrial contamination) can not be determined without other methods.

More is needed in the future and I hope for SAM doing that job.