A total of four Martian samples, one surface and one subsurface sample at each of the two Viking landing sites, Chryse Planitia and Utopia Planitia, have been analyzed for organic compounds by a gas chromatograph‐mass spectrometer. In none of these experiments could organic material of Martian origin be detected at detection limits generally of the order of parts per billion and for a few substances closer to parts per million. The evolution of water and carbon dioxide, but not of other inorganic gases, was observed upon heating the sample to temperatures of up to 500°C. The absence of organic compounds seems to preclude their production on the planet at rates that exceed the rate of their destruction. It also makes it unlikely that living systems that behave in a manner similar to terrestrial biota exist, at least at the two Viking landing sites.

We have confirmed the discovery of N2 and 40Ar by the Entry Science Team, and we have also detected Ne, Kr, Xe, and the primordial isotopes of Ar. The noble gases exhibit an abundance pattern similar to that found in the terrestrial atmosphere and the primordial component of meteoritic gases. Xenon appears to be underabundant in comparison to the meteoritic ratio, as it is on earth. The isotopic ratios 15N/14N, 40Ar/36Ar, and 129Xe/132Xe are distinctly different from the terrestrial values, implying different evolutionary histories for volatiles on the two planets. The noble gas abundances indicate that at least 10 times the present atmospheric amount of N2 and 20 times the CO2 abundance were released by the planet during geologic time; the outgassing of a large amount of water must also have taken place. There is thus an explanation for the high surface pressure and abundance of water required at some early epoch to cut the dendritic channels observed on the Martian surface.

Two surface samples collected from the Chryse Planitia region of Mars were heated to temperatures up to 500 degrees C, and the volatiles that they evolved were analyzed with a gas chromatograph-mass spectrometer. Only water and carbon dioxide were detected. This implies that organic compounds have not accumulated to the extent that individual components could be detected at levels of a few parts in 10(9) by weight in our samples. Proposed mechanisms for the accumulation and destruction of organic compounds are discussed in the light of this limit.

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