The Viking Biological Investigation: Preliminary Results

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Science  01 Oct 1976:
Vol. 194, Issue 4260, pp. 99-105
DOI: 10.1126/science.194.4260.99


Three different types of biological experiments on samples of martian surface material ("soil") were conducted inside the Viking lander. In the carbon assimilation or pyrolytic release experiment, 14CO2 and 14CO were exposed to soil in the presence of light. A small amount of gas was found to be converted into organic material. Heat treatment of a duplicate sample prevented such conversion. In the gas exchange experiment, soil was first humidified (exposed to water vapor) for 6 sols and then wet with a complex aqueous solution of metabolites. The gas above the soil was monitored by gas chromatography. A substantial amount of O2 was detected in the first chromatogram taken 2.8 hours after humidification. Subsequent analyses revealed that significant increases in CO2 and only small changes in N2 had also occurred. In the labeled release experiment, soil was moistened with a solution containing several 14C-labeled organic compounds. A substantial evolution of radioactive gas was registered but did not occur with a duplicate heat-treated sample. Alternative chemical and biological interpretations are possible for these preliminary data. The experiments are still in process, and these results so far do not allow a decision regarding the existence of life on the plonet Mars.

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