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Published October 1, 1976 | metadata_only
Journal Article

The Viking Biological Investigation: Preliminary Results


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, ^(14)CO_2 and ^(14)CO 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 O_2 was detected in the first chromatogram taken 2.8 hours after humidification. Subsequent analyses revealed that significant increases in CO_2 and only small changes in N2 had also occurred. In the labeled release experiment, soil was moistened with a solution containing several ^(14)C-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 planet Mars.

Additional Information

© 1976 American Association for the Advancement of Science. Received 6 September 1976. We acknowledge the effective and tireless efforts of the engineers who are part of the Viking Biology Flight team and without whom these experiments could not have been accomplished. R. I. Gilje is chief engineer on this team, which also includes S. Loer, C. Reichwein, G. Bowman, and D. Buckendahl. Supported, in part, by NASA contracts NAS1-9690 (to G.V.L.), NAS1-12311 (to N.H.H.), NAS1-13422 (to J.S. H.), and by NASA grants NGR-05002308 (to N.H.H.) and NSG-7069 (to J.S.H .). We also acknowledge the profound contribution to the Viking mission and particularly to the development of life detection concepts, of our former colleague and deputy team leader, Dr. Wolf Vishniac. His untimely accidental death in Antarctica in 1973 deprived us of his keen insight and inquiring mind at a crucial time in this study. The invaluable assistance of Dr. Richard S. Young in the preparation of this manuscript is also acknowledged.

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August 19, 2023
August 19, 2023