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The Viking Labeled Release Experiment:

Current Status of Flight Data and Laboratory Simulations


G. V. .Levin and P. A. Straat

Biospherics Incorporated, Rockville, Maryland


            The Viking Labeled Release (LR) extraterrestrial life detection experiment onboard the Viking spacecraft on Mars has now (5/77) completed all radiorespirometric analyses of the Martian surface material.  Both landing sites provide remarkably similar evolution of radioactive gas upon addition of the 14C-labeled radioactive nutrients.  The active response is consistent with a microbiological response, as is the control.  However, possible non-biological explanations remain (1/77) and center around UV-induced soil activation, perhaps mediated by peroxides or superoxides.  Laboratory experiments with Mars analog soils indicate that treatment with various peroxides or radiation doses can cause a positive LR response.  The quantitative aspects of the laboratory simulation of active and control cycles will determine the acceptability of a chemical explanation of the observations on Mars.  Failing that. the biological explanation will gain strength.