Viking 1976: The Signal of Life on Mars Buried Under a Safe Conclusion

On July 20, 1976, Viking 1 landed in Chryse Planitia. On September 3, Viking 2 reached Utopia Planitia, about 6,400 kilometres away. Each lander carried biological experiments. One of them, Labeled Release, mixed Martian soil with a nutrient solution containing carbon-14 and measured radioactive gas. If microbes used the nutrients, they should release gas carrying the carbon label.

The first response came quickly, clearly, and more than once. When the team heated a soil sample to kill anything alive, the signal fell sharply. Gilbert Levin, the experiment’s principal investigator, read this as evidence of active microorganisms. NASA did not call it a discovery of life. Its gas-chromatograph mass spectrometer found no organic material, other tests did not agree, and the agency used the phrase “inconclusive.”