In his fifth lecture, Carl Sagan takes a look at the design, launch and accomplishments of the Viking mission, a major chapter in the history of planetary exploration.
After Mariner 9s remote orbital inspection of Mars, the Viking program finally allowed scientists to study the Martian surface in detail. The photography of the terrain, the chemical analysis of the soil and testing for microbiological life yielded stunning, yet enigmatic results.
Results returned from the microbiology experiments gave signs consistent with life, however the search for organic molecules in the Martian soil turned up completely negative. The conflict between these results suggested either the presence of microbiological life or a non-biological, inorganic process occurring within the Martian soil.
Four decades later – following the success of subsequent Mars rovers – the question concerning life on Mars is one that still remains unanswered.