‘Viking to Mars’: a journey back in time to the early days of the search for life on the Red Planet

By Salvador J. Ribas

The exploration of space is full of turning points that have redefined human knowledge of the cosmos. One of the most extraordinary milestones in the history of astrobiology and planetary exploration took place in July 1976, when NASA’s Viking 1 spacecraft became the first human-made artefact to land successfully on the surface of Mars and to operate there continuously.

I invite you to look back to understand how these missions marked the beginning of the modern era in the study of the Red Planet, by reviewing the historic impact and legacy of NASA’s Viking missions, which in July 1976 forever changed our view of Mars.

The great challenge of 1976: touching down on the Martian surface

In the mid-1970s, space technology faced a colossal challenge: traversing millions of kilometres of space, entering Mars’s tenuous atmosphere and safely depositing two scientific laboratories on its surface. The Viking 1 and Viking 2 probes (each comprising an orbiter and a lander) not only achieved this historic milestone, but also sent back the first high-resolution photographs of Mars’s desolate, reddish, and fascinating landscape.

The Vikings did not just photograph the landscape: they were equipped with complex biological experiments specifically designed to analyse the Martian soil in search of possible traces or signs of microbial life.

A scientific legacy that lives on with Perseverance and Curiosity

Although the results of the Viking missions’ biological experiments sparked an intense scientific debate that continues to this day, the mission provided fundamental data on the composition of the Martian atmosphere, its meteorology and its geology.

This first step laid the methodological and technological foundations for all subsequent missions, from the Spirit and Opportunity rovers to the current Curiosity and Perseverance missions, which continue to search for ancient evidence of habitability on the Martian surface.

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