50 Years After Viking 1: The Mission That Changed the Search for Life on Mars

For thousands of years, Mars has inspired myths, speculation and scientific curiosity. Fifty years ago today, humanity took a major step toward understanding our neighboring world when Viking 1 became the first spacecraft to successfully land and operate on the Martian surface.

From Martian Myths to Martian Reality

Long before spacecraft explored the Red Planet, astronomers could only speculate about what lay there. In the late 1800s, Giovanni Schiaparelli mapped faint linear features on Mars that he called canali, meaning channels. The word was later mistranslated as canals, fueling the now-famous belief that an intelligent civilization had engineered waterways across the Martian landscape. The myth was finally dispelled by NASA’s Mariner 4 flyby in 1965 which returned close-up images.

While the Mariner missions were a massive accomplishment, humanity would have to wait another decade before landing successfully on the red planet’s surface. This year, we celebrate the 50th anniversary of the Viking 1 landing, which occurred on July 20, 1976. (The Soviet Mars 3 lander did touch down in 1971, but contact was lost mere seconds later.)

The First Laboratory on Another World

Both orbiters carried cameras for global mapping, while the landers were equipped with instruments to analyze rocks, soil, weather and the chemistry of Mars’ surface, including the first experiments specifically designed to search for signs of life.

But Viking is remembered for more than its engineering. It was humanity's first serious attempt to answer one of our oldest questions: Are we alone?

What is perhaps most remarkable is that we not only placed the first successful landers on Mars, but those missions ran far longer than expected, setting a trend for many more Mars missions to follow. Viking 1 operated for over six Earth years and may have continued longer had a fault command not been sent.

A New Way to Think About Life

Viking 1 gathered soil samples and tested them, recorded atmospheric temperature readings across seasons, and even attempted to look for evidence of life. Most of Viking's life-detection results were interpreted as not supporting biological activity. One experiment, however, produced results consistent with metabolic activity, leading to a debate that continues today. While the accepted answer remains that life was unlikely to have been detected, more recent work has questioned whether the methods used in the experiments may have harmed organisms unlike any life the experiments were designed to detect.

The debate surrounding Viking's life-detection experiments raised a bigger question: What exactly does life look like, and how should we search for it?

Mars today is very different from most environments on Earth -- but not all. Regions in the Arctic and Antarctic are used as analogs for Mars in testing and research, and studying organisms that thrive in some of Earth's most extreme environments could offer another explanation for the life-detection results.

In the decades since Viking landed, our understanding of life itself has changed dramatically. Many extremophiles - organisms that thrive in extreme environments - have been cataloged around the world. They have been found in dry, dark, salty, and acidic regions. There’s a pink alga that grows on snow, and even tardigrades can survive in the vacuum of space. Astrobiology as a field has expanded as a result of searching for life in stranger and stranger places, raising the possibility that life, if it ever existed on Mars, might survive in places once thought impossible.

A Legacy Beyond Mars

Viking's legacy went beyond the laboratory and into popular culture. As Ann Druyan recently wrote, the fading public interest in the Viking missions inspired Carl Sagan to rethink how scientists communicated with the public, eventually leading to the creation of the television series Cosmos. Science communication shifted from buzzwords and technological jargon to more thoughtful, evocative language, allowing everyone to feel the joy and wonder of the universe. That philosophy continues today at the SETI Institute, where understanding the universe is inseparable from helping people experience the wonder of exploration and discovery.

The Questions That Remain

Now, we take the presence of landers and rovers on Mars nearly for granted. From Pathfinder to Curiosity, Perseverance, and future missions, humanity’s work studying the Red Planet continues, due in part to the success and tenacity of Viking 1.

Viking 1 proved that we could land safely on another world. Just as importantly, it transformed Mars from a distant point of light into a place that could be explored, questioned and ultimately understood. Fifty years later, every rover, orbiter and future astronaut mission follows a path Viking helped chart. The questions remain as compelling as ever—and so does our determination to answer them.