NASA's Viking I mission: A look back at the first spacecraft to land on Mars 46 years ago

NASA’s quest to find life on Mars is decades old as the agency made its first attempt to arrive on the red planet with the Mariner 4 mission in 1964. It was in 1971 when the first satellite was installed in the Martian orbit, however, NASA made its first landing on Mars with the Viking I mission on July 20, 1976. 

On August 21, NASA celebrated the 46th anniversary of the mission’s launch which paved way for the touchdown of five rovers in the years to come.

About the pioneering mission

Viking I was the first mission of the Viking Project which consisted of two large orbiters, each weighing 2,325 kilograms and each orbiter carried a lander, weighing 576 kilograms. While Viking 1 lifted off on August 21, 1975, Viking 2 was launched three weeks later on September 9, 1975. Nearly a year after its launch, the Viking I lander landed on July 20, 1976, on the western slope of Chryse Planitia of Mars whereas the Viking 2 lander settled down at Utopia Planitia on September 3, 1976. 

Following their touchdown, each of these landers conducted three biology experiments designed to look for possible signs of life. According to NASA, these experiments discovered unexpected chemical activity in the Martian soil, however, no evidence of signs of life was discovered. 

After analysing results from the lander's experiments, scientists concluded that the characteristic of Mars of self-sterilisation prevents the survival of living organisms. According to experts, this blockade in the formation of life was because of the combination of the sun's ultraviolet radiation, the extreme dryness, and oxidizing nature of the Martian soil.

Lifespan of the mission

Both the landers and their respective orbiters stood the test of time and exceeded their estimated lifespan. Expected to last just 90 days, the Viking I orbiter lasted for four years and completed 1,489 orbits of Mars before concluding its mission on August 7, 1980. On the other hand, the Viking II orbiter lasted until July 25, 1978.

NASA says that the landers were able to survive for so long due to their power source-- radioisotope thermoelectric generators. These devices make use of the electricity that is generated through the natural decay of plutonium. "That power source allowed long-term science investigations that otherwise would not have been possible", NASA said in a statement.

It was on April 11, 1980, when the Viking II lander made its first transmission to Earth whereas the first lander lasted a little longer and sent its last dataset on November 11, 1982.