MVP ARCHIVE NASA | SEARCH FOR LIFE Phase 01-02 : Viking Biology / The first mission to conduct life detection experiments on Mars
The first mission to conduct life detection experiments on Mars
In 1976, NASA's Viking 1 and Viking 2 landed on Mars, conducting the first life detection experiments on the surface of an extraterrestrial planet in human history.
The purpose of the Viking program was not just to photograph Mars.
A major scientific goal was to directly collect Martian soil and investigate whether there were any signs of microbial-like life activity.
Viking Martian Soil Analysis
The Viking landers were equipped with biological experimental instruments to analyze Martian soil. The experiments included methods such as providing nutrients to the soil to observe reactions, checking for gas evolution, and observing reactions using light and carbon dioxide.
The results were not simple.
In some experiments, reactions suggestive of life activity were observed. In particular, in the Labeled Release experiment, when a nutrient solution was added to the Martian soil, radioactively labeled gas was released, leading to discussions about the possibility of microbial metabolism.
However, at the same time, another analytical instrument did not clearly detect the organic matter required for life.
Therefore, the Viking results could not be concluded as having 'discovered life.' NASA also states that while the Viking biological experiments discovered unexpected chemical reactions in the Martian soil, no clear evidence of living microorganisms was obtained in the vicinity of the landing sites.
The Importance of Ambiguity
This ambiguity is precisely the importance of Viking Biology.
Viking was not a failure.
Rather, it showed that Martian soil has chemical properties significantly different from Earth's soil, and it clarified that life exploration requires carefully distinguishing between 'life-like reactions' and 'abiotic chemical reactions.'
Later explorations revealed the presence of highly reactive substances such as perchlorates in Martian soil, and research to reinterpret the Viking results continues.
Even in recent studies, the Viking experimental results cannot be definitively concluded as evidence of life, and the possibility that they can be explained as chemical reactions on the Martian surface is being discussed.
ScienceDirect
Nevertheless, the questions left behind by Viking Biology have not disappeared.
Did life exist on Mars?
Is there a possibility that it still exists somewhere today?
What should we measure to search for life?
Viking was not the mission that provided the answer to Martian life exploration.
It was the mission where humanity first asked a question to the soil of another planet, and it was the starting point for life exploration that continues to current Mars Exploration, Astrobiology, and Mars Sample Return.