One of these experiments, called the Labeled Release (LR) experiment, was designed to detect microbial respiration in the Martian soil.
The LR experiment involved injecting a nutrient solution containing radioactive carbon into the soil samples and measuring the amount of radioactive gas released.
If the soil contained living organisms, they would consume the nutrients and emit gas with radioactive carbon, indicating their presence. The LR experiment detected a positive response, suggesting that some form of microbial life was metabolizing the nutrients and producing gas.
However, this result was not confirmed by other experiments that looked for organic molecules or changes in the soil chemistry. The scientific consensus at the time was that the LR experiment was detecting a chemical reaction, not a biological one, and that Mars was sterile.
But what if the LR experiment was right, and the other experiments were wrong? What if there was life on Mars, and we inadvertently killed it with our probes?
This is the provocative question that some researchers have been asking in recent years, based on new evidence and analysis. They argue that the Martian soil may contain a type of chemical compound called perchlorate, which is highly reactive and can destroy organic molecules when heated.
The problem is that the Viking probes used heat to sterilize their instruments and to analyze the soil samples, potentially destroying any traces of life before they could be detected.
Furthermore, they suggest that the LR experiment may have been detecting a type of extremophile organism that can survive in harsh conditions and use perchlorate as an energy source. Such organisms have been found on Earth in places like Antarctica and Chile’s Atacama Desert, which are similar to some Martian environments.
If this hypothesis is true, it would mean that we might have accidentally killed the only life we ever found on Mars nearly 50 years ago, and missed a historic opportunity to study it.
It would also raise ethical questions about how we should explore other worlds and protect them from contamination.
However, this hypothesis is not widely accepted by the scientific community, and there are many uncertainties and challenges in testing it. For one thing, perchlorate has not been definitively detected on Mars, only inferred from indirect measurements.
For another thing, the LR experiment results were not consistent across different locations and seasons, and could have been influenced by other factors such as humidity and temperature.
Moreover, there is no conclusive evidence that any organism can survive solely on perchlorate without any other source of carbon or nitrogen.
Therefore, while it is possible that we might have killed Martian life in 1976, it is far from certain.
The only way to know for sure is to send more missions to Mars and conduct more experiments with better instruments and protocols.
In fact, several missions are currently underway or planned for the near future, such as NASA’s Perseverance rover and ESA’s ExoMars rover, which aim to search for signs of past or present life on Mars.
Hopefully, these missions will shed more light on the mystery of Martian life and help us answer one of the most fundamental questions in science: Are we alone in the universe?