Could Mars Have Hosted Life? How NASA’s Viking Missions May Have Missed It

In all our explorations of Mars so far, no conclusive evidence of life has been found. However, in the 1970s, when the Viking landers became the first US mission to land on Mars, we may have been closer than we thought.

Astrobiologist Dirk Schulze-Makuch of the Technical University Berlin suggests that life may have been present in Martian soil samples, but our methods of detection may have accidentally destroyed the evidence. In an article for *Big Think* and a commentary in 'Nature Astronomy', Schulze-Makuch explores this possibility and argues that future missions should take the ecology of Mars into account when searching for life.

The Viking landers, which arrived on Mars in 1976, conducted experiments to detect biosignatures—molecules that could indicate the presence of life.

These were the only biological experiments conducted on Mars. One of the key experiments, the gas chromatograph-mass spectrometer (GCMS), found chlorinated organics.

At the time, this result was dismissed as contamination from human cleaning products, but we now know that chlorinated organics are native to Mars. Whether they are the result of biological or non-biological processes is still unclear.

In recent years, researchers have speculated that the Viking experiments may have accidentally destroyed evidence of life.

For example, the GCMS heated Martian soil samples to separate materials. This heat could have burned away any organic compounds present.

Similarly, two other experiments—the labeled release and pyrolytic release tests—suggested signs of metabolism and photosynthesis.

However, the results from these tests were unclear and contradictory.

These experiments injected liquid into Martian soil samples.

But life on Mars might be adapted to survive in extremely dry conditions.

As a result, the experiments could have harmed any microbial life that might have been present.

Schulze-Makuch argues that by adding water, we may have overwhelmed any dry-adapted microbes, much like "drowning" them.

Interestingly, the pyrolytic release experiment showed stronger signs of life when no water was added, suggesting that we may have overlooked or misinterpreted potential signs of life.

Schulze-Makuch suggests that Mars could host life adapted to dry conditions and possibly using hydrogen peroxide. He believes the Viking results support this idea. Instead of just looking for water, he proposes searching for hydrated salts, which could point to microbial life.

Nearly 50 years after the Viking missions, Schulze-Makuch argues it's time for a new mission focused on finding life on Mars. With our improved understanding of Mars, this mission could help answer the big question: is there life on Mars?