Did NASA's Viking Landers destroy signs of life on Mars? A new hypothesis emerges

Taken by the Viking 1 lander shortly after it touched down on Mars, this image is the first photograph ever taken from the surface of Mars. (Image Credit: NASA)

Despite decades of exploration, no conclusive evidence of life has been found on Mars. However, in the 1970s, NASA’s Viking lander missions may have come tantalizingly close to uncovering life on the Red Planet, only to inadvertently destroy it, according to a new hypothesis.

Astronomer Dirk Schulze-Makuch from the Technical University of Berlin believes that experiments conducted during the Viking missions might have unintentionally harmed potential Martian microbes. Writing in Big Think in 2023 and later in Nature Astronomy in 2024, Schulze-Makuch speculated that the methods used to search for microbial life may have been fatally flawed.

The Viking 1 mission, which landed two spacecraft on Mars in 1976, aimed to detect life by adding water and nutrients to soil samples, assuming Martian life would need liquid water to survive, much like life on Earth. Early findings hinted at the possibility of microbial life, but after years of analysis, these results were largely dismissed as false positives.

Schulze-Makuch’s theory suggests that Martian microorganisms might thrive in extremely dry conditions, similar to certain microbes in Earth’s Atacama Desert, which rely on salts to extract moisture from the atmosphere. He posits that the Viking landers’ approach of introducing liquid water could have overwhelmed these potential microbes, killing them instead of revealing their presence.

This idea challenges the traditional NASA strategy of "following the water" in the search for extraterrestrial life. Schulze-Makuch argues that future missions should expand their focus to include hygroscopic salts—compounds that absorb atmospheric moisture—such as sodium chloride, the dominant salt on Mars. Similar mechanisms sustain certain salt-loving bacteria on Earth, even in briny environments.

Drawing a parallel, Schulze-Makuch cited an incident in the Atacama Desert where unexpected rain wiped out a significant portion of local bacteria because they couldn’t adapt to the sudden abundance of water.

Nearly five decades after the Viking missions, Schulze-Makuch advocates for renewed efforts to detect Martian life, leveraging advancements in technology and a deeper understanding of extreme environments. His hypothesis calls for a shift in approach, prioritizing conditions that align with Mars' unique ecology rather than imposing Earth-based assumptions.