Did We Kill Life on Mars? Scientist Suggests Viking Landers May Have Destroyed Evidence of Martian Microbes
A startling hypothesis suggests that NASA may have inadvertently destroyed evidence of life on Mars nearly 50 years ago, during the Viking lander missions. As the search for extant or extinct life on the Red Planet intensifies – with the ambitious Mars Sample Return program slated to bring Martian samples to Earth in the early 2030s – a new perspective on decades-old data is gaining traction, raising the possibility that we already had a positive detection, only to eliminate it ourselves.
The Viking Project: A Pioneering, Yet Puzzling, Search for Life
Long before the Curiosity rover began its explorations, the Viking Project represented humanity’s first attempt to directly search for life on Mars. In the 1970s, two NASA landers not only transmitted the first images from the Martian surface but also conducted a series of biological experiments designed to detect signs of microbial activity in the Martian soil. The results, however, were far from conclusive, leaving scientists baffled for decades.
Initial experiments yielded ambiguous results. While some detected traces of chlorinated organics, these were largely dismissed as potential contaminants originating from Earth. One key experiment involved adding water containing nutrients and radioactive carbon to Martian soil samples. The premise was simple: if life existed, microorganisms would consume the nutrients and release the radioactive carbon as a detectable gas.
The first experiment did detect the radioactive gas, a promising sign. However, subsequent tests produced inconsistent results. Adding more nutrients and extending the incubation period failed to generate a corresponding increase in the radioactive gas, leading scientists to attribute the initial positive result to perchlorate, a chemical compound found in rocket fuel and fireworks, which could have interfered with the experiment.
A Radical New Hypothesis: Could Water Have Been the Problem?
Now, a new theory challenges this long-held assumption. Dirk Schulze-Makuch, a professor for planetary habitability and astrobiology at the Technical University Berlin, proposes that the addition of water itself may have been a fatal mistake, potentially extinguishing the very life the experiment was designed to find.
Schulze-Makuch draws parallels to life on Earth thriving in extremely arid environments, such as the Atacama Desert, where microorganisms exist entirely within salt rocks, extracting moisture directly from the air. “Pouring water on these microbes would kill them,” he explains, suggesting this could explain the lack of subsequent gas production. He vividly illustrates the point, stating, “When you’ve just been drowned by an alien robot, you don’t tend to be all that hungry.”
He further elaborates on the analogy, posing a thought experiment: “Imagine something similar happened to you [as a human]. For example, if there was an alien in a spaceship coming down to Earth and found you somewhere in the desert. Then they said ‘OK, look, that’s a human and it needs water,’ and puts you directly in the middle of the ocean. You wouldn’t like that, right? Even though that is what we are. We are water-filled bags, but too much water is a bad thing, and I think that’s what happened with the Viking life-detection experiments.” Schulze-Makuch shared this perspective with Space.com in 2024.
Hydrogen Peroxide and the Viking Results
Schulze-Makuch’s research extends beyond the water hypothesis. He has previously suggested that Martian life might utilize hydrogen peroxide within its cells, a unique adaptation that could also explain the Viking results. A 2007 study co-authored with Joop M. Houtkooper posited that hydrogen peroxide could provide a low freezing point, a source of oxygen, and hygroscopicity – all advantageous traits in the harsh Martian environment.
According to Schulze-Makuch, if Martian cells contained hydrogen peroxide, the heat generated by the gas chromatograph mass-spectrometer during sample analysis would have destroyed them. Furthermore, the hydrogen peroxide would have reacted with any organic molecules present, producing large amounts of carbon dioxide – precisely what the instrument detected.
“If we assume that indigenous Martian life might have adapted to its environment by incorporating hydrogen peroxide into its cells, this could explain the Viking results,” Schulze-Makuch wrote for BigThink.
A Lost Opportunity?
While the possibility remains highly speculative, the implications are profound. If Schulze-Makuch’s hypothesis proves correct, it would mean that humanity detected life on Mars nearly half a century ago, only to inadvertently destroy it. It’s a scenario reminiscent of cautionary tales about interfering with alien civilizations, a humbling reminder of the potential consequences of our explorations. The upcoming Mars Sample Return mission offers a renewed opportunity to finally answer the question of whether we are alone, and to avoid repeating the potential mistakes of the past.
An earlier version of this story was published in August 2023.
