In 1975, NASA’s Viking program made a groundbreaking achievement when its twin landers successfully touched down on Mars, marking the first American spacecraft to reach the Martian surface. These missions were pivotal in the search for life beyond Earth, as the landers conducted a series of experiments aimed at detecting microbial life on the Red Planet. Over six years, the Viking landers analyzed Martian soil samples, attempting to uncover any signs of life. However, a new and controversial theory suggests that the very experiments designed to detect life may have inadvertently destroyed any potential Martian microbes.
Dirk Schulze-Makuch, an astrobiologist from Technische Universität Berlin, has raised concerns about the methods used during the Viking missions. In a recent commentary in Nature Astronomy, he proposed that the addition of liquid water to Martian soil samples may have been too disruptive for any microbes that might have existed. Mars is known for its extreme dryness, more arid than Earth’s Atacama Desert, and it is hypothesized that any potential life forms on the planet would be specially adapted to extract moisture from salts in the atmosphere. Introducing liquid water, Schulze-Makuch suggests, could have overwhelmed these microbes, leading to their destruction rather than detection.
The Viking program’s assumption that Martian life would require liquid water, similar to life on Earth, may have been a key flaw in its approach. The experiments involved adding water and nutrients to Martian soil and monitoring any metabolic reactions, hoping to find evidence of living organisms. While some initial signs of microbial activity were detected, these results were later dismissed as inconclusive. Schulze-Makuch argues that these reactions could have been evidence of life forms adapted to Mars’ extremely dry environment, but the addition of liquid water may have killed them before they could be properly studied.
To avoid repeating this mistake in future missions, Schulze-Makuch advocates for a different approach to life detection on Mars. Instead of focusing on the presence of liquid water, he proposes a “follow the salts” strategy. This would involve searching for organisms that might thrive in environments where moisture is absorbed from salt compounds, potentially offering a more accurate method of detecting life in Mars’ harsh conditions. By rethinking how we search for life, we may be better prepared to recognize the signs of Martian organisms that have adapted to survive in a radically different environment from Earth.