Martian life: Discovered and destroyed?

Nearly half a century after NASA’s Viking landers searched for life on Mars, new analysis suggests their water-based experiments may have inadvertently killed microbes adapted to the planet's hyper-arid conditions, according to a German astrobiologist. His theory highlights the need to reconsider Earth-centric approaches in the search for extraterrestrial life, Kazinform News Agency reports.

Dirk Schulze-Makuch, an astrobiologist at Technische Universität Berlin, suggests that the Viking experiments, which added liquid water to Martian soil, could have been fatal to potential life forms uniquely adapted to Mars' extreme aridity.

In a commentary published in Nature, Schulze-Makuch explores the role of salts that draw moisture from the atmosphere, enabling survival in hyper-arid environments like Earth’s Atacama Desert. “In hyperarid environments, life can obtain water through salts that draw moisture from the atmosphere. These salts, then, should be a focus of searches for life on Mars. The experiments performed by NASA’s Viking landers may have accidentally killed Martian life by applying too much water,” he explains, suggesting the water-based experiments could have overwhelmed life forms finely tuned to extract moisture from their surroundings.

The Viking experiments in 1976 aimed to detect microbial life by adding water to Martian soil samples, but the results were inconclusive, leaving scientists divided for decades. Schulze-Makuch believes these methods may have been too Earth-centric.

“Now, nearly 50 years later, we can reexamine those experiments with a much better grasp of Mars' environment — its complexities — and how certain reactions could unfold there,” he said in an interview with Space.

There is, however, a silver lining to the debate. Schulze-Makuch emphasizes that modern knowledge of extremophiles, organisms that thrive in Earth's most inhospitable conditions, has reshaped how scientists interpret the Viking findings.

“We've also gained invaluable insights into extremophiles on Earth... that knowledge helps us interpret the Viking data with a new perspective,” he remarked.

Rather than solely “following the water,” Schulze-Makuch advocates a more targeted approach to future Mars missions. “If these inferences about organisms surviving in hyperarid Martian conditions are correct, then... we should in addition follow hydrated and hygroscopic compounds — salts — as a way to locate microbial life,” he writes. He points to regions like the Eastern Margaritifer Terra and the Southern Highlands, rich in NaCl-dominated salt rocks, as prime candidates for exploration.

With decades of scientific progress and refined strategies, Schulze-Makuch urges a renewed effort to detect life on Mars. “Nearly 50 years after the Viking biology experiments, it is time for another life detection mission — now that we have a much better understanding of the Martian environment.”