For nearly five decades, the search for life on Mars has been an enigma shrouded in both hope and mystery. While no conclusive evidence has been found to date, a recent theory by astrobiologist Dirk Schulze-Makuch of the Technical University of Berlin raises a provocative question: could early experiments by NASA’s Viking landers in 1976 have inadvertently destroyed Martian life?
Schulze-Makuch, writing in Nature Astronomy and Big Think, suggests that the methods used in the Viking experiments intended to detect biosignatures in Martian soil might have been harmful to any potential microorganisms on the red planet. This speculation underscores the importance of adapting future missions to the unique environmental conditions of Mars.
In 1976, NASA’s Viking 1 and Viking 2 landers made history as the first U.S. missions to land on Mars. Among their objectives was a suite of biological experiments designed to test Martian soil for signs of life.
One of these, the gas chromatograph-mass spectrometer (GCMS), detected chlorinated organics. At the time, these were dismissed as contamination from Earth-based cleaning products. Decades later, however, scientists recognized that these compounds are native to Mars, though their origin biological or non-biological remains uncertain.
Another experiment, the pyrolytic release, heated soil samples in search of organics. Subsequent analysis revealed that this heating process could have incinerated the very materials the test sought to identify.
Could Viking’s Methods Have Killed Martian Microbes?
Schulze-Makuch highlights the potential destructiveness of the Viking experiments, particularly the release experiments, which introduced liquid water to Martian soil. While life on Earth thrives with water, Mars is an exceptionally dry planet. Modern research shows that some microbes adapt to hyperarid conditions, and an influx of water could overwhelm and destroy them a process he likens to “drowning” desert-adapted organisms.
Interestingly, Schulze-Makuch points out that the dry control runs of the pyrolytic release experiments showed stronger signals for potential life than the runs with added water. This discrepancy suggests that Viking’s methods may not have been well-suited to detecting life adapted to Mars’ extreme dryness.
Time for a New Approach
Schulze-Makuch proposes a shift in strategy for future missions, moving beyond the long-standing NASA motto of “follow the water.” Instead, he advocates for focusing on hydrated and hygroscopic compounds, such as salts, which could harbor dry-adapted microbial life.
“Rather than drowning potential Martian microbes with water, we must design experiments that respect and adapt to Mars’ hyperarid conditions,” Schulze-Makuch argues.
The Viking experiments remain the only biological tests conducted on Mars to date. With modern knowledge of the Martian environment, Schulze-Makuch calls for a new mission dedicated solely to life detection, one equipped to avoid the potential pitfalls of past methods.
Nearly 50 years after the Viking landers’ groundbreaking mission, the search for life on Mars continues. The lessons learned from Viking and the possibility of missed opportunities offer a compelling case for designing future missions with a deeper understanding of Mars’ unique conditions.
As Schulze-Makuch concludes, “The time has come to revisit Mars with a fresh perspective and more advanced tools. We owe it to science and to ourselves to try again.” The full commentary is published in Nature Astronomy.
