Re-evaluating the 1976 Viking Mission Data: Did We Find Life on Mars Decades Ago?

A fresh look at data from NASA’s 1976 Viking missions is challenging the long-held scientific belief that Mars is a sterile wasteland. A provocative study recently featured in the journal Astrobiology posits that the positive findings from the Labeled Release (LR) experiment—previously dismissed as mere chemical artifacts or terrestrial contamination—might actually indicate the presence of indigenous microorganisms on the Red Planet.

The Viking program, which successfully landed Viking 1 on Chryse Planitia and Viking 2 on Utopia Planitia, represented humanity's first sophisticated attempt to detect extraterrestrial life directly. During the LR experiment, researchers observed a distinct biological signature: the release of radioactive 14CO2 following the introduction of labeled nutrients into Martian soil samples. However, this promising result was overshadowed when the Gas Chromatograph-Mass Spectrometer (GC-MS) failed to detect significant organic molecules. This discrepancy led the scientific community, famously summarized by project scientist Gerald Soffen as "no bodies, no life," to conclude that the LR results were non-biological.

The narrative began to shift in 2008 when the Phoenix lander discovered perchlorates within the Martian regolith. Experts such as Steven Benner from the Foundation for Applied Molecular Evolution have since highlighted that these salts are incredibly powerful oxidizers. When the Viking GC-MS heated soil samples to 500 degrees Celsius, the presence of perchlorates likely triggered a reaction that incinerated any organic matter present. In 2010, researcher Rafael Navarro-Gonzalez demonstrated that reacting organics with perchlorates produces chloromethane and dichloromethane—the exact chlorinated compounds that Viking scientists had incorrectly attributed to Earth-based cleaning solvents. Consequently, the apparent lack of organic material may have been a false negative caused by the very methods used to find it.

A new theoretical framework, dubbed the BARSOOM hypothesis (Bacterial Autotrophs that Respire with Stored Oxygen On Mars), offers a plausible survival strategy for these hypothetical Martian microbes. This model suggests that such organisms could utilize photosynthesis to generate oxygen and nutrients during the day, storing the oxygen to maintain respiration during the freezing Martian nights. This mechanism would explain the oxygen spikes observed in another Viking study, the Gas Exchange experiment. Furthermore, the initial surge and subsequent drop in the LR experiment's signal could be attributed to osmotic shock, where drought-resistant microbes were overwhelmed by the sudden influx of liquid water and nutrients.

This comprehensive re-evaluation of data collected nearly half a century ago carries significant weight for future planetary protection protocols and the design of upcoming life-detection missions. The realization that perchlorates can constitute up to 1% of the Martian soil by weight provides the missing piece of the puzzle, resolving the long-standing paradox of "metabolism without organics." As a result, the scientific community is now forced to confront the possibility that humanity may have discovered Martian life in 1976 but lacked the chemical context necessary to recognize its existence.