It was back in 1976 when NASA’s Viking landers made their groundbreaking touchdown on Mars. Ever since, the findings from their life detection experiments have stirred up quite the buzz in the scientific circles, reopening the ongoing question: Is there, or was there, life on the Red Planet?
Fast-forward to today, and a new paper dives into those Viking results, aiming to shed more light on them.
Discovering Perchlorate
One of the biggest revelations since those 70’s experiments is the identification of high amounts of perchlorate on Mars. This discovery, along with other non-biological oxidants, provides a framework for interpreting the Viking data without needing to suggest life existed on Mars.
As the new research points out, “The detection of perchlorate on Mars, courtesy of the Phoenix mission, offers insights into the Viking landers’ findings.” It’s noted that the thermal breakdown of perchlorate could explain the absence of organic compounds detected by Viking instruments. Additionally, the build-up of hypochlorite from cosmic ray disintegration of perchlorate might clarify the reactions witnessed when nutrients were added to Martian soil during the Viking experiments.
Nonetheless, the authors clarify that “just because there is a non-biological explanation for the Viking results doesn’t mean Mars is devoid of life.”
Time to Review the Findings
The new paper, titled “The Viking Biology Experiments on Mars Revisited,” includes insights from prominent Mars experts Christopher McKay, Richard Quinn, and Carol Stoker, all aligned with NASA’s Ames Research Center stationed near San Francisco.
They propose that with Mars sample return missions on the horizon—and the potential for future life detection missions—it’s a good moment to rethink the implications of the Viking Biology Experiments. Their contention is that while a lot has changed since Viking landed, our grasp of the limits under which life can exist in cold, dry conditions hasn’t greatly shifted over the past 50 years.
In a chat with Space.com, Christopher McKay emphasized, “We’re not saying Viking completely rules out life on Mars, but also, we’re not claiming it definitively means life exists there, either.” McKay reiterates that what their findings highlight is the presence of perchlorate and various oxidants, which the Viking biology tests responded to.
This indicates that data from Viking can’t justify health and safety protocols—or quarantine procedures for astronauts returning to Earth—assumed by default that Mars is lifeless.
Fresh Insights
In the published paper in the scientific journal Icarus, the research trio highlights the substantial updates provided by recent Mars missions. They underline that the groundbreaking finding from the Phoenix mission revealed that Martian soils contain about 0.5% perchlorate. This notably high concentration poses questions regarding the Viking data and its broader implications.
The authors explain that utilizing the perchlorate framework to conclude Viking did not detect life in Martian surface soils carries weight in discussions about sample return or astronaut safety during potential returns from Mars.
The researchers stress that due to the guidelines outlined in the Outer Space Treaty—preventing any detrimental changes to Earth’s environment from extraterrestrial materials —there is a dire need for further exploration into Martian soil chemistry and any potential for life continuing there.
Supporting the Search
In wrapping up their research, the team argues that while the perchlorate model doesn’t discount the existence of life on Mars, it also does not mean that looking for life—past or present—is a waste of time. They strongly advocate for continued evidence search in future Mars missions, targeting deposits of salt and polar ground ice as ripe areas of inquiry.
This important study has been published in the journal Icarus.
