Forty years ago, two landers in a Martian experiment known as the Viking Labeled Release produced positive evidence for microbial life on the red planet.
Separated by 4,000 miles, both of the Viking landers yielded similar, repeatable results, prompting researchers to conclude – controversially – that Martian life had been detected.Though many have dismissed the findings as non-biological, the soil materials that would support this explanation have yet to be identified.
With the historical data considered, along with recent evidence of water, complex organic molecules, and methane on Mars, astrobiologists are now warning against ruling out the possibility of life, and instead argue that the evidence shows it ‘must be considered.’
In an article published to the journal Astrobiology, experts from Arizona State University, Tempe, and the National Institutes of Health, Bethesda say the evidence is ‘consistent with a biological explanation,’ suggesting microorganisms on Mars adapted and evolved to meet harsh environmental conditions.
The researchers delved into the findings from the 1976 Viking Labeled Release (LR) experiment, and evaluated the ‘non-biological hypotheses.’
In the LR experiments, samples of Martian soil from both landers were subjected to nutrient injection, preheating, and were even stored in the dark for roughly two months.
The results showed striking similarities to responses seen in terrestrial soil, including data from samples collected in California, Alaska, and Antarctica.
‘Each of these characteristics is reminiscent of responses by a compendium of terrestrial microorganism species, including the initial positive responses, the 160C and 50C heat controls, the reabsorption of evolved gas upon second injection of nutrient, and death from isolated long-term storage,’ the authors note.