Reviewing the Data
With all the attention Mars has been getting lately, scientists have been revisiting data from past mission to the red planet. Data from the Viking landings show evidence of of water, organic molecules, and methane. This increase in the potential signs of ancient life on Mars prompted researchers Gilbert V. Levin from Arizona State University and Patricia Ann Straat from the US National Institutes of Health to reexamine data from NASA's 1976 Mars Viking landings.
The researchers found traces of ambiguous chemical signals (radioactive 14CO2 isotope) in Martian soil collected in 1976 by the Viking landers. They don't claim that the landers (whose locations were 6,500 km (4,000 miles) apart) definitively found life on Mars.
"[I]n the absence of a non-biological agent that satisfies all Viking findings, and in view of environmental evidence that Mars may well be able to support extant life, it seems prudent that the scientific community maintain biology as a viable explanation of the LR experimental results," the researchers say, going against the widely-accepted opinion that Viking labeled release (LR) experiment on soil collected by the landers didn't show signs biological processes.
An Unlikely Scenario
"Even if one is not convinced that the Viking results give strong evidence for life on Mars, this paper clearly shows that the possibility must be considered. We cannot rule out the biological explanation," said Chris McKay, NASA astrobiologist senior editor of Astrobiology that published the study.
It's true that recent studies reveal that Mars had large swaths of water. And we believe that, if the circumstances for life in other planets is similar to Earth, water can point to the existence of life. Yet, given that it water on Mars disappeared some 3 billion years ago, it is highly unlikely for the 1976 Viking landings to have found extant life.
Still, the researchers remain hopeful: "Life may therefore still exist, if only in a cryptobiotic state, subject to resuscitation whenever water becomes available."