When NASA's Viking 2 Lander touched down on Mars in 1976, one of its missions was to seek out evidence of life.
Using a variety of tests, the robot found an indication that there was some form of life on the planet, but further review dismissed the likelihood that the finding represented evidence of life. Researchers, who have since reanalyzed Viking 2's discovery, said they're almost 100 percent certain the results weren't a false positive.
While the rover didn't find any organic materials on the red planet, it did find evidence of metabolic activity, a byproduct of life. When NASA scientists analyzed the data, they initially wrote it off as a false positive caused by soil oxidation. According to a new study, however, the rover did discover life -- and it wouldn't take a manned mission to prove it.
The ultimate proof is to take a video of a Martian bacteria. They should send a microscope -- watch the bacteria move, Joseph Miller, lead researcher and associate professor of cell and neurobiology at the University of Southern California, told Discovery News. On the basis of what we've done so far, I'd say I'm 99 percent sure there's life there.
The rover conducted an experiment called Labeled Release, scooping up a bunch of Martian soil then dumping it in a sealed chamber with some radioactive nutrients. It then monitored the sample for signs of organisms metabolizing the solution and, surprisingly, detected metabolization shortly after.
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Since no other tests conducted found any evidence of life, NASA scientists at first called the experiment a false positive. When NASA scientists conducted the test again a few months later, there was no response, which piqued Miller's curiosity. If it was indeed a non-biological process causing the false positive, the finding should have been repeatable.
It is unclear why sample storage for 3-5 months at 10°C [50°F] in the dark would virtually destroy the response, researchers wrote.
Miller used a new technique that boils down the data the Viking 2 Lander sent back to Earth into a series of numbers that he then analyzed for complexity. Since biological life is much more complex than non-biological life, a high degree of complexity would indicate that the lander found life. Not only did the data indicate a high degree of complexity, but it also was very closely correlated to the complexity of microbial life on Earth.
We believe that these results provide considerable support for the conclusion that the Viking LR experiments did, indeed, detect extant microbial life on Mars, the researchers wrote.
Yet, not everyone is on board with Miller's findings. Critics are quick to point out that the technology the researchers used is still new and hasn't been determined to be able to differentiate biological processes from non-biological processes in an iron-clad way.
Ideally to use a technique on data from Mars one would want to show that the technique has been well calibrated and well established on Earth, Christopher McKay, a planetary scientist at NASA's Ames Research Center, told Discovery News. The need to do so is clear; on Mars we have no way to test the method, while on Earth we can.
While the scientists admitted their findings weren't concrete indication of life on Mars, the researchers said it not only provides evidence, but also it supports the value of further research and missions.
In November, NASA will launch its latest rover, called Curiosity, to search for life on the red planet, and then in 2016, the ExoMars Trace Gas Orbiter, which will study Mars' atmosphere, will be launched.
The International Journal of Aeronautical and Space Sciences published the study on Thursday.