Although it’s not all that commonly known, an experiment conducted by NASA’s Viking Mars lander in 1976 really did come back positive for signs of life on Mars. The experiment produced not one but four separate positive results, each indicating microbial respiration and standing in stark contrast to the “control” samples captured by a different lander some 4,000 miles away. It seemed at the time that one of mankind’s most longstanding mysteries had been solved: we are not alone in the universe, and apparently, life is common enough to be found on two neighboring rocks in our own solar system.

But then a subsequent test, meant to confirm this mind-blowing revelation by identifying organic matter in the soil, came back negative. NASA quickly concluded that the first test, dubbed LR for “Labeled Release” tests, must have produced four false positives. Not only did they dismiss the four life-affirming tests out of hand, but in the four intervening decades since, they have never attempted to recreate the original tests. In fact, they’ve never even conducted similar testing again. Now, Gilbert V. Levin, who was the principal investigator assigned to the LR tests, has come out to contend that the tests conducted by the Viking lander on July 30, 1976 were proof positive of life on the Red Planet, and he’s got more evidence to back it up.

In a piece Levin penned for Scientific American, he lays out his argument, first pointing out that the test NASA so readily dismissed back in 1976 underwent a rigorous vetting process to ensure that it was both effective as a means to detect life and, more importantly, extremely reliable.

The Viking LR sought to detect and monitor ongoing metabolism, a very simple and fail-proof indicator of living microorganisms. Several thousand runs were made, both before and after Viking, with terrestrial soils and microbial cultures, both in the laboratory and in extreme natural environments. No false positive or false negative result was ever obtained. This strongly supports the reliability of the LR Mars data, even though their interpretation is debated,” Levin wrote.

Levin isn’t simply resting on the laurels of the tests he oversaw forty years ago, however. He also goes on to list a number of subsequent tests NASA has conducted that seem to support his assertion that, not only was life discovered on our nearest neighbor in 1976, but since then, NASA has been ignoring evidence that confirms that discovery. Levin’s suppositions don’t extend to intelligent life, but rather point to a number of test results and discoveries that support the idea of a hidden population of micro-organisms inhabiting the planet.

Some of his additional bits of evidence to support his assertion aren’t enough to suggest life on their own, but when coupled with the affirmative tests from Viking, Levin posits, they point to the idea that life is present. Some of that evidence includes:

• Surface water sufficient to sustain microorganisms was found on Mars by Viking, Pathfinder, Phoenix and Curiosity;
• Complex organics, have been reported on Mars by Curiosity’s scientists, possibly including kerogen, which could be of biological origin;
• The excess of carbon-13 over carbon-12 in the Martian atmosphere is indicative of biological activity, which prefers ingesting the latter;
• The Martian atmosphere is in disequilibrium: its CO₂ should long ago have been converted to CO by the sun’s UV light; thus the CO₂ is being regenerated, possibly by microorganisms as on Earth;
• Formaldehyde and ammonia, each possibly indicative of biology, are claimed to be in the Martian atmosphere;
• Large structures resembling terrestrial stromatolites (formed by microorganisms) were found by Curiosity; a statistical analysis of their complex features showed less than a 0.04 percent probability that the similarity was caused by chance alone;

In summary, we have: positive results from a widely-used microbiological test; supportive responses from strong and varied controls; duplication of the LR results at each of the two Viking sites; replication of the experiment at the two sites; and the failure over 43 years of any experiment or theory to provide a definitive nonbiological explanation of the Viking LR results,” Levin wrote.

Levin closes his argument by calling on NASA to include a LR experiment module on the forthcoming 2020 Mars lander, which currently does not contain any life-detection testing equipment. Levin posits that discovering life on other planets is one of NASA’s primary objectives, but thus far, they’ve done a poor job of exploring viable possibilities. Instead of looking for life, Levin argues, NASA has been looking for evidence of a habitat that supports life.

He also called on NASA to assign a panel of researchers and scientists to review and re-evaluate data collected on previous missions dating back to Viking. He argues that an objective review will conclude, as he has, that we already have proof of life on other planets… we’ve just been choosing to ignore it.