NASA had high hopes of finding life on Mars when its twin Viking landers arrived on the red planet in 1976. But after a combined 10 years of activity on the Martian surface, neither lander returned any confirmed traces of life. Now, new research done on Viking's old data suggests that mission scientists missed something. There might be life on Mars after all.Both Viking landers carried a suite of instruments designed to look for life to Mars: a gas metabolism experiment tested the Martian soil for traces of atmospheric changes by metabolism; the "label release" experiment looked for radioactive carbon dioxide released by metabolism from organic material labeled by radioactive carbon; the pyrolytic release experiment searched for radioactive compounds by exposing the soil to radioactive carbon dioxide; and a mass spectrometer looked for the organic compounds that are known to be essential to life on Earth.The label release experiment was the only to yield positive results in support of the idea of life on Mars. But when the other experiments failed to back up these findings, many mission scientists dismissed the positive result, chalking it up to non-biological chemical reactions from the highly oxidizing soil conditions on Mars. The general consensus was that Viking found interesting geological history on Mars, but nothing biological.But the question of life remained open because an oxidative agent couldn't be found in the Martian soil. Then one was discovered in 2008; the Mars Phoenix Lander found perchlorate salts in 2008.After this find, scientists posited that organic compounds must have been present in the soil analyzed by both Viking 1 and 2. It was simply masked by the presence of perchlorate. Perchlorate salts destroy organics when heated and will produce chloromethane and dichloromethane, the same chlorine compounds both Viking landers found when they heated an analyzed the soil on Mars.The latest study of the label release data took a different approach. Researchers turned the data into sets of numbers and looked for complexity. The idea behind the approach was that looking at the data from a purely numerical standpoint would make it easier to spot the organic system since they're vastly more complicated than inorganic systems.Looking through the numeric data, neuropharmacologist and biologist Joseph Miller at the University of Southern California's Keck School of Medicine, found significant similarities between the Viking data and terrestrial biological data sets. In short, it looked to Miller like there was numeric evidence for life on Mars.Critics are quick to counter that this method hasn't been used enough to make such a grand, definitive claim about life on Mars. There isn't enough data of tests done on Earth to calibrate the results of the Viking tests.But Miller isn't too concerned, and instead looks at the new results as a step in the right direction. "On the basis of what we’ve done so far, I’d say I’m 99 percent sure there’s life there," he said. "If it looks like a microbe and acts like a microbe, then it probably is a microbe." The new data presents compelling, if uncertain, evidence in the ongoing search for life on Mars.
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