How Habitable Is Mars? A New View of the Viking Experiments

Almost 40 years ago, two NASA probes on the surface of Mars scooped the soil in search of signs of microbes. The results that came back from the twin Viking missions were, to say the least, ambiguous. The scientific literature contains decades of debate over what they found.

A new study took a bit of a different track. Rather than focusing on the question of life, the SETI Institute-lead study, which was carried out at NASA Ames and recently published in the journal Astrobiology, was more interested in defining the martian environment that the Vikings sampled. The results suggest the landers not only found evidence of perchlorate salts on the surface, but there also should be highly reactive related compounds that can decompose organic compounds at low temperatures and explain the results of the Viking biology experiments.

Was that environment habitable, however? Richard Quinn, who is a SETI Institute researcher with Ames' Planetary Systems Branch, says the more relevant question now is how well Mars can preserve evidence of ancient biosignatures, or chemical signs of life. This focus began to shift in 2009, he said, after published results showed NASA's Mars Phoenix mission detected perchlorates at the north pole.