Although there has never been anything close to conclusive evidence of the existence of life on Mars, it seems to be a favorite topic for many researchers. Nearly every month, it seems, some group of scientists finds evidence that “could” indicate life on Mars, either from long ago or still living today. Nonetheless, such reports are long on speculation and short on evidence.
Even if organic molecules are present on Mars, such molecules are not life itself and could have formed naturally.
Now, researchers are taking another look at data from the Phoenix Mars lander, concluding that compounds in the soil do, in fact, indicate conditions favorable to life—a reversal from the initial interpretation. (Read our coverage of that story in August 2008.)
The new appraisal is based on a different view of the chemical perchlorate, a powerful oxidant whose presence in Martian soil was thought to indicate an inhospitable environment. But a team led by Rafael Navarro-González of Mexico’s National Autonomous University is challenging that conclusion.
The scientists traveled to Chile’s Atacama Desert, with conditions thought to resemble those on Mars. They mixed perchlorate with soil samples and heated it, and discovered that the gases produced—mostly carbon dioxide, along with small amounts of chloromethane and dichloromethane—were the same discovered in tests conducted by the Viking Mars landers of the 1970s. More importantly, the reactions destroyed all organic compounds in the soil samples.
But how could that be interpreted favorably to speculation of life on Mars? Because the emissions from heating the soil samples match what the Viking landers’ tests produced, Navarro-González notes, “Our results suggest that not only organics, but also perchlorate, may have been present in the soil at both Viking landing sites.” In other words, perhaps the evidence of organic molecules in the soil were destroyed (“corrupted” into chloromethane and dichloromethane) in the tests.
Of course, even if organic molecules are present on Mars (contamination from landers confounding that question), such molecules are not life itself and could have formed naturally. Thus, the news changes nothing in the debate over whether Mars ever had life; it is merely another layer of speculation (one partially fueling the upcoming Curiosity Mars Science Laboratory rover).
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