The Viking Mars landers detect chemical signatures indicative of life | fr584's Blog

Tests performed on Martian soil samples by NASA's Viking landers hinted at chemical evidence of life. One experiment mixed soil with radioactive-carbon-labelled nutrients and then tested for the production of radioactive methane gas.

The test reported a positive result. The production of radioactive methane suggested that something in the soil was metabolising the nutrients and producing radioactive gas. But other experiments on board failed to find any evidence of life, so NASA declared the result a false positive.

Despite that, one of the original scientists - and others who have since re-analysed the data - still stand by the finding. They argue that the other experiments on board were ill-equipped to search for evidence of the organic molecules - a key indicator of life.