Did Viking find life on Mars?

Did the Viking landers find life on Mars? Siddiqi’s chronicle says the results were suggestive, but inconclusive. Viking 1 collected four soil samples, and their combined biology results could be construed as a “weak positive” for life^[1].

The evidence did not line up neatly. The gas chromatograph test gave a negative result for organic compounds, despite being capable of detecting them when they made up more than 10–100 parts per billion of the soil^[2]. That finding weighed against a straightforward biological reading of the tests, though the stated detection threshold means it was not a test for every possible trace of organic material^[3].

Viking 2’s biology experiments produced similar results. Scientists proposed that ultraviolet radiation had created reactive substances in Martian soil that could produce some characteristics resembling those of living organisms in Earth soil^[4]. Siddiqi therefore leaves the question unresolved: the landers neither established life on Mars nor settled whether life had ever existed on its surface^[5].