Is microbial life on Mars possible?
There is life on Mars – almost certainly we have delivered terrestrial bacterial spores via probes. But is there indigenous life on Mars? In the May 2008 edition of Microbiology Today, Charles Cockell answers this hotly debated question:
It is not often apparent to microbiologists or members of the public that we know for certain that there has been life on Mars. Since the crash of the Soviet’s Mars 2 lander on the surface of the planet in 1971, a diversity of landed and crashed probes of various kinds, many of them not sterilized, have been delivered to the surface of Mars by the world’s space-faring nations. Only the Viking spacecraft, which landed in 1976, were completely heat sterilized to kill spores. Many of these spacecraft have delivered an inventory of spores found in spacecraft assembly facilities, including Bacillus species. A fascinating scientific question is whether there is, on the surface of Mars today, a viable spore hidden and shielded from Mars’ intense UV radiation in one of these various contraptions. There seems to no reason why a spore, cooled to Mars’ average temperature of –60 °C should not have survived since the 1970s. So on the face of it the answer to the question is likely to be ‘yes’.