From Ernest Ager, High Peak, Derbyshire, UK
With the recent news of some possible signs of ancient life on the Martian surface, there will naturally follow the usual comments – that even if there were any life long ago, there won’t be any living now, due to the hostile surface conditions(20 September, p 12).
However, once life started on Earth, it quickly spread to an enormous range of habitats, such as deep underground. It can survive in the absence of light, without oxygen and by using chemical redox reactions as an energy source.
If we find that life did indeed start on Mars and was present for a reasonably long time, I would suggest that it is highly likely that it still exists somewhere there, possibly below the ancient seabeds. As the atmosphere was slowly lost and the planet cooled, life would gradually have migrated deeper and evolved to the new conditions.
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