The news – but also misunderstanding – about NASA’s press conference today is spreading. They did not find alien life in the sense of life of extraterrestrial origin. Nor did they find life that showed signs of having evolved independently of all other life on this planet. What they found was bacteria that had evolved to substitute arsenic for phosphorous and thus thrive in an arsenic-rich environment. This expands the definition of life and the range of compounds that it can consist of. But it is a further example of evolution at work, doing things more impressive than most of us imagined, rather than an example of life arising independently or any of the other things that some were speculating NASA might announce.
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