Although Mars is a seemingly lifeless, cold and bone-dry world today, this has not always been the case. Some 4 billion years ago, scientists believe Mars resembled a young Earth and was home to a humid climate and flowing surface waters. If this was the case, it would not be farfetched to assume simple microbial life emerged in these primordial waters.
And there is a very small - though not entirely unlikely - chance some of that life has survived till today.
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