Its a great question – the more we learn about Mars the more it appears that it was quite earth-like a long time ago (before it lost its atmosphere).
There was clearly liquid water and the type of atmosphere that could sustain microbes at some point in Mars past so I think its possible that there WAS life on Mars. It seems that there are no signs of life at the moment, but this does raise the intriguing possibility that perhaps life started on Mars and then was transferred to earth by a meteorite…
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