> Maybe there was life on Mars, but the main motivation to believe that right now is that many people have read about it in fantasy books. Life effectively beg

> Maybe there was life on Mars, but the main motivation to believe that right now is that many people have read about it in fantasy books. Life effectively began on Earth around 400 million years after it formed, and that's about the time that Mars' core cooled off and atmosphere got blown away. It seems that there was just enough time for life to start on Mars before it got snuffed out by the planetary geology of Mars and loss of its magnetosphere. If we ever find life on Mars, it's most certainly likely to be single-celled organisms.