Mars Curiosity Photos Suggest Life May Have Existed on Red Planet

“A careful study of images taken by the NASA rover Curiosity has revealed intriguing similarities between ancient sedimentary rocks on Mars and structures shaped by microbes on Earth. The findings suggest, but do not prove, that life may have existed earlier on the Red Planet”:

Mars Curiosity Photos Suggest Life May Have Existed on Red Planet

Here is the pdf of the paper just published that proposed the hypothesis:

Life on Mars Hypothesis-Noffke-Astrobilogy-2015