n a new paper published in the International Journal of Astrobiology, Vincenzo Rizzo from the National Research Center in Cosenza, Italy, asks a provocative question: Why are many scientists reluctant to accept the use of geological methods to identify biological processes on Mars, when those methods are commonly used on Earth?
He points to a case in Germany from 1908, when a scientist by the name of Ernst Kalkowsky proposed that layered mounds, columns, and sheet-like sedimentary rocks called stromatolites were of biological nature. His contemporaries did not believe him. But Kalkowsky was later proven correct, when it was recognized that stromatolites formed because biofilms—composed of cyanobacteria and other microorganisms—trapped sediments. Stromatolites are now known to be the oldest evidence for life on Earth, stretching back at least 3.5 billion years, and they still exist in some remote regions, such as Shark Bay, Australia.
In his paper Rizzo follows in Kalkowsky’s footsteps by analyzing images from the Spirit, Opportunity, and Curiosity rovers on Mars that indicate the presence of biotic macrostructures such as stromatolites. He suggests that if no non-biological explanation can be found, the images should be considered as possible candidates for Martian stromatolites. Rizzo shows many examples of structures that have an amazing resemblance to stromatolites on Earth.
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