Opportunity Rover's image analysis: Microbialites on Mars?

The Mars Exploration Rover Opportunity investigated plains at Meridiani Planum, where laminated sedimentary rocks are present. The Opportunity rover's Athena morphological investigation shows microstructures organized in intertwined filaments of microspherules: a texture we have also found on samples of terrestrial (biogenic) stromatolites and other microbialites. We performed a quantitative image analysis to compare 45 microbialites images with 30 rover's ones (approximately 25,000/15,000 microstructures). Contours were extracted and morphometric indexes obtained: geometric and algorithmic complexities, entropy, tortuosity, minimum and maximum diameters. Terrestrial and Martian textures resulted multifractals. Mean values and confidence intervals from the Martian images overlapped perfectly with those from terrestrial samples. The probability of this occurring by chance was less than 1/28, p<0.004. Terrestrial abiogenic pseudostromatolites showed a simple fractal structure and different morphometric indexes than those of terrestrial biogenic stromatolite images or Martian images with a less ordered texture (p<0.001). Our work show the presumptive evidence of microbialites in the Martian outcroppings: i.e., the presence of unicellular life on the ancient Mars.