*4.2.2 Fractal morphometry: comparison of "rice grains" with various crystals and algae*

"Rice grains" images were enlarged 10 x by Paint Shop software in order to reach the final size of the sample.

Images were then loaded on paint.net software (https://www.getpaint.net/ download.html) in order to extract the specimen of interest. The extracted image was loaded on Digital Image Magnifier (Nikolao Strikos, https://sourceforge. net/projects/digitalimagemag/) in order to apply a Canny edge filter to the image, fixed Sigma, High and Low thresholds were used.

A negative of the skeletonized image was then obtained. The skeletonized image was loaded on Benoit Fractal Analysis software (https://www.trusoft-international. com/) in order to evaluate the Fractal Dimension of the image: Fractal dimension, D0, a measure of the space-filling properties of a structure, was calculated on the skeletonized images by the box-counting method. Briefly, each image was covered by nets of square boxes (from 5 to 100 pixels) and the amount of boxes containing any part of the outline was counted. A log–log graph was plotted on the side length of the square against the number of outline-containing squares, the slope of the

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**5. Results**

**Figure 3.**

*Life on Mars: Clues, Evidence or Proof? DOI: http://dx.doi.org/10.5772/intechopen.95531*

linear segment of the graph representing the local fractal dimension of the image (**Figure 3**). The linearity of the log log plot was assessed by the Pearson's correlation test, in order to demonstrate that the "rice grains" owns a fractal structure and fractal dimension may be performed. Variance analysis was used in order to compare fractal dimension of the Martian "rice grains" vs. the mineral (abiologic) gypsum or

*Top: From a Martian sample (rover image MAHLI, taken at Sol 809, "rice grains"), a single "rice grain" is enlarged, a canny filter is applied and the negative obtained. Bottom: the log log plot is a straight line (p < 0.01): the "rice grain" owns a fractal structure or self-similarity, its exponent is the fractal dimension.*

versus *Euglena viridis*, as a model of a complex (eukaryotic) microorganism.

Curiosity landed on a flat plain (the Bradbury landing site) to the North of Mount Sharp in August 2012. Subsequently, the rover travelled to reach the extensive strata of a lacustrine sedimentary sequence at the base of Mount Sharp (around Sol 750), detecting along this track a heterogeneous assemblage of sedimentary rocks, representing a fluvial-deltaic-lacustrine environment (the Yellowknife Bay

**5.1 Environmental and morphological evaluations.**

*5.1.1 Sedimentological context and possible biogenic structures*

#### **Figure 3.**

*Top: From a Martian sample (rover image MAHLI, taken at Sol 809, "rice grains"), a single "rice grain" is enlarged, a canny filter is applied and the negative obtained. Bottom: the log log plot is a straight line (p < 0.01): the "rice grain" owns a fractal structure or self-similarity, its exponent is the fractal dimension.*

linear segment of the graph representing the local fractal dimension of the image (**Figure 3**). The linearity of the log log plot was assessed by the Pearson's correlation test, in order to demonstrate that the "rice grains" owns a fractal structure and fractal dimension may be performed. Variance analysis was used in order to compare fractal dimension of the Martian "rice grains" vs. the mineral (abiologic) gypsum or versus *Euglena viridis*, as a model of a complex (eukaryotic) microorganism.
