*4.2.1 Euclidean morphometry: comparison of "rice grains" with various crystals and algae*

The purpose of this section was to investigate quantitatively the features referred by NASA as light toned lozenge-shaped microstructures (**Figure 2**). This investigation determined, using a series of metrics, including degree of dispersion, variability in lengths and widths, length/width ratio, fit of lengths to a log-normal distribution, fit of orientations to a rectangular distribution, and morphological analysis, the similarity between the "rice grains" and various abiotic mineral deposits and terrestrial life forms. In particular: images of Gypsum and Jarosite crystals, an image of Feldspar phenocrysts, and a population of terrestrial *Euglena viridis* (O. F. Müller) Ehrenberg, 1830, (**Table 2**) were observed. These images were analyzed using 'Image J' software developed by the National Institute of Health (NIH), Bethesda, USA [42–44].

Each image was magnified to clearly reveal the objects of interest. Images were manipulated using brightness, contrast, sharpening and edge detection to optimize the appearance of the objects and to establish their boundaries. A grid of squares was then superimposed over each image to establish a number of sample fields. Each of the "rice grains", with at least 50% of its area within a sample field, was measured. Various relative measures based on degree of variation, ratios, fit to various distributions and proportions exhibiting a specific morphology, were used because scale measures were not always available for all images or those that were quoted were unreliable.

The following data were obtained from each sample field containing "rice grains": (1) total number of profiles, (2) the maximum length of each profile in relative units, (3) the width of each profile taken at the midpoint, (4) the orientation of each profile, measured as the angle between the horizontal and a line drawn along the maximum length of the profile, (5) the proportion of the profiles which had a fusiform shape and (6) the proportion which exhibited a degree of flexibility or curvature relative to a straight line drawn connecting the two ends of the profile. A number of metrics based on the profiles were analyzed and compared: (1) spatial

#### **Figure 2.**

*A set of amplified image samplings (rover image MAHLI, taken at Sol 809) showing chaotically arranged whitish forms, many of which are bezel or fusiform-shaped bodies. Such structures were interpreted by NASA as lozenge-shaped crystals (report PIA 19077; central image). Samplings were obtained by using contrast adjustments of 40% (above) and 30% (below), and the more appropriate luminosity, case by case.*

pattern, i.e., whether the profiles were distributed at random, uniformly, or were clustered, (2) degree of variation in length and width, measured as the coefficient of variation (CV) (3) size frequency distribution of lengths, (4) size frequency

**105**

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

**Figure Section Type Sol Source** 4 A,B Terrestrial: Stromatolite — Web site

5 A′B′ Terrestrial: Microbiolites — Web site

6 A,D,F Mars: Filaments 871 Curiosity

2 All Mars: 'rice grains' 809 Curiosity 8 All Mars: 'rice grains' 880 Curiosity

morphologies

Epimastopora(f)

fragments(f)

filaments (f)

(f)

*viridis*

14 A,B,C Mars: Filaments 880 Curiosity

Cianobacters

septate bodies

2 Terrestrial: *Gymnocodium*

3 Terrestrial: *Euglena* 

L Terrestrial: Algae and

15 — Terrestrial: tubular

10 A,B,D,E Mars: 'conical bodies' (f) 1103 Opportunity

structures

structures

A Mars: Laminate

B Mars: Laminate

9 Up, Lw L Mars: Various

11 A,B,C,L,G Terrestrial: Dasyclad

12 1 Terrestrial: Stromatolite

Lw R Dasycladales-

C Mars: Concretions 767 Curiosity D Mars: Concretions 871 Curiosity E,F Mars: Concretions 758 Curiosity

B Mars: Filaments 758 Curiosity C,E Mars: Filaments 899 Curiosity G Mars: Filaments 598 + 715 Opportunity H,I Mars: Filaments 780 Curiosity

Up inset Terrestrial: *Euglena* — G. Bianciardi

C Terrestrial: Dasyclad (f) — Web site

D,E,F,H,I,M Mars: Shell fragments (f) 1273 Curiosity O,Q Mars 'rice grains' 880 Curiosity

4 Terrestrial: Gypsum — V. Rizzo 5 Terrestrial: Jarosite — (jarosite4138d, www.

6 Terrestrial: Feldspar — (1200px-granite-

D Mars: Filaments — Opportunity

890 Curiosity

810 Curiosity

880 Curiosity

— Web site

— Web site

— [41]

— G. Bianciardi

— A. Munneke

— Hong Hua

[63]

dakotamatrix.com)

phenocrysts, it.wikipedia. org)
