**7. Further experimental observations for compelling evidence of life on Mars**

Will never be able to definitively prove the existence of life on the Red Planet? The search for definitively proving the presence of life on Mars is one of the outstanding scientific challenges of our time [69, 83, 84]. We have described in this paper how the Curiosity landed region was clearly demonstrated as a fluvialdeltaic-lacustrine environment [2]. There are strong evidences that the whole surface of early Mars was habitable and several biomarkers were found (including microbialite/stromatolite-like structures and *bona fide* microfossils). Orbital and rover data reveal fluvial valley networks, paleolake deposits, alluvial fans/deltas entering these lakes, clearly revealing sustained precipitation during the Noachian, Hesperian and Amazonian periods, since 4.5 to 0.9 Gy ago, when an extensive glacial event resurfaced the paleolakes themselves [85, 86].

Nevertheless we need complex approaches for conclusively establish the presence of life [58] (NASA MEPAG's program at http://mepag.jpl.nasa.gov/reports/ index.html), and, in particular, when tests need to be performed by rovers or landers in a planet hundred million kilometers far from Earth. E.g., we can recall the lot of papers supporting the presence of stromatolites on Mars by morphological approaches, as also here discussed.

**127**

grateful.

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

reach the goal.

**8. Conclusion**

**Acknowledgements**

The meaning of the possible presence of stromatolites on Mars is enormous. Stromatolites result from the activity of different microbial communities and not the product of a single microorganism, suggesting a real ecosystem on the planet if the presence of stromatolites should be definitively proved. But the morphology of stromatolites as indicator of biogenicity may be ambiguous, similar shapes can be produced by both abiotic and biotic processes [87]. In effect, geologists on Earth needs to study macro-, micro- and ultramicroscopic details of the putative stromatolites, as well as their geochemistry, Raman spectroscopy of their constituents, additional chemical, mineralogical (e.g. magnetite and pirite) and isotopic ratios analysis of redox-sensitive heavy elements (mainly of C, Fe, S, N, Mo, Cu, U, Ce), together which the sedimentological, stratigraphic and palaeoenvironmental context examined [69, 88, 89], to arrive at a reasonable conclusion about the biotic or abiotic origin of the hypothesized biostructures. Much more, the presence of carbonaceous matter (e.g., kerogen, bitumen, molecular biomarkers) in the same area needs to be evaluated, together which their isotopic compositions, drilling meters below the surface in order to collect organics that had no destroyed by the UV flux of the Sun in the present-day Mars. Analysis that involve the use of traditional tested technology, as well new experimental and miniaturized biosensors for "in situ" testing. Not a simple work, so it's not strange that till today it was not possible to reach unanimous agreement among astrobiologists concerning the presence of life on the Red Planet. However, we feel that the next Mars missions by NASA and ESA, together which Mars Sample Return missions, should be able to

On Mars, at Gale Crater, a past environment favourable to life and for a broad span of geological time, has been discovered by various authors [1, 2, 49], as well as the occurrence of many micro, meso and macrostructures similar to terrestrial stromatolites, microbialites and algae [18, 50]. All these items are suggestive of possible biological parallels between Earth and Mars. In the present paper, we show morphological and morphometric analyses of the whitish millimetric shapes (we nicknamed "rice grains"), detected by the rover Curiosity at sols 809 and 880 (Mojave target) in the lacustrine Murray Formation (attributed to pseudomorph crystals of sulfate by previous Authors, [7]). Specimen which are incompatibile to Gypsum, Jarosite, or Feldspar crystals, but show a high shape affinity to life forms such as the Euglenoids. Hence, the microstructures investigated in this study, together with chemical and mineralogical converging data of the outcropping where they are embedded, suggest the possible existence of microbial, and/or little

We thank Filippo Barattolo, Professor at University of Naples (IT) and Joan Bucur, Professor at Department of Geology of Babes-Bolyai University (RO) for the support given in the analysis of algal-like biota and in excluding Dasycladales attribution. We are particularly grateful to Prof. Munneke, Professor at Friederich-Alexander University of North Bayern, for providing us the images of the terrestrial septate filaments shown on **Figure 15**. This work would not have been possible without NASA"s images and data availability, for which we are

more complex life forms, in the past history of Mars.

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

The meaning of the possible presence of stromatolites on Mars is enormous. Stromatolites result from the activity of different microbial communities and not the product of a single microorganism, suggesting a real ecosystem on the planet if the presence of stromatolites should be definitively proved. But the morphology of stromatolites as indicator of biogenicity may be ambiguous, similar shapes can be produced by both abiotic and biotic processes [87]. In effect, geologists on Earth needs to study macro-, micro- and ultramicroscopic details of the putative stromatolites, as well as their geochemistry, Raman spectroscopy of their constituents, additional chemical, mineralogical (e.g. magnetite and pirite) and isotopic ratios analysis of redox-sensitive heavy elements (mainly of C, Fe, S, N, Mo, Cu, U, Ce), together which the sedimentological, stratigraphic and palaeoenvironmental context examined [69, 88, 89], to arrive at a reasonable conclusion about the biotic or abiotic origin of the hypothesized biostructures. Much more, the presence of carbonaceous matter (e.g., kerogen, bitumen, molecular biomarkers) in the same area needs to be evaluated, together which their isotopic compositions, drilling meters below the surface in order to collect organics that had no destroyed by the UV flux of the Sun in the present-day Mars. Analysis that involve the use of traditional tested technology, as well new experimental and miniaturized biosensors for "in situ" testing. Not a simple work, so it's not strange that till today it was not possible to reach unanimous agreement among astrobiologists concerning the presence of life on the Red Planet. However, we feel that the next Mars missions by NASA and ESA, together which Mars Sample Return missions, should be able to reach the goal.
