**5. Conclusions**

**4.5 Possible existence of chlorophyll pigment-producing organisms on Mars**

After the analysis carried out at the pixel level, in order to find some trace of vegetal life, it has been obtained that the PPR index [14] has varied between �0,10 and 0,09 mol � mol�<sup>1</sup> of chlorophyll (**Figure 13**). It must be specified that on Earth, values between 0 and 0,1 mol � mol�<sup>1</sup> chlorophyll (both inclusive) correspond to

According to [29], Neoxanthin is a type of carotenoid and xanthophyll existing in some types of plants, and whose function is to protect the plant against photo-

It must be taken into account that, on Earth, the production of Neoxanthin by vegetables remains constant at temperatures of up to �20°C, easily achievable on Mars, while the production of Carotenoids and Beta-Carotenoids decreases at temperatures below 0°C. For this reason, there is a certain probability that organisms

After the bibliographic review carried out, and according to [30], one of the organisms that synthesizes Neoxanthin, and that may possibly be present on the Mars surface, are microalgae with a protected cell wall. These organisms can survive

It is known that microalgae proliferate on Earth in conditions of contamination of the aqueous environment, which can be found on Mars due to the existence of perchlorate salt. In the same way, and after the analysis of the spectral signatures, acidic water and turbid water have been found, so the existence of microalgae is

Given the possible existence of microalgae on Mars, the new CNDVI (Eq. (2)) was obtained, whose relationship with the PPR index is presented in **Figure 14**. As can be seen in **Figure 14**, relationship between both variables is quite good, so the idea of the possible existence of microalgae, or Neoxanthin-producing organisms,

that synthesize, mainly, Neoxanthin may exist on Mars surface.

in extreme conditions as long as they are adapted to the environment.

**surface**

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Neoxanthin.

reinforced.

**Figure 13.**

**90**

on Mars becomes more consistent.

*Relationship between the MSIM and the PPR index in study area.*

oxidative stress.

In this study, different novel aspects related to Meridiani Planum, as well as Opportunity, have been shown.

Logically, despite the fact that the results obtained are encouraging in many aspects, other hypotheses must be taken into account in order to complement not only this research work, but also all those that are carried out from this study.

However, we must pay attention to the well-known seasonal process of water mobility on Mars as a result of perchlorate salts, since a phenomenon similar to FVAT [31] can exist, due to which the transit of water and salt of perchlorate towards the surface is possible from certain environmental conditions of relative humidity, pressure, temperature, as well as a determined concentration level of perchlorate salt in the water, be it acidic or turbid.

During the present work, the presence of aqueous minerals has been corroborated, although it is true that the samples collected by Opportunity, as well as other rovers that are in operation on Mars, have sufficient reliability. In this regard, this study shows that the data obtained (from the 942 images analyzed) by the Viking Orbiter have the same reliability, especially as a result of the fact that they have made it possible to corroborate aspects, phenomena and situations that occurred on Mars, and that Opportunity, Spirit and Curiosity had demonstrated. A special mention should be made of Perseverance, whose data will allow us to advance our knowledge of the red planet.

Authors want to highlight, given that they have carried out the same study in the areas covered by Spirit and Curiosity, that the results obtained are similar, although in the area covered by Curiosity there is evidence of a lower amount of PPR. On the other hand, in the Gusev crater, area where Spirit is located, a spectral signature corresponding to saltwater has been found.

Finally, it must be emphasized the importance of new technologies, patented processes, as well as the development of new advanced calculation tools capable of jointly simulating all possible situations that may occur on any rocky planet or moon existing, since in this way the advancement of knowledge in those worlds will be more efficient.

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