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Antarctic nunataks, terrestrial analogues of early Mars?

For a long time, scientists have considered some Antarctic environments as environments with conditions analogous to those present in other celestial bodies in the Solar System, for example, the planet Mars or the icy moons Enceladus of Saturn and Europa of Jupiter. However, very few places have been considered environments analogous to those of those same celestial bodies in past times, despite the great information that this fact could provide us about the evolution of the habitats existing in them.

A multidisciplinary team of scientists from the Center for Astrobiology (CAB), dependent on the Higher Council for Scientific Research (CSIC) and the National Institute of Aerospace Technology (INTA), all these institutions in Spain, has analyzed different biomarkers detected in lithic substrates of the nunataks (an Inuit word that refers to the rocky outcropping of a mountain range that protrudes from a mass of glacial ice or snow) of Livingston Island, located in the South Shetland Islands of Antarctica. The study carried out has focused on the geomicrobiological analysis and on the characterization of the microbial communities present in the nunataks, and has recently been published in the academic journal Frontiers in Microbiology.

Thanks to the wide variety of techniques used (including the ‘LDChip’ immunoassay, a basic part of the SOLID instrument, designed at the CAB for participation in future space missions), it has been possible to recognize the nunataks for the first time. as analogous environments of early Mars. The climatic characteristics, especially the temperature and the incident and reflected ultraviolet radiation in these nunataks, much more extreme than in other nearby environments also devoid of ice, produce conditions similar to those found in other Antarctic places such as the classic McMurdo Dry Valleys. analogs of Martian environments.

Detail of the sampling in one of the studied nunataks. (Photo: MA Fernández-Martínez et al.)

In order to develop on the slopes of the nunataks, microbial communities have to find a compromise between an environment that is sufficiently protected from prevailing environmental conditions, but that houses a minimal amount of nutrients. Thus, the team has detected that the endolithic environments of the bedrock outcrops and the most superficial layers of the soil (up to 10 cm deep) are mostly colonized by microorganisms capable of generating protective structures, such as spores.

For his part, as Miguel Ángel Fernández-Martínez, CAB researcher and lead author of the study points out, “We discovered that the endolithic environments of disintegrated and loose rocks on the slopes of the nunataks presented a great diversity of microorganisms, less adapted to more extreme, but also more metabolically diverse and potentially active (although the techniques used in this study do not allow us to say whether they really are) ”.

This is because the environments that are generated inside these rocks are much less extreme than outside, with temperatures that can be up to 10 or even 15 degrees Celsius higher, and because the rocks can act as nutrient ‘traps’ and moisture, which microorganisms can use more easily. Fernández-Martínez comments that “Surprisingly, these variations between the substrates turned out to be much more important in structuring the microbial communities than could be other existing environmental gradients in the nunataks (for example, those due to altitude or slope – north or south – of the nunatak), thus making us reject the initial hypothesis ”.

“Thanks to these findings, we have been able to better understand what would be the strategies that the possible microorganisms that were present at the time of primitive Mars could adopt to survive, as well as learn what techniques would be most useful to detect them (such as the ‘LDChip’) and to expand the knowledge about what possible biomarkers we hope to find depending on the Martian substrate that we are going to analyze in future space missions ”, concludes Fernández-Martínez. (Source: CAB)

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