Rio Tinto's subsoil as a terrestrial analogue of Mars


Image: Photograph of the Rio Tinto (Huelva), where the reddish hue of its waters due to the presence of iron-rich minerals is appreciated. © CAB

The Centro de Astrobiología (CAB, CSIC-INTA), in collaboration with NASA, has been studying the Rio Tinto environment since 2014 as part of the Life-detection Mars Analog Project (LMAP). The purpose of these researches is to test instrumentation designed to collect samples from Mars in future space missions, such as the SOLID (Signs Of Life Detector) instrument, designed at CAB.

Searching for traces of life, present or past, on Mars is one of the great goals of current and future space exploration missions. In order to test the instrumentation designed for this purpose, scientists frequently turn to the so-called terrestrial analogues of Mars. These are extreme environments that we find on Earth and that, because of their characteristics (extreme aridity, high ultraviolet radiation, high salt content, extreme temperatures, etc.) bear some kind of similarity with certain regions of Mars.

One of these Martian analogues is placed in Spain, southwest of the Iberian Peninsula, in Huelva. It is the Rio Tinto basin, considered analogous to Mars because of the mineralogical composition of its lands that, by crossing the largest deposit of massive sulphides in the world (the Iberian Pyritistic Strip), has high content of sulfates and iron oxides. This composition gives its waters an extreme acidity (pH between 1.7 and 2.7. –Water for human consumption has a pH around 7-). Among the iron oxides that we can find in Rio Tinto is hematite, and among the sulfates we find jaroste. Both minerals were found on Mars by NASA's Opportunity rover. These are therefore minerals with great astrobiological relevance. On the one hand, because their presence suggests the existence of water in the past and, on the other, because as compounds rich in iron, they are considered good preservatives of organic matter and, therefore, of possible remains of life.

In 2017, the Centro de Astroibología, together with the NASA Ames Research Center in the USA, conducted in the area of the birth of the Rio Tinto the last campaign within the LMAP project, of which the data are still being analyzed today and draw new conclusions. Thus, a recent paper published in the journal Astrobiology, involving several CAB researchers, describes what this campaign consisted of and collects the results of the analyzed data.

LMAP-2017 consisted of a campaign in which, through an autonomous drill team, installed aboard a NASA platform (based on the landing pads of the InSight and Phoenix missions), a 1 meter deep drill was performed on the ground of Rio Tinto. The system collected soil samples at intervals 20 cm deep and transferred them to different analysis equipment. In addition, to check the fidelity of the robotic system, the researchers carried out a manual collection of samples in parallel and subsequently subjected both to the same analysis battery. 

As the article includes, on the one hand, the samples were analyzed in situ with the SOLID instrument (Signs Of LIfe Detector), a portable biomarker detector based on immunological compatibility against antibodies and which is being developed in the CAB. On the other hand, once in the laboratory, the collected samples were analyzed for lipids and DNA; so that the three types of biomarkers (immunological, lipid and genetic) were interpreted in context with mineralogy and geochemistry of the area. "They resulted in a widespread presence of microbial communities largely associated with abiotic variables, such as mineralogy," says Laura Sánchez-García, CAB researcher and lead author of the study. 

"The spatial heterogeneity that was observed highlights the relevance of considering more than one sampling point to achieve good local coverage and representativeness for future astrobiological missions on Mars," Sánchez-García explains. "The results further show that a Martian-like soil sample up to 1 meter deep can be acquired and transferred in a robotic and intelligent way, as well as retrieving molecular biomarkers of different nature," he adds.

The high lipid preservation potential and the high sensitivity of antibodies to detect biological remains makes both types of biomarkers critical components for the IceBreaker mission, proposed to seek molecular evidence of life in the icy subsurface of Mars.


Fuente: UCC-CAB

Fecha: 2020-01-30


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