Free Astronomy Magazine January-February 2021

6 JANUARY-FEBRUARY 2021 ASTRO PUBLISHING E SA’s Rosalind Franklin rover com- pletes environmental tests. F eatures of the Yungay site. (a) Diagram of the structure, composition and mean water activity of soil layers with depth. (b) General view of the sampled site. The red arrow marks the first pit from where samples were taken, seen in detail in (c). (d) Another pit dug 4 km away from the pit shown in (c). Pit dimensions are approximately 1 m length, 60 cm width and 60 cm depth. Both (c, d) show a clear color change between the lower wet clay-rich layer and the upper soil layers. [Nature Scientific Reports, A. Azua-Bustos et al.] two rovers will discover during their missions, researchers are experiment- ing on Earth with different scenarios in which smectites are involved. To date, diametrically opposite results regarding their ability to host and protect organic compounds and mi- croorganisms have been obtained. Let’s take for example two studies published in the last few months in Nature Scientific Reports . The first, carried out by a team led by Armando Azua-Bustos (Centro de Astrobiología, CSIC-INTA, Madrid), demonstrated that in the subsoil of a limited area of the arid core of the Atacama Desert, more precisely in the Yungay region, there are clay layers inhabited by microorganisms. That region is not only the driest place on Earth (less than 1 mm of annual rainfall) but it is also one of the most UV-exposed regions, as well as one of those regions with the most oxidized soil on Earth. For these reasons, it is considered a hab- itability analogue to conditions on Mars. It is no coincidence that the Yungay region was where experi- ments carried out on Mars by the Viking 1 and Viking 2 landers were reproduced in the first years of this century. Just as the Viking lander ex- periments results in many discus- sions and debates, the Yungan re-