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The Atacama Desert in Chile hides in its center the driest spot on the planet. For the first time since there are records, it has been raining for three years in the hyper-arid heart of Atacama, and ephemeral lagoons have formed that have altered the ecological balance of the region. The study of the new Atacama lagoons makes it possible to better understand the astrobiological evolution of Mars.
The Atacama Desert, located between the Andes Mountains and the Pacific Ocean in northern Chile, is the driest and oldest desert on Earth. However, the rains are not uncommon in Atacama, because geographically the desert includes areas of cultivation and grazing, as well as coastal areas, which periodically generate news of flowers covering areas of Atacama. But the Atacama Desert has a hyper-arid heart in which at least 500 years ago no rain was recorded. The soils of this extremely dry desert center are very salty and rich in nitrates, sulphates and perchlorates. And although life is rare here, she has managed to prosper. Its inhabitants are micro-organisms capable of tolerating the high levels of desiccation and radiation that characterize the Atacama Desert during the last 15 million years.
During the 2015-2017 triennium, and for the first time since we have record rainfall rainfall The region has enjoyed a lot in the hyper-arid heart of Atacama. As a result, a set of hypersaline lagoons that persist for several months has formed for the first time in the region. In a study published today, a group of Spanish researchers coordinated by the Center for Astrobiology, Joint Center of the CSIC and INTA of Madrid, describes our research on the geochemistry and microbiology of lagoons .
Our group discovered that, contrary to what we could intuitively think, the inflow of water did not bring about a flowering of life in Atacama. On the contrary, the rains caused an enormous devastation in the microbial species that inhabited these places before the precipitations. The extinction range reaches 85%, due to the osmotic stress that caused the sudden abundance of water: indigenous microorganisms, perfectly adapted to live in extreme drought conditions and optimized for the Extracting little moisture from their environment, were unable to adapt to the new sudden flood conditions and died from excess water.
Our study of the effects of lagoon formation in the hyper-arid heart of the Atacama desert, probably another consequence of climate change The Earth, which suffers from it, is also used to draw an badogy with what It's gone on Mars at the moment its own climate change left it without liquid water, and helps explain the fate of a possible primordial Martian biosphere. Mars experienced a first geological period, the Noeico (there are between 4.5 and 3.5 billion years ago), during which it housed a lot of water on its surface; we know this because of the many preserved hydrogeological evidence, in the form of ubiquitous hydrated minerals on the surface, traces of rivers, lakes, deltas and perhaps even a hemispherical ocean in the northern plains. If life ever arose on Mars, it must have been during this first period, which coincides with the moment of the origin of life on Earth. Later, Mars lost its atmosphere and hydrosphere and became the dry and arid world we know today. But sometimes, during the hesperian period (between 3.5 and 3 billion years ago), large amounts of water dug its surface in the form of overflow cbads, the most important of the solar system . If there were still microbial communities resistant to the extreme drying process, they would have been subjected to osmotic stress processes similar to those described in Atacama. Therefore, the study of Atacama helps us to propose that the recurrence of liquid water on Mars could have contributed to the disappearance of Martian life, if it had existed, instead of representing an opportunity for the regrowth of Mars. a resilient microbiota. 19659002] Similarly, our work provides a coherent explanation of the negative results obtained by the Viking probes on the surface of Mars in the 70s of the last century, the only time we searched for life on another planet. . Viking experiments were performed by incubating samples of the Martian surface in aqueous solutions, with the aim of creating a favorable environment for potential Martian microorganisms to accelerate their metabolism and develop. However, our work suggests that any type of living being that could survive even today on Mars would be perfectly adapted to the extreme dryness of the Martian surface and would have died instantly by osmotic shock in Viking instruments. Future experiments in the search for life on Mars should take into account the devastating effects of the first rains over the centuries on the microbial communities that populate the hyper-arid heart of the Atacama Desert.
Source: El País
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