Thursday , June 8 2023

The driest place on Earth is so barren that the last rains have caused mass extinction


Lakes that formed in the heart of the Atacama desert during the rains.
Photo: © Carlos González Silva (Center for Astrobiology)

It is supposed that if it dries in an extremely dry place, water should act as a blessing of nature that leaves the earth to enjoy life, right? It turns out that reality is not always like fairy tales and rain in a place as dry as the desert of Atacama may be a curse.

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In June 2017 it was raining in the Atacama desert. Two years ago he found himself again. These are two exceptionally rare events and, when we say extremely rarely, we mention the fact that there are no rain records in Atacama over the last 500 years. Geological records indicate that the desert was an area anhydrous for the last 150 million years and that over the past 15 million years it has been a super-dry area. The driest desert on the planet is also the oldest.

Such a panorama makes Atacama a privileged place to study the ecosystem to try to explain how extreme ecosystems can exist on other planets. Although it is a hell on Earth, Atacama is not free of life. Over its barren land there are millions of bacteria and extreme microorganisms used to live in an extremely dry environment, with a high degree of salinity, and are constantly bombarded by high doses of ultraviolet radiation. In many ways, Atacama is a terrestrial analogue of Mars. The deposits of nitrate in the soil, for example, are very similar to those found in the Curiosity Rover.

Needless to say, astrobiologists have been enthusiastic to study how the Atacama environment has responded to the rains. "We expect to find a huge explosion of life," says astrobiologist Alberto González Fairén of the Spanish Center of Astrobiology (CAB). Instead, what they found was a true revelation.

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"Contrary to what one would expect, the contribution of water did not mean a flowering of life in Atacama but just the opposite," says Armando AzúaBustos, CAB researcher and first author of the study. "Rainfall has caused huge damage to the microbial species that lived in these areas before the rains." Even the small lakes formed after the rain managed to accommodate life. Researchers, the results of which have just been published in the journal Physical Scientific Reports, have not found cyanobacteria or micro-algae that could restart the ecosystem.

Understand the destiny of Mars

Rainbow was photographed for the first time in the heart of the Atacama desert.
Photo: © Carlos González Silva (Center for Astrobiology)

The analogy is particularly interesting because it gives us clues about what could happen on Mars. The red planet followed a cycle of drying water and rainfall very similar to that of Atacama. Alberto González Fairén explains:

Mars had a first geological period, Novice (between 4,500 and 3,500 million years ago), during which he was hiding a lot of water on his surface. We know of the amount of hydrogeological data that is retained, such as the traces of rivers, lakes and vouchers.

Had it ever occurred to Mars, it should have happened during this period, which coincided with the origin of life on Earth. Later Mars lost its atmosphere and its atmosphere, transforming the dry and dry world we know today.

But during the period of Esperion (between 3,500 and 3,000 million years), large quantities of water excavated its surface in the form of overflow channels. If there were still microbial communities that resisted the extreme drying process, they would have undergone osmotic stress procedures similar to those we studied at Atacama.

In other words, Mars died after the loss of his atmosphere, but he experienced another period of rain later. These precipitation, instead of helping to recover Mars's biosphere, might have destroyed it. [CAB y Nature]

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