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The first great rain for centuries triggers the dullness of death in the deepest desert of the earth

A small, temporary lagoon in the Atacama desert caused by never-seen rain showers. Image: Carlos González-Silva After experiencing no meaningful…

A small, temporary lagoon in the Atacama desert caused by never-seen rain showers. Image: Carlos González-Silva

After experiencing no meaningful amounts of precipitation for at least 500 years, Chile’s Atacama desert finally becomes a bit of rain. Pretty unexpected, but these rains – instead of promoting life – exactly do the opposite.

Life on Earth can not exist without water, but for microbes that are highly adapted to dry conditions, the sudden introduction of excess water can be completely devastating. Such is the conclusion of a new paper published this week in Scientific Reports. Fascinating, these findings, although applicable to life on earth, may also apply to ancient Mars-a planet that may promote microbial life during its ancient past but at the same time susceptible to catastrophic floods.

Located in northern Chile, the Atacama Desert is one of the oldest and driest deserts on earth, and it has been 150 million years old. This desert has a hyperarid nucleus, with climate models predicting large rain events at a weak pace once per century. With that said, no significant precipitation had been recorded in this region for the past 500 years.

But things change in the Atacama desert – and not necessarily for the better.

An ephemeral Atacama lagoon. Image: Carlos González Silva

Since 2015, this desert has experienced three significant precipitation events-two years 2015 and a year 2017. Water from these rains gathered in super-lagoons, which remained for several months before they were released. In view of these earlier meteorological events, a team of astrologers from Cornell University and Spain’s Center for Astrobiology (AAB) visited Atacama to see how the rain and these hypersaline lagoons may have affected microbial life in this exceptionally dry place.

Water can be sharp in the Atacama desert, but that does not mean that the area can not support life. The ground there is a lot of salt, nitrates and sulphates. Organic compounds, not so much. It is said that a surprising amount of life is known to exist in the dry soil, organisms representing all three areas of life (bacteria, archaea and eukaryota). Extremophile microbes succeeded in evolving millions of years to find a niche in this extraordinary environment.

The recent rains, as the new study shows, did not appeal to these little vegetables. Instead of triggering a blossom of life, the rain has caused enormous devastation to the microbial species that have made the desert its homes for millennia.

“Here we show that the sudden and massive water supply in regions that have remained hyperarid for millions of years is detrimental to most surface microbial species that are exquisitely adapted to survive with mild amounts of liquid water and retard quickly by osmotic shock when the water suddenly becomes abundant, “the authors writes in the study.

With “osmotic shock”, researchers refer to a process where a sudden change in water concentration interferes with the normal function of a cell. It is basically a fine expression of cellular drowning.

Rain clouds are responsible for the rare rainfall in the Atacama Desert in June 2017. Image: A. Azua-Bustos et al., 2018 / Science Advances

The unusual rain, the authors say, is the result of changing climatic conditions across the Pacific Ocean. An extensive “cloud mass” came to the desert from the Pacific Ocean – an “unrivaled phenomenon,” the researchers said, which occurred twice in three years.

The resulting precipitation resulted in the widespread extinction of many native microbial species. The local eradication rate, according to the new study, reached as high as 85 percent in the hardest hit places. Extremophile organisms, habits in dry conditions, could not cope with the influx of water.

“The hyperdrical lands before the rain were inhabited by up to 16 different ancient microbears,” said Alberto G. Fairén, an astrobiologist at Cornell and co-author of the new study, in a statement. “After it rained, there were only two to four microbears found in the lagoons,” said Fairen, who is also a researcher at Centro de Astrobiología, Madrid. “The outburst event was massive.”

Among the microbes that survived the liquid attack was a newly identified bacterium called Halomonas .

This study shows that the already low microbial biodiversity found in these extreme environments becomes even smaller when water suddenly appears on stage and in large amounts.

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