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First rain in Atacama desert since 500 years caused a devastation among local microbial life – as it may have happened on Mars, too

The Atacama Desert. Photo: Carlos González Silva

The rains in the last three years are attributed to changing climate over the Pacific Ocean

The Atacama Desert, the driest and oldest desert on Earth, located in northern Chile, hides a hyper-arid core in which no rain has been recorded during the past 5 centuries. But this situation has changed in the last 3 years: for the first time, rainfall has been documented in the hyper-arid core of the Atacama and, contrary to what was expected, the water supply has caused a great devastation among local life.

These recent rains are attributed to changing climate over the Pacific Ocean.

The study was directed by researchers from the Center for Astrobiology (CAB), a mixed center of the Spanish National Research Council (CSIC) and the National Institute of Aerospace Technology (INTA).

„Contrary to what could be expected intuitively, the never-before-seen rainfall has not triggered a flowering of life in Atacama, but instead the rains have caused enormous devastation in the microbial species that inhabited the region before the heavy precipitations“, explains Dr. Alberto G. Fairén.

„The extinction range reaches 85%, as a result of the osmotic stress that has caused the sudden abundance of water: the autochthonous microorganisms, which were perfectly adapted to thrive under conditions of extreme dryness, have been unable to adapt to the new conditions of sudden flooding and have died from excess water,“ adds Fairén.

This study represents a great advance to understand the microbiology of extremely arid environments.

It also presents a new paradigm to decode the evolutionary path of a hypothetical early microbiota of Mars, since Mars is a hyper-arid planet that experienced catastrophic floods in ancient times.

„Mars had a first period, the Noachian (between 4.5 and 3.5 billion years ago), in which there was a lot of water on its surface,“ says Fairén. „We know this from the enormous amount of hydrogeological evidence still present in the Martian surface, in the form of ubiquitous hydrated minerals, traces of dried rivers and lakes, deltas, and perhaps a hemispheric ocean in the northern plains.“

Mars eventually lost its atmosphere and its hydrosphere, and became the dry and arid world we know today. „But at times during the Hesperian period (from 3.5 to 3 billion years ago), large volumes of water carved its surface in the form of outflow channels, the largest channels in the Solar System. If there were still microbial communities withstanding the process of extreme drying, they would have been subjected to processes of osmotic stress similar to those we have studied in Atacama“, Fairén details.

Earlier this year, Fairén and colleagues discovered that short-term wetter environments in early Mars, occurring sporadically in a generally hyperdry early planet, explains the observed martian mineralogy.

The study was published under the title of „Unprecedented rains decimate surface microbial communities in the hyperarid core of the Atacama Desert“ in Scientific Reports.

Source: Spanish National Research Council (CSIC)

(28.11.2018, USA: 11.28.2018)