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The Atacama Desert's First Rain In Centuries Had A Horrific Effect On Its Life

When rains fell in the Atacama Desert for the first time in centuries, scientists had expected to see life blossom. Instead, almost everything died.

The shocking discovery was published in the journal Scientific Reports this week. Found in northern Chile, the arid core of the Atacama Desert hadn’t experienced rain for the past 500 years. But three years ago, rain started to fall once again in the region.

A changing climate in the Pacific Ocean resulted in the desert’s arid core experiencing rain on March 25 and August 9, 2015, and it rained again on June 7, 2017. There was no evidence of rain in this region for the past 500 years, although climate models suggest it should occur every century.

The international team of astrobiologists who studied the region were “hoping for majestic blooms and deserts springing to life,” study co-author Alberto Fairén from Cornell University said in a statement. “Instead, we learned the contrary, as we found that rain in the hyperarid core of the Atacama Desert caused a massive extinction of most of the indigenous microbial species there."

Before the rain had fallen, this region of the Atacama had been home to 16 different ancient microbe species. But after the rain fell, just two to four species were still found to be surviving in the resultant lagoons.

The cause of the extinction event, believed to have been about 85 percent of life in the soil, was the “osmotic stress” caused by the arrival of water, Fairén said. In particular, these microbes were adapted to survive in extreme dryness. They were unable to adapt quickly enough to the sudden influx of water.

While it was bad news for the Atacama, the study may also represent bad news for life on Mars. We think Mars had a lot of water on its surface at some point between 4.5 and 3.5 billion years ago. But after losing its atmosphere and becoming dry, it likely experienced more intermittent wet periods from 3.5 to 3 billion years ago.

“If there were still microbial communities withstanding the process of extreme drying [on Mars], they would have been subjected to processes of osmotic stress similar to those we have studied in Atacama," said Fairén.

What they’re basically saying is that the reappearance of water could have wiped out life on Mars, if it was ever there. And that, well, could paint a whole different picture of what we know about life in the Solar System.

But it’s not all bad news. The team also found that large deposits of nitrates in the Atacama Desert were indicative of a lengthy dry period, while also acting as food for the microbes. And we’ve recently found nitrates on Mars – which could be hinting at a similar process there.

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