The rain fell in the Atacama desert in Chile for the first time in hundreds of years and caused a mass extinction.
It might seem natural to think that such rain would follow bloomed flowers and a new life. But an international team of planetary astrobiologists found that this precipitation killed most of the microbial life in the region.
"When the rains arrived at Atacama, we were expecting majestic flowers and deserts to go live. Instead, we learned the opposite, as we discovered that rainfall in the hyperbaric core of the Atacama desert caused a massive extinction of most indigenous microbial species there "Co-author Alberto Fairen, an astrobiologist, said in a statement.
Before the precipitation, which occurred in 2015, in this arid and Martian desert, scientists estimate that there were up to 16 different species of microbes. But after rain, there were only two to four species left. "The extinction event was huge," Fairen said.
"Our results demonstrate for the first time that suddenly providing large amounts of water to microorganisms – exquisitely adapted to extract the low humidity and elusive of the hyperiodos environments – will kill them from osmotic shock," said Fairen. Osmotic shock refers to a sudden arrival of water to a cell through its membrane. Flooding can literally cause bacteria to explode.
Scientists estimate that this recent flood was the first time the rain fell in Atacama in about 500 years. Despite this dry history, on March 25 and August 9, 2015 and on June 7, 2017, the rains shed. They suggested that these rains were caused by the changing climate over the Pacific Ocean, as climate models predict that such rains should only be passed there once per century.
The Atacama desert and its historical precipitation could have a parallel life on Mars, the researchers suggest. Like Atacama, the planet is dry today (the water is blocked in ice or under the ground), but it saw a catastrophic flood that interrupted extremely dry periods. Such events would be devastating until the microbial life, the researchers suggest it was still there.
Atacama microbes were also observed to feed the nitrate deposits that formed in the desert about 13 million years ago. Mars deposits have also been found and could provide another analogue to Mars.
In addition, researchers believe they could use these discoveries to continue exploring the experiments that the Viking spacecraft did in the seventies. The Martian solo was saturated with liquids in these experiments and knowing that nitrobated microbes can be damaged by water, these efforts are put in a new light.
This research is published in Scientific reports of nature