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2018-11-12. Atacama Desert’s Unprecedented Rains Are Lethal to Microbes.

posted Nov 19, 2018, 12:46 PM by Alan Gould
By Katherine Kornei, Eos/AGU. [https://eos.org/articles/atacama-deserts-unprecedented-rains-are-lethal-to-microbes] For GSS A Changing Cosmos chapter 7. Excerpt: Chile’s Atacama Desert is the driest place on Earth. It receives just millimeters of rain each year, on average, and its parched conditions make it a commonly used stand-in for Mars. Last year, scientists working in the Atacama were astounded to find multiple lagoons of liquid water there—the ephemeral runoff from an unusual rain event. But the rainfall that created these ponds didn’t result in a bloom of life, the researchers found; it was actually lethal to the majority of microbes adapted to the extreme aridity of the Atacama. These findings have implications for future spacecraft missions that will collect samples from other planets: Incubating dry soil samples in aqueous solutions, as was done with the Viking landers on Mars in the 1970s, may have the inadvertent effect of killing microbial life. ...Azua-Bustos and his team hypothesized that the microbes were killed by osmotic stress after they absorbed water. “They burst like balloons,” he said. ...Not using water would represent a change from previous protocols. “The Viking experiments involved incubation of Mars soil samples in aqueous solutions,” said Fairén. The Viking landers used these solutions to determine whether any hypothetical microbes on Mars were consuming carbon-based compounds....