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Pay attention to what you want – even if you really need it. Take, for example, the Atacama Desert in Chile. Widely regarded as the driest place in the world, it rains an average of only 0.04 inches per year, and significant rainfall of about 1.5 inches (enough to leave shallow lagoons at short lifetime) once a century on average. Even such a quantity of water has been difficult to obtain, as climate data suggest that no significant rainfall has occurred in the last 500 years.
So you would think that would have been welcome when the desert had two storms in 2015 and 2017, not to mention a few much smaller rains in between. The Atacama should have – or at least could have – exploded, with what the astrobiologist Alberto Fairén of Cornell University has termed "majestic flowers". But, according to a new article by Fairén and his colleagues, published in the newspaper Scientific reportswhat followed was much more death than life. This has implications not only on the Earth, but also on arid planets like Mars.
Although Atacama is actually an almost barren place, some organisms manage to erase its existence. At least sixteen microbial species are known to populate the deep soils of long dry drought lakes, using nitrates – a saline form of nitric acid – as food. The most minimal wetness is from rainstorms and so-called altiplanic winter, between December and March, when relatively humid air sets in the Andes to the east.
The authors may write that microbes capable of feeding these ruthless conditions "are extremely suitable for extreme conditions of desiccation". This not only helps to survive with so little water, but also to resist radiation, to survive the intense ultraviolet energy of the sun bathing the desert.
After Atacama was bathed in real, honest water, things deteriorated, however. Not only did the expected flowers not bloom, but when Fairen and her colleagues investigated the transient salt lagoons left by the rains, they found that an average of 12 microbial soil species below had disappeared.
"The extinction event was massive," Fairen said in a statement accompanying the newspaper's publication. Nearly 87% of all lives have disappeared in some areas. The cause of death was what is known as "osmotic shock", when unicellular organisms absorb too much water through their outer membranes and burst. If a microbe can drown, that's how it happens. This also announces bad news potential for Mars.
For scientists studying hypothetical life on other worlds, Atacama was considered a good analog for the Martian environment. Like Atacama, Mars was once a very humid place. And like Atacama too, the planet has lost most of its water, although in the case of Mars, it has disappeared into space, while the Atacama has dried up due to climate change. The water of Mars lasted only about the first billion of its 4.5 billion years, but that would have been enough for the formation of at least a microbial life. Even when the planet has dried up, the sturdiest of these microbes may have survived, as they did with Atacama. Drying on Mars, however, was uneven, with occasional local flooding due to the emptying of underground aquifers or the rupture of canal walls.
"As a result," the authors wrote, "hypothetical local ecosystems … would have been exposed episodically to even greater osmotic constraints than those described here for Atacama's microorganisms. "The result: a microbial disappearance Martian also.
Humans visiting Mars could have a similar impact on all the lives that could remain there, at least if we try to do ground duty by giving it a little water. Indeed, our spaceship might have already done that. In 1976, Viking landers used aqueous solutions to test the life of Martian soil samples, looking for control gases that would signal biological processes. This may have been a serious mistake. Not only was no conclusive evidence of life found, but, Fairen and his colleagues wrote, applying water to the cells "would have caused their osmotic burst, then the destruction of organic molecules".
There is no evidence that this happened – but no evidence that it did not happen either. The search for life on Mars and other worlds will surely continue, and this should be the case. But ecosystems are ecosystems, whatever their planet, and if we have learned anything from those on Earth, it can be difficult to protect and extremely easy to destroy.
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