The range of extinction in the microbial species that lived in the Atacama before the rains is 85%

Only a few types of bacteria continued to be active and play

Due to its resemblance, in Atacama it examines whether there is or there might have been life on Mars

extreme Science to search for other planets

they Say that water is life but for the microbes accustomed to subsist without it, the unexpected fall of rain has led to the death. Just check in the heart of the Atacama desert (chile), probably the driest place on Earth. The first significant rains of the record in 500 years have caused havoc in their microbial life, according to an international team led by Spanish scientists of the Centre of Astrobiology (CAB/CSIC-INTA). The results were presented this week in the journal Scientific Reports.

In this place extremely unwelcoming situated in the north of Chile it rains so little that your average annual rainfall is usually below four millimeters per square meter, compared to, for example, the 576 mm of precipitation average recorded Sevilla or 359 mm Santiago of Chile.

Despite its extreme aridity, during the so-called altiplanic winter, which takes place between December and march, the currents of damp air from the Andes lead sometimes fall a bit of snow. However, in the last three years, there have been three amazing episodes of weather in the heart hyperarid Atacama that have challenged its climate usual and that the authors of this study linked with the climate change: in 2015, it rained significantly on two occasions (25 march and 9 August). And June 7, 2017 there was a rainfall which, according to Alberto G. Fairén, a co-author of the study, “for the first time from which there are records, formed lagoons and ephemeral”.

Death by excess of water

After studying the microbiology of these lakes hypersaline found something unexpected: “Contrary to what you might expect intuitively, we have discovered that the water supply has not led to a flowering of the life in the Atacama. It has caused a huge devastation in the microbial species that inhabited these places before the rains,” says Fairén, a researcher of the CAB, through an e-mail.

Rainbow captured in the Atacama desert, CARLOS GONZALEZ SILVA

Only some bacteria, called Halomonas, continued to be active from the point of view of metabolic and remained capable of playing in those gaps that were formed with the water of rain, according to this study.

So, says Fairén, “the range of extinction was 85%, mainly due to osmotic stress”, that is to say, a situation of unbalance due to changes in the water supply. The most common in nature is that the osmotic stress is caused by the absence of water but in the Atacama, these alterations have taken place because of the abundance sudden rain: these organisms were perfectly adapted to live in conditions of extreme dryness and optimized to take full advantage of the very low humidity. In the face of new conditions, unexpected flooding, he says, “have not been able to adapt and have died by excess of water”.

Their results, says Fairén, have been amazing, especially taking in regard the conclusions of other recent studies carried out in this chilean desert. “Other groups had seen that the rains bring a flourishing of the life in the Atacama but their study was done in areas hiperáridas, where it tends to rain every decade more or less, and ours has been done in the heart hyperarid desert, the most of the dry Land, where there have never been any rainfall from 500 years ago. The response of the microorganisms that inhabit in one and another place after the rainy season has been totally different”, explains the scientist.

Mars on Earth

Atacama, a vast desert that occupies an area of 105,000 square kilometers, is one of the best laboratories in the open air for scientists interested in studying the habitability of Mars because of how similar they are. Its surface is very saline, rich in nitrates, sulfates and perchlorates and is extremely poor in organic substances. In addition, the radiation is very high. And despite this, there are organisms adapted to this environment so hostile.

therefore, since 2003, carried out there investigations that seek to better understand the mechanisms that make life possible and clarify what happened on the red planet, where it is between 4,500 and 3,500 million years ago there were large amounts of liquid water on its surface. Know thanks to tests hydrogeological that have been preserved in the form of minerals hydrated in the surface and traces of rivers, lakes and deltas and what they think could be an ocean.

After, the red planet was losing its atmosphere and its hydrosphere, to become the dry world that you have found the robotic vehicles that explore. However, between 3,500 and 3,000 million years ago, there were occasions in which large volumes of water had carved its surface forming channels and causing catastrophic flooding. The hypothesis of this team of scientists is that, if there were still communities of microbes are used to the dry climate end, these microbes martians would have suffered a stress similar to that have seen it now in the Atacama to the face of the sudden plenty of water.

therefore, as he argues Fairén, his work serves “to establish a parallel with what happened in Mars in the period in which it lost its liquid water, and helps to explain the fate of a possible biosphere martian primordial”.

Looking at the past, scientists know that the heart of the Atacama has been arid during the last 150 million years, and hyperarid since 15 million years ago. The great dryness of their environment has also made this desert one of the best places for astronomical observation. So, here we have installed some of the largest and most powerful telescopes in the world, as a SOUL, the Very Large Telescope (Very Large Telescope, VLT) and the Telescope Extremely Large (ELT), which is being built currently.

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