#Scientists #discover #life #beneath #driest #desert #Earth
A remarkable discovery in the bone-dry Atacama Desert in Chile. There, researchers found microbes at a depth of more than 4 meters. It reveals that life finds its way even here – in the driest place on earth. And that could have important implications for our search for life on other planets, the researchers think.
This can be read in the magazine PNAS Nexus. For the study, the researchers traveled to the Yungay area: the driest spot in the otherwise extremely dry Atacama desert. Here the researchers drilled into the soil, to a depth of 4.2 meters. Soil samples were collected every 10 centimeters in the top 3 meters. And beyond 3 meters, the researchers took a soil sample every 30 centimeters. These samples were then transferred for analysis to the German research center GFZ (which stands for GeoResearch Center).
Intact cells
The laboratory then specifically looked for DNA from intact and possibly active cells. And the researchers found this, even in samples collected meters below the driest desert surface on Earth.
Lifeless
It was long thought that the extremely dry soil of the Atacama Desert supported no life at all. And at first glance that is really not a crazy thought. After all, it is – as mentioned – the driest place on earth; the desert often has to go without water for decades in a row. What also does not help is that the desert surface – partly due to its high altitude and an almost permanent lack of cloud cover – is exposed to a lot of UV radiation that is harmful to life. It should be clear: on paper the Atacama Desert is not very hospitable. And yet previous research has now shown that microbial life can be found in the desert soil. However, those previous studies mainly looked at the upper part of the soil – up to about 1 meter deep. In the new research, scientists have also looked much deeper for the first time.
In the top 80 centimeters of the soil, the researchers mainly found microbes belonging to the stem Firmicutes. But as the researchers probed deeper into the desert floor, the numbers increased Firmicutesbacteria. That’s not surprising; The deeper you go, the less water there is and the higher the salt concentration, the researchers say. And these are simply not pleasant conditions for many bacteria. And yet life was also found beyond a depth of 80 centimeters. At more than two meters depth, researchers even found a microbial community that turned out to be much more diverse than microbial societies near the surface. The microbial community found at a depth of more than 2 meters turned out to be located in a so-called debris fan. This is a fan-shaped deposit of sediments that, in this case, must have been left by a river thousands of years ago and later became buried under other sediments. “The discovery of this subterranean society, which thrives in rubble-fan sediments at depths of two meters and exhibits incredible diversity and ecological stability, challenges our current understanding of desert ecosystems,” concludes researcher Lucas Horstmann.
Water from plaster
In their study, the researchers suggest that the bacteria already colonized the river sediments about 19,000 years ago. In the thousands of years that followed, the debris fan – and with it the bacteria – became increasingly buried under other sediments. And in the end they had to survive in complete independence from the surface. It naturally raises the question of how the microbes achieved this. The researchers refer to the fact that gypsum can be found in the sediments surrounding the microbes. The plaster contains water and the microbes may use that water to survive, say the researchers, who actually expect that society extends much deeper than they were able to demonstrate in their study.
The research once again reveals that life can also find its way to the most extreme places on Earth. But it doesn’t stop there; the study may also have implications for our search for life on other planets. And in particular the search for life on Mars. According to researchers, there are quite a few similarities between the Atacama Desert and the red planet. For example, Mars (today) is also dry and the red planet is also lashed by UV radiation. What the new findings now show is that in theory this does not have to be an obstacle to the maintenance of possible Martian life. In theory, life could well have a chance of survival deeper in the soil. This idea is further supported by the fact that the Martian soil also has gypsum deposits. First of all, these deposits hint that the Martian surface harbored liquid water in the past – a requirement for the origin of life as we know it. But they also suggest that, if life forms ever emerged on Mars, some of them deep below the surface – aided by hydrous gypsum – may have found a habitable place on an otherwise apparently unlivable planet to this day.
