According to a study, microorganisms have adapted to one of the most hostile environments on Earth, a sulphurous and acidic lake in Costa Rica considered an analogue of the ancient lakes of Mars.
One of the most hostile environments in the world
Located at 2300 meters above sea level, Laguna Caliente is one of the harshest environments on the planet. This very sulphurous and also very acidic lake displays pH values between -0.87 and 1.5, while its temperatures vary between 38°C and 90°C. It is of particular interest to exobiologists insofar as the mineral compositions seem similar to those recorded in 2004 on Mars by the rover Spirit, in the Gusev crater.
In other words, if the presence of life could be identified in this lake, then we could imagine that microorganisms may have also evolved on Mars several billion years ago under the same conditions. This is at least the basic idea that motivated Justin Wang and his team from the University of Colorado to go there to carry out analyzes in 2013. And indeed, there was a lot of life there. At the time, researchers had identified only one microbial species from the genus Acidiphilium. This type of bacteria is commonly found in acid mine drainages and hydrothermal systems.
In 2017, researchers returned after a series of eruptions to see if there had been any changes in diversity. They also studied in more detail the biochemical processes of these organisms.
Perfectly adapted organisms
This latest work, published in Frontiers in Astronomy and Space Science, shows that there was a little more biodiversity, but still a dominance acidiphilium bacteria. By sequencing the DNA of these organisms in the lake samples, the researchers also confirmed that these bacteria developed a wide variety of biochemical capacities facilitating their tolerance to extreme and dynamic conditions. These included pathways to create energy using sulphur, iron, arsenic, carbon fixation, as well as simple and complex sugars and bioplastic granules used as energy and fuel stores. carbon during times of stress.
So far, efforts to search for life on Mars have mostly focused on the beds of ancient streams. This new work suggests that more attention should be paid to ancient hot springs. “Our research provides a framework for how ‘terrestrial life’ might have existed in hydrothermal environments on Mars,” the authors note. “We hope our research will guide the conversation to prioritize finding signs of life in these environments.”
Incidentally, several of these sites can be found on the rim of Jezero Crater, where Perseverance is currently located. Maybe we should take a look?
