For several years, the planet Mars has attracted the interest of scientists around the world, particularly because of the presence of methane in its atmosphere. This molecule, although commonplace on Earth, is intriguing on the Red Planet because it could be the sign of biological activity. Seasonal fluctuations in methane observed by Mars rovers have suggested that biological processes could be to blame, but research to date has been inconclusive. On the other hand, the idea of life on Mars remains difficult to imagine, given the extreme conditions of the planet's surface. More recently, scientists have finally identified a specific location where conditions are more suitable for life.
The mystery of Martian methane: A key clue
The methane was first detected in the atmosphere of Mars in 2003, sparking intense scientific curiosity. On Earth, this molecule is in fact often associated with biological processes, notably the production of methane by microorganisms called methanogenswhich thrive in anoxic environments. From then on, the detection of methane on Mars immediately fueled the hypothesis that microscopic life forms could exist or have existed on the red planet. Indeed, terrestrial methanogens, which produce methane as a byproduct of their metabolism, could be a plausible source of this gas on Mars.
However, this biological interpretation is not the only possible explanation. Methane can also result from geological phenomenasuch as chemical reactions between water and minerals, a process known as serpentinisation. This reaction generates methane, but it does not require the presence of life. In addition, phenomena of volcanic activity or other geochemical processes could also explain the presence of methane in the Martian atmosphere.
The seasonality of these methane fluctuations, observed by Mars rovers and orbiting satellites, further adds to the mystery. If these variations are linked to biological processes, they could correspond to cycles of biological activity. However, no definitive answer has yet been provided, and this dilemma continues to fuel research on Mars.
The Earth Analogy: Searching for Life in Extreme Environments
Faced with this uncertainty, scientists have focused their studies on the planet's extreme environments, looking for analogues on Earth in places where life could arise under similar conditions, and where water and energy could be present. . These environments involve deep seabeds, icy deserts and even underground caves. In these inhospitable places, life has found creative ways to survive, including producing methane in conditions where oxygen is absent.
By studying these extreme habitats on Earth, scientists have begun to draw parallels with Mars, looking for similar places where life could thrive beneath the surface of the red planet. One of the most interesting of these analogues on Earth is the habitat of methanogens, which were found in deep cracks in the Earth's crust, subglacial lakes and salt basins deprived of oxygen. These habitats are similar to certain locations on Mars, and the search for methanogens in these extreme conditions has become a major goal.
Acidalia Planitia: The ideal site to search for life
After years of research and analysis, a specific location on Mars has emerged as the best candidate to harbor life: Acidalia Plainiaa vast plain located in the northern hemisphere of the planet. This region indeed presents particularly interesting geological characteristics, notably areas where liquid water could exist at depths ranging from 4.3 to 8.8 kilometers below the surface. The temperature at these depths is notably high enough to allow the presence of water, and the researchers estimated that the salinity, pH and availability of hydrogen in this region make it an ideal place to harbor methanogens, micro -methane producing organisms.
The combination of these factors therefore makes it the most promising place to detect life, even in the form of primitive microorganisms.
Next steps
Although conditions on Acidalia Planitia appear ideal for life, there is still much to be done before its presence can be confirmed. Currently, rovers cannot probe the depth necessary to reach environments suitable for subterranean life. Researchers are therefore banking on future missions that will allow drilling deeper beneath the surface of Mars. Scientists hope that future Mars missions, some of which include the possibility of returning samples to Earth, will offer more concrete answers.
In the meantime, the study of Martian conditions, coupled with knowledge gained about Earth's extreme environments, provides a solid framework to guide research. This advance is a key step in the quest for extraterrestrial life, and the hope of discovering signs of life on Mars remains stronger than ever.
