we now have the certainty that the basic ingredients of life were on its surface


Since 2012 the rover Curiosity is conducting investigations on the surface of Mars with the aim of better binding the climatic evolution of the Red Planet and the presence of water liquid in its past, but also to determine if Mars was ever able to sustain life.

If we know now many lakes and rivers they shaped the Martian landscape and this is his climate it was a favorable day for life, no direct biological trace has yet been found. Never mind, scientists continue to search, particularly by examining the presence of the elementary chemical building blocks needed for theemergency of life.

A quantity of organic carbon comparable to that of some terrestrial regions

In 2014, Curiosity then carried out a series of experiments to measure the fraction of carbon total organic matter contained in Martian rocks. After eight years of data analysis, the results are finally available in the journal PNAS and reveal that Martian rocks are relatively rich in organic carbon, which is one of the key components for setting chemical reactions in motion. prebiotics and potentially the construction of biological molecules.

It has been a while since scientists found traces of organic carbon on the red planet. But the assessment of its available quantity is an important parameter, which determines the development potential of life. And the results are quite surprising, as they show that Martian rocks contain a significant fraction of organic carbon, comparable to some regions on Earth. Admittedly, the values ​​are quite similar to those of hostile environments depleted of organic carbon (for the storage area terrestrial), as the Atacama Desert, but these are encouraging results for Mars. Because it shows that carbon was available in sufficient quantity for construction (hypothetical) organic moleculeswhich are the basis of all forms of life known to date.

Water, carbon, sources of energy … all the ingredients of life together

Total organic carbon is defined as the amount of bonded carbon atoms in organic molecules (usually composed of hydrogen atoms,oxygen and’nitrogen). If much of the organic carbon on Earth is biological in origin, it may have non-biological origins, in particular meteorites, volcanic activity or certain chemical reactions on the planet’s surface. The presence of organic carbon on Mars therefore in no way proves that life ever developed on this planet.

With water in the liquid state, the presence of organic carbon in significant quantities is instead a new element that indicates that the basic ingredients necessary for life were present on Mars a few billion years ago. It would have been the Gale crater in which Curiosity evolves a quite favorable place for the appearance of lifesince in addition to water and carbon, the environment had the other essential elements: the sources ofpowerlow acidity, oxygen, nitrogen and sulfur.

Curiosity could therefore be in the right place to discover the first traces of Martian life so sought after. However, if they exist, access may be more difficult than we thought.

Review the search strategy for organic molecules such as amino acids

A new experiment conducted by the NASA suggests that in order to be able to find organic molecules, the rover would have to drill two meters deep into the Martian subsoil. This applies in particular to researchamino acidswhich may or may not be of biological origin, but which in all cases are considered constituent elements for the construction of proteins. in any case, the acids amino acids are fragile and easily destroyed Cosmic rays reach the surface of Mars whose thin atmosphere it does not provide effective protection. Currently, the rovers are drilling to a depth of five centimeters. Scientists estimate that at this depth, amino acids are destroyed in just 20 million years. Knowing that potential Martian life may have developed several billions of years ago, investigating this very superficial level therefore appears completely futile.

These results, published in Astrobiology, show the need to implement a new search strategy for rovers currently in operation, which unfortunately are not equipped to drill to the required depth. A solution would be sought outcrops having recently exposed deep parts of the subsoil, such as in small impact craters less than 10 million years old or in material ejected from such craters.

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