Various forms of organic matter, the basic element of life on Earth, have been detected on Mars in the Jezero crater that the robot Perseverance explores since he landed on the red planet. The presence of these organic molecules increases the possibility that life could have existed on Mars, but it will be necessary to wait for the return of soil samples to Earth to confirm their origin by further analysis, warn the experts.
In an article which appeared this Wednesday in Natureresearchers from NASA and various American universities describe the various forms of organic matter and the minerals with which they are associated that the SHERLOC instrument (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals), with which the robot is equipped Perseverancedetected in two different geological formations present at the bottom of the crater.
“Each of these geological formations does not seem to have the same variety of organic molecules. Moreover, with the data collected by SHERLOC, it is quite difficult to know exactly the process that led to the formation of this organic matter. There could be several,” summarizes Richard Léveillé, geologist in the Department of Earth and Planetary Sciences at the McGill University Space Institute.
Where do these molecules come from?
Several hypotheses are advanced by the authors of the article of Nature to explain the origin of this organic matter. According to some of them, these organic molecules would result from an interaction between rocks and water, called serpentinization, “which is a reaction that takes place on Earth with rocks of mafic composition, that is to say rich in magnesium and iron, which when mixed with water at a certain temperature above 60°C, gives hydrogen and fairly simple organic molecules”, explains Mr. Léveillé, while stating that “this reaction is possible on Mars”. Organic molecules could also arise from a reduction of CO2 by electrochemistry.
They could also come from meteorites and interstellar dust that fell on Mars. And it is not excluded that they derive from a biological source.
“It is possible that there was life on Mars and that the organic molecules quite simple in terms of the complexity of carbon chains and aromatic rings that we have detected are traces of these life forms, including molecules such as DNA and RNA [qu’elles contenaient] degraded into molecules similar to those found. We cannot rule out this possibility, but there is nothing to indicate that these molecules come from a biological form”, underlines Richard Léveillé who is a member of the scientific team of Perseverance.
This article tells us that the carbon cycle on Mars is more complex than we imagined, says the geologist. “Observations do not confirm that there was life on Mars, but it is very encouraging to detect organic molecules in such ancient rocks [2,3 à 2,6 milliards d’années], because if there was life, it means that traces of this life may have persisted in the rocks. »
“When samples of these rocks are returned to Earth, we will be able to carry out further analyzes and probably determine whether these molecules are abiotic in nature or come from a form of life. We have more efficient instrumentation on Earth, which is one of the main reasons why we want to bring samples back to Earth,” explains the researcher.