Radiation has erased any traces of potential life on Mars.

On the Red Planet, an increasing number of locations are being discovered where organic traces of ancient life may have been preserved. However, the authors of a new study express skepticism about the success of these searches: it turns out that potential signs of life are deteriorating due to cosmic radiation more quickly than previously thought. Furthermore, the saline environment, often considered promising for the preservation of life signs, actually accelerates these processes.

2024-12-14 10:00:15https://naked-science.ru/article/astronomy/radiatsiya-sterla

Robotic devices traversing the surface of the fourth planet from the Sun are searching for signs of life by analyzing surface rocks. Data obtained from the Curiosity and Perseverance rovers have allowed for a better understanding of the conditions that prevailed on the Red Planet in the past and the locations where biomarkers—indicators of life—might have been preserved.

However, there is a problem: the rocks and soils on Earth are shielded from cosmic radiation by the atmosphere and magnetic field, while the Red Planet has existed without such protection for about four billion years (the Martian atmosphere is 160 times less dense than that of Earth). The authors of a new study published in the journal Astrobiology concluded that prolonged exposure to cosmic rays—high-energy particles penetrating deep into Martian soil—could have led to the accelerated breakdown of organic molecules.

By exposing various classes of organic molecules to gamma radiation (a stand-in for cosmic rays) and studying their behavior both in pure form and in the presence of sodium, potassium, and magnesium salts under laboratory conditions, a research team led by Anais Roussel from Georgetown University (USA) discovered that lipid biomarkers such as hopanes, steranes, alkanes, and fatty acids can decompose much faster than previously thought.

Specifically, lipid signatures broke down 6-20 times faster than amino acids, and the addition of salts further increased their degradation rate. This means that even if life once existed on Mars (especially in areas rich in salts within Martian soil), much of its evidence in surface rocks was likely destroyed long before our attempts to detect them.

The laboratory experiment also revealed the formation of intermediate products (such as aldehydes and alkanes) during the radiolysis of fatty acids. In this process, more complex lipids either "evaporated" from the material, breaking down into simpler volatile compounds, or transformed into such complex structures that standard analytical methods failed to detect them.

The findings of this new study are crucial for selecting landing sites for future Mars missions: searching for preserved traces of life on the Red Planet should occur in areas less exposed to radiation, such as lava tubes, as previously discussed by Naked Science reported. Consideration should also be given to methods of protecting Martian soil samples from radiation exposure before their return to Earth.