Diligence failed to detect signatures of life on the Martian surface, study finds

Illustration de Perseverance sur Mars. © Tryfonov, Adobe Stock

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[EN VIDÉO] Persistence, searching for life on Mars
Perseverance, NASA has decided to name the rover it will send to Mars in the summer of 2020. The most anticipated rover by researchers. He was the first to collect rock samples brought back to Earth. Objective: To detect traces of microbial life.

This is one The main missions of the Perseverance rover : Find traces of life in Martian soil rocks, or at least try to. Because these are not Fossils Companies you are looking for PersistenceBut Molecules, more or less complex, is synthesized by biological processes. rover curiosity He would have made sure and taken the first step Presence of organic molecules (mixtures of methane and carbon) on Mars. If persistence succeeds in finding more complex biomolecules, it means the planet may have experienced the beginnings of more basic organic life. An amazing opportunity!

The problem of UV radiation

The target was one of the next rover to join Mars: Rosalind Franklin. This new rover ESA and Roscosmos’ ExoMars program It carries a set of instruments for performing Raman spectroscopic measurements. The Raman spectroscopy Chemical analysis is a method of identifying the structure of molecules present in a sample. This type of instrument already equips the Perseverance rover. If this method is useful on Earth and is used more widely to detect biomolecules, things seem complicated on Mars.

Because there is a big difference between Mars and Earth: TheAtmosphere. If Mars had one, it would be much thinner than Earth. However, Earth’s atmosphere plays an important role in protecting life: it intercepts most of the radiation. Ultraviolet (UVR), can be harmful to organisms at high doses.

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Is this method of analysis more appropriate for due diligence?

Could biomolecules remain stable under the fire of solar radiation affecting Martian soil? Some studies prior to the mission showed that the regolith had the ability to preserve some biomolecules, although the decay rate was certainly very high in the first centimeters of the surface. Considering this hypothesis, there is another problem connected with this method of analysis. In fact, these experiments were not carried out using Raman spectroscopy to carry out the analyses, although the scientists showed that biomolecules would be detectable despite the atmospheric conditions of Mars.

A team of researchers has therefore come to question the analytical capability of this type of instrument under Martian conditions. Thus a series of experiments (Biomex) were carried out on board International Space Station. Seven different types of biomolecules were exposed to solar radiation for 469 days outside the station. They were mixed with Martian analogs to better simulate environmental conditions on the Red Planet. The samples were then analyzed by Raman spectroscopy.

The regolith signal overlaps with biomass

During analyzes of samples highly exposed to UVR (simulating the surface of Mars), the researchers realized that this was the relevant signal. Minerals The regolith partially or completely masked the signal associated with biomolecules. For example, a particularly strong signal from hematite, A mineral Mars has the most, falling in the same range of values Chlorophyllof Cellulose or other biomolecules, preventing their detection. Models with lots ofClay Analysis was even more difficult. However, this mineral is thought to act as a protective matrix for organic molecules on Mars.

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This study, published Scientific advances, showing the difficulty in analyzing samples containing inorganic phases using Raman spectroscopy in the presence of high UVR exposure. On the other hand, samples located at depth, and therefore protected from UV radiation, can be correctly detected by this method.

Diligence can only analyze surface samples, so even if there are biomolecules in the analyzed sample, a biosignature can be completely missed!

Drilling Deeper, Rosalind Franklin’s Solution

So all hopes turn to Rosalind Franklin Rover Drilling ability Up to 2 meters deep to retrieve UV-protected specimens.

Adapting the analytical technique to Raman spectroscopy has also shown good results on Earth, but the equipment still needs to be miniaturized before it can be integrated into a possible Mars mission. Meanwhile, a new data processing approach makes it possible to extract some information from diligently analyzed samples. Otherwise, you will have to wait Returning samples to EarthScheduled for 2033.

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