Perseverance would not be able to detect biomolecules on the surface of Mars, according to a study

Perseverance would not be able to detect biomolecules on the surface of Mars, according to a study

Perseverance would not be able to detect biomolecules on the surface of Mars, according to a study

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[EN VIDÉO] Perseverance, in search of life on Mars
Perseverance, so NASA has decided to name the rover it will send to Mars in the summer of 2020. A rover from which researchers expect a lot. He will be the first to collect rock samples to bring back to Earth. Objective: to find traces of microbial life.

Is one of main missions of the Perseverance rover : find traces of life in the rocks of the Martian soil or at least proof. Because these are not fossils organizations you are looking for Perseverancebut molecules, more or less complex, which would have been synthesized by biological processes. the rover Curiosity he would take the first step by confirming the presence of organic molecules (compounds of methane and carbon) on Mars. If Perseverance were able to find more complex biomolecules, it could mean that the planet would have experienced the beginning of a very rudimentary organic life. Quite an exciting prospect!

The problem of UV radiation

This goal is also one of the next rover who should join Mars: Rosalind Franklin. This new rover of the ExoMars program of ESA and Roscosmos will carry on board a suite of instruments to perform Raman spectroscopic measurements. The Raman spectroscopy is a chemical analysis method that identifies the structure of the molecules present in a sample. This type of tool already equips the Perseverance rover. If this method is effective on Earth and widely used for detecting biomolecules, things look complicated on Mars.

Because there is a big difference between Mars and Earth: theatmosphere. If Mars has one, it is still much thinner than Earth’s. However, the Earth’s atmosphere plays an essential role in preserving life: it blocks much of the radiation ultraviolet (UVR), which in high doses are harmful to living organisms.

Is this method of analysis best suited for perseverance?

Biomolecules could remain stable under the stoplight solar radiation hitting the Martian soil? Some studies prior to the mission showed that while the degradation rate is certainly very high in the first few centimeters of the surface, the regolite however, it had the ability to protect some biomolecules. Considering this hypothesis, however, there is another problem, linked this time to the method of analysis. Indeed, if the scientists showed that biomolecules could remain detectable despite the atmospheric conditions of Mars, these tests would not have been carried out using Raman spectroscopy to carry out the analyzes.

A team of researchers has therefore come to question the analytical capacity of this type of instrument in Martian conditions. A series of experiments (Biomex) was then conducted aboard the International Space Station. Seven different types of biomolecules were exposed to solar radiation outside the station for 469 days. They have been mixed with analogues of the Martian regolith to better simulate the environmental conditions prevailing on the Red Planet. The samples were then analyzed with Raman spectroscopy.

The regolith signal overlaps with that of the biomolecules

The researchers then realized that, during the analysis of the samples most exposed to UVR (simulating those of the Martian surface), the signal associated with the minerals the regolith partially covered or even completely masked the signal associated with the biomolecules. For example, the particularly strong signal of hematite, a mineral very present on Mars, it falls in exactly the same range of values ​​as that of chlorophyllof the cellulose or other biomolecules, preventing their detection. Samples containing a lotclay proved even more difficult to analyze. However, this mineral is considered to be the matrix most likely to have stored organic molecules on Mars.

This study, published in Science advances, shows the difficulty of analyzing samples containing mineral phases by Raman spectroscopy, in the presence of high exposure to UVR rays. On the other hand, samples located in depth and therefore more protected from UV rays, could remain correctly detectable with this method.

Perseverance, which can only analyze surface samples, could therefore completely miss a bio-signature, even if the biomolecules were actually present in the analyzed sample!

Drilling deeply, Rosalind Franklin’s solution

All hopes then turn to the rover Rosalind Franklin, who will have it the ability to pierce up to 2 meters deep to recover samples protected from UV rays.

A modification of the Raman spectroscopy analysis technique also shows good results on Earth, but the equipment still needs to be miniaturized before it can be integrated into a potential Mars mission. In the meantime, a new IT approach could still allow some information to be extracted from the samples analyzed by Perseverance. Otherwise, you will have to wait the return of the champions to Earthscheduled for 2033.

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