Illustration de Perseverance sur Mars. © Tryfonov, Adobe Stock

Perseverance failed to detect biosignatures on Mars surface, study finds

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[EN VIDÉO] perseverance, looking for life on mars
Perseverance, that’s what NASA has chosen 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 that will be brought back to Earth. Goal: Find traces of microbial life.

It’s one of Main missions of the rover Perseverance : Find, or at least try, traces of life in the rocks of the Martian soil. Because they are not fossils…” data-image=” ” data- url=”” data-more=”Read more”>fossils organizations you are looking for persistencebut the so-called simple covalent bond…” data-image=”” data-url=” https: //” data-more=”Read more”>molecules, more or less complex, which would have been synthesized by biological processes. the Rover curiosity would have taken the first step with the confirmation the presence of organic molecules (methane and carbon compounds) on Mars. If Perseverance had managed to find more complex biomolecules, it could mean that the planet would have seen the beginnings of even very rudimentary organic life. Quite an exciting prospect!

The problem of UV radiation

This target is also one of the next rovers set to join Mars: Rosalind Franklin. This new Rover of the ExoMars program of ESA and Roscosmos will have a set of instruments on board to perform Raman spectroscopic measurements. That Raman spectroscopy is a chemical analysis method that identifies the structure of the molecules present in a sample. The Rover Perseverance is already equipped with this type of instrument. If this method is effective on Earth and very commonly used to detect biomolecules, then things seem complicated on Mars.

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

Is this analysis method best for Perseverance?

Could biomolecules remain stable under the fire of solar radiation hitting the Martian soil? Some pre-mission studies showed that while the degradation rate is certainly very high in the first few centimeters of the surface, the regolith had the ability to protect certain biomolecules. However, considering this hypothesis, there is another problem, this time related to the analysis method. Indeed, if the scientists showed that biomolecules could remain detectable despite Martian atmospheric conditions, these tests had not been performed using Raman spectroscopy to conduct the analyses.

A team of researchers has therefore questioned the analytical capacity of this type of instrument under Martian conditions. A series of experiments (Biomex) was therefore carried out on board the International Space Station (ISS), the only operational orbital station, and represents a major step for the…” data-image=”https://cdn .futura-” data-url=” /” data-more=”Read more”>International Space Station. Seven different types of biomolecules were exposed to solar radiation outside the station for 469 days. They were mixed with analogues of Martian regolith to better simulate the environmental conditions found on the red planet. The samples were then analyzed using Raman spectroscopy.

The regolith signal overlays that of the biomolecules

The researchers then found that during the analyzes of the samples most exposed to UVR (simulating those of the Martian surface), the signal was associated with the minerals Regolith partially or even completely masked the signal associated with the biomolecules. For example, the particularly strong signal from hematite, a mineral very present on Mars, falls in exactly the same range of values ​​as that of chlorophyll, a polysaccharide formed from numerous glucose molecules linked by b-1,4-glycosidic bonds. It is a dietary fiber that is part of the structure of plants. It is not digested in…” data-image=”” data-url=” https: / /” data-more=”Read more”>cellulose or other biomolecules, thereby preventing their recognition. Samples with many particles
It is a particle less than 4 microns in size, regardless of its mineralogical nature.
Clay is a mineral (more specifically, a family…” data-image=” 20. jpg” data-url=”” data-more=”Read more”>volume proved even more difficult to analyze. However, this mineral is believed to be the matrix most likely to have preserved organic molecules on Mars.

This study, published in scientific advances, showing the difficulty of analyzing samples containing mineral phases using Raman spectroscopy in the presence of high UVR exposure. On the other hand, samples that are located at depth and are therefore better protected from UV radiation could remain correctly detectable with this method.

So Perseverance, which can only analyze surface samples, could miss a biosignature completely, even if biomolecules were actually present in the analyzed sample!

Drill deep, Rosalind Franklin’s solution

All hopes are therefore pinned on the Rover Rosalind Franklin that will have the ability to drill up to 2 meters deep to obtain UV-protected samples.

A modification of the analysis technique using Raman spectroscopy also shows good results on Earth, but the equipment still needs to be miniaturized before it can be integrated into a possible Mars mission. In the meantime, a new data processing approach could still make it possible to extract certain information from the samples analyzed by Perseverance. Otherwise you will have to wait returning the samples to Earthplanned for 2033.

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