bennu asteroide molecole della vita

Discovered on the asteroid Bennu the “bricks of life”: what they are and why the discovery is important

Credit: NASA/Goddard/University of Arizona

There are aminoaicides And nitrogen bases – the “bricks of life” fundamental for building proteins, DNA and RNA – in the champions ofAsteroid Bennu taken in 2018 and reported on the ground in 2023 by the mission Osiris-Rex of the NASA (on which other fundamental ingredients had already been found for life, that is, water and carbon). Two scientific articles published on Nature And Nature Astronomy. The discovery is important because it strengthens the hypothesis of a possible extraterrestrial origin of organic matter At the base of all life on earth.

These results indicate that the chemical bases of terrestrial biology could originating in the primordial universe on primitive asteroids Like Bennu, through complex chemical reactions that took place billions of years ago, and then be transported to earthprobably following collisions with our planet.

This discovery represents one of the most important results of the Osiris-Rex mission, launched by NASA in 2016 with the primary objective of deepening details about the Solar system formation And The origin of life precisely through the study of material taken from Bennu, an asteroid near our planet but that It is not at risk of impact with the earth At least for the next 150 years (there are small probability for the second part of the next century, but they will be recalculated after a close passage of Bennu with the earth in 2135).

What are the “bricks of life” discovered on the Asteroid Bennu

Bennu’s surface proved incredibly rich in organic moleculesincluding 14 of the 20 amino acids which constitute terrestrial proteins and all and the five nitrogen bases that make up DNA (in which the genetic information of living beings is codified) and RNA. Furthermore, the presence of inorganic compounds crucial for the synthesis of these organic molecules suggests that Bennu may have hosted chemical conditions in favor of their training in Primordi of the Solar System.

The amino acids are the bricks that are used to build the proteinmacromolecules that perform various roles in cells: they facilitate biological chemical reactions, provide structure and support and regulate movements and cellular communications. The nitrogen baseson the other hand, are an essential part nucleic acids (DNA and RNA), which have the delicate task of guarding genetic information and regulating the expression of our genes. Without these macromolecules, the cells that make up all living organisms could not exist and their origin could derive from the universe.

nitrogen bases
Nitrogen bases of DNA and ARN (where the Timina is replaced by eggity). The succession of the nitrogen bases encodes the genetic information of living organisms.

On Bennu, in fact, they were found 33 different amino acidsof which 14 are those present in terrestrial proteinsand all 5 nitrogen bases (Adenina, Timina, Cytosine, Guanina and Uracile) present in nucleic acids. Sophisticated structural analyzes confirm that the presence of these molecules does not derive from one terrestrial contaminationan important and often inevitable risk when carrying extraterrestrial material on earth. To confirm this, the amino acids found on Bennu are in racemic formthat is, in a mixture containing the same parts of the two different forms in which the amino acids can exist, which differ in the position of their atoms, called L and D. since the amino acids present in the terrestrial proteins belong all to form lthis detail excludes the hypothesis of terrestrial contamination.

In addition to these biomolecules, traces of inorganic compounds rich in carbon and nitrogen In the form of crystals, which resemble the accumulations of salt that form close to the coasts when the sea water withdraws or evaporates. The presence of these formations indicates that in a distant time, when Bennu was at the cold Boundaries of the Solar Systemits surface was covered with water solutions and inorganic compounds containing carbon and nitrogen, which represent The ideal ecosystem For the formation of the same organic molecules found on its surface.

Because the discovery of organic matter on Bennu is important

The discovery of organic material Found on Bennu supports the possibility of an extraterrestrial origin of theOrigin of organic matter from which life has developed on our planet. Similar tests are difficult to obtain on earth, if not proceeding by hypothesis. The terrestrial rocks, in fact, do not retain traces of the oldest organic compoundssince the geological processes have canceled or altered any form of this material, making it difficult (if not impossible) to trace to direct tests About the origin of the first molecules that generated life. On the contrary, primitive asteroids Like Bennu, who have trained together with the Solar System and since then they have remained relatively uncontaminated in the composition, allowing to reconstruct a portrait of the chemical composition of the Solar System at its origins.

Bennu Asteroid
Mosaic of the Bennu Asteroid composed of images collected by the Osiris -Rex probe. Credit: NASA/Goddard/University of Arizona

The presence of the material extracted from the Bennu surface highlights that the organic molecules Fundamental for life may have formed in extraterrestrial environments long before the first forms of life emerged on our planet.

But be careful: this discovery does not imply that forms of life have migrated directly to the earth transported by asteroids. In fact they have not been found traces of organisms on the surface of Bennu. However, the discovery strengthens the idea that asteroids have played A crucial role in the birth of lifeproviding an ideal environment for the chemical reactions necessary for the synthesis of organic molecules. These, once transported to earth following collisions with asteroids and meteorites, could then have found on our planet Suitable conditions to give rise to organic macromolecules fundamental for the life on earth.

Through a similar mechanism, we cannot exclude that the same organic molecules may have also been transported On other planetswhere similar conditions may have favored the birth of life forms.