🧬 The five letters of the code of life discovered on an asteroid

Asteroids still hold surprises. A Japanese team has just discovered that samples brought back from the asteroid Ryugu contain all five nucleobases, the molecules that form the alphabet of the genetic code. This observation reveals that the building blocks of life could have formed in space before reaching Earth.

These nucleobases are essential nitrogenous molecules: they constitute the letters of DNA and RNA – adenine, guanine, cytosine, thymine and uracil. Without them, no organism could reproduce or evolve. Their discovery on an asteroid as ancient as Ryugu, 4.5 billion years old, adds a major piece to the puzzle of the origin of life.


To avoid any contamination, the researchers used ultrapure laboratory conditions. They extracted the organic molecules with water and hydrochloric acid, then purified them. The two analyzed samples contained all the bases, in roughly equivalent amounts. These results confirm previous work on the Murchison and Orgueil meteorites.

However, these asteroids show chemical differences. Murchison is rich in purines, while Bennu and Orgueil contain more pyrimidines. This balance could depend on the ammonia present, which influences the formation of bases. Ryugu, thanks to its direct sampling in space, offers a unique view of the primitive chemistry of the Solar System.


The discovery that all bases are present on Ryugu reinforces the idea that these molecular ingredients were common in the young Solar System. They could have been delivered to the early Earth by asteroid impacts. Thus, the story of life on our planet may be deeply linked to the chemistry of these ancient bodies.