The building blocks of life could have different origins in the Universe: what new studies on Bennu reveal

What is theorigin of life on Earth remains one of the most complex questions that science has not yet found an answer to. A new study published in the journal PNAS tries to shed light on training processes of some prebiotic molecules, i.e. the “progenitors” of the organic molecules of living things. This new research expands on the information obtained in recent years thanks to discoveries from Bennu (a carbon-rich asteroid orbiting near the earth) e Murchison (a meteorite that fell in Australia in 1969), which had opened the way to a fascinating hypothesis: the “building blocks of life”, the organic molecules that make up all terrestrial organisms could arrive from space. Already in 2025, with two studies published in journals Nature And Nature Astronomy, NASA had detected the presence of on the asteroid Bennu amino acids (the building blocks that make up proteins) e nitrogenous bases (components of DNA and RNA). The new study, published in February and conducted by the University of San Diego in California, suggests that the molecules of life may have formed several times, in different environments and at different times, following different mechanisms.

The new study on the birth of the building blocks of life in the Universe

In the most recent samples taken on Bennu, researchers analyzed in glycine detailthe amino acid with the simplest chemical structure, by studying the enrichment of carbon and nitrogen isotopes, that is, stable variants of these elements that differ in the number of neutrons. The relative abundance of a particular isotope, in fact, represents a sort of chemical scar which helps researchers reconstruct the mechanism and the environment in which a molecule was formed.

In the Murchison meteoritethe isotopic composition of amino acids is compatible with the so-called Strecker synthesisa reaction that can occur in the presence of liquid water (and therefore at relatively mild temperatures) inside the asteroid. In the case of Bennuhowever, the isotopic signature of glycine appears different and more consistent with a formation that occurred in extremely cold environmentslike i interstellar ice or in the nebula at the beginning of the Solar Systemthrough reactions triggered by ultraviolet radiation or cosmic rays.

A more complex chemistry than expected

In some cases, mixtures of the same amino acid (the so-called enantiomersmirrored forms of the same molecule, like our hands) found on Bennu show slight differences in isotopic composition. Since enantiomers are molecules that are identical in composition (they have exactly the same atoms and the same bonds), but mirrored in spatial arrangement of atomsany differences in their isotopic signature indicate that they were not necessarily formed in the same environment or through the same chemical process. An unusual detail, which suggests how some amino acids may have been formed through different chemical reactions or in different moments of the primordial history of the Solar System.

Because it is an important discovery

These new analyses they don’t provide a definitive answer about the extraterrestrial origin of the “building blocks of life” on earth but, indeed, they broaden the scenario about the possible mechanisms of formation of the prebiotic chemistryrevealing how primordial chemistry may be more complex and layered than we imagined. In putting together all the pieces of this intricate puzzle, Bennu e Murchison they are turning out to be real cosmic chemistry laboratoriessuggesting that organic molecules may have formed several times in the history of the Solar System, through different mechanisms, at times and places more remote than we had assumed.