🪐 Discovery of a Second Pathway for the Emergence of Life

The emergence of molecules essential for life on Earth is a major question for science.

A recent advance shows that amino acids, these fundamental building blocks of life, may have emerged in icy environments exposed to radiation, far from the clement conditions previously considered. This discovery comes from the examination of minuscule dust grains brought back from the asteroid Bennu.


In 2023, NASA's OSIRIS-REx mission brought samples from Bennu, an asteroid considered primitive, back to our planet. Analyses allowed the identification of amino acids that are 4.6 billion years old, establishing that these components of life do indeed exist in space and are even building blocks of our Solar System and, consequently, of Earth.

The study published in the Proceedings of the National Academy of Sciences indicates that their genesis does not match current models.

Researchers from Penn State University used instruments specially designed to detect isotopes, slight differences in atomic mass. Their focus was on an amount of dust equivalent to a teaspoon, concentrating on glycine, the most elementary amino acid. This molecule often serves as an indicator for reconstructing primordial chemical mechanisms.

The data obtained show that the glycine present on Bennu likely formed in the absence of liquid water, within ice subjected to radiation at the frontiers of the young Solar System. This finding contradicts the Strecker process, long seen as the preferred pathway, which requires warm water and compounds like ammonia.


A comparison with the Murchison meteorite, which fell in Australia in 1969, highlights this divergence. The amino acids in Murchison appear to come from an environment containing liquid water and moderate temperatures, potentially similar to those of early Earth. Bennu, on the other hand, testifies to significantly more hostile conditions.

This work suggests that the parent bodies of Bennu and Murchison originated from chemically distinct zones within the Solar System. Consequently, the ingredients necessary for life could have taken multiple trajectories to reach us, multiplying the possibilities for their emergence in other places in the Universe.

New questions arise, such as why two mirror-image forms of an amino acid present distinct isotopic signatures. The team plans to examine other meteorites to establish a map of the diversity of prebiotic conditions.