A distant chemical signature, captured by the infrared eye of the James Webb Space Telescope, has just opened a new window onto the molecular universe. For the first time, an international team has identified complex organic molecules in the ices surrounding a young star located far beyond our Milky Way.
This unprecedented detection, made under extreme cosmic conditions, sheds new light on the chemical processes capable of giving rise to the elementary building blocks of life.
This major discovery is the work of a scientific collaboration led by Marta Sewiło of the University of Maryland and NASA. Using the MIRI instrument on the James Webb Telescope, researchers analyzed the composition of the ices surrounding the nascent star ST6, located in the Large Magellanic Cloud, a satellite galaxy of our own. The exceptional quality of the spectra obtained made it possible to detect the presence of five distinct organic molecules, some of which had never been observed in such an environment.
A natural laboratory with extreme conditions
The Large Magellanic Cloud represents a particularly hostile environment for complex chemistry. This galaxy has only one-third to one-half the diversity of heavy elements present in our Solar System, while being subjected to intense ultraviolet radiation. These characteristics make it a valuable analog of the primordial galaxies that populated the young universe, where elements heavier than helium were much less abundant than today.
The detection of organic molecules in this impoverished environment demonstrates the robustness of the chemical processes at work in interstellar space. Researchers believe these molecules form primarily on the surface of cosmic dust grains, where atoms and simple molecules gradually assemble under the influence of ambient radiation. This hypothesis, previously supported by theoretical models and laboratory experiments, finds decisive observational confirmation here.
The presence of these organic compounds in such a harsh environment suggests that prebiotic chemistry could be a widespread phenomenon throughout the cosmos, including in the most primitive galaxies. This potential universality reinforces the idea that the basic ingredients necessary for the emergence of life could be available in a wide variety of galaxies, far beyond our Milky Way.
Implications for the origin of life
Among the identified molecules are methanol, ethanol, methyl formate, acetaldehyde and acetic acid, the latter never having been conclusively detected before in interstellar ices. These carbon compounds, well-known on Earth where some like ethanol and acetic acid have common applications, represent chemical intermediates that can lead to the formation of more elaborate biological molecules.
The team also spotted spectral signatures suggesting the presence of glycolaldehyde, a molecule related to sugars and considered a potential precursor to RNA components. Although this detection requires further confirmation, it opens up perspectives regarding the possibility that precursor molecules for the emergence of life could form in interstellar space even before the birth of planets.
The survival of these organic molecules during the planetary formation process represents a fundamental challenge for understanding how the ingredients of life can be incorporated into young forming worlds. Researchers estimate that these compounds could withstand the initial phases of planetary accretion and thus be delivered intact to the surfaces of protoplanets, where they would participate in the chemical reactions leading to the appearance of life.
Article author: Cédric DEPOND