☄️ 3I/ATLAS: the alcohol-rich interstellar object

The passage of an interstellar object through our Solar System remains a rare event. After 'Oumuamua and Borisov, the third confirmed object from elsewhere, named 3I/ATLAS, is now the most studied.

Astronomers have revealed a striking detail: this object contains an exceptional abundance of methanol, a type of alcohol. This characteristic clearly distinguishes it from local comets and offers us a glimpse into the conditions that presided over the birth of distant planetary systems.


To reach this conclusion, observations were conducted with the powerful ALMA antenna array, located in Chile. Its instruments analyzed the gas cloud, or coma, surrounding the visitor's nucleus. The signals captured show a strong presence of methanol compared to another molecule, hydrogen cyanide. This chemical imbalance is notable because it deviates from the ratios usually measured in our own Solar System.

This composition suggests that 3I/ATLAS formed in an environment radically different from ours. Lower temperatures or a specific initial composition of the ices likely favored the production of this alcohol. Nathan Roth, the lead author of the study, compares this data to the fingerprint of another stellar system, revealing unique aspects of its raw material. Indeed, comets from our cosmic neighborhood generally show very different proportions.

Other space observatories, such as Hubble and James Webb, have followed the comet's trajectory. Their images allowed us to see a diffuse coma and a faint dust tail. These phenomena are caused by the heating of ices under the effect of sunlight, which releases gas and dust into space. This activity offers scientists the opportunity to observe how materials are ejected and interact with the solar wind.

The detailed analyses by ALMA also enabled the mapping of gas emissions. They indicate that hydrogen cyanide comes mainly from the nucleus, while methanol escapes from both the nucleus and the icy grains in the coma. This is the first time such behavior has been observed with such precision for an interstellar object.

For researchers, such celestial visitors constitute precious messengers. They indeed preserve the chemical conditions of their place of formation, as it was billions of years ago. Studying 3I/ATLAS therefore allows us to explore the building blocks of distant planets without leaving our Solar System, which broadens our vision of cosmic diversity and the processes that shape worlds.

The role of methanol in astronomy

Methanol is a simple organic molecule. It forms in space on icy dust grains in interstellar clouds, where low-temperature chemical reactions transform carbon monoxide and hydrogen into alcohols. Its presence often serves as an indicator of environmental conditions during the genesis of celestial objects.

In comets, methanol is incorporated from the earliest stages of planetary formation. Its relative quantity compared to other molecules, such as hydrogen cyanide, can reveal information about the temperature and composition of the protoplanetary disk. A high proportion, for example, indicates colder temperatures or active prebiotic chemistry.

Astronomers detect methanol using instruments like ALMA, which capture the specific radio emissions of molecules in the interstellar medium. These observations help map the distribution and abundance of compounds, thus reconstructing the chemical history of planetary systems.

The analysis of methanol in objects like 3I/ATLAS improves our knowledge of cosmic chemistry. It shows how organic molecules, essential for life, are dispersed in the Universe and how they can influence the formation of planets.