Alcohol-filled interstellar comet 3I/ATLAS shocks astronomers: Its alien chemicals could reveal information about planet formation |

Astronomers have discovered something unusual in a comet passing through the solar system. 3I/ATLAS is the third interstellar visitor confirmed so far, and it appears to be filled with methanol, an alcohol you might find in a lab rather than your drink. Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile reportedly measured levels of methanol that were much higher than levels of hydrogen cyanide, a molecule commonly found in comets.It seems that 3I/ATLAS is not like the comets we are used to. Its icy core and surrounding coma reveal chemical conditions that may hint at how planets formed in other solar systems. Experts say it could be a rare glimpse into the chemistry of an alien planet, something scientists have been waiting decades to study. The comet shone as it approached the sun, sending a distinct signal that ALMA could detect.

Comet 3I/ATLAS: ALMA detects higher than expected methanol levels

The numbers are staggering. Methanol to HCN ratios of approximately 70 and 120 were reported in two separate observations. This is huge compared to most comets in our own system, where methanol is usually far less dominant. Lead researcher and professor at American University, Nathan Roth, said it was like getting a fingerprint from another solar system. And it seems that this fingerprint is very rich. It’s really rich.The ALMA Morita array (sometimes called the Atacama Compact Array (ACA)) tracked the comet for several days in late 2025. As sunlight warms its icy surface, 3I/ATLAS releases gas and dust. This creates a glowing halo, or coma, around its core. By analyzing this haze, scientists can see exactly what chemicals are present in it. The methanol gush was far greater than anyone expected.

Comet 3I/ATLAS reveals methanol patterns not seen in solar system comets

Interestingly, methanol behaves differently in coma than other molecules. Hydrogen cyanide appears to originate primarily from atomic nuclei, like typical solar system comets. Methanol, on the other hand, appears to be released from the comet’s nucleus and tiny ice particles floating in the coma. The particles are like mini comets, releasing methanol when sunlight hits them.This is a strange thing. Some solar system comets can do this, but seeing it in an interstellar object is new. This may indicate that the formation or processing conditions of 3I/ATLAS are different from those in China. The James Webb Space Telescope has hinted at something strange going on, finding that carbon dioxide dominates farther from the sun. Methanol adds another layer of mystery.

Comet 3I/ATLAS gives us a glimpse into the chemistry of distant planets

Each interstellar visitor is a snapshot of a distant planetary system. 3I/ATLAS follows 1I/’Oumuamua and 2I/Borisov, both of which generated huge scientific interest. These objects may be rare, but each carries clues about how planets and comets formed in the Milky Way. Seeing such a methanol-rich comet gives astronomers a chemical window into places we’ll never be able to reach.Observations of 3I/ATLAS also help improve models of comet chemistry. It seems that different star systems may produce very different mixtures of ice and organic matter. This could change how we think about planet formation, and even suggest that some systems are more like “chemical cocktails” than the tidy solar system we know.