- Astronomers found unusually high methanol levels in interstellar comet 3I/ATLAS
- The comet's methanol content surpasses most known solar system comets
- Observations used ALMA and James Webb Space Telescope data for analysis
Astronomers have discovered unusually large amounts of methanol in the interstellar comet 3I/ATLAS. The comet contains higher levels of this simple alcohol than almost all known comets from our solar system. Scientists say the finding offers a rare look at the chemical conditions in planetary systems beyond our own, reported Newsweek.
Researchers used the Atacama Large Millimeter/submillimeter Array (ALMA) to study the comet. This observatory allowed scientists to analyse 3I/ATLAS's chemical composition and understand how planetary systems outside our solar system form and evolve over time.
According to Nathan Roth, lead author of the study and a professor at American University, studying this comet is like taking a "fingerprint" of another solar system. He says this reveals the elements the comet is composed of, and the methanol content is significantly higher than most comets in our solar system.
All of these observations were made using ALMA, an international observatory located in Chile. The National Science Foundation's National Radio Astronomy Observatory is also a partner in this project.
Scientists observed 3I/ATLAS several times in late 2025 as the comet approached the Sun. As the Sun's heat heated its icy surface, it began to eject gas and dust. This created a cloud-like ring around the comet, called a coma. By studying this material, astronomers were able to determine the comet's chemical composition.
Unusual Amounts Of Methanol
The research team paid particular attention to two molecules commonly found in comets: methanol (CH₃OH) and hydrogen cyanide (HCN). Although both are organic compounds, their concentrations in 3I/ATLAS were significantly different from those found in typical comets in our solar system.
Data from ALMA revealed a much higher concentration of methanol than hydrogen cyanide. On two different observation dates, scientists recorded a ratio of methanol to HCN of approximately 70 and 120. Based on these results, 3I/ATLAS joins the comets with the highest methanol content ever detected, including comets in our solar system.
Scientists say this high presence of methanol indicates that this comet likely formed under chemical conditions quite different from those of most comets in our solar system.
Hints From Earlier Telescope Observations
These findings are consistent with earlier observations made with the James Webb Space Telescope. Those studies found that when 3I/ATLAS was farther from the Sun, its coma was dominated by carbon dioxide.
The combined results from the Webb Telescope and ALMA indicate that this comet's chemical composition differs from that of most known comets. This suggests that interstellar objects may be quite different from those formed around the Sun.
ALMA's high-resolution images also helped scientists understand how different molecules are ejected from comets.
Hydrogen cyanide appears to be primarily released from the comet's solid nucleus, a pattern commonly observed in comets in our solar system. In contrast, methanol behaved differently. The data indicated that methanol is released not only from the nucleus but also from icy particles in the coma.
A Rare Interstellar Visitor
Comet 3I/ATLAS is the third known object to have entered our solar system from interstellar space. Previously, objects like 1I/'Oumuamua and 2I/Borisov have also been observed.
Both of these objects also revealed several unusual features, leading scientists to try to understand how diverse objects formed around other stars might be.
