The interstellar comet 3I/ATLAS has extraordinary levels of methanol in its chemical composition, as revealed by recent observations carried out with the ALMA radio telescope, in the Atacama desert, in Chile. The abundance of this organic compound, a simple type of alcohol, far exceeds what is observed in most comets originating from our Sistema Solar. Cientistas highlight that the proportion between methanol and hydrogen cyanide (HCN) reaches values between 70 and 120 on different measurement dates, positioning the object as one of the richest in methanol ever recorded. Essa feature offers valuable clues about chemical conditions in other stellar systems.
3I/ATLAS was initially detected on July 1, 2025 by the ATLAS telescope, at Chile. Sua hyperbolic trajectory confirms interstellar origin, as it is not tied to the gravity of Sol and continues at a high speed of approximately 61 km/s. The comet passed its perihelion in October 2025 and is now moving away from Sistema Solar, with no possibility of return.
Different chemical composition
ALMA observations focused on the submillimeter signatures of methanol (CH₃OH) and hydrogen cyanide (HCN). The data indicate that methanol is released from both the core and ice grains in the coma, while HCN comes mainly from the core. Essa difference in the outgassing pattern suggests heterogeneity within the comet.
Methanol appears enriched in the direction facing Sol in some measurements. The high methanol/HCN ratio highlights 3I/ATLAS compared to typical solar comets, where these values are much lower.
Main features detected
- Methanol abundance between 70 and 120 times greater than HCN in varying measurements
- Release of methanol from both the nucleus and ice grains in the coma
- Chemical heterogeneity confirmed by distinct emission patterns
- Presence of carbon dioxide dominant in coma in previous analyzes
Origin in another star system
The comet formed in an environment distinct from our Sistema Solar, possibly more than seven billion years ago, which would make it older than Sol itself. Sua coma has already been dominated by carbon dioxide in previous analyzes with Telescópio Espacial James Webb. Preliminary Estudos indicate ejection from another planetary system millions of years ago. The abundant presence of methanol reinforces the chemical diversity between stellar systems.
Additional observations
Other telescopes, including Hubble and ESA instruments, captured images of the comet showing jets and filaments of gas and dust. The object passed close to the orbit of Júpiter, about 670 million kilometers from Sol at one stage. Atualmente, 3I/ATLAS continues its journey out of Sistema Solar, with activity observed even after perihelion. Emissions include water vapor, methane and other organic compounds.
Implications for interstellar chemistry
The detection reinforces the importance of studying interstellar objects to understand planetary formation processes in other regions of the galaxy. Methanol is an organic molecule linked to prebiotic chemistry in astrochemical contexts. 3I/ATLAS provides a unique sample of material from another star system. Pesquisas continues with data collected on multiple dates in 2025.
The comet demonstrates material release behaviors that vary with distance to Sol. Modelos indicate an increase in methanol production as perihelion approached.
