Astronomers using a powerful telescope in Chile recently found that interstellar comet 3I/ATLAS contains unusually high levels of methanol, a type of alcohol. This discovery gives scientists a rare look into the chemical makeup of a distant star system. The comet, only the third confirmed object from outside our solar system, showed methanol levels far beyond what is typical for comets formed in our own cosmic neighborhood.[almaobservatory+5]
Distant Visitor Reveals Chemical Secrets
Scientists made the discovery using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.They observed comet 3I/ATLAS in late 2025 as it moved closer to the Sun.As sunlight warmed the comet's icy surface, it released gas and dust, forming a glowing cloud around its core called a coma.By studying the chemical signatures in this coma, astronomers identified the materials making up the comet.[almaobservatory+20]
The research team focused on two key molecules: methanol (CH₃OH), an alcohol, and hydrogen cyanide (HCN), an organic molecule commonly found in comets. ALMA data showed that 3I/ATLAS is very rich in methanol compared to hydrogen cyanide. On two separate dates, researchers measured methanol-to-hydrogen cyanide ratios of about 70 and 120. These high ratios place 3I/ATLAS among the most methanol-rich comets ever studied.[almaobservatory+17]
Nathan Roth, lead author of the research and a professor at American University, compared observing 3I/ATLAS to "taking a fingerprint from another solar system." He stated that the details show what the comet is made of, and it is "bursting with methanol in a way we just don't usually see in comets in our own solar system." This suggests the icy material of 3I/ATLAS formed under different conditions than most comets in our solar system.[almaobservatory+21]
Unpacking the Comet's Chemistry
Methanol, also known as wood alcohol, is poisonous and cannot be consumed. It is an organic molecule made of carbon, hydrogen, and oxygen. Methanol forms in extremely cold regions of space where icy grains collect complex organic compounds. When these grains come together to form comets and planets, they carry these molecules. Scientists are interested in these organic molecules because they are considered building blocks of life.[universemagazine+6]
Earlier observations of 3I/ATLAS by the James Webb Space Telescope showed that carbon dioxide dominated the comet's coma when it was farther from the Sun. The new ALMA observations add methanol as another major and unusual component of its chemical makeup. This adds to the complex chemical profile of this interstellar visitor.[universemagazine+10]
The way molecules escape from the comet also provides clues. Hydrogen cyanide appears to come mainly from the comet's nucleus, which is typical for comets in our solar system. However, methanol seems to be released from both the nucleus and from tiny icy grains floating within the coma. These icy grains act like miniature comets. As sunlight warms them, the ice they contain turns into gas, releasing methanol into space. While similar behavior has been seen in some solar system comets, this is the first time such detailed outgassing processes have been tracked in an interstellar object.[almaobservatory+13]
A Glimpse into Other Star Systems
Comet 3I/ATLAS is only the third confirmed interstellar object scientists have detected passing through our solar system. The first was 1I/'Oumuamua in 2017, followed by 2I/Borisov in 2019. 3I/ATLAS was discovered on July 1, 2025, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Chile. Its highly curved path and high speed confirm its origin outside our solar system.[almaobservatory+19]
Interstellar objects like 3I/ATLAS are like time capsules from other star systems. They formed in different parts of the galaxy and then drifted through space for millions or even billions of years before entering our solar system. Their unique compositions reveal much about the conditions present during their formation.[en+9]
For example, 2I/Borisov, the previous interstellar comet, showed unusually high amounts of carbon monoxide. This suggested it formed in an extremely cold environment. The methanol-rich nature of 3I/ATLAS similarly indicates that its icy material formed under chemical conditions different from our own solar system. These factors, such as low temperatures or cosmic radiation in the interstellar medium, may have favored the accumulation of methanol.[almaobservatory+12]
Scientists will continue to study these rare interstellar visitors. Each new object offers valuable clues about how planetary systems form and change across the galaxy. The discoveries from 3I/ATLAS help astronomers better understand the diversity of chemical environments where stars and planets are born.[mixvale+1]
