Interstellar comet 3I/ATLAS found rich in methanol, ALMA observations show

Saturday 07 - 11:20

By: Dakir Madiha

Interstellar comet 3I/ATLAS found rich in methanol, ALMA observations show

Astronomers using the Atacama Large Millimeter Submillimeter Array have detected unusually high levels of methanol in the interstellar comet 3I/ATLAS, revealing a chemical composition rarely seen in comets formed within our solar system.

The findings, reported by the National Radio Astronomy Observatory on March 6, indicate that 3I/ATLAS contains far more methanol than typical solar system comets. The research was led by Nathan Roth of American University and offers scientists a rare chemical fingerprint of material formed around another star without leaving our own planetary system.

Researchers used ALMA’s compact array in Chile during multiple observation campaigns in late 2025 to examine gas and dust escaping from the comet as sunlight heated its icy surface. The team focused on methanol, a simple organic alcohol, and hydrogen cyanide, a nitrogen containing compound commonly observed in comets.

Data analysis revealed methanol to hydrogen cyanide ratios of about 70 and 120 during two separate observation periods. These values place 3I/ATLAS among the most methanol rich comets ever measured.

“Observing 3I/ATLAS is like taking the fingerprint of another solar system,” Roth said in a statement from the National Radio Astronomy Observatory. He added that the comet contains methanol in quantities rarely observed in comets originating from our own system.

High resolution imaging from ALMA also revealed a distinctive pattern in how the methanol escapes from the comet. Hydrogen cyanide appears to originate directly from the comet’s nucleus, which is typical behavior in solar system comets. Methanol, however, is released both from the nucleus and from small icy grains drifting in the surrounding coma.

These grains act like miniature comets, releasing methanol as they warm in sunlight. Researchers say this is the first time such a detailed outgassing process has been traced in an interstellar object.

The discovery adds to an already unusual chemical profile for 3I/ATLAS. Earlier observations by the James Webb Space Telescope showed the comet’s coma is dominated by carbon dioxide, with one of the highest carbon dioxide to water ratios ever recorded in a comet.

Another study published in February 2026 using NASA’s SPHEREx telescope observed the comet releasing water ice, carbon dioxide, methane, methanol and cyanide months after its closest approach to the Sun. Scientists attributed the delayed outburst to solar heat slowly penetrating beneath a crust hardened by cosmic radiation.

The comet was discovered on July 1, 2025 by the NASA funded ATLAS telescope in Chile. It is only the third confirmed interstellar object detected passing through the solar system, following 1I Oumuamua in 2017 and 2I Borisov in 2019.

3I/ATLAS posed no danger to Earth and passed no closer than about 270 million kilometers from the planet. It is now traveling outward beyond Jupiter’s orbit and will eventually return to interstellar space.

Scientists from more than 20 missions coordinated observations during its passage, assembling the most detailed chemical profile yet obtained for material formed around another star.