Subaru Telescope Finds Interstellar Comet 3I/ATLAS Has Methanol Levels Far Exceeding Solar System Comets

The third known interstellar object to pass through our solar system, comet 3I/ATLAS, is unveiling chemical secrets as it retreats toward the outer reaches of the solar system — and the surprises are mounting. New observations from the Subaru Telescope and the Atacama Large Millimeter/submillimeter Array have revealed unexpected chemical transformations in the comet's outer envelope, offering astronomers their best evidence yet that planetary systems around other stars forge comets with interior compositions distinctly different from those in our own solar neighborhood.

First detected on July 1, 2025, by the NASA-funded ATLAS survey telescope operating in Chile's Río Hurtado valley, comet 3I/ATLAS — formally designated C/2025 N1 — arrived from beyond our solar system traveling at hyperbolic speed, meaning it was never gravitationally bound to our Sun. It was only the third confirmed interstellar interloper ever identified, following the elongated object 'Oumuamua in 2017 and comet 2I/Borisov in 2019.

After making its closest approach to the Sun in December 2025, 3I/ATLAS began releasing chemical compounds at a rate that surprised observers. The Subaru Telescope captured detailed spectra on January 7, 2026, analyzing the composition of the comet's coma — the gaseous cloud surrounding its nucleus — and finding that the ratio of carbon dioxide to water was significantly lower than earlier measurements taken by space telescopes before perihelion. Lead researcher Yoshiharu Shinnaka of Kyoto Sangyo University, whose team published the findings in The Astronomical Journal, said the shift indicated the comet's outer layer and interior are chemically stratified — organized in layers with different compositions.

The most striking new result came in April 2026, when astronomers using ALMA detected methanol in 3I/ATLAS at concentrations far exceeding those typically observed in Solar System comets. Methanol, a simple organic molecule, is a common comet ingredient but rarely seen in such abundance. Scientists believe the surplus may reflect a warmer formation environment around a different type of parent star.

Simultaneously, the European Space Agency's JUICE spacecraft captured new images of 3I/ATLAS as both objects passed near the gas giant's gravitational domain. The photos showed the comet's dust tail stretching approximately five million kilometers from the nucleus. Scientists said the tail's structure suggested relatively large dust particles, consistent with a porous nucleus that has not been eroded by close solar passes over billions of years.

As of April 2026, 3I/ATLAS has passed beyond the orbit of Jupiter and is accelerating outward. Astronomers estimate they have a diminishing window — perhaps weeks — to gather high-quality observations before the comet becomes too faint for even the world's largest telescopes. Follow-up campaigns using the Very Large Telescope in Chile and the Keck Observatory in Hawaii were underway Monday.

The 3I/ATLAS experience is already informing designs for the proposed Comet Interceptor spacecraft, a joint ESA-JAXA mission that would be positioned at the Sun-Earth L2 Lagrange point to intercept the next interstellar visitor, potentially in the early 2030s. "What 3I/ATLAS is teaching us about chemical heterogeneity in interstellar comets will directly shape how we design the mass spectrometers and remote sensing instruments for Comet Interceptor," said Dr. Cecilia Tubiana of the Max Planck Institute for Solar System Research.