Images of the interstellar comet 3I/ATLAS captured during the September 7 total lunar eclipse have sparked intrigue among astronomers, suggesting that this latest visitor to our Solar System may be exhibiting a striking green hue. This phenomenon is not entirely unusual for comets, as many in our Solar System emit a green glow when they heat up sufficiently to release vapor. However, the case of 3I/ATLAS is particularly peculiar, given that the comet's chemical analysis has revealed minimal signs of the dicarbon (C2) molecules, which are typically responsible for the characteristic green fluorescence of comets.
The absence of C2 raises questions about the comet's composition. It’s possible that C2 molecules are present but remain undetected, or there could be an alternative molecule contributing to the comet's green appearance. Either scenario suggests that the chemistry of 3I/ATLAS is complex and holds secrets yet to be uncovered. This fascinating mystery invites further investigation and analysis as scientists strive to understand the comet's unique characteristics.
The captivating images of 3I/ATLAS were taken by renowned astrophotographers Gerald Rhemann and Michael Jäger from Namibia during the remarkable lunar eclipse on the night of September 7, 2025. As comets approach the Sun, the ices surrounding their rocky nuclei begin to sublime, transforming into a gas atmosphere known as a coma. This gas, energized by solar radiation, fluoresces and emits light across various wavelengths, including visible, near-infrared, ultraviolet, and radio.
Recent observations from the James Webb Space Telescope (JWST) have revealed that 3I/ATLAS possesses a peculiar chemical composition, featuring higher than normal levels of carbon dioxide. Additionally, other studies have detected the presence of nickel and cyanogen. However, these elements typically do not induce the green fluorescence associated with comets, and the specific molecule responsible for this glow has yet to be identified.
The mystery deepens with a recent preprint authored by astronomer Luis Salazar Manzano from the University of Michigan, Ann Arbor. His research suggests that the early detection of cyanogen in 3I/ATLAS indicates a significant depletion of carbon-chain molecules, including both C2 and C3. The findings suggest that the ratio of C2 to CN places 3I/ATLAS among the most carbon-chain depleted comets identified to date, adding another layer of intrigue to this celestial visitor.
As 3I/ATLAS prepares for its closest pass to Earth in December, scientists hope to gather more data to unlock the mysteries surrounding its unique chemical makeup and green glow. The anticipation surrounding this comet continues to grow, and astronomers are eager to solve the enigma of its composition and behavior, which could reveal significant insights into the nature of interstellar comets.
