An Intriguing Cosmic Visitor

The interstellar comet 3I/ATLAS has captured the attention of scientists and skywatchers alike, especially after it was spotted glowing a puzzling green during the total lunar eclipse on September 7, 2025. This unexpected hue has left researchers scratching their heads, as it starkly contrasts with what is typically observed in comets.

The Green Glow: What Does It Mean?

Comets commonly emit a green glow as they approach the Sun, created by the vaporization of ice around their rocky cores. However, in the case of 3I/ATLAS, standard observations show a surprising lack of dicarbon (C2) molecules, the usual culprits behind such a glow. This raises the tantalizing question: Could there be an unknown molecule at play, or is C2 simply evading detection?

Captivating Imagery From the Eclipse

Astrophotographers Gerald Rhemann and Michael Jäger from Namibia snapped stunning images of 3I/ATLAS during the eclipse, adding to our intrigue about this celestial visitor. As comets approach the Sun, their icy surfaces sublimate, forming a glowing atmosphere. Solar radiation then excites the molecules within this atmosphere, resulting in a brilliant display of fluorescence.

Unusual Chemistry and Its Implications

Recent observations from the James Webb Space Telescope (JWST) shed light on 3I/ATLAS's unique chemical makeup, revealing an abnormally high concentration of carbon dioxide, alongside nickel and cyanogen. Despite this intriguing chemistry, these components are not typically associated with green fluorescence, leaving the mystery of the comet’s glow unsolved.

A Deeper Challenge

Adding to the complexity, a recent study led by astronomer Luis Salazar Manzano from the University of Michigan suggests that the presence of cyanogen hints at a depletion of carbon-chain molecules, including both C2 and C3. With 3I/ATLAS ranking as one of the most carbon-chain deficient comets identified, the mystery surrounding its green glow becomes even more profound.

A Cosmic Puzzle Yet to Be Solved

With 3I/ATLAS expected to make its closest approach to Earth in December, astronomers are hopeful that further observations can unravel this enigma. What secrets does this interstellar traveler hold? Only time will tell, but one thing is certain: the fascination with this comet is just beginning.