Spectroscopic studies of the comet 3I/ATLAS have unveiled significant chemical compositions including nickel-bearing species in its coma, a characteristic that mirrors observations of the interstellar comet 2I/Borisov. The presence of nickel indicates that 3I/ATLAS originated from a metal-rich protoplanetary disk where both silicate and metal grains became part of its icy core. This enhances our understanding of the early chemical environment in its system of origin.
Furthermore, the detection of cyanide radicals (CN) around 3I/ATLAS confirms the existence of typical volatile compounds found in comets like those in the Solar System. CN is a breakdown product of hydrogen cyanide (HCN), which is implicated in organic chemistry pathways. Its detection suggests that 3I/ATLAS formed in the colder outer regions of its parent star system—a habitat conducive to the condensation and preservation of nitrogen-rich ices over vast time spans.
An interesting aspect of 3I/ATLAS is its apparent depletion of carbon-chain molecules, such as C₂ and C₃. This phenomenon reflects a chemical pattern also recognized in 2I/Borisov, as well as several carbon-depleted comets within our Solar System. This depletion indicates either a formation zone lacking in carbon-rich organic materials or prolonged exposure to interstellar radiation, which can degrade organic compounds over time.
Long periods in interstellar space, subjected to cosmic ray interactions, can lead to the breakdown of complex organic chains or even their complete destruction. The low levels of C₂ and C₃ detected in 3I/ATLAS support the theory that this comet has existed in the harsh conditions of interstellar space, far removed from any sun’s protective influence.
The detection of nickel traces suggests that 3I/ATLAS was likely formed in warm, dust-rich settings, while the prevailing presence of cyanide and other volatiles indicates extremely low temperatures during its formation. This duality suggests that the comet emerged from just beyond the snow line of its home star system, where metals, water, and nitrogen-based materials could coexist in solid states before being integrated into cometary nuclei.
Overall, the unique mixture of nickel-bearing compounds, cyanide, and an absence of carbon chains sets 3I/ATLAS apart from known Solar System comet classes. These distinctive characteristics bolster the hypothesis that 3I/ATLAS is truly an interstellar object, having formed under markedly different chemical conditions than those in our solar environment, and has undergone substantial alteration due to extensive cosmic-ray exposure over billions of years.