A trio of recently published<\/a> studies<\/a> shed light on the origins of this exotic comet. 3I\/Atlas<\/a> appears to have been born in a cold environment, possibly around 12 billion years ago.<\/p>\n The comet is an interstellar object (ISO), meaning an asteroid<\/a> or comet that originated outside the solar system. It is the third such object found, after 1I\/\u02bbOumuamua and 2I\/Borisov. It was discovered almost exactly one year ago, travelling inbound on a trajectory that has taken it through the inner solar system and out the other side.<\/p>\n These distant origins make ISOs incredibly interesting to astronomers because they are physical pieces of other planetary systems, delivered to us on galactic tides so that they can be studied from the comfort of our own solar system.<\/p>\n As a comet, 3I\/Atlas contained frozen ices that \u201csublimated\u201d \u2013 turned directly from a solid to a gas. These escaped (outgassed) from the comet as it was heated by the Sun, creating a visually spectacular coma (bright atmosphere surrounding the object) and tail.<\/p>\n A comet has no internal light source of its own, instead dust in its coma reflects sunlight and its volatiles (chemicals that readily vaporise or sublimate) display fluorescence.<\/p>\n But this is no mere light show: each fluorescing molecule leaves a spectral fingerprint on the light reaching our telescopes. These fingerprints allow us to identify the chemicals contained within the comet.<\/p>\n They are revealed by splitting the light into its constituent wavelengths with a technique called spectroscopy, allowing astronomers to deduce the comet\u2019s chemical composition.<\/p>\n Unique chemical cocktail<\/p>\n This revealed in 3I\/Atlas a cocktail of water, carbon dioxide and monoxide, methane, cyanides, sulphides, and even free-floating iron and nickel atoms. These ingredients are actually quite expected, as each of them are regularly detected in our own domestic solar system comets. However, their relative abundances are different in 3I\/Atlas: high levels of carbon dioxide (CO\u2082) and low levels of ammonia (NH\u2083) mark it as an outsider.<\/p>\n Additionally, molecules made up from atoms with different isotopes (distinct forms of the same chemical element) also have subtly different spectral signatures. With a bright comet such as 3I\/Atlas, and with our largest and most sensitive telescopes, these signatures can be distinguished, allowing astronomers measure the comet\u2019s isotope ratios.<\/p>\n Matthew Hopkins is a Postdoctoral Fellow at the University of Canterbury.<\/p>\n This article was first published by The Conversation <\/a>and is republished under a Creative Commons licence. Read the original article<\/a>.<\/p>\n![\"The](\"https:\/\/static.independent.co.uk\/2026\/07\/02\/12\/38\/3IATLAS-contents.avif\")
The Webb telescope\u2019s Nirspec (Near-Infrared Spectrograph) instrument can detect specific chemical and molecular signatures. These images of comet 3I\/ATLAS each highlight a part of the comet\u2019s contents (Nasa, Esa, CSA, STScI, M.Cordiner (Catholic University of America, GSFC))<\/p>\n