Interstellar Comet 3I/Atlas May Be 12 Billion Years Old, Carrying 10 Times More Deuterium
Updated
Updated · The Guardian · Jun 22
Interstellar Comet 3I/Atlas May Be 12 Billion Years Old, Carrying 10 Times More Deuterium
3 articles · Updated · The Guardian · Jun 22
Summary
Nature study data from the James Webb Space Telescope and Chile’s Alma observatory suggest 3I/Atlas is up to 12 billion years old—far older than the 4.5-billion-year-old solar system.
Its isotope ratios show an elemental makeup unlike any known solar system body, including about 10 times more deuterium, pointing to formation in an extremely cold environment near -243C.
Scientists say the object may be a relic from “cosmic noon” roughly 10 billion years ago, though they caution alternative edge-case explanations could still account for the chemistry.
3I/Atlas is only the third interstellar object ever observed, and its unusual brightness enabled isotopic measurements that were not possible for 1I/’Oumuamua in 2017 or 2I/Borisov in 2019.
The comet is now leaving the solar system for good, limiting future study, but astronomers expect many more such detections as the Vera C. Rubin Observatory comes online.
What secrets from the dawn of galaxies does this 12-billion-year-old interstellar visitor hold?
Webb spotted a fossil from the universe's dawn. How many more ancient messengers are passing through our system undetected?
This comet’s alien chemistry is unlike our own. How rare are the conditions that created life on Earth?
3I/ATLAS—A Chemical Fossil from Beyond: What the Third Interstellar Object Reveals About Water, Life, and Planet Formation
Overview
Comet 3I/ATLAS, discovered by the ATLAS survey telescope in Chile on July 1, 2025, quickly drew global attention as the third known interstellar visitor to our solar system. Its hyperbolic trajectory confirmed its origin from beyond the Sun’s influence, prompting an extensive observational campaign. The Rubin Observatory tracked it multiple times, and major telescopes like Hubble, JWST, and ALMA, along with NASA spacecraft, joined the effort to study this rare object. The rapid, coordinated response highlights how new interstellar comets can reveal unique insights about the origins and diversity of planetary systems across the galaxy.