Comet 3I/ATLAS formed in an ultra-cold planetary system
Updated
Updated · Sci.News · Apr 28
Comet 3I/ATLAS formed in an ultra-cold planetary system
12 articles · Updated · Sci.News · Apr 28
ALMA found the interstellar comet’s water deuterium-to-hydrogen ratio is over 30 times solar system comets’ and more than 40 times Earth’s oceans.
University of Michigan researchers said the chemistry points to formation below about 30 kelvin under unusual radiation conditions, with the signature preserved after ejection into interstellar space.
Observed days after perihelion as it emerged from behind the Sun, 3I/ATLAS offers a rare way to compare another planetary system’s origins with our own; the study appeared in Nature Astronomy.
How might these findings about interstellar comet water challenge our assumptions about where life-friendly planets can form?
Is it possible that future interstellar comets will show even more exotic chemistry, reshaping our understanding of the galaxy’s history?
The 2025 Discovery of Comet 3I/ATLAS: A Galactic Time Capsule with Unprecedented Chemical Signatures
Overview
Discovered on July 1, 2025, Comet 3I/ATLAS is the third confirmed interstellar object, originating from the Milky Way's ancient thick disk. As it neared the Sun, solar heating caused volatile ices to sublimate, producing intense cometary activity with a coma, tail, and jets. Detailed analysis revealed an exceptionally high carbon dioxide-to-water ratio, likely due to its unique formation environment. ALMA observations showed an extreme deuterium-to-hydrogen ratio in its water ice, indicating it formed in an ultra-cold, CO-depleted environment within the thick disk. These chemical signatures preserve a record of primordial galactic conditions, challenging assumptions about planetary system formation and highlighting the need to intercept such interstellar visitors for closer study.