This image reveals the coma of 3I/ATLAS, the third interstellar object ever identified crossing our Solar System. An international team, including Nicolas Biver, Dominique Bockelée-Morvan, and Jacques Crovisier from LIRA, combined observations from the James Webb Space Telescope and ALMA to investigate the composition of this comet from another planetary system.
The three panels map different gases released as the comet’s ices sublimate under the Sun’s heat : from left to right, water (H₂O), carbon dioxide (CO₂), and carbon monoxide (CO). Their distribution around the nucleus, shown on a scale of 1,300 km per arcsecond, reveals the chemical structure of the gaseous envelope surrounding 3I/ATLAS.
These observations show that although the comet contains familiar molecules, their abundances—and especially their isotopic signatures—differ significantly from those measured in Solar System comets. 3I/ATLAS therefore represents a true time capsule, preserving valuable clues about the formation conditions of small bodies in a distant and ancient planetary system.
