In 2025, astronomers discovered 3I/ATLAS, only the third confirmed interstellar object. 1 year later, its heavy water revealed clues to a cold alien planetary system

In 2025, astronomers discovered 3I/ATLAS, only the third confirmed interstellar object. 1 year later, its heavy water revealed clues to a cold alien planetary system. ALMA and the James Webb Space Telescope found high deuterium levels in its water. The result suggests that its ice formed below about 30 kelvin and preserved chemical evidence from another planetary system for billions of years before entering the Solar System.