NASA’s SPHEREx mission has detected a dramatic surge in sublimation on the interstellar comet 3I/Atlas following its close approach to the Sun.

Observations show carbon dioxide, carbon monoxide, and water vapor emissions spiked as previously insulated ices beneath the comet’s surface became active inside the solar system’s ice line.

Earlier in 2025, the comet’s activity was dominated by large icy grains releasing mainly carbon dioxide, but perihelion triggered a deeper, multi-phase sublimation.

These findings provide the first clear evidence that interstellar objects can change activity depending on solar proximity and suggest 3I/Atlas contains complex ices and organic compounds similar to those in the early solar system, the Daily Galaxy has reported.

Scientists say continued monitoring by SPHEREx and future missions like JWST could reveal more about the composition of such alien comets and their role in cosmic evolution.