NASA’s SPHEREx Mission Tracks Brightening of Interstellar Comet 3I/ATLAS

Key facts

• NASA’s SPHEREx mission observed comet 3I/ATLAS in December 2025, detecting infrared light from dust, water, organic molecules, and carbon dioxide in its coma.
• Comet 3I/ATLAS is only the third interstellar object discovered passing through our solar system.
• SPHEREx detected organic molecules including methanol, cyanide, and methane within the comet’s coma.
• The comet showed a dramatic brightness increase two months after its closest approach to the Sun, due to sublimation of water, carbon dioxide, and carbon monoxide.
• The mission is managed by NASA’s Jet Propulsion Laboratory (JPL) and launched on March 11, 2025.
• SPHEREx completed the first of four planned all-sky infrared maps of the cosmos in late 2025.
• Comet 3I/ATLAS was discovered by the NASA-funded ATLAS survey telescope in Rio Hurtado, Chile, on July 1, 2025.