NASA’s SPHEREx Spots Interstellar Comet Flaring With Gas and Organic Molecules

NASA's SPHEREx space telescope has captured a rare sight: an interstellar comet that has brightened as it leaves the solar system. The object, dubbed 3I/ATLAS, surprised astronomers by giving off a burst of gas, dust, and complex molecules two months after its closest approach to the sun. Instead of fizzling into the emptiness of deep space, the comet burst with activity, producing a glowing cloud containing water vapour, carbon dioxide, and organic molecules. The event provided scientists a rare opportunity to examine material formed around another system of stars.

SPHEREx Detects Unusual Chemical Outburst From Rare Interstellar Comet 3I/ATLAS After Solar Flyby

According to a NASA statement and findings published in Research Notes of the AAS, SPHEREx imaged the outburst in December 2025, when the comet was already receding from the inner solar system. The infrared numbers showed the water ice quickly converting to a gas, as well as methane, methanol, and cyanide. The activity was described by scientists as unusually strong for a comet that had already passed perihelion, its closest approach to the sun.

3I/ATLAS was found in July 2025 by the ATLAS survey and is just the third known interstellar object to have been spotted visiting our solar system. Unlike previous visitors like 'Oumuamua and Borisov, this comet displayed extended chemical activity and is particularly useful to study.

Delayed Ice Release Reveals Ancient Material, Offering Clues to Planet Formation Beyond Our Solar System

The material is released from layers deep within the ancient ice beneath the comet's surface as sunlight has gradually filtered down to them. Observations revealed a dusty tail shaped like a pear from ejected rocky particles, and the comet's chemistry allows for comparisons of material across star systems.