NASA’s SPHEREx Captures Stunning Flare from Comet 3I/ATLAS

NASA has recently observed an unexpected surge in activity from interstellar comet 3I/ATLAS as it exits the solar system. This unusual phenomenon, captured by the agency’s SPHEREx space telescope, has sparked interest among scientists and online observers alike. The comet flared dramatically in December 2025, shortly after making its closest approach to the Sun, defying typical comet behavior.

Comets usually grow more active around perihelion, the point at which they are nearest to the Sun. For 3I/ATLAS, the most intense activity occurred after this point. Instead of gradually fading, the comet released a significant amount of gas, dust, and complex molecules. Images from SPHEREx revealed a glowing coma rich in water vapour, carbon dioxide, and organic compounds, along with a distinct pear-shaped dust tail formed as rocky material was expelled into space during the outburst.

According to Carey Lisse, lead author of the study, “Rather than quietly dimming as it moved away, the comet became significantly brighter. Even water ice was rapidly turning into gas far from the Sun.” This unexpected behavior has raised questions about the comet’s origins and nature.

Scientific Insights from the Flare-Up

3I/ATLAS was first discovered in July 2025 by the ATLAS asteroid survey and marks only the third confirmed interstellar object observed in the solar system. The first was 1I/’Oumuamua in 2017, recognized for its unusual shape and trajectory, while the second, 2I/Borisov, identified in 2019, exhibited traits typical of comets.

Though some social media users have speculated that the comet’s brightening resembles a spacecraft “powering up,” scientists assert there is no evidence to support such claims. They propose a more natural explanation: sunlight may have taken longer to penetrate a hardened outer crust, eventually reaching ancient ice buried beneath the surface. When this ice warmed, the resultant gas and material surged outward, producing the observed outburst.

SPHEREx’s capabilities are particularly suited for this analysis. Operating in infrared wavelengths, the telescope can identify not only dust but also various molecules streaming from the comet, including methane, methanol, and cyanide—compounds considered vital in the early stages of planet formation. The chemical composition of 3I/ATLAS offers a unique opportunity to compare local comets with icy bodies formed around other stars.

Implications for Understanding Interstellar Objects

Initial findings indicate the presence of many common ingredients, supporting the hypothesis that the fundamental building blocks of planets may be prevalent throughout the Milky Way. Additionally, scientists believe that the comet’s long journey through interstellar space, exposing it to cosmic radiation, played a role in its composition. Over time, this radiation likely altered the surface, sealing off pristine ice layers beneath. When solar energy finally reached these untouched areas, it triggered the rapid release of materials.

The results of this research were published in February 2026 in the Research Notes of the AAS. While 3I/ATLAS is now fading as it moves deeper into space, the unexpected flare has provided valuable insights into the nature of interstellar visitors. It highlights the ongoing fascination that such objects inspire, both within the scientific community and among the public.