NASA has recently published striking new observations of interstellar comet 3I/ATLAS, which exhibited an unexpected flare-up as it exited the solar system. Captured by the SPHEREx space telescope, this surge of activity occurred in December 2025, several months after the comet made its closest approach to the Sun.
Instead of following the typical pattern of fading away gradually, comet 3I/ATLAS released a sudden burst of gas, dust, and complex molecules while moving beyond the inner solar system. These observations revealed a glowing coma surrounding the comet, filled with water vapour, carbon dioxide, and various organic compounds. Scientists also noted a distinctive pear-shaped dust tail formed as rocky material was ejected during this outburst.
Unexpected Activity Challenges Comet Behavior Norms
The timing of this flare-up is particularly intriguing, as comets usually exhibit peak activity near perihelion—the point of closest approach to the Sun. Typically, solar heating causes surface ice to sublimate at this stage. Yet, in the case of 3I/ATLAS, the most intense activity occurred well after reaching that point.
Carey Lisse, lead author of the study, remarked in a NASA statement, “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 behavior has sparked renewed interest and speculation regarding the comet’s origins, with some social media users likening the flare-up to a spacecraft “powering up” as it departs. However, scientists emphasize that there is no evidence supporting the idea of artificial origins.
Research indicates that sunlight may have taken time to penetrate the comet’s hardened outer crust, ultimately reaching buried ice that had remained frozen for billions of years. Once warmed, these ancient materials rapidly escaped into space, leading to the outburst observed by the SPHEREx telescope.
Significance of the Findings
The SPHEREx telescope, operating in infrared wavelengths, is particularly adept at identifying not only dust but also a range of molecules streaming from the comet, including methane, methanol, and cyanide. These substances are considered vital in the early stages of planet formation. Given that 3I/ATLAS originated from beyond the solar system, its chemical composition allows for a rare comparison between local comets and icy bodies formed around other stars.
Preliminary results suggest that many familiar ingredients are present in 3I/ATLAS, reinforcing the notion that the basic building blocks of planets may be prevalent throughout the Milky Way. Additionally, scientists believe that the comet’s prolonged exposure to cosmic radiation during its interstellar journey may have altered its surface, thereby sealing in more pristine ice layers. When solar energy finally reached these untouched areas, it triggered the sudden release of material that was observed.
The findings from this research were published in February 2026 in the Research Notes of the AAS. Although comet 3I/ATLAS is now gradually fading as it ventures deeper into space, scientists assert that its unexpected farewell has provided valuable insights into the nature of interstellar objects. This study serves as a reminder of why such cosmic visitors continue to captivate both scientific communities and the public alike.
