The interstellar object 3I/ATLAS has undergone significant transformation following its close approach to the Sun, emerging as a highly active celestial body releasing hazardous gases. Observations from the SPHEREx space observatory reveal that the intense heat from its perihelion has resulted in a chaotic change, marked by the release of a toxic mix of chemicals. This shift suggests that 3I/ATLAS is behaving less like a typical comet and more like a volatile entity, creating a hazardous environment in its vicinity.
Data captured from SPHEREx between December 8 and December 15, 2025, showcases a detailed view of the object’s transformation. The observatory’s infrared images, spanning wavelengths from 0.75 to 5.0 microns, cover an area approximately 300,000 kilometres wide, highlighting a distinct pear-shaped distribution of dust and organic material. Notably, an ‘anti-tail’ extends towards the Sun, contrasting sharply with the nearly round gas plumes identified by researchers.
Among the significant chemical signatures detected were cyanide at 0.93 microns and carbon monoxide at 4.7–4.8 microns, creating a toxic envelope around the nucleus of 3I/ATLAS. The observatory also recorded clear signals of water, organics, and a vast carbon dioxide plume, which extends hundreds of thousands of kilometres outward. This carbon dioxide emission is particularly noteworthy, as it marks a considerable increase in activity compared to previous observations.
Comparing current data to observations taken prior to the perihelion in August 2025 reveals striking differences. Water-ice absorption features, prominent before the close solar pass, have vanished. As noted by Harvard professor Avi Loeb in a January 16, 2026, post, the spectrum now highlights organo-silicaceous dust grains instead of ice. Additionally, the production of water gas has surged, increasing by a factor of roughly 20 compared to pre-perihelion levels.
As the water emissions intensified, they appeared to carry other materials with them, leading to the emergence of spectral features for cyanide and organics that were previously undetected. Interestingly, the absence of submicron dust particles aligns with the object’s unusual behavior, suggesting a lack of a typical cometary tail driven by radiation pressure. The mass loss rate of 3I/ATLAS further illustrates this phenomenon, with new research led by Carey Lisse indicating the object is losing water at approximately 180 kilograms per second. This rate matches the carbon dioxide loss and is about two-thirds that of carbon monoxide.
Bright maps of brightness indicate distinct origins for these emissions. The cyanide and organic materials appear to originate from the dust itself, while the gases of water, carbon dioxide, and carbon monoxide seem to emanate from a symmetric region around the nucleus. This symmetry, coupled with the extensive carbon dioxide plume, suggests a deeper internal process driving the object’s emissions.
Further insights came from images captured by the Hubble Space Telescope on January 14, 2026. These images revealed a glowing halo extending more than 130,000 kilometres towards the Sun. Inside this structure, processed images showcased a sunward-directed anti-tail flanked by three evenly spaced mini-jets. Research co-authored by Avi Loeb and Toni Scarmato indicates that the orientation of this jet system oscillates with a period of 7.1 hours.
These findings challenge traditional cometary models regarding composition and geometry, illustrating a unique configuration for 3I/ATLAS that defies established norms in celestial behavior. As researchers continue to analyze the data, the implications of this transformation will likely reshape our understanding of interstellar objects and their interactions with the solar system.
