Kathrine Frich
Astronomers watching a rare visitor from beyond the Solar System have spotted something they did not expect.
New data suggest the object is behaving differently than predicted as it moves away from the Sun.
The findings come from fresh observations made by a NASA space telescope.
Rare cosmic visitor
Comet 3I/ATLAS, discovered in the summer of 2025, is only the third confirmed interstellar object ever observed passing through the Solar System.
Because it will soon leave the Sun’s vicinity, scientists are racing to collect as much data as possible.
NASA researchers stress that the comet poses no danger to Earth. Instead, it offers a rare opportunity to study material formed beyond our own planetary system.
In December 2025, the SPHEREx space telescope examined the comet using infrared observations.
Unexpected chemistry
The SPHEREx data confirmed the presence of organic compounds, including methanol, cyanide and methane.
On Earth, such substances are associated with life, although NASA notes they can also form through non-biological processes.
These findings help scientists better understand how complex molecules arise in different cosmic environments.
Researchers say interstellar objects like 3I/ATLAS preserve information from regions far outside the Solar System.
The results underline why even short observation windows are scientifically valuable.
Sudden brightening
Roughly two months after its close approach to the Sun, Comet 3I/ATLAS unexpectedly became much brighter.
Scientists attribute this surge in activity to the rapid release of water, carbon dioxide and carbon monoxide.
“Comet 3I/ATLAS spectacularly ejected material into space after passing close to the Sun, and the water immediately converted to gas in interplanetary space,” said Carey Lisse of the Johns Hopkins Applied Physics Laboratory.
Such outbursts are typical of comets heated by solar radiation, but the scale drew particular attention.
Larger fragments emerge
SPHEREx analysis also showed that the comet released not only fine dust, but also larger rocky material. Scientists observed “large grains and clumps” that were less affected by solar radiation pressure.
Despite the intense activity, the comet developed only a small, pear-shaped dust tail. Researchers say this combination suggests unusual surface properties.
SPHEREx’s ability to track emissions across 102 infrared wavelengths allowed scientists to identify a wide range of gases at once, offering insight into the object’s structure and history.
Sources: NASA, JPL-Caltech, WP.
