Interstellar comet 3I/ATLAS may carry material far older than our own solar system, according to new research published in Nature Astronomy.
A team led by NASA scientists analysed observations from the James Webb Space Telescope, taken in late December 2025 as the comet moved away from the Sun. They found that methane in the comet holds far more deuterium, a heavier form of hydrogen, than any body in the solar system. The level measured 13 times the value recorded at comet 67P by the Rosetta spacecraft.
The researchers read the result as a sign that the comet’s ice formed in a cold, metal-poor cloud, consistent with isotope evidence that its material formed 10 to 12 billion years ago. That would make it billions of years older than the solar system, which formed about 4.5 billion years ago.
3I/ATLAS is only the third confirmed object from another star system seen passing through ours. It was first spotted on July 1, 2025, by an ATLAS survey telescope in Chile. Its hyperbolic path showed it was passing through, rather than bound to the Sun.
The age figure is an estimate drawn from chemical evidence, rather than a direct measurement. The researchers note the finding rests on observations from two days in December 2025, and further study will refine the comet’s origin story.
Source: ScienceAlert
