NASA's James Webb Space Telescope has found new clues about the origin of the interstellar comet 3I/ATLAS. This object is suspected to have formed 10 to 12 billion years ago, long before the Sun and the solar system were born.
As reported on NASA's official website, quoted Tuesday, June 23, Webb measured the chemical composition of the comet as 3I/ATLAS began to move away from the Sun in December 2025. The comet just passed its closest point from the Sun so that its primordial ice turned into a bright gas sheath that is easy to observe.
The results of the observations show that the ratio of carbon and deuterium in 3I/ATLAS is different from that of comets originating from the solar system. Deuterium is a heavy hydrogen. This element can give clues about the temperature and environment where a celestial body is formed.
The name 3I/ATLAS refers to its status as the third confirmed interstellar comet. That is, this comet comes from outside the solar system. ATLAS is a NASA-funded sky monitoring system and was the first to discover the object.
"This is a unique opportunity to study ancient objects from distant galaxies, possibly older than the Sun and our solar system," said Martin Cordiner, a NASA Goddard astrochemist and lead author of the study, as quoted from NASA's official website.
The research was published on June 22 in the journal Nature.
The research team used the NIRSpec instrument on Webb. NIRSpec is a tool that reads near-infrared light to recognize chemical elements in space objects.
The instrument found deuterium levels about 30 times higher than comets in the solar system. This finding suggests that 3I/ATLAS was likely born in a very cold system in the early history of the galaxy.
The material that forms comets is suspected to have been exposed to a lot of radiation, but it did not experience long heating. Therefore, the heavy water ice does not turn into H2O ice like water known on Earth.
Webb also found only a small amount of carbon-13 compared to the lighter carbon-12. This pattern points to a very old origin. This is because the star system is usually richer in carbon-13 as the birth and death of stars from generation to generation.
Therefore, the carbon-13 levels around the Sun are higher. Our solar system is relatively young, formed about 4.5 billion years ago.
The team estimates that 3I/ATLAS formed during a period called cosmic noon, when star formation reached its peak. The comet's parent system likely resided in a cold and dense cloud.
Another study using the European Southern Observatory's Very Large Telescope also reinforced Webb's findings. The study, led by Cyrielle Opitom of the University of Edinburgh, examined variations in carbon and nitrogen in 3I/ATLAS in cyanide compounds.
Stefanie Milam of NASA Goddard said the discovery of this rare isotope is important for understanding the chances of prebiotic chemistry elsewhere in the galaxy. Prebiotic chemistry is a chemical process that can be the initial material for the formation of life.
"So far, we only know of one place in the vast cosmos where chemical ingredients give rise to life, namely our solar system, our Earth," Milam said, quoted from NASA's website.
According to Milam, the analysis of interstellar objects such as 3I/ATLAS is an important step to understand whether the conditions for the emergence of life in the universe are common or rare.
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