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New Delhi: Astronomers studying the interstellar comet 3I/ATLAS have made a discovery that is leaving the scientific community puzzled. Nickel vapor has been detected coming off the comet even though it is still far away from the sun, in a region where temperatures are too cold for metals to turn into gas. This is not just a minor detail. It challenges the way scientists understand the chemistry of comets coming from beyond our solar system.
3I/ATLAS is only the third interstellar object ever discovered. Unlike the previous two, it was spotted early, giving scientists a rare chance to watch it activate as it travels toward the sun. This comet may be carrying material that formed around another star billions of years ago, making it a natural time capsule.
During observations with the Very Large Telescope in Chile, scientists identified atomic nickel in the gas cloud surrounding the comet, called the coma. This was unusual because the comet was still nearly four times farther from the sun than Earth, where temperatures are extremely low.
Nickel normally vaporises at very high temperatures. Yet, the signal from 3I/ATLAS was clear. Scientists detected nickel repeatedly, even when iron, which usually appears along with nickel, was missing.
As one group of researchers explained in their study, “Our observations… recorded spectral lines consistent with atomic nickel vapor in the comet's tenuous atmosphere at a distance of 3.88 astronomical units (AU) from the sun.”
In simple terms, nickel was appearing as gas where it should still be frozen solid.
This unusual chemical behaviour may indicate that nickel is not being released directly from metal, but from special types of molecules that contain nickel and break apart when exposed to sunlight. These molecules may be bonded with carbon monoxide or other organic compounds that can release nickel at much lower temperatures.
Researchers also detected cyanogen (CN) gas when the comet moved closer, along with high levels of carbon dioxide. Observations from the James Webb Space Telescope confirmed that the comet’s coma has more carbon dioxide than water, unlike most comets in our solar system.
This means 3I/ATLAS is chemically different and possibly formed in a planetary system with completely different conditions from our own.
The new data also shows that 3I/ATLAS has a much higher nickel-to-iron ratio than any known comet. Scientists wrote, “The presence of nickel and iron atoms in cometary coma is extremely puzzling… 3I/ATLAS exhibits extreme properties in the early phases of its activity with regard to the production rates and abundance ratios of nickel and iron.”
This suggests the comet’s chemistry is not easily explained by current models. It could also indicate that interstellar comets carry materials not commonly found in our solar neighbourhood.
As 3I/ATLAS moves closer to its closest point to the sun on October 29 (IST date conversion pending final observation timings), astronomers expect more chemical reactions to become visible. There is also speculation from astronomers like Harvard’s Avi Loeb, who noted that 3I/ATLAS displays “extreme” and “unexpected” qualities that set it apart from normal comets.
With global teams watching the comet through space and ground-based telescopes, scientists hope to uncover whether its chemistry reflects an exotic star system or some unknown interstellar process.
This discovery is not just about nickel. It is about rewriting our understanding of planetary materials across the galaxy.
