An extraordinary visitor from beyond our solar system, the interstellar comet 3I/ATLAS, is baffling scientists as it streams out carbon-rich chemical compounds at a rate rarely seen in our own cosmic backyard. What makes this icy relic truly remarkable is the sheer amount of methanol it's belching out—a key ingredient for prebiotic chemistry and a compound never before detected in another interstellar object.
This is only the third time we've observed an object from another star system passing through our solar neighbourhood, following the mysterious 1I/'Oumuamua in 2017 and 2I/Borisov in 2019, and 3I/ATLAS is proving to be unlike any native comet we know.
The comet was first spotted in July 2025 by the NASA-funded ATLAS survey telescope in Chile. As it journeyed towards the Sun, a massive cloud of water vapour and gas rapidly formed around it.
Crucially, this envelope contained significantly greater amounts of carbon dioxide than what is typically found in solar system comets. Scientists also noted its light was surprisingly redder than usual, suggesting an unusual surface chemistry, and it began releasing gases while still relatively far from the Sun, an indication that it may not have passed close to another star for hundreds of millions of years, or since it left its home star system.
Unlocking the Mysteries of 3I/ATLAS: An Alien Chemical Signature
To investigate this spectacular, deep-space interloper, NASA's Martin Cordiner and his team at the Goddard Space Flight Center in Maryland turned the powerful Atacama Large Millimeter/submillimeter Array (ALMA) in Chile toward the rogue comet to uncover its secrets. They were astonished to discover that 3I/ATLAS is producing substantial quantities of hydrogen cyanide gas, and an even greater volume of gaseous methanol.
'Molecules like hydrogen cyanide and methanol are at trace abundances and not the dominant constituents of our own comets,' Cordiner explained. 'Here we see that, actually, in this alien comet they're very abundant.'
The team tracked the hydrogen cyanide to the comet's rocky core, where it was being produced at a rate of approximately a quarter to a half a kilogram per second.
Methanol was also detected in the core, but it was also being created in significant quantities in the comet's coma—the long, hazy tail of dust and gas that extends for many kilometres away from the nucleus itself.
The methanol production dwarfs that of hydrogen cyanide, clocking in at around 40 kilograms per second. This makes up roughly 8 per cent of the total vapour streaming from the comet, which is an enormous figure compared to the typical 2 per cent seen in standard solar system comets.
The differences in location for these two molecules also suggests that the comet's nucleus is not uniform, which could eventually tell us about how it formed, says Cordiner.
The Chemical Blueprint: Why 3I/ATLAS Matters for Life
The discovery of such high methanol levels isn't just a scientific curiosity; it has profound implications for the search for life's origins across the Galaxy. While methanol is a relatively simple carbon-containing compound, it's considered a key stepping stone to generating the more complex molecules that are absolutely essential for life to begin.
Cordiner is convinced of its significance, noting: 'It seems really chemically implausible that you could go on a path to very high chemical complexity without producing methanol'. This suggests that wherever complex chemistry is happening in the cosmos, methanol is likely a major intermediary product.
The findings also lend weight to a theory proposed by Josep Trigo-Rodríguez at the Institute of Space Sciences in Spain. He and his colleagues had previously predicted that a comet rich in metals like iron should also produce relatively large amounts of methanol.
This is because the Sun's heat would free up liquid water within the nucleus, allowing it to chemically react with iron compounds in a process that generates methanol. Therefore, the evidence of abundant methanol streaming from the 3I/ATLAS coma could be a strong indicator that this comet is relatively metal rich, he says.
In essence, this mysterious, deep-space wanderer isn't just passing through; it's providing astronomers with a chemical blueprint unlike any other, offering a unique opportunity to study the prebiotic chemical conditions of a completely alien star system.
Ultimately, 3I/ATLAS is more than just a passing rock; it is a cosmic time capsule. Its bizarre chemical signature confirms that the essential building blocks of life are not unique to our quiet corner of the Galaxy but are being forged in star systems light-years away.
Originally published on IBTimes UK
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