Heavy hydrogen in 3I/ATLAS's methane points to a frigid birthplace
The interstellar comet 3I/ATLAS carries a chemical clue to conditions in the planetary system of its origin, locked away long before it reached our sun. Its methane signature is unusually rich in heavy hydrogen, suggesting that the comet's frozen ingredients took shape in an intensely cold environment around another star—or in the cloud that preceded it.
Scientists have discovered that interstellar comet 3I/ATLAS carries a chemical signature indicative of its formation in a frigid birthplace. The comet, observed by the James Webb Space Telescope, exhibits an unusually high ratio of heavy hydrogen to ordinary hydrogen in its methane. This heavy hydrogen, also known as deuterium, is present in 3I/ATLAS at a ratio of approximately 3.2% - significantly higher than any other methane measured in the solar system.
This enrichment suggests that the comet's icy ingredients took shape in an intensely cold environment around another star or in the cloud preceding its journey to our solar system. The discovery provides valuable insights into the early chemistry of other planetary systems, as the observation of deuterium-bearing methane in 3I/ATLAS was made possible by the telescope's ability to detect faint signals from distant objects.
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