Interstellar Comet: Water 14 Times Heavier Than Earth's ⚡ экспресс
Based on near-infrared spectra of the coma of interstellar object 3I/ATLAS obtained by the James Webb Telescope, the D/H ratio in methane was determined: (3.31±0.34)%. This value is 14±2 times higher than that for comet 67P/Churyumov-Gerasimenko — the only other body where CH₃D has been detected. At the same time, the ratio of the degree of methane deuteration to water deuteration is consistent for both objects within 1.2σ. The high deuterium content in methane and water of 3I/ATLAS is explained by formation in an environment with initially high D/H due to low temperatures in the protoplanetary disk and the preceding molecular cloud. Thus, the birth conditions of 3I/ATLAS were fundamentally different from those in the vicinity of the young Sun.
Comet 3I/ATLAS was spotted when it entered the Solar System from interstellar space. The James Webb Telescope split the light from its gas cloud into a rainbow—a spectrum—and in this pattern, the lines of rare molecules with deuterium (heavy hydrogen) appeared.
For 3I/ATLAS, this 'thermometer' is off the charts: for every 30 ordinary hydrogen atoms, there's one deuterium atom—in Earth's oceans, that ratio is hundreds of times poorer. This means the comet was born in the icy darkness of a distant protoplanetary disk—a region where planets are just beginning to coalesce from cosmic dust and gas. This alien world is far colder than the cloud that gave birth to our Sun and Earth.
🎯 The deuterium abundance points to a comet birth temperature below –250°C — colder than the eternal shadows on the Moon.
🎬 Interstellar wanderers like 3I/ATLAS come to life in the pages of science fiction: for example, in Arthur C. Clarke's novel 'Rendezvous with Rama'.