The European Space Agency (ESA) and NASA are jointly investigating interstellar comet 3I/ATLAS, a celestial visitor first observed on July 1, 2025, by the ATLAS telescope in Chile. This marks the third confirmed interstellar object detected in our solar system, following 'Oumuamua and Borisov.
3I/ATLAS is currently traversing our solar system at a speed of approximately 60 km/s relative to the Sun. Its closest approach to the Sun is anticipated on October 30, 2025, passing within Mars' orbit. While estimated to be up to 20 kilometers wide, the comet poses no threat to Earth, maintaining a safe distance of at least 240 million kilometers.
The ESA's Planetary Defence Office, along with NASA, is actively monitoring 3I/ATLAS using telescopes in Hawaii, Chile, and Australia. The Hubble Space Telescope provided detailed imagery on July 21, 2025, revealing a distinctive teardrop-shaped coma of dust. The James Webb Space Telescope observed the comet on August 6, 2025, delivering crucial data on its composition and activity, confirming water activity and detecting hydroxyl emission. Analysis indicates a CO2/H2O mixing ratio of 8.0 ± 1.0, higher than typically seen in comets from our solar system, suggesting a different formation environment.
As of September 3, 2025, 3I/ATLAS continues its journey, offering scientists a rare opportunity to study an object from another star system. Studies suggest 3I/ATLAS could be as old as 7 billion years, potentially originating from the Milky Way's thick disk. Its high excess velocity (v∞=58 km/s) and orbital eccentricity of 6.141±0.002 further support its ancient origins and unique trajectory through the solar system. The comet's composition also includes nickel but not iron, a finding that puzzles scientists and points to unique chemical processes in its home system.
The extended observation period, from July through December 2025, provides an invaluable opportunity to study the evolution of cometary activity and composition as it approaches the Sun. The collaborative research by ESA, NASA, and international partners aims to unravel the comet's composition, activity, and trajectory, significantly advancing our understanding of interstellar objects and planetary system formation.