Mars Orbiters Capture Images of Interstellar Comet 3I/ATLAS
ESA's Mars Express and ExoMars Trace Gas Orbiter have captured images of interstellar comet 3I/ATLAS during its close approach to Mars, providing valuable data on this rare celestial visitor.
Between October 1 and 7, 2025, the European Space Agency's (ESA) Mars Express and ExoMars Trace Gas Orbiter (TGO) observed interstellar comet 3I/ATLAS as it passed approximately 30 million kilometers from Mars. This event marks the third recorded instance of an interstellar object entering our solar system, following 'Oumuamua in 2017 and 2I/Borisov in 2019.
Discovered on July 1, 2025, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Chile, 3I/ATLAS is estimated to be between 5 and 11 kilometers in diameter. Its trajectory suggests an origin from the outer regions of the early Milky Way, potentially making it around 10 billion years old.
During its closest approach to Mars on October 3, the TGO's Colour and Stereo Surface Imaging System (CaSSIS) captured images of the comet's coma—a cloud of gas and dust surrounding its nucleus. Due to the comet's distance, the nucleus itself was not resolved. Mars Express also attempted observations, but the comet's faintness posed challenges for its instruments.
ESA's Jupiter Icy Moons Explorer (Juice) is scheduled to observe 3I/ATLAS between November 2 and 25, 2025, when the comet is expected to be more active following its closest approach to the Sun on October 30. Data from these observations are anticipated to arrive in February 2026.
The study of interstellar objects like 3I/ATLAS offers unique insights into the composition and dynamics of celestial bodies from other star systems, enhancing our understanding of the broader galaxy.