ESA Turns Mars and Jupiter Missions toward 3I/ATLAS
The European Space Agency (ESA) is repurposing a fleet of its planetary missions to monitor the interstellar comet 3I/ATLAS as it speeds through the inner solar system. First spotted in July 2025 by Chile’s ATLAS telescope, 3I/ATLAS is only the third confirmed interstellar object, distinguished by its hyperbolic, open orbit and a velocity of about 130,000 mph (219,000 km/h). Ground-based observatories can track the comet through September 2025, but its trajectory will soon take it into a region where Earth-based viewing becomes impractical as it skims past the Sun.
Leveraging Existing Space Assets
To bridge the observational gap, ESA will employ the Mars Express and the ExoMars Trace Gas Orbiter to observe 3I/ATLAS as it nears Mars in early October. The plan includes coordinated measurements during October 1–7, with a close approach around October 3 at roughly 30 million kilometers from Mars. NASA’s Psyche mission and other orbiters, such as Tianwen-1, will participate in the broader observational network, ensuring that 3I/ATLAS remains under continuous study as it passes by Mars.
Post-Perihelion Monitoring with JUICE
Crucially, ESA’s JUICE probe, en route to Jupiter, will join the effort after 3I/ATLAS’ perihelion phase (November 2–25). perihelion—its closest approach to the Sun—will trigger peak activity, with solar heat driving the sublimation of ices and the generation of a coma and tail. JUICE is uniquely positioned to observe the comet as it resumes activity in the intense solar environment, a phase difficult to capture with Earth-based instruments because of daylight and glare near the Sun.
Why This Matters
Lead scientists emphasize that observing 3I/ATLAS across multiple vantage points will reveal its chemical fingerprint, helping determine whether interstellar comets resemble those born in our own solar system. By combining data from Mars, Jupiter, and Sun-adjacent observations, researchers can infer the comet’s composition, structure, and possibly its origin story—whether its ice, dust, and organic materials are typical of other stellar systems.
Implications for Interstellar Science
ESA describes the project as a milestone in understanding how material travels between star systems. The multi-mission approach leverages existing assets, reducing the need for new spacecraft while maximizing scientific return. The data set could inform models of comet formation, interstellar delivery of organic compounds, and the diversity of planetary system architectures across the galaxy.
Scientist Voices and Future Prospects
Scientists—citing experts like T. Marshall Eubanks—note that perihelion presents a unique test for detecting chemical signatures in a challenging observational window. The collaboration framework also serves as a blueprint for future interstellar visitors, offering a proven path to capture high-priority data when space agencies need to improvise with available missions.
As 3I/ATLAS voyages toward the inner solar system’s most intense solar heat zone, ESA’s integrated observatory network stands ready to convert fleeting glances into lasting insights about interstellar matter and the secrets it carries from distant stars.
