ESA to Repurpose Mars and Jupiter Missions for 3I/ATLAS Observation
The European Space Agency (ESA) is adapting its existing fleet of Mars and Jupiter mission spacecraft to observe interstellar comet 3I/ATLAS as it travels through our solar system. The plan leverages the near-identical orbits and complementary vantage points of Mars Express, the ExoMars Trace Gas Orbiter, and the upcoming JUICE mission to capture data during 3I/ATLAS’s peak activity, providing a unique glimpse into a visitor from another star system.
Why 3I/ATLAS is a Rare Visitor
3I/ATLAS was first spotted in July 2025 by Chile’s ATLAS telescope. It stands out as only the third known interstellar object, distinguished by its hyperbolic trajectory and a high velocity around 130,000 mph (219,000 km/h). Unlike long-period comets bound to the Sun, interstellar comets arrive from outside our solar system and carry clues about planetary formation and materials from distant stars. Ground-based telescopes will track 3I/ATLAS through September 2025, but its upcoming approach to the Sun will soon hinder Earth-based observations.
Strategic Observation Windows
To maximize data collection, ESA has mapped observations across multiple windows. Mars Express and the ExoMars Trace Gas Orbiter will observe 3I/ATLAS as it passes near Mars from October 1–7, with closest approach around 30 million kilometers on October 3. NASA’s Psyche mission and other orbiters such as Tianwen-1 will contribute complementary measurements from different vantage points. Crucially, ESA’s JUICE (Jupiter Icy Moons Explorer), en route to Jupiter, has a pivotal role in tracking the comet after perihelion in November, enabling sustained monitoring during its most active phase near the Sun.
What JUICE Brings to the Table
JUICE is uniquely positioned to study 3I/ATLAS’s post-perihelion activity. As the comet nears its closest solar approach, solar heating triggers the sublimation of ices, releasing gas and dust that form a coma and tail. Observations from JUICE can capture chemical signatures and changes in activity that are most pronounced when the comet is closest to the Sun. This data is valuable for understanding the nucleus’s composition, outgassing rates, and the physical processes at play when rocky material interacts with intense solar radiation.
Anticipated Scientific Payoffs
According to ESA scientists, data gathered from repurposed platforms will help determine whether interstellar comets share chemical fingerprints with those from our own solar system, or whether they carry exotic materials formed in different stellar nurseries. The combined observations will also shed light on the mechanisms by which material travels between star systems, offering clues about how common such interstellar visitors are and what they can tell us about planetary formation across the galaxy.
Collaborative Effort and Future Implications
The mission plan integrates ESA’s Mars Express and ExoMars Trace Gas Orbiter with JUICE, along with NASA’s Psyche and other international assets. This collaborative approach optimizes sky coverage, cross-calibration of instruments, and data sharing. If successful, the campaign could become a template for future interstellar object studies, demonstrating how existing spacecraft can be re-purposed to answer new, high-priority science questions without waiting for dedicated missions.
Expert Commentary
“JUICE is best positioned for perihelion, when Earth observations are hardest,” explained scientist T. Marshall Eubanks, underscoring the value of a multi-mission strategy. The forthcoming measurements will help scientists extract a chemical fingerprint for 3I/ATLAS and assess how interstellar comets compare with their solar-system counterparts. ESA contends that this data could reshape our understanding of how material moves between star systems and across the galaxy.
Why This Matters for the Public
Beyond the scientific thrill, studying 3I/ATLAS can expand humanity’s knowledge of the cosmos and the diversity of materials formed in other star systems. As researchers piece together the comet’s composition and behavior, we gain a broader perspective on planetary formation, the distribution of organic compounds in space, and the potential for future interstellar visits.
