ESA uses Mars, Jupiter missions to track interstellar comet 3I/ATLAS

The European Space Agency (ESA) is repurposing Mars and Jupiter mission spacecraft to monitor interstellar comet 3I/ATLAS as it moves through the solar system, aiming to unlock secrets of interstellar comets during its peak active phase.

First spotted in July 2025 by Chile's ATLAS telescope, 3I/ATLAS is only the third known interstellar object—identified by its open (non-closed) orbit and speed of 130,000 mph (219,000 km/h). Ground-based telescopes will be able to observe it until September 2025, but its path near the Sun will soon block Earth's view.

To fill this gap, ESA's Mars Express and ExoMars Trace Gas Orbiter will observe the comet near Mars (Oct 1-7, closest at 30M km on Oct 3), joined by NASA's Psyche mission and other orbiters like Tianwen-1. Critically, ESA's JUICE probe (bound for Jupiter) will track 3I/ATLAS post-perihelion (Nov 2-25)—its closest Sun pass, when solar heat triggers maximum activity, vaporizing core ices into a gas/dust coma and tail.

"JUICE is best positioned for perihelion, when Earth observations are hardest," said scientist T. Marshall Eubanks, noting that this data will help reveal 3I/ATLAS's chemical fingerprint and determine whether interstellar comets resemble those from our own solar system. ESA says the data will reshape our understanding of how material moves between star systems.