Mars and Jupiter Probes to Observe Interstellar Comet 3I/ATLAS This Month

The European Space Agency (ESA) is set to utilize missions originally intended for Mars and Jupiter to observe interstellar comet 3I/ATLAS. First detected in July 2025 by the ATLAS telescope in Chile, this comet is recognized as the third known interstellar object to traverse our solar system.

Understanding Interstellar Comet 3I/ATLAS

Astronomers confirmed the extrasolar origin of 3I/ATLAS due to its atypical trajectory and high velocity, estimated at around 130,000 mph (219,000 km/h). The comet is expected to remain visible from Earth until September 2025. After that period, it will move too close to the sun, becoming obscured from our vantage point.

Observation Scheduling

The ESA plans to capitalize on the unique opportunity to monitor 3I/ATLAS using various space missions positioned within the inner solar system. These spacecraft will continue their observations even as the comet moves out of reach from Earth.

• Between October 1 and 7, Mars orbiters, including Mars Express and the ExoMars Trace Gas Orbiter, will observe the comet.
• The closest approach will occur on October 3, with the two spacecraft positioned about 30 million km away from 3I/ATLAS.
• Nasa’s Psyche mission, en route to asteroid 16 Psyche, will also be in a position to observe the comet.

Significance of the Perihelion Phase

From November 2 to 25, the ESA’s Jupiter Icy Moons Explorer (JUICE) will direct its instruments towards 3I/ATLAS after the comet reaches its perihelion, the closest point to the sun. This phase is critical, as solar radiation activates the comet’s core, leading to an increase in surface activity due to the vaporization of ices.

T. Marshall Eubanks, Chief Scientist at Space Initiatives Inc, emphasized that JUICE will have the best observational position during the perihelion phase, where Earth-based observations will be significantly hampered. The instrumentation on various Mars orbiters, such as the Mars Reconnaissance Orbiter (MRO), Tianwen-1, and Hope, is expected to contribute valuable data as well.

Implications of Observations

Observing 3I/ATLAS during this peak activity period will provide scientists with crucial insights into the comet’s composition and behavior. The intense solar heating will cause the comet to develop a luminous halo of gas and dust, enabling astronomers to analyze its chemical makeup through the materials being released.

Committing to this research offers the potential to compare the chemicals of 3I/ATLAS with those of comets formed in our solar system. If similarities arise, it may imply universal building blocks across planetary systems. Conversely, any differences could highlight unique components from another stellar system. This active phase of 3I/ATLAS presents an exciting opportunity for breakthroughs in the understanding of interstellar comets.