The interstellar comet 3I/ATLAS grazes Mars : observation plans and scientific prospects

On October 3, 2025, the interstellar comet 3I/ATLAS will make a close approach to Mars, approaching about 30 million kilometers from the red planet. This encounter offers a unique opportunity for scientists to study an object coming from beyond our solar system.

An exceptional observing opportunity

Discovered on July 1, 2025 by the ATLAS system in Chile, 3I/ATLAS is the third interstellar object identified traversing our solar system, after 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019. Its hyperbolic trajectory and its high velocity indicate an origin outside our solar system. The close passage of 3I/ATLAS near Mars represents a rare opportunity for missions in Martian orbit to directly observe an interstellar comet.

The Martian missions mobilized

The European Space Agency (ESA) plans to use its Mars-orbiting missions to observe 3I/ATLAS. Mars Express, in service since 2003, and the Trace Gas Orbiter (TGO) of the ExoMars mission, operational since 2016, are equipped with instruments capable of analyzing the chemical composition and the structure of the comet. These observations could provide valuable information about the nature of the materials constituting 3I/ATLAS and about the physical processes at play during its passage near the Sun.

Scientific objectives and expectations

The study of 3I/ATLAS offers scientists the opportunity to compare the composition and characteristics of an interstellar comet with those of comets originating from our solar system. This could help to better understand the processes of planetary formation and the evolution of materials in different galactic environments. Researchers also hope to detect complex organic molecules, which are precursors to life, and thus explore the diversity of planetary environments in our galaxy.

Visibility from Earth

For ground-based observers, 3I/ATLAS will remain difficult to observe. Its magnitude estimated at about 18.8 makes it too faint to be detected without the aid of professional telescopes. Moreover, its minimum distance from Earth, estimated at more than 240 million kilometers, excludes any risk of collision or notable effect on our planet.

In short, the close passage of 3I/ATLAS near Mars constitutes an unprecedented opportunity for the scientific community to study an interstellar visitor up close, thanks to the instruments in Martian orbit. The data collected could enrich our understanding of interstellar objects and the processes of planetary formation in the universe.