3I/Atlas’ journey becomes clearer thanks to Mars Orbiter observations, say astronomers

Astronomers have a much clearer idea of where interstellar comet 3I/Atlas is going, all thanks to an unlikely assistant in the shape of a Mars-orbiting probe.

To date, most of the tracking had been done from Earth, but this new Martian perspective has helped researchers achieve a far better understanding of the path of this comet. 

3I/Atlas was first spotted on July 1, 2025, by the Gemini South Observatory.

It immediately made headlines in the astronomy world because it is only the third interstellar object ever seen to pass through our Solar System.

Since then, scientists have been working to figure out where this object came from and where it will go next.

​A new angle from Mars

Before October, astronomers could track the comet only with telescopes on Earth. But 3I/Atlas moved close enough to Mars that two ESA spacecrafts — the ExoMars Trace Gas Orbiter (TGO) and Mars Express — were able to see it from a completely different angle. This second viewpoint made a big difference.

However, taking these images was not easy. The cameras on the orbiters were built to photograph Mars’ surface, which is bright and close.

Instead, they had to capture a tiny, faint comet almost 30 million kilometers away.

On top of that, TGO moves extremely fast — about 14,000 km per hour — so the team had to calculate the exact position of the spacecraft every moment in order to track the comet correctly.

The first time Mars helped us track an interstellar visitor

ESA’s Near-Earth Object Coordination Center (NEOCC) took on the challenge. Their experts usually track asteroids that may come close to Earth, but this time they applied the same methods to an interstellar comet.

They combined:

• data from Earth-based telescopes
• images and movement data from the TGO orbiting Mars

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By putting these two views together, the team improved the accuracy of the comet’s predicted path by 10 times.

This is the first time in history that data from a spacecraft orbiting another planet has been used to map the trajectory of an interstellar object.​

Where the comet is going next

3I/Atlas passed closest to the Sun on October 30, 2025. It is now moving at almost 250,000 km per hour, heading toward its closest approach to Earth on December 19, 2025.

Even then, it will stay at a safe distance of about 270 million kilometers, so there is no danger to our planet.

The improved tracking will help astronomers point their telescopes more accurately in the coming weeks.

This is important because every clear view of the comet helps scientists learn more about where it came from and what it is made of.

​A useful test for the future

Even though 3I/Atlas is harmless, tracking it has been a helpful “practice run” for planetary defense.

It showed how useful it is to combine Earth-based observations with those taken from spacecraft across the Solar System.

More missions watching the comet

ESA’s JUICE spacecraft, currently on its way to Jupiter, is also observing 3I/Atlas and collecting data.

Meanwhile, ESA is preparing new missions like Comet Interceptor and NEOMIR, which will help study future comets in even more detail.

As 3I/Atlas continues its journey out of the Solar System, astronomers believe it will offer valuable clues about objects from far beyond our cosmic neighbourhood.