Researchers update the route of 3I/ATLAS with support from ExoMars Trace Gas Orbiter

Researchers have updated the route of 3I/ATLAS with support from the ExoMars Trace Gas Orbiter (TGO). The new data has improved predictions of the comet’s trajectory by a factor of ten compared to previous estimates.

This update was made possible by combining spacecraft observations from TGO, orbiting Mars, with Earth-based telescope measurements, providing a more accurate path for the third interstellar object ever observed passing through the Solar System.

Universe Today reported that this method allowed astronomers to track 3I/ATLAS as it approached and passed Mars in October 2025.

The refined trajectory also facilitates better planning for upcoming spacecraft observations and enables continued monitoring of the comet’s activity as it leaves the inner Solar System.

Observations from Mars

The​‍​‌‍​‍‌​‍​‌‍​‍‌ astronomers at the Gemini South Observatory first spotted the comet 3I/ATLAS on July 1, 2025. The planet-facing telescopes tracked the comet’s location and movement from the Earth until October.

When 3I/ATLAS was getting close to the Red Planet, the ESA’s ExoMars Trace Gas Orbiter and Mars Express orbiters, going there from another direction, took the pictures and thus helped to refine the trajectory.

Conforming to the closest encounter with Mars, the comet was orbiting at about 30 million kilometers or close to 18 million miles, let the orbiters be the ones who made the measurements that telescopes on the ground ​‍​‌‍​‍‌​‍​‌‍​‍‌couldn’t.

Universe Today emphasized that this observation provided a unique opportunity to refine predictions of the comet’s path using spacecraft orbiting another planet.

The combination of Earth- and Mars-based observations also allowed scientists to measure subtle variations in the comet’s velocity and trajectory caused by gravitational influences.

Data integration and trajectory refinement

The Colour and Stereo Surface Imaging System (CaSSIS) on TGO was used to capture images of the comet while orbiting Mars at speeds up to 14,000 kilometers per hour.

Sci.News reported that scientists at the European Space Agency accounted for the spacecraft’s precise position and motion while combining the data with ground-based observations.

This triangulation led to a tenfold improvement in determining the comet’s ephemeris.

The updated trajectory allows astronomers to track 3I/ATLAS more accurately as it continues to move through the Solar System and eventually exits toward interstellar space.

The refined path also provides insight into the comet’s outgassing patterns and allows for better characterization of its nucleus size and composition.

Predicted path and future monitoring

With the refined trajectory, astronomers can plan observations with greater precision.

3I/ATLAS passed its closest point to the Sun on October 30, 2025, and will pass safely by Earth on December 19, 2025, at a distance of 270 million kilometers.

Universe Today reported that these calculations enable telescopes and spacecraft to observe the comet’s outgassing and changes in brightness more effectively.

The improved trajectory also supports ongoing missions such as ESA’s Jupiter Icy Moons Explorer, which can use the data for calibration and comparative studies of interstellar objects.

Triangulating spacecraft data with Earth-based measurements also sets a precedent for monitoring other interstellar or long-period objects in the future.

Implications for planetary defense

Though​‍​‌‍​‍‌​‍​‌‍​‍‌ 3I/ATLAS isn't a threat to Earth, the updated path shows how effective it is to mix data from different places for planetary defense.

As per the report by Universe Today, this is the very first time ESA used the information of a Mars-orbiting spacecraft to pinpoint the location and the path of an object in space.

ESA teams remarked that these techniques might be utilized in the future for the surveillance of a flammable asteroid or a comet that is heading towards Earth.

The activity also serves as a rehearsal of far future deep space voyages, like the Comet Interceptor, which is going to be launched, by delivering confirmed methods of locating the movement of objects.

The new trajectory of 3I/ATLAS exemplifies how combining measurements taken by a Mars orbiter with those from Earth-based telescopes can be quite effective.

Such methods lead to better prediction of the path of interstellar objects, more accurate observation scheduling, and also continuous planetary defense activities.

Stay tuned for more updates.