Thanks to data gathered by the Color Stereo Surface Imaging System (CaSSIS) on board ESA’s Trace Gas Orbiter (TGO) spacecraft orbiting Mars, scientists have enhanced the predicted location of interstellar comet 3I/ATLAS by a factor of 10.
This image of interstellar comet 3I/ATLAS was captured on October 3, 2025, by the CaSSIS instrument aboard ESA’s Trace Gas Orbiter. Image credit: ESA/TGO/CaSSIS.
3I/ATLAS was discovered on July 1, 2025, by the NASA-funded ATLAS (Asteroid Terrestrial Impact Last Alert System) telescope located in Rio Hurtado, Chile.
Prior to September, researchers depended on Earth-based telescopes to track the positions and orbits of interstellar comets.
From October 1 to 7, TGO concentrated on 3I/ATLAS from its orbit around Mars.
The comet came relatively close to Mars, achieving a distance of roughly 29 million km at its closest approach on October 3.
The Mars rover observed 3I/ATLAS from approximately 10 times closer than Earth telescopes and from a fresh vantage point.
By triangulating data from TGO/CaSSIS and Earth-based observations, scientists significantly improved the accuracy of the comet’s predicted trajectory.
Initial expectations were for a modest improvement, but the findings revealed an impressive tenfold increase in precision.
“Utilizing data from the Mars rover made it challenging to refine the interstellar comet’s path through space,” stated TGO team members.
“The CaSSIS instrument is crafted to provide high-resolution observations of the nearby Martian surface.”
“This time, the camera was directed high above Mars, capturing the minute, distant 3I/ATLAS streaking across the star-filled sky.”
Planetary Defense Team Astronomer from ESA’s Near Earth Object Coordination Center was already adept at determining asteroid and comet orbits, necessitating consideration of the spacecraft’s unique position.
“Generally, orbital observations are conducted from fixed terrestrial observatories, but occasionally from spacecraft in near-Earth orbit, such as the NASA/ESA Hubble Space Telescope or the NASA/ESA/CSA James Webb Space Telescope,” the researchers noted.
“Astronomers excel at factoring in the positions of celestial bodies to ascertain their future positions, known as ephemerides.”
“In this instance, the accuracy of the 3I/ATLAS ephemeris—especially its predictions—relied on accounting for the precise location of TGO, including Mars and its rapid orbit around it.”
“Achieving this required a collaborative effort from various ESA teams and partners, ranging from flight mechanics to science and instrumentation.”
To attain the highest possible accuracy, we needed to address challenges and nuances typically overlooked and minimize margins as much as we could.
Source: www.sci.news
