The European Space Agency’s (ESA) Jupiter Icy Moons Explorer (Juice) has successfully imaged the interstellar comet 3I/ATLAS, providing fresh data on an object unlike anything previously observed in our solar system. This comet, first detected in July 2025 by the ATLAS survey telescope in Chile, represents a rare opportunity to study material originating from outside our planetary neighborhood.
A Comet From Another Star System
3I/ATLAS is not just any comet: its trajectory confirms it entered our solar system from the direction of Sagittarius, moving at an unprecedented speed. The comet’s orbit is the most extreme ever measured, proving it’s not a resident of our solar system but a visitor from another star. On October 30, 2025, it reached perihelion – its closest approach to the Sun – coming within 1.4 AU (approximately 130.5 million miles) inside Mars’ orbit.
Juice Mission Observations
Throughout November 2025, Juice deployed five of its instruments – JANUS, MAJIS, SWI, PEP, and UVS – to observe the comet. The team had to wait to analyze the data fully, as Juice used its high-gain antenna as a heat shield during its orbit around the Sun and transmitted data at a reduced rate via a medium-gain antenna. The JANUS camera alone captured over 120 images across a broad spectrum, along with spectrometry and particle data.
Unexpected Jet Activity
Initial analysis of the JANUS images reveals an intriguing anomaly: jets of material are erupting from the comet’s nucleus opposite the direction of the Sun. This contradicts standard comet behavior, where sunlight warms the sun-facing side, creating jets directed toward the Sun. According to Harvard University’s Professor Avi Loeb, this suggests unusual ice pockets on the comet’s surface or an unknown mechanism driving the jet activity.
“The behavior of 3I/ATLAS challenges our understanding of how comets behave, hinting at unique processes governing its composition and evolution,” said Loeb.
Studying this comet is critical because it offers insight into the building blocks of other solar systems and may help us understand how planets form elsewhere in the galaxy. The data from Juice will be crucial in determining the comet’s composition, particle emissions, and the nature of its unexpected jet activity.
This mission highlights how rare interstellar objects can reshape our understanding of planetary systems, providing invaluable data for future astronomical research.
