Coordinated Observations of Interstellar Comet 3I/ATLAS by Gemini and Europa Clipper Ahead of Jupiter Flyby

The study of the interstellar comet 3I/ATLAS (also designated C/2025 N1 (ATLAS)), which was first detected in July 2025, presents astronomers with a rare chance to examine pristine material originating from beyond our Solar System. This celestial body marks the third confirmed interstellar visitor, following 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019. Estimates suggest this comet could be as old as seven billion years, potentially making it the most ancient object ever observed, predating the Sun itself.

The comet completed its perihelion passage on October 29, 2025, and achieved its closest approach to Earth on December 19, 2025, coming within approximately 269 million kilometers (or 1.8 astronomical units). Looking ahead, a significant close encounter with Jupiter is scheduled for March 16, 2026. During this event, the comet will pass within about 53.6 million kilometers of the gas giant. This gravitational interaction is expected to permanently alter its trajectory, setting it on a hyperbolic path out of the Solar System.

Valuable data was successfully gathered in late 2025 through synchronized efforts involving both ground-based and space-based assets. On November 26, 2025, the Gemini North telescope, situated in Hawaii, captured detailed imagery and spectral readings of the comet, revealing a compact coma—the cloud of gas and dust surrounding the icy nucleus. Concurrently, on November 6, 2025, NASA’s Europa Clipper spacecraft, en route to Jupiter, conducted its own observations from a distance of roughly 164 million kilometers.

The Europa Clipper’s Europa-UVS instrument, originally designed to probe Jupiter’s moon Europa, was repurposed to analyze the comet’s coma composition, specifically measuring the ratios of gases to dust particles. This provided a unique vantage point for the Clipper team. Because the comet’s trajectory positioned it between the spacecraft and the Sun, the UVS instrument was able to capture tail emissions flowing “downstream” along the path of the solar wind. This contrasted with ground-based observations, which were hampered by solar interference.

The instrument detected key elements such as oxygen and hydrogen, corroborating evidence of high outgassing activity following the comet’s perihelion passage. Furthermore, as part of a comprehensive investigation, radio signals emanating from 3I/ATLAS were recorded with a statistical significance exceeding 10 sigma, offering robust scientific confirmation of radio emissions likely tied to dust or plasma dynamics. However, when the Green Bank Telescope was utilized by the Breakthrough Listen project on December 18, 2025, no artificial technosignatures were detected.

The scientific community continues to debate the nature of observed anomalies, including a slight non-gravitational acceleration and shifts in the comet’s color. These peculiarities have fueled speculation regarding a possible technological origin, a viewpoint notably advanced by Avi Loeb. Nevertheless, the prevailing consensus, bolstered by the lack of confirmed technosignatures, strongly favors a natural astrophysical explanation. Some research suggests that the unusual chemical makeup, featuring elevated levels of carbon monoxide and carbon dioxide, might stem from billions of years of exposure to galactic cosmic rays impacting the object’s surface while it resided in interstellar space.

The coordination of efforts across major institutions—including Harvard (represented by Avi Loeb), NASA (with assets like Europa Clipper and Juno), and the Gemini Observatory—highlights the high degree of international scientific collaboration underway. The presence of the Juno probe, already orbiting Jupiter, positions it for potential observations of 3I/ATLAS as it makes its close approach in March 2026. Data collected during the late 2025 observation window is absolutely critical for understanding the composition and dynamics of this ancient interstellar matter before the comet completes its transit past Jupiter.