For the better part of a decade, space enthusiasts have scanned the horizon for the next 'interstellar interloper'—a celestial wanderer from a distant star system passing through our neck of the woods. First came the enigmatic 'Oumuamua in 2017, followed by the comet Borisov in 2019.
Now, a third stranger has arrived, and it is currently being poked and prodded by some of the most sophisticated hardware humanity has ever launched into the deep. This latest visitor, 3I/ATLAS, has proven to be the fastest and most eccentric of the three, sporting a record-breaking orbital eccentricity of 6.14 and a top speed of 153,000 miles per hour reached during its perihelion passage.
NASA's Europa Clipper spacecraft, currently on a long-haul journey to Jupiter, has successfully captured the interstellar comet 3I/ATLAS in ultraviolet light. What makes this feat particularly impressive is that the spacecraft captured these images while the object was completely obscured from Earth-based observatories.
According to a statement from the SETI Institute on Tuesday, the mission's ultraviolet spectrograph—originally designed to study the icy moon Europa—was rapidly repurposed to catch the visitor. The spacecraft was approximately 102 million miles from the comet at the time, providing a 'sunward' viewpoint that was impossible to achieve from Earth's orbit.
A Rare Glimpse Into The Frozen Heart Of 3I/ATLAS
The data retrieved by Europa Clipper has provided vital clues about the comet's composition. By detecting hydrogen and oxygen within the comet's coma—the hazy cloud of gas surrounding its solid nucleus—scientists have confirmed the presence of water-ice sublimation. But separate results from the James Webb Space Telescope (JWST) have added a twist: they show that 3I/ATLAS is actually 72.7% carbon dioxide, with an 8:1 ratio of CO₂ to water production.
Basically, the comet's frozen water turns into gas when it gets close to our sun, which is what the spacecraft sees as the comet's glow. The observations were very important because they showed that the comet was not breaking apart because of the stress of its journey, whether from gravity or heat.
The discovery of 3I/ATLAS was first reported on 1 July 2025 by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) survey in Chile. While the term 'interstellar visitor' often sparks headlines about potential hazards, NASA has been quick to reassure the public that the object will not come close enough to pose any threat to Earth.
The comet made its closest approach to our planet on 19 December 2025, maintaining a safe distance of 170 million miles (1.8 AU). It is currently on what mathematicians call a hyperbolic trajectory; it is essentially a tourist just passing through, not bound by the sun's gravity, and it is expected to remain visible in the pre-dawn sky until the spring of 2026.
The Europa Clipper team, operating out of NASA's Jet Propulsion Laboratory (JPL), utilised the Europa-UVS instrument for a seven-hour observation window on 6 November 2025. At the time, the craft was roughly 102 million miles away from the comet.
The resulting composite images are a celestial work of art, depicting gas in vibrant blues and greens and dust in deep reds, with streaks perfectly aligned to the comet's dust and ion tails. While the comet is outbound now, it is scheduled for a 'Jupiter encounter' on 16 March 2026, passing the gas giant at a distance of 0.358 AU.
Scanning For Life: The Search For Signals From 3I/ATLAS
Whenever a rogue object enters our solar system, the question of its origin—and nature—inevitably arises. To that end, the Breakthrough Listen programme turned the massive 100-metre Robert C. Byrd Green Bank Telescope toward the comet on 18 December, just a day before its closest approach to Earth. They were looking for 'technosignatures'—radio signals that might suggest the object was something other than a lump of ice and rock.
The results, published in a recent preprint, were a 'null' find. Researchers scanned frequencies between 1 and 12 gigahertz, searching for transmitters as weak as 100 milliwatts. Whilst nine potential candidate signals were initially flagged, they were all eventually dismissed as terrestrial radio-frequency interference.
Specifically, the Green Bank scan confirmed an absence of transmitters above 0.1 watts—roughly equivalent to the power of a mobile phone. Lead researcher Benjamin Jacobson-Bell, from the University of California, Berkeley, admitted the result was expected. 'We all would have been thrilled to find technosignatures coming from 3I/ATLAS, but they're just not there,' he told Space.com.
However, the scientific community isn't done yet. Europe's JUICE mission also joined the watch party in November, using five different instruments to track the comet. Additional sightings have come from the Mars Reconnaissance Orbiter and even the Perseverance rover, which paused its Martian exploration to photograph the comet in October 2025.
Experts think we are entering a new era of discovery as the Rubin Observatory prepares to launch its 10-year Legacy Survey of Space and Time in the coming months. For now, 3I/ATLAS is a silent but interesting messenger from the stars that reminds us of how much more there is to learn in the vast, cold emptiness of space.
