How often does humanity get to watch a visitor from another star system slip past the Sun, hidden from Earth’s view? For scientists, the answer is almost never making NASA’s recent campaign to observe comet 3I/ATLAS an extraordinary opportunity.
From October 18 to November 5, 2025, NASA’s Parker Solar Probe employed its Wide-Field Imager for Solar Probe-or WISPR-instrument to capture a rare series of images of 3I/ATLAS during a period when the comet was invisible from Earth. This third confirmed interstellar object skimmed just outside Mars’ orbit, at about 130 million miles from the Sun, and Parker’s vantage point afforded an unobstructed view of its solar-side passage.
1. Discovery and Trajectory
3I/ATLAS was discovered on July 1, 2025, by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) survey telescope in Rio Hurtado, Chile. Its hyperbolic trajectory guaranteed an origin beyond the solar system, and hence it will never return. Coming in from the direction of Sagittarius, the comet passed within 0.194 AU of Mars on October 3 before perihelion on October 30.
2. Parker Solar Probe’s Imaging Campaign
During its outbound leg after the 25th solar flyby on September 15, Parker Solar Probe recorded about ten images per day of the comet. The WISPR team is currently processing the data to eliminate stray sunlight and account for various exposure times that made the comet seem to fluctuate in brightness. Once calibrated, these images will allow researchers to study the coma and tail structure of the object in unprecedented detail.
3. Fleet-Wide Observations
NASA mobilized a diverse array of missions to track 3I/ATLAS. The Earth-orbiting observatories Hubble, James Webb, and SPHEREx combined efforts with interplanetary spacecraft: Psyche, Lucy, and Europa Clipper. When the comet flew within just 19 million miles from the Red Planet, Mars-based assets such as the Mars Reconnaissance Orbiter, MAVEN, and even the Perseverance rover provided close-range imagery.
4. Solar-Proximate Tracking by Heliophysics Missions
Heliophysics spacecraft designed to study the Sun played a pivotal role in monitoring the comet near perihelion. STEREO observed 3I/ATLAS from September 11 to October 2, using image stacking to reveal the faint object. SOHO’s LASCO coronagraph captured it between October 15 and 26 from 222 million miles away, while PUNCH revealed its tail during September 20 to October 3. “We’re really pushing the limits of the system,” said Dr. Kevin Walsh, who led PUNCH’s observations.
5. Chemical Clues and Activity Obtained Unexpectedly
NASA’s Neil Gehrels Swift Observatory detected hydroxyl-a byproduct of water vapor-when the comet was nearly three times Earth’s distance from the Sun, a range within which such activity rarely occurs. This early release of water suggests that 3I/ATLAS contains volatile materials unusually sensitive to solar heating, offering clues about its formation environment beyond the solar system.
6. Ultraviolet Spectroscopy by Europa Clipper
On November 6, Europa Clipper repurposed its Europa Ultraviolet Spectrograph to study the comet’s coma from 102 million miles away. By stacking ultraviolet observations and converting them to visible wavelengths, scientists began mapping the distribution of elements within the gas cloud surrounding the nucleus. This data complements Parker’s optical imagery, creating a multi-spectral profile of the interstellar visitor.
7. Technosignature Searches
Given the rarity of interstellar objects, a series of radio observations were conducted under the Breakthrough Listen Initiative in search of artificial emissions from 3I/ATLAS. Using the Green Bank Telescope across 1–12 GHz, the sensitivities achieved were enough to detect transmitters with an effective isotropic radiated power of just 0.1 W. No technosignatures detected, and all evidence speaks toward a natural astrophysical origin.
8. Departure into Interstellar Space
3I/ATLAS is now outbound following its December 19 closest approach to Earth at 168 million miles. It will pass Jupiter in March 2026 before being flung into the vast reaches of interstellar space. Scientists are in a mad dash to analyze the collected data, knowing this is their only chance to study this particular comet. From the solar-side imaging with Parker Solar Probe to ultraviolet spectroscopy of Europa Clipper, NASA’s leveraging of its coordinated campaign has generated a dataset across multiple wavelengths, distances, and vantage points. Collectively, these observations will enhance our knowledge of the composition, activity, and origins of one of the rarest kinds of objects ever seen passing through our solar system.