NASA has released remarkable images of the interstellar comet 3I/ATLAS, captured during its close flyby of Mars in October. This event is significant as 3I/ATLAS is only the third known interstellar object to pass through our Solar System, coming within approximately 30 million kilometres of the Red Planet. The unique opportunity allowed multiple missions to gather unprecedented data and visuals.
The Mars Reconnaissance Orbiter (MRO), Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, and the Perseverance rover successfully recorded images of 3I/ATLAS as it traversed the Martian sky. Although the European Space Agency and China’s Tianwen-1 orbiter released their findings earlier, NASA’s data was delayed due to a government shutdown. With operations resumed, scientists now have access to a variety of observations, including optical, ultraviolet, and surface-based data.
Detailed Observations and Discoveries
The MRO’s HiRISE camera, generally utilized for studying Martian terrain, was repositioned to capture the comet on October 2. The resulting images reveal a glowing white smudge surrounded by a halo of dust and gas, measuring around 1,500 kilometres across. These visuals rank among the closest ever taken of a comet, providing scientists with vital information to estimate the size and composition of its icy nucleus.
MAVEN’s Imaging Ultraviolet Spectrograph (IUVS) observed 3I/ATLAS from September 27 to October 7, yielding detailed ultraviolet images. This data unveiled the chemical composition of the comet’s coma, the cloud of gas and dust enveloping the nucleus, while also offering insights into the hydrogen-to-deuterium ratios. These measurements are crucial for elucidating the comet’s origin, potentially revealing whether it formed in a distant star system with conditions akin to those of our own.
Shannon Curry, MAVEN’s principal investigator at the University of Colorado Boulder, described the findings as “significant,” adding that analysis is just beginning to uncover the wealth of information contained within the data.
The Perseverance rover, stationed on the Martian surface, captured faint images of 3I/ATLAS using its Mastcam-Z instrument on October 4. Given the comet’s dimness, long exposure times were necessary, resulting in streaks of stars in the background while the comet appeared as a faint dot. This marked a historic moment, being the first time an interstellar object has been imaged from the surface of Mars.
The Future of 3I/ATLAS
Since re-emerging from behind the Sun, 3I/ATLAS has exhibited new behaviours, such as increased brightness, ultraviolet and X-ray activity, and a more pronounced colour. These changes indicate dynamic processes within the comet as it continues its journey through the Solar System. Shane Byrne, principal investigator for HiRISE at the University of Arizona, highlighted the rarity of such occurrences: “Interstellar objects are still rare enough that we learn something new on every occasion. We’re fortunate that 3I/ATLAS passed this close to Mars.”
Looking ahead, 3I/ATLAS is set to make its closest approach to Earth on December 19, 2025, at a distance of two astronomical units—almost twice the distance between Earth and the Sun. While it poses no threat, the comet presents a unique opportunity for scientists to study material from beyond our Solar System.
The release of these images represents a significant milestone in interstellar research for NASA and its partners. Each observation contributes to an expanding understanding of how such objects form, evolve, and traverse galaxies, potentially unlocking insights into the origins of planetary systems.
