A Rare Cosmic Visitor Photographed from the Red Planet
A significant milestone in deep space exploration has been achieved by China’s Tianwen-1 probe, which is currently orbiting Mars. The spacecraft successfully captured detailed images of comet 3I/ATLAS, a rare object originating from outside our solar system. This observation, made in early October 2025, marks the first time an interstellar “visitor” has been photographed from Martian orbit, demonstrating a remarkable advance in the ability to monitor distant and dynamic celestial bodies. The comet was observed at an approximate distance of 30 million kilometers from the Chinese orbiter while traveling at an impressive speed of 58 kilometers per second. This unprecedented observation provides valuable data for the international scientific community, which is dedicated to studying the composition and trajectory of objects formed in other star systems.
The images released by the China National Space Administration (CNSA) display the comet’s nucleus and gaseous coma with remarkable clarity, allowing for an in-depth analysis of its structure. The operation tested the limits of Tianwen-1’s instruments, which were originally designed to map the surface of Mars. The success of this mission confirms the versatility of the probe’s hardware for tracking high-speed targets in deep space. The data acquired by the high-resolution camera was received, processed, and displayed by a ground-based application system in Beijing, where specialized algorithms processed the multiple exposures to create the sharp images later released to the public.
Secrets of a Distant Star System Revealed
The passage of 3I/ATLAS close to Mars provided a unique opportunity for scientists that extends far beyond a simple photograph. Interstellar objects are seen as true cosmic time capsules because they carry crucial information about the chemical and physical conditions of their stellar systems of origin. Analysis of the comet’s composition can reveal details about the formation of planets in other regions of the galaxy, offering a practical counterpoint to theoretical models that are based solely on our own solar system. Every gas molecule and dust fragment ejected by these comets bears the signature of a distant stellar environment, allowing astronomers to study, indirectly, worlds that are light years away.
According to the CNSA, 3I/ATLAS may have formed around an ancient star near the center of the Milky Way galaxy, with an estimated age of about 3 to 11 billion years. This makes it potentially older than the solar system itself. It is a rare sample for detecting the composition, evolution, and early stellar history of exoplanets. Scientists suspect the comet originated in a cold protoplanetary disk, a distant region where volatile elements such as water ice, carbon dioxide, and carbon monoxide can remain preserved for billions of years. The spectral analysis of these components is essential to determine the temperature and density of the nebula where the comet was born. Understanding these conditions is essential for refining theories about how planetary systems, including our own, evolve over time.
The Third Confirmed Interstellar Object
Comet 3I/ATLAS is the third confirmed interstellar visitor to be detected by astronomers, following the passage of ‘Oumuamua in 2017 and 2I/Borisov in 2019. Its discovery was made in July 2025 by the ATLAS telescope system (Asteroid Terrestrial-impact Last Alert System) in Rio Hurtado, Chile. Confirmation of its extrasolar origin came quickly from the analysis of its trajectory, which is described as hyperbolic. This is a clear mathematical signature that indicates an origin external to our planetary system.
Unlike the elliptical orbits of local comets and asteroids, a hyperbolic trajectory means the object has enough speed to escape the gravitational pull of the Sun. This allows it to continue its journey through interstellar space after its brief passage through our cosmic neighborhood. The comet reached its closest point to the sun in late October at a distance of about 1.4 astronomical units, or 210 million kilometers, just inside Mars’ orbit.
An Unprecedented Orbital Engineering Maneuver
Capturing images of comet 3I/ATLAS by Tianwen-1 was an engineering feat that required meticulous and innovative planning. The probe’s high-resolution camera, known as HiRIC, was developed to photograph Martian topography with extreme precision. This is a fundamentally different task from tracking a small, dimly glowing, fast-moving object against the dark background of space. To achieve the objective, the mission team on Earth needed to develop a new observation strategy from scratch.
Wang Yanan, chief editor of Aerospace Knowledge magazine, explained the significance of this achievement to the Global Times. He noted that originally designed for Mars exploration, the Tianwen-1 was able to capture images of such a distant object from its orbit around Mars. This suggests that spacecraft launched to detect planets could serve as new platforms for observing even more remote celestial bodies. Wang pointed out that precise attitude control during orbital operations, possibly involving multi-axis coordination, is needed to align optical sensors accurately with an extremely distant point and re-aim. This represents a comprehensive test of orbital observation and attitude control.
The preparation involved completely recalibrating the probe’s targeting systems and performing precise orbital maneuvers to align the equipment with the comet’s predicted trajectory. The team performed exhaustive simulations to determine ideal exposure times. These needed to be short enough to avoid blurring caused by the relative motion between the probe and the comet, but long enough to capture the faint light reflected by its nucleus and coma. The thermal stability of the instruments was also a critical factor, requiring adjustments to ensure the lenses and sensors operated in their optimal temperature range during the observation window, which lasted just a few minutes.
Overcoming Extreme Technical Challenges
The task of imaging 3I/ATLAS was particularly challenging because of its distance and small size, approximately 5.6 kilometers in diameter. However, the speed at which the interstellar object and orbiter are traveling added another layer of complexity. Whereas 3I/ATLAS travels at around 58 kilometers per second, the orbiter has a relative speed of 86 kilometers per second. Furthermore, the HiRIC camera was designed to study brightly lit features on the Martian surface.
According to the CNSA, this was the first attempt to capture such a distant and relatively dim target, which appeared 10,000 to 100,000 times fainter than targets on the Martian surface. The mission pushed the high-resolution camera’s capabilities to the limit for such faint target detection. For comparison, the European Space Agency’s Mars Express and ExoMars Trace Gas Orbiter also captured images using their cameras, the High Resolution Stereo Camera and Colour and Stereo Surface Imaging System, respectively, facing similar challenges with exposure times and sensitivity.
Initial Clues About the Comet’s Composition
The spectral data and initial images collected by Tianwen-1 already offer important indications about the nature of 3I/ATLAS. The photographs show a dense, well-defined core, which is likely composed of a mixture of rock and different types of ice. Analysis of the light reflected by its surface points to the presence of reddish organic dust, a common feature in celestial bodies formed in cold regions far from their host star. However, interestingly, a pre-press paper published in late October found the comet “appears distinctly bluer than the Sun,” creating a scientific puzzle regarding its dust composition.
Additionally, spectrometers aboard other missions have detected signatures of water ice and carbon dioxide sublimating from the surface, along with traces of carbon monoxide. These detections confirm typical cometary activity. The comet has shown distinct signs of being active, such as the development of a rare anti-tail and an unusual chemical makeup. Most recently, the object has apparently changed course slightly and may have lost a significant amount of mass. These are signs that the object is a comet outgassing and experiencing a resulting change in acceleration.
A Collaborative International Effort
The observation of 3I/ATLAS was not an isolated initiative by the Chinese space agency. The presence of an international fleet of probes in Mars orbit enabled a coordinated observation campaign. This significantly expanded the quantity and quality of data collected about the object. The European Space Agency (ESA) and NASA also directed their orbiters to study the gaseous composition of the comet’s coma and attempt to obtain even higher resolution images of its nucleus.
Avi Loeb, the head of the Galileo Project and former chair of the astronomy department at Harvard University, noted that the highest resolution images of 3I/ATLAS were obtained by the HiRISE camera onboard NASA’s Mars Reconnaissance Orbiter. This camera, with a 50-centimeter aperture, reached a spatial resolution of about 30 kilometers per pixel. On the surface, the Perseverance and Curiosity rovers were programmed to attempt to locate and observe the comet in the Martian sky, contributing a unique perspective from the ground.
Chinese Mission Versatility Proven in Deep Space
For the Tianwen-1 team, the successful comet tracking operation served as a rigorous test of the probe’s capabilities beyond its primary mission of studying Mars. The success of the maneuver demonstrated the flexibility and robustness of the orbiter’s navigation and attitude control systems. This achievement qualifies the spacecraft for future opportunity observation tasks that may arise. The CNSA stated that the ability to observe faint celestial bodies provided a chance to perform useful technical tests and accumulate experience.
Wang Yanan emphasized that such in-orbit precise adjustments of aligning sensors to a designated direction are essential skills for future asteroid exploration missions. He noted that China’s space program has consistently upheld the principle of sharing achievements with the international community. By pooling observational resources and information from major spacefaring nations, humanity can better understand this mysterious object. The successful observation marks a significant step for Tianwen-1, acting as an “unexpected harvest” that carries great significance for advancing humanity’s knowledge in studying exoplanets.
Next Steps for China’s Space Exploration
Launched in July 2020, the Tianwen-1 mission represents a milestone in the history of Chinese space exploration. The probe reached Mars orbit in February 2021 and successfully landed the Zhurong rover in May of that same year. Currently, the orbiter continues its mapping work, expanding scientific knowledge about the Red Planet. It has been operating stably in Mars orbit for over four years.
The experience gained from observing 3I/ATLAS is considered extremely valuable for future Chinese missions, specifically Tianwen-2. Launched in May 2025, this new mission has the ambitious objective of collecting samples from a near-Earth asteroid and studying a main-belt comet. The protocols developed to observe the interstellar visitor will be directly applied to these new and complex deep space exploration missions. The technical tests conducted on Tianwen-1 pave the way for the advanced maneuvering required for Tianwen-2’s upcoming encounters.
The Bottom Line
- Tianwen-1 captured images of interstellar comet 3I/ATLAS from Mars orbit in early October 2025.
- The comet is the third confirmed interstellar object, following ‘Oumuamua and 2I/Borisov.
- Observations occurred from a distance of approximately 30 million kilometers.
- The comet travels at 58 kilometers per second with a relative velocity to the orbiter of 86 kilometers per second.
- The maneuver tested the limits of the HiRIC camera, designed for bright Martian surface imaging.
- 3I/ATLAS is estimated to be between 3 to 11 billion years old.
- Data provides clues about the composition of other star systems and planetary formation.
- The success aids preparations for China’s Tianwen-2 asteroid sample return mission.
- An international fleet of Mars orbiters and rovers coordinated to study the object.
