Chinese probe Tianwen-1 records comet 3I/ATLAS in unprecedented images during its passage by Mars

In a milestone for interplanetary astronomy, China’s Tianwen-1 probe made an unprecedented observation by capturing detailed images of the interstellar comet 3I/ATLAS. The operation, conducted in October 2025, took place while the orbiter monitored Marte, uniquely positioned to record the rare cosmic visitor from a distance of approximately 30 million kilometers. Este feat represents the first time that an object from outside our solar system has been observed from the orbit of another planet, providing crucial data for the global scientific community.

Comet 3I/ATLAS is only the third object of confirmed interstellar origin to be detected by astronomers, following in the footsteps of the enigmatic ‘Oumuamua in 2017 and 2I/Borisov in 2019. our solar system. The comet’s passage through perihelion, its closest point to Sol, on October 29, mobilized space agencies around the world for a coordinated observation campaign.

Administração Espacial Nacional of China (CNSA) reoriented the instruments on Tianwen-1, originally designed to study Marte, in order to track the comet. The maneuver demonstrated the probe’s versatility and its ability to perform opportunistic scientific tasks, significantly expanding the scope of its original mission. The images obtained not only confirm the comet’s activity, but also offer a new perspective for studying its composition and behavior.

Historical Capture Technical Details

The Tianwen-1’s high-resolution camera, known as HiRIC, was the central instrument in this operation. Projetada to map the Martian surface in precise detail, its engineering team adapted it to track a faint, fast-moving target against the dark background of space. The complexity of the task required meticulous planning to optimize exposure times, avoiding blur caused by the orbital speed of the probe and the comet itself.

Advanced simulations were run to ensure the short observation window was made the most of. The data, transmitted to the control center at Pequim, was processed by a dedicated system that generated 30-second image sequences. Ajustes in the guidance system and the probe’s thermal stability were crucial to ensuring the sharpness necessary to visualize the comet’s nucleus and coma from a distance of almost 29 million kilometers.

The revealed characteristics of the interstellar visitor

The photographs released by CNSA reveal a rocky and icy core of 3I/ATLAS, surrounded by a coma of gas and dust. The coma, a cloud of material sublimated by solar heat, reached a diameter of thousands of kilometers, indicating intense cometary activity. Essa activity is critical to understanding how much volatile material the comet carries from its home star system.

The object is estimated to be about 5.6 kilometers wide and moving at an impressive speed of 58 kilometers per second. Sua tail, initially faint, expanded to more than 56,000 kilometers, pointing in the opposite direction to Sol due to solar radiation pressure. Preliminary spectral analysis suggests the presence of water ice and carbon dioxide, with weak signals of carbon monoxide.

This chemical composition provides clues about the environment where the comet formed, likely a cold, distant protoplanetary disk. The reddish glow of the nucleus suggests the presence of organic dust, while the anomalous acceleration, a slight deviation from the purely gravitational trajectory, is being analyzed with combined data from several agencies to better understand the gas ejection processes.

A global space collaboration

The 3I/ATLAS study was a truly international effort, highlighting the importance of cooperation in space exploration. Agência Espacial Europeia (ESA) contributed observations from its Mars Express and ExoMars Trace Gas Orbiter (TGO) probes, which recorded the comet during the same period. The European data, obtained from different angles, complemented the Chinese images, allowing for a more complete geometric analysis.

In turn, NASA used the Mars Reconnaissance Orbiter (MRO) to try to obtain even higher resolution images with its HiRISE camera. Embora the target was challenging, the data collected helped refine models of the comet’s trajectory. The agency also attempted a remarkable feat: detecting the comet from the surface of Marte.

The Perseverance and Curiosity rovers were programmed to point their cameras at the Martian night sky in hopes of capturing a glimpse of the interstellar visitor. Although detection from the ground is extremely difficult due to the thin atmosphere and dust, the effort represented a new frontier for planetary surface astronomy. The collaboration was extended even further with the participation of the Hope probe, from the Emirados Árabes Unidos.

The Hope probe, together with NASA’s MAVEN mission, provided valuable spectrometric data on the comet’s interaction with the space environment around Marte. Combining all these data sets from different nations and instruments allowed scientists to triangulate information, refine estimates about the orientation of the comet’s axis, and better understand the non-gravitational forces that affect its motion.

Preparations for an extended mission

The Tianwen-1 team began planning to observe the comet in September 2025, based on refined orbital projections. Calculations took into account the comet’s extreme speed and relatively faint brightness to determine ideal observation windows, which lasted just a few minutes each orbital pass. Testes of telemetry were performed to ensure that the transmission of high-volume images occurred without failure, as the opportunity to capture them would be unique and fleeting.

The focus on short, multiple exposures was a strategy to maximize the useful signal from the target, which was nearly 18 million miles away at the time of capture. Esta extension of the original mission served as a rigorous test for the probe’s faint celestial body tracking capabilities. The successful results validate protocols that will be implemented in future deep space exploration missions, confirming the robustness of Chinese technology for complex and dynamic observations.

The history of mission Tianwen-1 in Marte

Mission Tianwen-1, whose name means “Questions to Céu”, represents China’s first independent foray into Marte and is one of the most ambitious ever launched. Lançada in July 2020, the spacecraft entered Martian orbit in February 2021, carrying an orbiter, a lander and a rover. In May of the same year, the mission achieved one of its greatest successes with the safe landing of the Zhurong rover on the vast plain of Utopia Planitia, a region of great geological interest. The Zhurong rover operated for approximately one Earth year, exceeding its designed useful life, while collecting soil samples, analyzing the mineralogical composition of rocks, and capturing panoramic images of the Martian landscape. Durante his operation, he provided crucial data on the local climate and underground geology, before going into hibernation. Enquanto this, the orbiter continued its scientific work, mapping the planet with the HiRIC camera and other instruments. Sua primary mission includes the study of polar ice, atmospheric dust and the magnetic field of Marte. The ability to redirect the orbiter to observe comet 3I/ATLAS demonstrates the flexibility and long-term value of the mission, which now serves as a versatile platform for opportunistic observations beyond Planeta Vermelho.

Legacy for deep space exploration

The successful 3I/ATLAS observations validate techniques that will be fundamental for the Tianwen-2 mission, scheduled to launch in the middle of this decade. Este’s next Chinese venture aims to collect samples from an asteroid near Terra and study a main-belt comet, applying lessons learned to tracking small, fast targets in deep space.