Chinese mission to Mars photographs the interstellar comet 3I/ATLAS in surprising detail

The Chinese probe Tianwen-1, operating in the orbit of Marte, performed a historic feat by recording images of the interstellar comet 3I/ATLAS. The capture occurred in October 2025, when the celestial object passed at a distance of approximately 30 million kilometers from Planeta Vermelho, marking the first time that a visitor from outside our Sistema Solar was observed from Marte.

This achievement represents a significant advance for astronomy and the China space program. The images provide crucial data for the international scientific community, which studies the composition and trajectory of rare celestial bodies like 3I/ATLAS. Global collaboration has been essential to maximize the use of information collected by various space agencies.

Comet 3I/ATLAS is the third object with confirmed interstellar origin to be detected, following the passes of Oumuamua in 2017 and 2I/Borisov in 2019. Sua discovery, made on July 1, 2025 by the ATLAS telescope on Chile, was validated by its hyperbolic orbit, which confirms its origin from beyond our planetary system.

Technical details of the capture

The Tianwen-1’s high-resolution camera, known as HiRIC, was the central instrument in this operation. Although Embora was designed primarily to map the surface of Marte, the mission engineering team successfully adapted its operation to track a small, dimly glowing, fast-moving target in deep space. Para To overcome the risk of blurry images due to the comet’s high orbital speed, engineers performed detailed simulations to optimize the exposure time while keeping it extremely short. The raw data was transmitted to the control center at Pequim, where a specialized processing system assembled the images into 30-second sequences, revealing the comet’s motion against the background of distant stars.

Features of the comet revealed

The photographs released by Administração Espacial Nacional of China (CNSA) clearly show the rocky core of 3I/ATLAS, which is surrounded by a coma, a cloud of gas and dust. Analysis indicates that the diameter of the coma reached several thousand kilometers, a sign of intense cometary activity caused by the sublimation of ice due to the approach to Sol. The object, about 5.6 kilometers wide, was traveling at an impressive speed of 58 kilometers per second.

Additional observations revealed that the comet’s tail, initially faint, expanded to 56,000 kilometers and was directed in the opposite direction to Sol, as expected. Initial spectra suggest a composition rich in water ice and carbon dioxide, with traces of carbon monoxide, indicating that the celestial body formed in a cold protoplanetary disk, possibly in a region distant from Via Láctea.

In-depth preparation of Tianwen-1

The Tianwen-1 mission team began observation planning in September 2025, as soon as the comet’s orbital predictions became sufficiently accurate. The calculations took into account the object’s speed and low luminosity to determine the ideal observation windows.

Several telemetry tests were conducted to ensure that the transmission of captured data, over a distance of 18 million miles, occurred without failure. The decision to focus on short exposures was critical to maximizing the target’s useful signal and minimizing background noise.

This operation extended the probe’s original mission by testing and validating its faint celestial body tracking capabilities. The positive results confirm the effectiveness of the detection protocols that will be used in future Chinese space missions.

Furthermore, the maneuver provided valuable experience in autonomous navigation. The integration of several probe subsystems optimized real-time data processing during the flyby, demonstrating the robustness of the technology on board.

Global contribution to data analysis

The 3I/ATLAS observation was a truly international effort. Sondas from Agência Espacial Europeia (ESA), like Mars Express and ExoMars Trace Gas Orbiter (TGO), also recorded the comet in the same period, providing data that complements Chinese information with different geometric perspectives.

NASA also actively participated, using the Mars Reconnaissance Orbiter (MRO) to capture ultra-high-resolution photographs with its HiRISE camera. On October 4, 2025, there were even attempts to record the comet from the Martian surface, using the Curiosity and Perseverance rovers.

The Hope probe, Emirados Árabes Unidos, and NASA’s MAVEN mission collected spectrometric data, which help analyze the composition of the coma. Esses Collaborative efforts are key to refining estimates about the orientation of the rotation axis and the non-gravitational forces acting on the comet.

Trajectory of the Tianwen-1 mission on Mars

Launched in July 2020, Tianwen-1 successfully entered the orbit of Marte in February 2021, a milestone for the space exploration of China. The mission included the landing of the Zhurong rover in May of the same year, on the vast plain of Utopia Planitia.

The rover operated for an Earth year, collecting soil samples, analyzing mineral composition and atmosphere, and sending back detailed geological images that deepened understanding of Martian geology.

Prospects for future exploration

The successful 3I/ATLAS observations serve as an important validation of the research methods that will be applied on the Tianwen-2 mission. Lançada in May 2025, this new probe aims to collect samples from an asteroid close to Terra and a comet from the main belt, further expanding China’s ability to study smaller bodies than