China’s Tianwen-1 probe captures unprecedented images of interstellar comet 3I/ATLAS as it passes by Mars By Luís Henrique Costa
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The Chinese probe Tianwen-1 performed a pioneering observation by recording images of the interstellar comet 3I/ATLAS during its approach to Marte in October 2025. Posicionada in the orbit of Planeta Vermelho, the spacecraft managed to capture the object at a distance of approximately 30 million kilometers.
This achievement represents the first time that a visitor from outside Sistema Solar has been observed from Marte, offering crucial data for the international analysis of its composition. Collaboration between different space agencies has been essential for the in-depth study of this celestial body.
Comet 3I/ATLAS is the third object with origins outside our Sistema Solar to have its origin confirmed, following Oumuamua in 2017 and 2I/Borisov in 2019. Descoberta on July 1, 2025 by the ATLAS telescope on Chile, its hyperbolic orbit validates its external origin.
HiRIC camera and detailed observation
The Tianwen-1’s high-resolution camera, known as HiRIC, played a key role in this complex operation. Originalmente designed to map planetary surfaces, the equipment has been cleverly adapted to track a low-light, fast-moving target in space.
Engineers ran thorough simulations to optimize the exposure time, which needed to be short, and to mitigate the blurring caused by the comet’s high orbital speed. The collected data was transmitted to Terra, in Pequim, and processed in a specialized system that generated 30-second sequences of images.
Overcoming technical challenges in capture
The considerable distance of 29 million kilometers between the probe and the comet posed a significant logistical challenge for the mission team. The accuracy of the equipment’s aiming and the maintenance of thermal stability were crucial factors in ensuring the sharpness of the images of the comet’s nucleus and coma.
An animation, developed from the photographs obtained, vividly illustrates the comet’s displacement against the stellar backdrop. Esses records are of great value for calculations of detected non-gravitational acceleration, which can provide important information about the internal activity of the celestial body.
Features revealed of 3I/ATLAS
The photographs released by Administração Espacial Nacional of China reveal details of the rocky core of 3I/ATLAS, which is surrounded by a coma composed of gas and dust. The diameter of the coma reached several thousand kilometers, an indicator of intense cometary activity.
The object is estimated to be 5.6 kilometers wide and moves at an impressive speed of 58 kilometers per second through space. Sua tail, initially faint, grew to 56,000 kilometers in observations carried out in August 2025 and was oriented in the opposite direction to Sol.
Initial spectra indicate the presence of water ice and carbon dioxide in its composition, with weaker signals of carbon monoxide. Essa composition suggests that the comet formed in a cold protoplanetary disk, possibly in a region distant from Via Láctea. Detailed data analysis allows specific components to be identified.
Mission preparations and enhancement
The team responsible for Tianwen-1 began planning this operation in September 2025, based on high-precision orbital predictions. The calculations took into account the comet’s speed and low luminosity, essential elements for defining the most appropriate observation windows.
Telemetry tests were performed to ensure secure transmission of captured images back to Terra. Focusing on short exposures was crucial to maximizing the useful signal from the target, which was a considerable distance away at 18 million miles, validating the probe’s ability to successfully track faint and distant celestial bodies.
Global efforts in comet analysis
Agência Espacial Europeia (ESA) probes, such as Mars Express and ExoMars TGO, also recorded 3I/ATLAS in the same period, providing complementary data to Chinese information. Essas additional observations offer different geometric perspectives of the object.
NASA, in turn, used the Mars Reconnaissance Orbiter (MRO) to capture high-resolution HiRISE photographs, while on October 4, 2025, rovers such as the Perseverance attempted to capture images from the Martian surface. Adicionalmente, the Hope probe, Emirados Árabes Unidos, and MAVEN also collected spectrometric data, joining collaborative efforts that refine estimates of the axial orientation and non-gravitational forces acting on the comet, deepening scientific understanding of the interstellar object.
The trajectory of Tianwen-1 and future explorations
Tianwen-1, launched in July 2020 and in orbit around Marte since February 2021, continues operations in 2025, expanding knowledge about Planeta Vermelho with its HiRIC camera and other tools. The 3I/ATLAS observations validate the investigation methods for Tianwen-2, launched in May 2025, which aims to collect samples from an asteroid close to Terra and a comet from the main belt, deepening China’s ability to study smaller bodies from Sistema Solar.
