Unpublished record from the Tianwen-1 probe reveals details of the interstellar comet 3I/ATLAS near Mars

Space exploration achieved a remarkable feat in late 2025, when the Chinese probe Tianwen-1, on its orbital mission around Marte, captured high-definition images of comet 3I/ATLAS. Este historic event marked the first time that an object of interstellar origin was photographed from the orbit of another planet, representing a significant advance for astronomy and planetary science on a global scale.

The maneuver, carried out with millimeter precision by Administração Espacial Nacional of China (CNSA), allowed the probe to record the comet at a distance of approximately 30 million kilometers. The images obtained are of invaluable value to the scientific community, which can now analyze in more detail the composition, structure and trajectory of a celestial body coming from outside our Sistema Solar.

The passage of 3I/ATLAS through the vicinity of Planeta Vermelho generated an international mobilization. Diversas space agencies redirected their instruments to observe the phenomenon, transforming Martian orbit into an interplanetary observatory. Essa collaboration was essential to cross-reference data and build a complete picture of the nature of this rare cosmic visitor.

The data collected by the Chinese probe, combined with observations from other missions, offers a unique window into understanding the formation of other star systems. By studying the composition of an “alien” comet, scientists can compare its materials with those of comets native to our system, such as those that inhabit the distant Nuvem of Oort, and unravel mysteries about the origin of the planets.

A visitor from another solar system

Comet 3I/ATLAS is the third object with a confirmed origin outside our Sistema Solar to be detected by astronomers, following in the footsteps of ‘Oumuamua in 2017 and 2I/Borisov in 2019. With an estimated diameter of 5.6 kilometers and moving at a breakneck speed of 58 kilometers per second, its analysis represents an unprecedented opportunity to study the raw material that made up the protoplanetary disk of another star. Direct observation of their composition and volatile behavior as they approach a star provides crucial clues about planetary formation processes elsewhere in Via Láctea, allowing scientists to compare these materials with the composition of celestial bodies in our own cosmic “backyard.”

Technical details of the unprecedented capture

The success of the observation was ensured by the use of the HiRIC (High Resolution Imaging Camera) high-resolution camera, one of the main instruments on board the Tianwen-1 orbiter. While Embora’s original design was focused on mapping the topography and geology of Marte’s surface in unprecedented detail, the mission’s engineering team adapted its operation for a completely different challenge: tracking a small, dimly glowing, ultra-high-speed target in deep space.

To overcome the difficulty of photographing such a fast-moving object without the images becoming blurred or blurry, the CNSA team carried out extensive simulations on land. The final strategy involved the use of extremely short exposure times, a technique that optimizes light capture and freezes movement, ensuring the sharpness essential for detailed scientific analysis of the comet’s nucleus and coma.

The maneuver required a precise realignment of the probe in space, a delicate operation that consumed resources and time, but which was considered a priority due to the rarity of the opportunity. Careful planning allowed HiRIC to capture a sequence of images that, combined, reveal the structure of 3I/ATLAS with impressive clarity, considering the distance and speed involved.

What the images reveal about 3I/ATLAS

The photographs released by CNSA clearly show the comet’s heart: its rocky, frozen core, which serves as the source of all its activity.

This core is surrounded by a coma, a vast and bright cloud of gas and dust that forms when the heat from Sol sublimates the ice present on the surface, transforming it directly into gas and creating a temporary atmosphere.

Preliminary analyzes indicate that 3I/ATLAS’s coma reached a diameter of thousands of kilometers, a sign of very intense cometary activity, possibly due to its first passage close to a star like Sol.

In addition to the coma, the images also captured the comet’s tail, formed by dust particles and ions ejected by the pressure of solar radiation, which extended an impressive distance of approximately 56,000 kilometers into space.

An international scientific collaboration

The 3I/ATLAS observation was not an exclusive effort by China. Agência Espacial Europeia (ESA) also actively participated, using its Mars Express and ExoMars Trace Gas Orbiter probes to perform spectrometric analyses. Esses instruments focused on studying gaseous emissions from the comet’s coma, identifying the chemical composition of the materials released and providing a complementary perspective to the visual data from Tianwen-1. Combining the data allowed a more complete view of the object’s activity, mapping the distribution of gases such as water and carbon dioxide.

NASA also contributed significantly, directing the powerful HiRISE camera on its Mars Reconnaissance Orbiter spacecraft (MRO) to capture ultra-high-resolution images. On the surface, rovers, including Perseverance, attempted to detect the comet from the Martian soil, a notable technical challenge. NASA’s Hope and MAVEN probes collected additional data, enriching the information set and helping to refine models about the comet’s rotation and the non-gravitational forces that influence its trajectory.

The journey of mission Tianwen-1 to date

Launched in July 2020, the Tianwen-1 mission is a pillar of China’s ambitious space program, being the country’s first initiative to send a probe, a lander and a rover to Marte in a single trip.

The probe successfully entered Martian orbit in February 2021 and, months later, deployed the Zhurong rover, which explored the vast plain of Utopia Planitia, collecting important geological data before ceasing operations.

Planning and execution of the maneuver

The Tianwen-1 mission team began planning to observe the comet in September 2025, as soon as the 3I/ATLAS orbital calculations became sufficiently accurate.

Engineers took into account the high relative speed between the probe and the comet, in addition to the object’s low luminosity, to define the ideal observation windows, ensuring that the orbiter was in the correct position and orientation at the exact moment.

Next steps for Chinese exploration

The successful observation of comet 3I/ATLAS validates the technologies and methods that China will employ in its future deep space exploration missions. The Tianwen-2 mission, launched in May 2025, is already on its way to collect samples from an asteroid close to Terra and, subsequently, study a comet from the main belt, consolidating the country’s capacity for complex operations in space.