Unprecedented images of the interstellar comet 3I/ATLAS are captured by the Chinese probe Tianwen-1 near Mars

Space exploration reached a new historic milestone in October 2025, when the Chinese probe Tianwen-1, operating in the orbit of Marte, managed to capture high-resolution images of comet 3I/ATLAS. The event represents the first time that an object of interstellar origin has been observed and photographed in detail from the orbit of another planet, consolidating a significant advance for planetary science and modern astronomy.

The photographic record was carried out at an approximate distance of 30 million kilometers from the celestial body, a feat that required highly precise maneuvers and meticulous planning on the part of Administração Espacial Nacional of China (CNSA). The images provide crucial data for the global scientific community, which studies the composition and trajectory of objects coming from outside our Sistema Solar.

The passage of comet 3I/ATLAS close to Planeta Vermelho mobilized several space agencies, which directed their equipment to collect as much information as possible. International collaboration was essential to cross-reference data and obtain a more complete understanding of the nature of this rare cosmic visitor, enriching knowledge about the formation of other star systems.

A visitor from another star system

Comet 3I/ATLAS is the third object with a confirmed origin outside our Sistema Solar, following the detections of ‘Oumuamua in 2017 and 2I/Borisov in 2019, but it is the first to be studied in such detail by a probe orbiting another world. The comet’s trajectory, described as a sharp hyperbolic orbit, is the main evidence that it does not belong to our system and is just passing through. About 5.6 kilometers in diameter and traveling at a speed of 58 kilometers per second, its analysis offers a unique opportunity to study materials formed in the protoplanetary disk of another star. Esses data provides valuable clues about the formation processes of other planetary systems in Via Láctea, functioning as a true sample of a distant cosmic “construction”, allowing scientists to compare the ingredients that formed our own system with those of others.

The technical challenge of observation

The high-resolution camera HiRIC (High Resolution Imaging Camera), on board Tianwen-1, was the central instrument for the successful observation. Originalmente designed to map the surface of Marte in unprecedented detail, the mission engineering team adapted its use to track a small, faintly glowing, fast-moving target in vast space. The complexity of the task was compared to trying to photograph a moving bullet from another bullet, requiring perfect coordination between the probe’s hardware and the commands sent from the Terra.

To overcome the challenge of capturing such a fast-moving object without generating blurry images, extensive simulations were carried out. The strategy adopted was to use extremely short exposure times, optimizing light capture and ensuring the necessary sharpness. The raw data was transmitted to the control center at Pequim, where a specialized processing system assembled the image sequences, revealing the comet in detail never before seen from an interplanetary perspective. The maneuver demonstrated the China’s advanced capabilities in deep space operations.

What the images reveal about 3I/ATLAS

The photographs released by CNSA clearly show the rocky and frozen core of 3I/ATLAS. The Este nucleus is surrounded by a coma, a cloud of gas and dust that forms when the heat from the Sol sublimates the ice on the comet’s surface.

The coma reached a diameter of thousands of kilometers, an indication of very intense cometary activity. Analyzing its size and density helps scientists estimate how much volatile material the comet is losing as it approaches Sol.

The tail, formed by particles ejected by solar radiation pressure, extended for approximately 56,000 kilometers. Durante observations, it was positioned in the opposite direction to Sol, a characteristic behavior of active comets.

Preliminary spectral analyses, based on the data collected, suggest the presence of water ice and carbon dioxide. Também weaker signals of carbon monoxide were detected, a composition that points to a formation in a very cold region of its home star system.

An international scientific collaboration

The passage of 3I/ATLAS through Marte was not observed only through China. The global scientific community seized the rare opportunity to direct multiple instruments at the comet, creating an unprecedented observation campaign.

Agência Espacial Europeia (ESA) used its Mars Express and ExoMars Trace Gas Orbiter probes to analyze gaseous emissions from the comet’s coma, providing a complementary perspective to Chinese visual data. Essa collaboration allowed us to obtain a more three-dimensional view of the object’s activity.

NASA also actively participated in the effort, directing Mars Reconnaissance Orbiter (MRO) to capture images with its powerful HiRISE instrument. On the surface, rovers like Perseverance tried to detect the comet from the Martian soil, while the MAVEN probe collected spectrometric data, enriching the set of information.

The Journey of Mission Tianwen-1

Launched in July 2020, the Tianwen-1 mission represents a milestone for the Chinese space program, being the country’s first mission, Marte. The probe successfully entered Martian orbit in February 2021, carrying an orbiter, a lander and the Zhurong rover.

In May 2021, the Zhurong rover landed on the vast plain of Utopia Planitia, where it operated for approximately one Earth year. Durante its mission on the surface, the rover collected geological data, analyzed the composition of the soil and atmosphere and sent back detailed images of the terrain, contributing to the understanding of the geological history of Marte.

Planning and execution of the maneuver

The Tianwen-1 mission team began planning to observe the comet in September 2025, as soon as orbital predictions became accurate enough. The calculations took into account the object’s high speed and low luminosity to determine the ideal observation windows, ensuring that the probe was in the correct position and the instruments were properly calibrated for recording.

Next steps for Chinese exploration

The success of the 3I/ATLAS observations serves as an important validation of the technologies and methods that will be used in future Chinese missions. The experience gained strengthens the Sistema Solar smaller bodies exploration program, one of the CNSA’s focuses for the next decade.

The Tianwen-2 mission, scheduled to launch in May 2025, is the next big step. Seu objective is to collect samples from an asteroid close to Terra and, subsequently, study a comet from the main belt. The successful tracking of 3I/ATLAS confirms the ability of China to conduct complex operations in deep space, paving the way for even more ambitious explorations.