Interstellar comet 3I/ATLAS is recorded in unprecedented detail by the Chinese probe Tianwen-1 on Mars

The Chinese probe Tianwen-1, operating in the orbit of Marte, performed a historic feat by recording images of the interstellar comet 3I/ATLAS with an unprecedented level of detail from Planeta Vermelho. The capture occurred in October 2025, when the celestial body passed approximately 30 million kilometers from Marte, marking the first time that a visitor from outside our Sistema Solar was observed in such close proximity by a Martian mission.

This milestone represents a significant advance for both astronomy and the China space program, consolidating its deep space exploration capabilities. The images provide crucial data for the international scientific community, which studies the composition and trajectory of rare celestial bodies like 3I/ATLAS, offering new clues about the formation of planetary systems beyond our own.

Comet 3I/ATLAS is the third object detected with confirmed interstellar origin, following the passes of Oumuamua in 2017 and 2I/Borisov in 2019. Sol.

Technical details of the capture

The main tool used in this operation was the Tianwen-1’s high-resolution camera, known as HiRIC. 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 combined the images into 30-second sequences, revealing the comet’s motion against the background of distant stars and allowing precise analysis of its trajectory and apparent angular velocity.

Features of the comet revealed

The photographs released by Administração Espacial Nacional of China (CNSA) clearly show the rocky core of 3I/ATLAS 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 ices as it approached Sol. The object, about 5.6 km wide, was traveling at an impressive speed of 58 kilometers per second relative to Marte.

Additional observations revealed that the comet’s tail, initially faint, had expanded to 56,000 kilometers and was, as expected, pointed in the opposite direction to Sol. Preliminary Espectros suggests 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, providing a chemical sample of another star system.

The thorough preparation of Tianwen-1

The Tianwen-1 mission team began planning observations in September 2025, as soon as predictions of the comet’s orbit became sufficiently accurate.

The calculations took into account the object’s speed and low brightness to determine the ideal observation windows, ensuring the probe was in the correct position for capture.

Several telemetry tests were carried out to ensure that the transmission of captured data, over a distance of 30 million kilometers, occurred without failures or loss of information.

The decision to focus on short exposures was crucial to maximize the target’s useful signal and minimize background noise, a technique that has proven highly effective for low-brightness objects.

Overall contribution to data analysis

The 3I/ATLAS observation was a truly international effort, highlighting the importance of collaboration in space science.

Probes from Agência Espacial Europeia (ESA), such as Mars Express and ExoMars Trace Gas Orbiter (TGO), also recorded the comet in the same period, providing complementary data that enriched Chinese information with different geometric perspectives.

NASA actively participated in the study, using the Mars Reconnaissance Orbiter (MRO) to capture very high-resolution images with its HiRISE camera, in addition to trying to record the comet from the Martian surface with the Curiosity and Perseverance rovers.

The importance of observing interstellar objects

The study of interstellar comets and asteroids like 3I/ATLAS offers a unique window into the composition of other planetary systems. Esses objects are messengers that carry information about the chemical and physical conditions of their home regions, allowing scientists to compare the formation of star systems and better understand the diversity of worlds in the galaxy.

Detailed analysis of these visitors helps refine models of planetary formation and understand how elements essential for life, such as water, can be distributed throughout the universe. Cada new observation contributes to a growing catalog that, in the future, may reveal patterns about the prevalence of certain materials in different parts of Via Láctea.

Mission trajectory Tianwen-1 in Marte

Launched in July 2020, the Tianwen-1 probe successfully entered the orbit of Marte in February 2021, setting 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, a region of great geological interest.

The rover operated for an Earth year, collecting soil samples, analyzing the composition of minerals and the atmosphere, and transmitting detailed geological images that deepened understanding of the history and evolution of Planeta Vermelho.

Perspectives for future explorations

The successful observation of 3I/ATLAS serves as an important validation of the research methods that will be applied in the Tianwen-2 mission. Scheduled for launch, this new probe aims to collect samples from a nearby asteroid Terra and a main-belt comet, further expanding China’s ability to investigate smaller bodies from Sistema Solar and beyond.