China’s Tianwen-1 orbiter has successfully captured high-resolution images of the interstellar object known as 3I/ATLAS, which recently passed by Mars. The China National Space Agency (CNSA) reported that the orbiter’s camera obtained these images from approximately 30 million kilometers (about 18.6 million miles) away. This achievement marks a significant milestone as Tianwen-1 has been in orbit around Mars for nearly five years, making it one of the closest missions to observe this interstellar object since its detection on May 7, 2025.
The images reveal distinct comet-like features of 3I/ATLAS, including its tail and the surrounding gaseous envelope known as the coma. The CNSA also noted that the captured images were compiled into an animation that illustrates the object’s trajectory as it approaches its closest pass to the Sun. This event further supports the classification of 3I/ATLAS as an interstellar comet, primarily composed of water and volatile materials that have been outgassing as it nears the Sun.
Preparation and Challenges in Imaging
The team overseeing Tianwen-1’s High-Resolution Imaging Camera (HiRIC) began preparations for this observation in early September 2023. Their work involved running simulations, theoretical modeling, and extensive instrument checks to ensure the mission’s success. Imaging 3I/ATLAS posed several challenges due to its small size of approximately 5.6 kilometers (3.5 miles) in diameter, as well as its high speed of around 58 kilometers per second (36 miles per second) relative to the orbiter, which was traveling at 86 kilometers per second (53.5 miles per second).
While the HiRIC camera was designed to study brightly lit Martian surface features, it succeeded in capturing this faint object. On October 3, 2023, other missions, including the European Space Agency’s Mars Express and ExoMars Trace Gas Orbiter (TGO), also photographed 3I/ATLAS. Their respective cameras, the High-Resolution Stereo Camera (HRSC) and Colour and Stereo Surface Imaging System (CaSSIS), demonstrated that 3I/ATLAS is roughly 10,000 to 100,000 times fainter than features on the Martian surface when viewed in daylight.
The Scientific Significance of Interstellar Objects
3I/ATLAS presents a unique opportunity for astronomical and astrobiological research. As a remnant from the formation of solar systems, studying such objects can provide insights into the conditions existing in other star systems. The potential for an interstellar object intercept mission—an endeavor that many organizations are exploring—could yield information that would otherwise require extensive and costly missions to other stars.
In the coming years, scientists aspire to launch missions capable of intercepting future interstellar objects for close-up studies. Notably, the European Space Agency’s Comet Interceptor is expected to be completed by 2029, further expanding our understanding of these fascinating celestial bodies. As the capabilities of missions like Tianwen-1 continue to evolve, the quest to uncover the mysteries of interstellar objects remains an exciting frontier in space exploration.
