A Chinese spacecraft orbiting Mars has captured an interstellar visitor racing through the solar system. The Tianwen-1 orbiter photographed comet 3I/ATLAS from roughly 30 million kilometers away, revealing its glowing coma and tail. The images offer scientists a rare look at material born beyond our solar system.
A Comet From Another Star System
The China National Space Agency released the images taken on October 3, 2025. Tianwen-1 has been circling Mars for four years and eight months, making it one of the closest spacecraft to observe 3I/ATLAS since the comet was discovered on May 7, 2025. The orbiter's high-resolution camera captured a faint but clear view of the object as it sped past the red planet.
The images confirm that 3I/ATLAS is a comet. A visible tail extends behind the object, and a cloud of gas and dust called a coma surrounds its nucleus. Researchers combined multiple images into an animation that shows the comet moving toward its closest approach to the Sun. The observations add to evidence that the comet contains water and other volatile materials that began escaping as it warmed during its journey through the inner solar system.
A Difficult Target to Photograph
The team behind Tianwen-1's High-Resolution Imaging Camera began preparing for the encounter in early September. They ran repeated simulations, built theoretical models, and inspected the instrument in detail. Photographing 3I/ATLAS was a challenge because the object was both distant and relatively small, measuring just 5.6 kilometers in diameter. Its speed added another major difficulty. The comet was moving at roughly 58 kilometers per second, and its motion relative to Tianwen-1 reached approximately 86 kilometers per second.
The camera was not originally designed to observe such a dim object. It was built to study bright features on the Martian surface, similar to instruments on European spacecraft. On October 3, two European orbiters also photographed 3I/ATLAS. Mars Express used its High Resolution Stereo Camera, and the ExoMars spacecraft used its Colour and Stereo Surface Imaging System. The comet was exceptionally hard to detect with these instruments. Compared with sunlit features on Mars, 3I/ATLAS appeared roughly 10,000 to 100,000 times fainter.
What This Means for Future Missions
The successful observation gives scientists a preview of the work China hopes to conduct with Tianwen-2, a mission expected to visit a near-Earth asteroid and later study a comet. The images of 3I/ATLAS show that existing Mars orbiters can be used to track interstellar objects passing through the inner solar system. For now, the data from Tianwen-1 and the European orbiters will help researchers understand the composition and behavior of material that originated beyond our solar system.
