A Chinese spacecraft has spent more than 400 days traveling toward a small asteroid, only to discover that the rock is nearly twice as big as scientists thought. The probe, part of the Tianwen-2 mission, is now closing in on the near-Earth asteroid 2016 HO3, a space object that has orbited the sun alongside Earth for centuries. But the asteroid’s size came as a surprise: new measurements show it is about 100 meters wide, not the 40 to 60 meters previously estimated.
A 400-day journey to a tiny world
The Tianwen-2 spacecraft launched from China in 2025 and has been chasing 2016 HO3 ever since. The asteroid, also known as Kamoʻoalewa, was first spotted in 2016 by a Hawaiian telescope. It orbits the sun in a path that keeps it close to Earth, making it a relatively easy target for a sample return mission. The probe is expected to arrive at the asteroid in the coming weeks, where it will study the rock from orbit before attempting to collect samples.
Why the size matters and what comes next
If the mission goes as planned, Tianwen-2 will touch down on the asteroid’s surface, scoop up material, and then return those samples to Earth. The new size estimate changes the mission’s scope. A larger asteroid means a different surface gravity and possibly a different composition. Scientists in China are now adjusting their plans for the landing and sampling procedures. The mission is China’s first attempt to bring back material from a near-Earth asteroid, and the country’s space agency sees it as a key step toward future planetary defense work and deeper space exploration.
Local observers in China have followed the mission closely. State media has highlighted the technical achievement of navigating a spacecraft to such a small target over a long distance. For researchers, the asteroid’s unexpected size adds scientific value: a larger body may hold more clues about the early solar system. The sample, once returned, could help answer questions about how planets formed and how often asteroids like this one hit Earth.
A closing note on the mission’s place
The Tianwen-2 mission is not just about one rock. It is part of a broader push by China to explore small bodies in the solar system, including a future mission to a main-belt comet. The size surprise does not change the mission’s core goal. It simply reminds everyone that space is full of unknowns, even when you have been flying toward one for over a year.
