Chinese Probe Captures First Image of Earth's Rare 'Micromoon'

Scientists have obtained the first image of a rare object orbiting Earth, known as a 'micromoon' or quasi-satellite. The China National Space Administration (CNSA) released the image captured by its Tianwen-2 probe, showing asteroid 2016 HO3, also named Kamoʻoalewa.

The image depicts a grey, jagged space rock against the backdrop of space. Kamoʻoalewa was first detected about a decade ago by the Pan–STARRS 1 telescope in Hawaii. While it is not a true satellite of Earth due to its distance, it is considered the most stable example of a near-Earth companion.

The Tianwen-2 probe, launched on May 29, 2025, from the Xichang Satellite Launch Center, successfully encountered Kamoʻoalewa on June 6 after a journey of approximately one billion kilometers. By July 2, the probe was within 20 kilometers of the asteroid, allowing it to capture detailed images. Scientists estimate Kamoʻoalewa to be between 40 to 100 meters in diameter.

As part of its mission, Tianwen-2 will conduct in-orbit observations and collect samples from Kamoʻoalewa to return to Earth. This mission is CNSA's first asteroid sample-return endeavor. Analysis of the returned samples may help confirm a previous suggestion that Kamoʻoalewa is a fragment of the Moon, based on its light-reflecting properties matching lunar rock minerals.

Kamoʻoalewa is one of only seven known Earth quasi-satellites, and it is the closest to Earth, located about 41.6 million kilometers away. These objects orbit the sun on paths similar to Earth's but remain gravitationally bound to the sun, appearing to orbit Earth. Paul Chodas, manager of NASA's Center for Near-Earth Object Studies, stated that Kamoʻoalewa has been a stable quasi-satellite for nearly a century and is expected to remain so for centuries to come.

The asteroid's orbit is characterized by a yearly cycle where it moves ahead of Earth, then falls behind, and a slower, multi-decade back-and-forth twist. Earth's gravity keeps it from drifting too far away or getting too close, maintaining a distance of roughly 38 to 100 times the distance of the Moon from Earth.

After spending nine months studying Kamoʻoalewa, the Tianwen-2 probe will drop off a sample capsule during a flyby of Earth before continuing its mission to the main-belt comet 311P, located beyond Mars. The mission's objectives and findings were detailed in a paper published in Space Science Reviews.