Chinese researchers have obtained the first close-up images of a celestial body known as Earth's "mini-moon," an asteroid designated 2016 HO3 and nicknamed Kamoʻoalewa. The images were captured by the Tianwen-2 probe, sent by the China National Space Administration (CNSA).
Kamoʻoalewa is not a true moon but an asteroid that orbits the sun. However, it is considered a "quasi-satellite" because its orbit brings it into relative proximity with Earth approximately every 45 years. It is the closest of the seven known quasi-satellites orbiting Earth, situated at a distance of about 25.8 million miles.
Mission Milestones
The asteroid was first discovered about a decade ago by the Pan–STARRS 1 telescope in Hawaii. The Tianwen-2 probe encountered Kamoʻoalewa earlier this July, marking a significant step in CNSA's first asteroid sample-return mission. The probe traveled over one billion kilometers (621 million miles) to reach the asteroid.
During its approach, the Tianwen-2 probe acquired image data at varying distances. It made its initial optical detection of Kamoʻoalewa on June 6, and thirteen days later, it had closed to within 1,242 miles of the asteroid. The probe has since moved closer to capture detailed images.
Scientific Exploration and Challenges
The Tianwen-2 probe is now beginning its scientific exploration phase, which includes in-orbit observations and sample collection for a planned return to Earth later this year. Scientists hope the mission will reveal Kamoʻoalewa's composition, orbital evolution, and potential water content. There is also a theory, based on telescope observations, that this object might be a fragment of the Moon.
Conducting reconnaissance is challenging due to Kamoʻoalewa's small size, estimated to be between 138 and 328 feet across, potentially making it the smallest asteroid ever visited by a human spacecraft. The asteroid's uneven gravitational field, complex terrain, and rapid spin rate of one revolution every 28 minutes further complicate sample collection.
Advanced Mission Capabilities
To overcome these difficulties, the Tianwen-2 probe has been equipped with hovering and anchoring capabilities designed to facilitate effective sample collection despite the asteroid's challenging surface. The CNSA has described the Tianwen-2 mission as more complex than previous deep-space explorations and a novel approach to space exploration.
Researchers believe that analyzing Kamoʻoalewa could provide answers to fundamental questions regarding the origin of Earth's quasi-satellites and the dynamics of their orbits. The mission aims to shed light on the nature of these rare celestial companions.