Japan and China spacecraft reach separate near-Earth asteroids
JAXA’s Hayabusa2 flew past Torifune, while China’s Tianwen-2 arrived at Kamoʻoalewa to begin work toward a sample return.
By Maya Lindqvist · Senior Technology Correspondent
3 min read
Two asteroid missions reached key targets over the weekend, giving Japan and China fresh data from small near-Earth objects. The encounters matter because one extends a successful Japanese sample-return mission into a second act, while the other begins China’s attempt to bring asteroid material back to Earth.
Japan’s Hayabusa2 spacecraft flew by 98943 Torifune on Sunday, according to JAXA, the Japanese space agency. Hours later, the China National Space Administration released images from Tianwen-2 after the spacecraft reached 469219 Kamoʻoalewa, a small asteroid that China plans to sample.
Hayabusa2 adds a new target after Ryugu
JAXA launched Hayabusa2 in December 2014 and guided it to the near-Earth asteroid 162173 Ryugu in June 2018. After collecting material there, the spacecraft used ion propulsion to head back toward Earth and released a sample capsule during a 2020 flyby, with scientists recovering 5.4 grams of asteroid material, according to the agency.
JAXA said Hayabusa2 still had a large reserve of xenon propellant after that primary mission, with about 30 kilograms left from the 66 kilograms it carried at launch. Engineers then set up an extended mission to visit two additional asteroids over the following decade.
The first of those extra targets was Torifune, which JAXA described as a roughly 450-meter-long, peanut-shaped asteroid. The agency said observations began about two weeks before the encounter and ended just before Hayabusa2 passed within about 10 kilometers of the object.
JAXA said only some of the instrument data had reached Earth by early Monday, with the rest scheduled for later transmission. The agency also said observations could not continue after closest approach because of the spacecraft’s geometry after the flyby.
If Hayabusa2 continues as planned, JAXA expects a final extended-mission encounter with 1998 KY26 in July 2031. That near-Earth object is believed to be about 11 meters across, according to the mission plan described by the agency.
Tianwen-2 begins work at Kamoʻoalewa
China’s Tianwen-2 spacecraft arrived within 20 kilometers of Kamoʻoalewa on July 2, the China National Space Administration said in an announcement carried by Xinhua. The spacecraft had traveled about 1 billion kilometers to reach the asteroid, according to the agency.
CNSA released an image of Kamoʻoalewa showing a small body with an arrowhead-like outline. The agency said the arrival starts a closer survey of the asteroid’s shape, composition, rotation and other properties before a sampling attempt.
Kamoʻoalewa is about 20 meters in diameter, according to CNSA’s description of the target. It is often described as a quasi-moon because it travels near Earth with a similar orbital period of 365 days, though it is not gravitationally bound to the planet.
At closest approach, Kamoʻoalewa comes within about 4.6 million kilometers of Earth, more than 10 times the Earth-Moon distance, according to the mission details released by China. CNSA has tentatively scheduled Tianwen-2’s sample return to Earth for November 2027.
China has also outlined a possible extended mission after Tianwen-2 releases its sample capsule. CNSA has said the spacecraft could continue to 311P/PanSTARRS, an object with tails that may be comet-like.
This story draws on original reporting from Ars Technica.