China's Tianwen 2 probe is scheduled for launch on a Long March 3B rocket in May 2025. The ambitious asteroid sample return and comet exploration mission is a challenging one as it is planned as a combined mission to collect samples from a near-Earth asteroid, deliver the material to Earth, and then take a gravitational slingshot back into deep space to study a comet.

The first objective is the near-Earth asteroid 469219, a quasi-satellite of Earth. After rendezvousing with Kamo'oalewa, as it is called after Haiwaiian language, the spacecraft will carry out remote sensing to assess the asteroid for potential landing sites. It will then attempt to collect samples using two different techniques — touch-and-go and anchor-and-attach — and the return to Earth to deliver the samples for analysis.

Kamo'oalewa is about 14.5 million kilometers away from the Earth, and this part of the mission will take around two and a half years. It is a challenging undertaking as this is the first time an asteroid sampling mission is using the anchor-and-attach method, with the autonomously operating lander employing four robotic arms with drills on the end to secure itself to the surface.

If the mission is successful it should be able to determine if Kamo'oalewa is a piece of the moon blasted into space by an asteroid impact as a French analysis of data from ground-based observations, released in April, concludes, or a primitive planetary body.

By collecting samples from Kamo'oalewa and coming back, Tianwen-2 also tests the technologies involved in round trip from asteroids, which brings hope of mining from the Asteroid Belt in the maybe not-so-near future.

Many of the asteroids there have high metal mineral content, of which a good example is Physche, with metals thought to compose 30 to 60 percent of its volume that might be worth $100,000 quadrillion.

After sending the sample capsule to Earth, the Tianwen-2 spacecraft will then use its close encounter with the planet to propel itself into a transfer orbit that will take it to the main-belt comet 311P/PANSTARRS. After arriving about seven years later, it will orbit the comet and conduct a remote sensing study.

China also has Tianwen 3 scheduled for launch in 2028, which is a round-trip mission to collect samples from Mars, and the ambitious Tianwen 4 mission, which is scheduled to launch around 2030 and involves both a Jupiter orbiter and a Uranus flyby spacecraft.

Relatively low-cost, such sample return missions can provide a better understanding of the early stages of the solar system and lead the way to the assessment of space resources and their utilization, as well as the development of asteroid defense strategies, with expectations high that an on-target-with-Earth encounter is only a matter of time.

— ZHANG ZHOUXIANG, CHINA DAILY