Japan's Hayabusa2 spacecraft, which previously returned samples from asteroid Ryugu to Earth, is now poised for one of the closest and riskiest asteroid flybys ever attempted. The encounter with the small near-Earth asteroid 2001 CC21 is scheduled for July 5, 2024, bringing the probe within just a few hundred meters of the surface.
The target is a fast-rotating, potentially metallic body that scientists believe may be a fragment from a larger collision. Project manager Makoto Yoshikawa described the flyby as an opportunity to 'discover another beast to put in the zoo of asteroids.' This close approach will test the spacecraft's autonomous navigation and high-speed imaging capabilities.
Hayabusa2 completed its primary sample-return mission in 2020 and was then retasked on an extended mission to visit two more asteroids. The July 5 flyby is the first of those encounters, with a second, longer-duration rendezvous planned for 2029 with a larger asteroid called 1998 KY26.
The risks are substantial. At such close range, a single navigation error or unexpected dust plume could lead to a collision. Mission engineers have programmed the spacecraft to autonomously abort if its sensors detect an unsafe trajectory, but the stakes are high given the probe's proven track record and remaining fuel.
Some planetary defense experts have questioned the scientific value of such a high-risk flyby, arguing the agency could gather comparable data from safer distances. But JAXA officials maintain that the unique characteristics of 2001 CC21—its rapid spin and potential metallic composition—justify the danger in pursuit of understanding how small asteroids evolve.