Japan’s Hayabusa2 probe faces a tougher mission after new measurements revealed its target asteroid is nearly three times smaller and spinning about twice as fast as originally estimated.
Having scooped up some asteroid material from 162173 Ryugu in 2018, which was returned to Earth in 2020, Hayabusa2 was sent on an extended expedition to another asteroid, 1998 KY26. The probe is due to reach its target in 2031.
The trip was always going to be a greater challenge. Part of it involves a high-speed flyby of another asteroid, 98943 Torifune, something Hayabusa2’s instruments (such as its fixed cameras) weren’t designed for, and after this a rendezvous with 1998 KY26. Keeping the spacecraft running for another decade was going to be tough enough, but now, rather than the 30-meter-object the probe was aiming for, recent observations have refined the size down to 11 meters wide.
An artist’s impression of Japan’s Hayabusa2 space mission touching down on the surface of the asteroid 1998 KY26 – click to enlarge (Credit: ESO/M. Kornmesser. Asteroid: T. Santana-Ros et al. Hayabusa2 model: SuperTKG (CC-BY-SA)
Furthermore, rather than spinning once every ten minutes, the asteroid is rotating once every five minutes.
Olivier Hainaut, an astronomer at the European Southern Observatory (ESO) in Germany, said: “The smaller size and faster rotation now measured will make Hayabusa2’s visit even more interesting, but also even more challenging.” Hainaut co-authored a paper in Nature Communications on the subject.
ESO has published the observations based on findings from the organization’s Very Large Telescope (VLT) in Chile’s Atacama Desert, as well as data from other observatories worldwide.
Current plans for the rendezvous include Hayabusa2 firing a tantalum projectile at the asteroid’s surface. However, these might need revision in light of the discoveries regarding the asteroid’s size and spin. Still, the probe isn’t due to arrive for another six years, giving planners plenty of time. There is also that asteroid flyby to think about.
Scientists would like some time with other telescopes to further refine the data, although observations from the James Webb Space Telescope won’t really be viable until 2028.
Should Hayabusa2 rendezvous with 1998 KY26, it will be the first time a space mission has encountered such a tiny asteroid. The mission, along with the subsequent observations, also has implications for planetary defense.
“The amazing story here is that we found that the size of the asteroid is comparable to the size of the spacecraft that is going to visit it! And we were able to characterize such a small object using our telescopes, which means that we can do it for other objects in the future,” said astronomer Toni Santana-Ros, a researcher at the University of Alicante, Spain, who led the study. “Our methods could have an impact on the plans for future near-Earth asteroid exploration or even asteroid mining.”
Hainaut added: “Moreover, we now know we can characterize even the smallest hazardous asteroids that could impact Earth, such as the one that hit near Chelyabinsk, Russia, in 2013, which was barely larger than KY26.” ®