Hayabusa2’s Closing Goal is 3 Occasions Smaller Than We Thought

In 2018, the Hayabusa2 mission efficiently encountered asteroid Ryugu. The Japan Aerospace Exploration Agency (JAXA) spacecraft arrived at, touched down on, collected samples of, and lifted off from the asteroid. It returned samples to Earth in 2020.

With loads of gas left for its prolonged mission, known as Hayabusa2# or “Hayabusa2 Sharp,” the spacecraft raced off to its subsequent goal, a high-speed flyby of asteroid 98943 Torifune in 2026. If all goes effectively with that rendezvous, the craft will try its last goal: an encounter with and landing on asteroid 1998 KY₂₆ in 2031.

But that last goal could show harder than initially imagined. New ground-based observations of 1998 KY₂₆ have revealed that the asteroid is 3 occasions smaller than beforehand thought and spins twice as quick.

“We found that the reality of the object is completely different from what it was previously described as,” Toni Santana-Ros, lead creator of a brand new examine on 1998 KY₂₆ and an asteroid researcher at Universidad de Alicante and Universitat de Barcelona in Spain, mentioned in a statement.

Small and Fast

Astronomers found 1998 KY₂₆ in 1998 when it got here inside 2 occasions the Earth-Moon distance. Radar and visible observations shortly after discovery estimated that the asteroid was about 30 meters throughout and rotated as soon as each 10.7 minutes, the fastest-rotating asteroid identified at the moment. As the asteroid moved away, it grew to become too faint to see for greater than 2 many years. When Hayabusa2’s mission scientists chosen targets for its prolonged mission, they relied on these 1998 calculations.

Finally, in 2024, 1998 KY₂₆ got here shut sufficient to Earth—12 occasions the space to the Moon—to look at once more. Using 4 of probably the most highly effective ground-based telescopes out there, Santana-Ros and his colleagues watched the diminutive asteroid tumble and spin from a number of angles, permitting them to calculate a extra correct spin fee than was potential with the restricted radar and photometry in 1998.

They calculated that the asteroid completes one spin each 5 minutes and 21 seconds, much less time than it takes to take heed to Queen’s “Bohemian Rhapsody.” The staff then mixed these new observations with the 1998 radar knowledge to recalculate the asteroid’s dimension. They discovered that as an alternative of being roughly 30 meters in diameter, 1998 KY₂₆ is simply 11 meters, or concerning the size of a phone pole. The staff published these ends in Nature Communications on 18 September.

“The smaller the asteroids get, the more abundant they are—but that also means that they are harder to find,” defined Teddy Kareta, a planetary scientist at Villanova University in Pennsylvania who was not concerned with the brand new discovery. “The fact that this new paper finds such a small size for KY₂₆ is tremendously interesting on its own—Hayabusa2 will be able to explore an extremely understudied population—but it also means that we might not have a tremendous number of known objects to compare to as well.”

A Challenge and an Opportunity

The new dimension and spin measurements of 1998 KY₂₆ will make Hayabusa2’s deliberate landing more difficult, the researchers wrote. However, this isn’t the primary time that an asteroid rendezvous mission has needed to alter its expectations mid-flight. Both Ryugu and Bennu, the primary goal of NASA’s Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer (OSIRIS-REx) mission, had rougher surfaces than anticipated, requiring the respective missions to regulate their pattern assortment strategies. Too, the OSIRIS-REx staff discovered that Bennu was actively spitting out materials solely when the spacecraft bought shut, which led them to vary their plan for orbital insertion.

Despite the brand new challenges with 1998 KY₂₆, Hayabusa2#’s staff has an enormous benefit: 6 years to remodel their recreation plan.

“The Hayabusa2 team are incredibly smart, hardworking, and have a ton of experience under their belts, but I’m sure that this kind of result is causing a bit of hand-wringing and concern for them even if the spacecraft is fully capable,” Kareta mentioned.

“I’m sure even the team has their doubts about whether or not the original plan was possible, but if I had to bet money, I still think the team will try [to touch down],” they added. “You set yourself up for success by building a great spacecraft and collecting a great team of engineers and scientists to staff it, but it’s still a bet every time you try something new.”

Even if a landing on 1998 KY₂₆ in the end proves unattainable and Hayabusa2# merely flies on by, asteroid scientists will nonetheless achieve useful details about an extremely widespread however hard-to-spot sort of small asteroid.

“We have never seen a ten-metre-size asteroid in situ, so we don’t really know what to expect and how it will look,” Santana-Ros wrote.

“In many ways, a spacecraft visit to it now is even more exciting than it was before,” Kareta mentioned.

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

Citation: Cartier, Okay. M. S. (2025), Hayabusa2’s last goal is 3 occasions smaller than we thought, Eos, 106, https://doi.org/10.1029/2025EO250353. Published on 18 September 2025.

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