A distant asteroid that a Japanese spacecraft is en route to visit could be a much harder target to reach than previously thought, according to new telescope data.
The asteroid, known as 1998 KY26, is about one-third the size of earlier estimates and spins about twice as fast in space as predicted, with each rotation taking just over five minutes. At about 36 feet wide, the asteroid is roughly the length of a school bus. It also reflects more sunlight than expected. Together these traits will likely make touching down on its surface more difficult.
The Japanese Aerospace Exploration Agency, or JAXA, expects its spacecraft to rendezvous with the asteroid in July 2031. The destination is part of an extended mission, called Hayabusa 2, following the spacecraft’s successful return of samples from another asteroid, Ryugu, in 2020.
Astronomers had a rare chance to study the little asteroid with several telescopes during its close approach to Earth last summer, which provided the new measurements. The results are now published in Nature Communications.
“The smaller size and faster rotation now measured will make Hayabusa2’s visit even more interesting,” said co-author Olivier Hainaut, a European Southern Observatory astronomer, in a statement, “but also even more challenging.”
The new findings suggest the asteroid could either be a single solid rock or a “rubble pile” loosely held together by weak forces.
Astronomers believe asteroids are the rocky leftovers from the formation of the solar system about 4.6 billion years ago. Most of that ancient material orbits far from Earth. But occasionally pieces get nudged into the inner solar system, which is why NASA and other organizations try to track them.
To better understand these objects, JAXA has visited asteroids Itokawa and Ryugu. NASA performed its own sample collection from asteroid Bennu through the OSIRIS-Rex mission, which successfully dropped off the specimen in a Utah desert in 2023. Another NASA mission, Psyche, is on its way to a metal-rich asteroid in 2029.
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About 20 years ago, NASA and the University of Arizona considered 1998 KY26 among potential targets for OSIRIS-Rex, Dante Lauretta, the mission’s principal investigator, told Mashable. It was eventually ruled out, he said, because the team already knew it was on the small side and unlikely to host the loose material needed for a sampling operation.
Regarding the newly published insight into the asteroid, Lauretta doubted the new measurements would significantly alter JAXA’s extended mission.
“I don’t think this will change the Conops,” Lauretta said, referring to the mission’s goals and strategies, “the operational challenges are similar.”
But according to the new paper, a smaller, faster, and brighter target will have an impact. Firing a metal projectile at the asteroid to make a crater, for instance, might not work as well because of its size. The brightness of the asteroid could “blind” navigation sensors. Its quick spin also may make it harder for instruments that need to stare at one spot for a long time.
“Importantly, these factors have been identified six years ahead of the rendezvous,” the authors wrote, allowing mission planners time to consider their options.
JAXA intentionally selected tiny asteroids for the extended Hayabusa 2 mission because none have been studied up close before.
Credit: ESO / M. Kornmesser. / T. Santana-Ros / JAXA / University of Aizu / Kobe University infographic
JAXA selected 1998 KY26 out of more than 350 candidates. Those candidates were all of the known celestial objects within reach of the spacecraft, which had about half of its xenon fuel left. The team then narrowed the list to the most scientifically interesting candidates.
The Japanese space agency settled on two asteroids — the other being 2001 AV43 — for the extra 11-year extension. The Hayabusa 2 spacecraft should reach 2001 AV43 first in November 2029.
The team intentionally picked tiny asteroids because none have been studied up close before — prior missions have only explored larger asteroids. Getting to know these small bodies and how they work is just as important, researchers say, because asteroids of this scale hit Earth more often than the dinosaur-killing ones.
And despite their small size, little space rocks can still have catastrophic consequences. An undetected meteor exploded over Chelyabinsk, Russia, in 2013, for example, causing an airburst and shockwave that affected six cities. That rock was just 60 feet across, according to NASA.
This is one of the main reasons why scientists believe robotic missions to study asteroids are so crucial.
“We are excited to see this new target up close,” Lauretta said. “Any encounter with an asteroid yields surprises and new knowledge.”
