An artist’s impression of Japan’s Hayabusa2 space mission touching down on the surface of the asteroid 1998 KY26. Credit: ESO/M. Kornmesser. Asteroid: T. Santana-Ros et al. Hayabusa2 model: SuperTKG (CC-BY-SA).
Just 6 years out from the Hayabusa2 spacecraft’s encounter with asteroid 1998 KY2, new data indicates its touchdown may be more difficult than anticipated.
With help from observatories around the world, astronomers have discovered that the asteroid is almost 3 times smaller than anticipated, and spinning much faster than previously assumed.
The Japanese Aerospace Exploration Agency’s (JAXA) Hayabusa2 will be the first spacecraft to encounter an asteroid this small. The researchers hope their study will help future astronomers examine other small asteroids that could potentially crash down onto Earth.
“Our methods could have an impact on the plans for future near-Earth asteroid exploration or even asteroid mining,” says Toni Santana-Ros, the lead researcher of the study from the University of Alicante, Spain.
Previous data had suggested that the asteroid was about 30m in diameter, or about the size of 2 basketball courts. However, when researchers combined new observations with existing radar data, they uncovered that the asteroid is only about 1m wide.
To the researchers’ surprise, the asteroid also completed a rotation in half the time they thought it would.
“One day on this asteroid lasts only 5 minutes!” says Santana-Ros. “We found that the reality of the object is completely different from what it was previously described as.”
One of the telescopes used to view the asteroid was the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in Chile. The team observed the asteroid over 8 days between 19 May and 7 November 2024.
The results from these observations have been published in Nature Communications.
When Hayabusa2 eventually reaches the asteroid it is expected to touchdown using a procedure in which it briefly ‘kisses’ the surface. However, now that it has been shown to be almost 3 times smaller than expected, this manoeuvre could be more difficult to control.
“The smaller size and faster rotation now measured will make Hayabusa2’s visit even more interesting, but also even more challenging,” says co-author Olivier Hainaut, an astronomer at ESO in Germany.
In 2018, Hayabusa2 landed on asteroid 162173 Ryugu and returned samples to Earth in 2020. The spacecraft still had fuel remaining, so it was then sent on an extended mission to 1998 KY26, which it is expected to reach in 2031.
Size comparison between the previous target asteroid for Japan’s Hayabusa2 space mission, 162173 Ryugu, and 1998 KY26. Credit: ESO/M. Kornmesser. Asteroid models: T. Santana-Ros, JAXA/University of Aizu/Kobe University
162173 Ryugu has a diameter of 900m, making 1998 KY26 tiny in comparison. Despite its small size, the researchers think there will still be valuable information to uncover from its samples.
Just last week, Cosmos reported that samples from Hayabusa2’s previous mission helped astronomers explore the origin of water on Earth.
“Moreover, we now know we can characterise even the smallest hazardous asteroids that could impact Earth, such as the one that hit near Chelyabinsk, in Russia in 2013, which was barely larger than KY26,” says Hainaut.
When Santana-Ros and his team observed the asteroid from the VLT, they noticed that 1998 KY26 had a bright surface, most likely formed from solid rock chunks from another planet or asteroid. However, they couldn’t confirm their theory.
“We have never seen a 10-metre-size asteroid in situ, so we don’t really know what to expect and how it will look,” says Santana-Ros.
“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 characterise such a small object using our telescopes, which means that we can do it for other objects in the future.”