Hayabusa2 Is Chasing the mysterious object 1998 KY26

Japan’s Hayabusa2 spacecraft, after delivering samples from asteroid Ryugu to Earth in 2020, is continuing its mission toward the tiny near-Earth object 1998 KY26, with an encounter planned for 2031. Reaching it will be difficult: the object is only about 11 meters across, roughly twice the span of the spacecraft’s solar panels, and completes a rotation every five minutes. Its orbit also shows unusual acceleration that gravity and the known effects of sunlight cannot explain. Earlier observations revealed that it is smaller and spinning faster than scientists had first estimated, adding to the challenge of attempting a touchdown and sample collection.

One proposed explanation is that 1998 KY26 is a “dark comet”: buried ice could vaporize as the object warms, releasing gas that pushes it through space. New temperature modeling, however, weakens that idea. Even the object’s coldest areas average at least 212 kelvin, well above the roughly 145-kelvin threshold needed to preserve buried ice; the predicted water loss would have depleted its reserves. Researchers instead suggest it may be a largely water-free asteroid, but that classification does not explain its acceleration. Hayabusa2’s close-up observations could help resolve the mystery when it arrives.