New Simulations Challenge Mystery Asteroid’s “Dark Comet” Label as Probe Closes in

WHO:

Phys.org - Japan’s Hayabusa2 spacecraft is traveling to asteroid 1998 KY26.

Futurism - Georgia Institute of Technology aerospace engineers Korbin Hansen and Masatoshi Hirabayashi authored the research published in *Icarus*.

Futurism - Harvard astronomer Avi Loeb proposed that 1998 KY26 could be a derelict Soviet spacecraft.

WHAT:

Phys.org - 1998 KY26 is a tiny near-Earth asteroid whose acceleration has been difficult for astronomers to explain; some studies have proposed that escaping water gas pushes it, making it a possible “dark comet.”

Futurism - The 36-foot object rotates once every five and a half minutes and is accelerating through a mechanism scientists have not identified.

Futurism - The researchers’ temperature model indicates that 1998 KY26 is too warm to retain buried ice that could sublimate into gas and produce thrust.

Futurism - The authors wrote: “Our temperature model results indicate that the water outgassing rate on 1998 KY26 would be too high to maintain buried ice, refining the understanding of the asteroid’s composition.”

Futurism - The team concluded that “1998 KY26 is likely a dehydrated asteroid.”

WHERE:

Futurism - The object is located 186 million miles from Earth.

WHEN:

Phys.org - Hayabusa2 is expected to arrive at 1998 KY26 in 2031.

Futurism - Hayabusa2 is expected to rendezvous with the object in July 2031.

Futurism - The researchers estimated that at the modeled temperatures, the asteroid would have exhausted its ice in 62 years.

WHY:

Futurism - If ice sublimation were driving the acceleration, the object would have run out of ice reserves long ago.

Futurism - The object’s coldest regions were modeled at more than 77 degrees below zero Fahrenheit, temperatures the researchers said were too warm to preserve ice stores capable of providing thrust.

HOW:

Futurism - Possible alternative explanations for the acceleration include solar radiation and “thermal emission forces.”

Futurism - Hansen and Hirabayashi modeled the object’s temperature using pre-existing data.

(UPDATED November 10, 2026 15:00 UTC)

Researchers say asteroid 1998 KY26 is likely dehydrated, challenging water-driven explanations for its acceleration. Its rapid spin and unexplained movement remain puzzling. Japan’s Hayabusa2 spacecraft is expected to arrive in 2031.