NASA’s Lucy spacecraft has shown that asteroid Donaldjohanson is a bilobate, tumbling object formed 155 million years ago. The flyby also detected traces of ancient liquid water on its surface.
On April 20, 2025, Lucy flew within 650 miles of Donaldjohanson in the main asteroid belt. The spacecraft recorded the asteroid’s unusual shape, surface features, and complex rotation.
Donaldjohanson spins end over end once every 10.5 days while also rocking around its long axis every 26.5 days. Researchers attribute the slowdown of its spin to the YORP effect caused by sunlight.
Instruments detected iron-rich clay minerals that form only in the presence of liquid water. The brief exposure suggests the asteroid’s parent body experienced limited water activity compared with Bennu and Ryugu.
Simone Marchi, Lucy deputy principal investigator, said the differences offer clues to solar system origins. The findings were published June 18 in the journal Science.