Flyby of NASA’s Lucy Spacecraft
On April 20, 2025, NASA’s Lucy spacecraft came within roughly 1,046 kilometers of the asteroid Donaldjohanson. This flyby marked a key milestone in studying this object, which lies in the main asteroid belt along the route to Jupiter’s Trojan asteroids. The encounter revealed that the asteroid is composed of two lobes connected by a narrow neck and exhibits a complex rotation pattern.
Donaldjohanson completes a full tumble every 10.5 days and wobbles around its long axis once every 26.5 days. Shortly after its formation, the asteroid spun at least ten times faster, but its rotation has slowed over the past 20 to 60 million years. During the flyby, Lucy was traveling at approximately 48,000 kilometers per hour.
Exploring Asteroid Donaldjohanson
Iron-rich clay minerals have been detected on Donaldjohanson’s surface, indicating past contact with liquid water. The asteroid is estimated to be 155 million years old. Studying Donaldjohanson alongside asteroids Bennu and Ryugu—which formed 1 to 2 billion years ago—offers scientists a clearer picture of the solar system’s origins.
As Simone Marchi noted, 'comparing Donaldjohanson with Bennu and Ryugu helps us better understand the solar system’s origin, because each difference between such objects provides new clues about its formation.'
The Lucy mission is NASA’s first program dedicated to a detailed investigation of Jupiter’s Trojan asteroids. This research opens new frontiers in the study of space objects and their significance for understanding our solar system’s evolution.
Investigating asteroids like Donaldjohanson is crucial for the scientific community, as they can yield valuable information about the early stages of solar system formation. By focusing on the Trojan asteroids, the Lucy mission helps gather data on the composition and evolution of these objects, which in turn can deepen our understanding not only of the asteroids themselves but also of planetary systems as a whole.