Examining the Donaldjohanson Asteroid
On April 20, 2025, NASA’s Lucy spacecraft flew within roughly 1,046 kilometers of the Donaldjohanson asteroid, located in the main asteroid belt. This close approach yielded fresh insights into the object’s structure and rotational behavior.
Donaldjohanson features a binary-like shape, made up of two segments joined by a narrow bridge. Its rotation is chaotic: it performs a full tumble every 10.5 days and wobbles around its long axis once every 26.5 days.
Significance of the Lucy Mission Findings
The data further reveal that the asteroid’s spin has been slowing down over the past 20 to 60 million years due to the YORP effect. This indicates that after its formation, the asteroid spun at least ten times faster than it does today. Iron-rich clay minerals detected on Donaldjohanson’s surface suggest that liquid water was present briefly in its past. The asteroid is estimated to be 155 million years old.
The Lucy mission is NASA’s first program dedicated to a detailed study of Jupiter’s Trojan asteroids. During this flyby, Lucy’s speed reached approximately 48,000 kilometers per hour. These discoveries could significantly advance our understanding of how asteroids like Bennu and Ryugu—which formed 1 to 2 billion years ago—evolved over time.
Investigating Donaldjohanson represents a key step in learning about the early evolution of the Solar System. The results from the Lucy mission may help clarify not only the nature of this particular asteroid but also the characteristics of other objects in the main belt. This knowledge could prove valuable for future missions aimed at studying potentially hazardous asteroids and assessing their impact on Earth.