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NASA's Lucy Spacecraft Reveals Donaldjohanson Asteroid's Complex Wobbling Rotation and Peanut Shape

NASA's Lucy spacecraft conducted a close flyby of asteroid Donaldjohanson on April 20, 2025, revealing it to be a peanut-shaped body with a complex two-axis rotation pattern formed from a collision 155 million years ago. The spacecraft detected evidence of past liquid water exposure and demonstrated that the asteroid's rotation has slowed significantly due to solar radiation effects over millions of years.




Quick Facts
Who
NASA
What
Lucy spacecraft conducted close flyby of asteroid Donaldjohanson
When
April 20, 2025 (flyby date)
Where
Asteroid Donaldjohanson
- Lucy spacecraft conducted close flyby of asteroid Donaldjohanson
- Revealed two-axis rotation pattern (wobbling like spinning top)
- Detected peanut-shaped bilobate structure with two connected lobes
- Captured evidence of past liquid water exposure via iron-rich clay minerals
- Documented craters and ridges on asteroid surface
NASA's Lucy spacecraft has made a remarkable discovery during its close flyby of the asteroid Donaldjohanson on April 20, 2025, revealing a celestial body with unexpected complexity. Passing within 650 miles of the asteroid, Lucy captured the first high-resolution images and data showing that Donaldjohanson exhibits a unique two-axis rotation pattern, wobbling like a spinning top rather than rotating on a single axis like most asteroids and planets. The asteroid rotates end-over-end once every 10.5 Earth days while simultaneously wobbling around its long axis once every 26.5 days—a pattern not visible from Earth-based telescopes that only showed regular light fluctuations.
The spacecraft's imaging revealed Donaldjohanson's distinctive peanut or "bilobate" structure, consisting of two lobes connected by a narrow neck. Scientists believe these two lobes are fragments from an ancient asteroid collision approximately 155 million years ago that gently coalesced through their mutual gravitational attraction. The asteroid's surface displays numerous craters and ridges bearing the marks of its complex geological history. Researchers estimate that Donaldjohanson has slowed significantly from its original rotation rate over the past 20 to 60 million years, likely due to the YORP effect—a subtle consequence of solar heating where infrared radiation from the asteroid's sun-warmed surface creates a net torque that gradually changes its spin.
Analysis of mineral signatures detected by Lucy's instruments revealed iron-rich clay minerals on Donaldjohanson's surface, indicating that liquid water once played a role in the asteroid's geological processes in the distant past. However, the water's presence appears to have been fleeting, as the magnesium replacement patterns in the clays suggest only brief exposure to liquid water. The encounter served as a successful dress rehearsal for Lucy's mission systems before the spacecraft's primary objectives begin with its August 12, 2027 flyby of the Trojan asteroid Eurybates. Scientists also used the opportunity to compare Donaldjohanson with other studied asteroids including Bennu and Ryugu, adding valuable data to humanity's understanding of asteroid composition and evolution.
Why This Matters
This discovery fundamentally advances our understanding of asteroid formation and evolution. The detection of complex rotation patterns and evidence of past water exposure helps scientists refine models of early solar system collisions and planetary formation processes. The data also validates Lucy's instruments before its primary mission to study Jupiter's Trojan asteroids in 2027, which will provide insights into the building blocks of planets and potentially inform asteroid deflection strategies for planetary defense.
Timeline & Sources
Apr 20, 2025
WireLucy spacecraft conducts close flyby of Donaldjohanson, passing within 650 miles
Jun 18, 2026
WireLucy science team publishes findings in journal Science
Aug 12, 2027
WireLucy scheduled to conduct primary flyby of Trojan asteroid Eurybates