NASA’s Lucy Finds 26.5-Day Wobble and Water Clues on 5-Mile Asteroid Donaldjohanson
Updated
Updated · SciTechDaily · Jun 27
NASA’s Lucy Finds 26.5-Day Wobble and Water Clues on 5-Mile Asteroid Donaldjohanson
3 articles · Updated · SciTechDaily · Jun 27
Summary
Lucy data show Donaldjohanson does not simply spin: the 5-mile asteroid tumbles end over end every 10.5 days while rocking around its long axis every 26.5 days.
Images from the April 20, 2025 flyby at 650 miles also showed a peanut-shaped body made of two rejoined collision fragments, with scientists estimating it formed about 155 million years ago.
Iron-rich clay minerals detected on the surface indicate liquid water briefly existed on the asteroid’s parent body, unlike Bennu and Ryugu, whose magnesium-rich clays point to much longer water exposure.
Researchers say sunlight-driven YORP torques likely slowed Donaldjohanson’s rotation over 20 million to 60 million years, reshaping its surface as debris slid downhill and softened craters.
The findings, published June 18 in Science, give Lucy a rehearsal target before its first Jupiter Trojan encounter—Eurybates on Aug. 12, 2027—and a new comparison point for early solar system evolution.