Overview
- NASA’s Lucy spacecraft flew within about 650–960 km of asteroid Donaldjohanson on April 20, 2025 and collected the images and spectra that underpin the new analysis.
- Close-up data show the 0.8-kilometer object is a bilobed contact binary with two large lobes joined by a narrow neck, giving the asteroid a peanut-like shape.
- Lucy’s instruments detected iron-rich clay minerals on the surface, a signature that requires past exposure to liquid water and points to a water-rich parent body.
- Team analyses published in Science report a two-axis tumbling rotation that flips end-over-end every 10.5 days and wobbles about its long axis every 26.5 days.
- Scientists link the unusual, slowed spin to long-term sunlight-driven YORP torques as a working explanation, and the flyby validated instruments and procedures ahead of Lucy’s Trojan campaign beginning with Eurybates in August 2027.