NASA's Lucy Finds 155-Million-Year-Old Asteroid Wobbling With Ancient Water
Updated
Updated · ScienceDaily · Jun 28
NASA's Lucy Finds 155-Million-Year-Old Asteroid Wobbling With Ancient Water
3 articles · Updated · ScienceDaily · Jun 28
Summary
Lucy’s close flyby of asteroid Donaldjohanson showed the object is not rotating normally but tumbling end-over-end every 10.5 days while rocking around its long axis every 26.5 days.
Images from 650 miles away also revealed a peanut-shaped, two-lobed body likely formed when collision fragments merged, then had its spin altered over 20 million to 60 million years by the sunlight-driven YORP effect.
Iron-rich clay minerals detected as Lucy sped past at about 30,000 mph point to a brief episode of liquid water, unlike Bennu and Ryugu, whose magnesium-rich clays suggest much longer water exposure.
Donaldjohanson appears far younger than those asteroids—about 155 million years old versus 1 billion to 2 billion—and has stayed in the main belt, giving scientists another benchmark for tracing solar system formation.
The April 20, 2025 encounter doubled as a rehearsal for Lucy’s main mission to Jupiter’s Trojan asteroids, with the first Trojan flyby, Eurybates, scheduled for Aug. 12, 2027.
Lucy’s rehearsal is done. What planetary formation mystery will Jupiter's ancient Trojan asteroids finally solve?
How does this young asteroid's brief water history rewrite the story of our solar system's oceans?
Sunlight makes this asteroid tumble. Could this subtle force also be creating entirely new asteroid pairs?
First Close-Up of Asteroid Donaldjohanson: Lucy Mission Finds Evidence of Ancient Water and Tumbling Spin
Overview
NASA's Lucy spacecraft made history with its close flyby of asteroid Donaldjohanson in April 2025, capturing the first detailed images and data of this unique object. Scientists discovered that Donaldjohanson has a distinctive peanut shape with visible craters and ridges, and it rotates in a complex, tumbling motion around two axes. Most remarkably, Lucy's instruments detected iron-rich clay minerals on the asteroid's surface, revealing that liquid water was present there in the distant past. These findings offer new insights into the asteroid's history and the early conditions of our solar system.