New insights reveal that the main-belt asteroid Donald Johansson—a remnant of a catastrophic breakup 155 million years ago—holds vital clues about the migration of water-rich worlds in the early solar system. This information comes from a detailed analysis of images and data captured by NASA’s Lucy spacecraft.
Asteroid Donald Johansson consists of two heavily cratered lobes connected by a smooth neck, with overall dimensions of 8.8 km x 4.4 km x 3.1 km. Image credit: NASA/Goddard/SwRI/Dan Gallagher.
On April 20, 2025, the Lucy spacecraft conducted a flyby of Donald Johansson, as part of its ambitious 12-year mission to explore eight asteroids.
Unlike conventional rotating asteroids, Donald Johansson rotates about two axes, wobbling around its horizontal axis every 10.5 Earth days while completing an upside-down rotation every 26.5 Earth days.
“We’ve uncovered numerous astonishing facts since Lucy’s flyby of Donald Johansson,” said Dr. Simone Marchi, Deputy Principal Investigator for Lucy at the Southwest Research Institute.
The images captured during the flyby reveal that Donald Johansson features two protruding crater-like lobes connected by a relatively smooth neck.
The density of craters aligns with the age of the Erigone asteroids, formed from catastrophic collisions that fragmented larger parent bodies.
“Lucy’s imagery confirms the elongated shape of Donald Johansson, initially indicated by Earth-based telescopic observations,” Dr. March noted.
The data from Lucy shows that this small asteroid, measuring 800 meters in diameter, resembles a peanut and has a unique two-lobed structure connected through a narrow neck.
Additionally, Lucy detected iron-rich clay minerals indicative of past liquid water presence.
These significant findings suggest that Donald Johansson originated from fragments of a larger, carbon- and water-rich asteroid that disintegrated 155 million years ago.
The encounter between Lucy and Donald Johansson serves as a precursor to the spacecraft’s primary mission, which focuses on exploring Trojan asteroids—ancient celestial bodies that lead or follow Jupiter in its solar orbit.
Scientists believe these populations of space rocks contain crucial insights about the early solar system’s formation.
“Comparing Donald Johansson with similar asteroids like Bennu and Ryugu is essential, as every detail provides hints to our cosmic origin,” Dr. March stated.
“As we learn more about the diverse Trojan population, our understanding of solar system formation is bound to evolve,” she added.
For more details, refer to the findings published on June 18 in Science.
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Simone Marchi et al. 2026. (52246) Donald Johansson’s Lucy Flight: A rolling two-lobed asteroid. Science 392 (6804): 1287-1291; doi: 10.1126/science.aec0503
Source: www.sci.news
