New Insights into Main-Belt Asteroid Donald Johansson: Recent analysis of images and data from NASA’s Lucy spacecraft reveals that the cratered asteroid, a remnant of a catastrophic breakup 155 million years ago, holds vital clues about the migration of water-rich bodies in the early solar system.
The structure of Asteroid Donald Johansson comprises two heavily cratered lobes connected by a smooth neck, measuring 8.8 km x 4.4 km x 3.1 km. Image credit: NASA/Goddard/SwRI/Dan Gallagher.
Nasa’s Lucy spacecraft, on its ambitious 12-year mission to explore eight asteroids, passed by Donald Johansson on April 20, 2025.
Asteroid rotations are unique; instead of spinning in a predictable manner, Donald Johansson wobbles around two axes—one rotation about its horizontal axis occurring every 10.5 Earth days and another upside down rotation every 26.5 Earth days.
“This is just one fascinating discovery that emerged during NASA’s Lucy spacecraft flyby of Donald Johansson,” stated Dr. Simone Marchi, Deputy Principal Investigator of Lucy and researcher at the Southwest Research Institute.
The images captured during the flyby illustrate that Donald Johansson features two prominent crater-like protrusions joined by a relatively smooth neck.
The asteroid’s crater density aligns with the age of the Erigone asteroids, formed by violent collisions that fragmented larger parent bodies.
“Lucy’s data confirms Donald Johansson’s elongated form, as initially indicated by Earth-based telescopic observations,” Dr. March highlighted.
The measurements reveal that this small asteroid is approximately 800 meters in diameter and has a peanut-like shape, characterized by its two-lobed structure connected by a slender neck.
Lucky detections also uncovered iron-rich clay minerals, suggesting the presence of liquid water in the asteroid’s ancient past.
These findings propose that Donald Johansson is likely composed of remnants from a larger, carbon- and water-rich asteroid that disintegrated 155 million years ago.
Lucy’s encounter with Donald Johansson serves as a precursor to its primary mission, which aims to investigate Trojan asteroids—ancient celestial bodies that lead or follow Jupiter in its orbit around the Sun.
Scientists believe that these ancient space rocks have remained intact since the early solar system’s formation.
“Comparing Donald Johansson with similar asteroids like Bennu and Ryugu provides additional insights into our origins,” Dr. March stated. “As we gather more knowledge about the Trojans, whose histories diverge, we anticipate a transformation in our understanding of solar system formation.”
For more on these findings, published in the June 18 issue of Science.
_____
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