Asteroid encounter reveals 150-million-year-old fracture: The Lucy spacecraft took stunning images of the asteroid Donaldjohansson, revealing it to be a pair in contact, in the unusual shape of an "ice cream cone" with two spheres.
On its second asteroid flyby, the Lucy spacecraft captured a close-up view of an unusually shaped asteroid fragment believed to have formed about 150 million years ago. On April 20, 2025, Lucy passed within about 960 miles (XNUMX km) of the asteroid, named Donald Johanson, and began transmitting images of the encounter.
Previous observations had shown that the asteroid's brightness varied significantly over a period of ten days, hinting at an unusual shape. These suspicions were confirmed when Lucy's first images revealed what appeared to be an elongated contact pair, an object formed when two smaller bodies merged. What surprised scientists was the narrow, winding neck connecting the two lobes, which resembles a pair of stacked ice cream cones.
Clues to planet formation hidden in geology
"The geology of the asteroid Donaldjohanson is very complex," says Hal Lewison, Lucy's principal investigator. "When we study these complex structures in detail, we will discover important information about the building blocks and collision processes that created the planets in our solar system."
Initial analysis of the images from Lucy suggests that the asteroid is larger than expected – 8 km long and 3.5 km wide at its widest point. The asteroid is too large to fit entirely into the camera's field of view, so only part of it is visible in this first set of high-resolution images. It will take about a week to receive the remaining data, which will help scientists create a more complete model of the asteroid's overall shape.
This image shows the satellite's "moonrise" as it emerges from behind the asteroid Dinkinsh as captured by Lucy's L'LORRI camera, one of the most detailed images sent back by Lucy during its flyby of the binary asteroid. The image was taken on 1.11.23, from a distance of about 430 km, one minute before closest approach. From this perspective, the satellite is behind the main asteroid. The image has been sharpened and processed to improve contrast.
Credit: NASA/Goddard/SwRI/Johns Hopkins APL/NOAO
A general review for bigger future discoveries
Like Lucy's previous flyby target, asteroid Dinkinsh, Donaldjohansson is not a primary science target of the Lucy mission. As planned, the Dinkinsh flyby was a system experiment for the mission, and this encounter was a dress rehearsal, in which the team performed a series of dense observations to maximize data collection.
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