In the vast reaches of space, where planetary formation left behind billions of rocky remnants, NASA’s Lucy spacecraft is carving a bold new path. Designed to explore the Trojan asteroids of Jupiter, those ancient, untouched fossils of solar system history, Lucy has already begun making headlines far earlier than expected. Its recent encounter with a previously unnamed asteroid, now dubbed Donaldjohnson, adds a fascinating twist to its mission.
An unexpected discovery
When NASA launched Lucy in October 2021, the spacecraft was set for an ambitious 12-year journey. It would visit one main-belt asteroid and seven Trojan asteroids locked in Jupiter’s orbit. But in the cosmic lottery of interplanetary travel, surprises are almost guaranteed. As Lucy prepared for its flyby of asteroid Dinkinesh in November 2023, mission scientists noticed something peculiar.
In the weeks leading up to that encounter, navigational images revealed a faint but consistent object trailing near Dinkinesh. It wasn’t part of the background stars. It moved just slightly, enough to suggest proximity, but not enough to be dismissed as a distant body. What they found was an entirely new asteroid, orbiting just beyond Dinkinesh: Donaldjohnson. This asteroid, estimated to be just a few hundred meters wide, was too small and faint to have been previously cataloged. But now, thanks to Lucy’s cameras, it had been immortalized.
The flyby that wasn’t planned
Donaldjohnson came into focus during Lucy’s high-speed encounter with Dinkinesh. Traveling at a blistering 4.5 kilometers per second, the spacecraft’s cameras were set to photograph Dinkinesh in sharp detail. But by tweaking the exposure timing and sequence slightly, engineers managed to capture high-resolution images of the smaller companion asteroid as well.
What the team found was compelling. Donaldjohnson isn’t just a tumbling rock. Its shape appears to be elongated, possibly even bi-lobed, suggesting it may have formed from the slow merger of two separate bodies. This kind of structure has been seen in other small asteroids, such as 67P/Churyumov–Gerasimenko (photographed by ESA’s Rosetta), and hints at a violent, clumpy past during the early solar system.
NASA/Goddard/SwRI/Johns Hopkins APL
Data beyond the pictures
While the images of Donaldjohnson were striking, Lucy’s other instruments added a scientific layer to the discovery. The L’LORRI (Long Range Reconnaissance Imager), Lucy’s high-resolution camera, mapped surface features—tiny craters, fractures, and what could be ejecta patterns from past impacts.
Simultaneously, Lucy’s thermal and infrared spectrometers gathered light signature data. This spectral analysis allows scientists to estimate surface composition—whether Donaldjohnson is a rocky silicate asteroid, rich in metals, or even composed of carbonaceous material, like the C-type asteroids that have been targets for missions like Hayabusa2 and OSIRIS-REx.
Preliminary readings suggest that Donaldjohnson has a somewhat different spectral profile than Dinkinesh, raising questions about whether the two objects formed together or if Donaldjohnson was captured later. This distinction matters because it could shed light on how smaller bodies interact and evolve in the chaotic environment of the asteroid belt.
The road ahead for Lucy
After its successful Dinkinesh and Donaldjohnson flybys, Lucy is now continuing its cruise toward Jupiter’s orbit. There, it will encounter a series of Trojan asteroids—objects that have shared the gas giant’s path around the Sun since the dawn of the solar system. These are the mission’s primary targets, and they hold the keys to understanding why the solar system evolved the way it did. Yet Donaldjohnson reminds us that the best discoveries are sometimes unplanned. In cosmic exploration, chance favors the prepared, and Lucy was more than ready.
Over the next decade, as Lucy completes its tour, scientists will continue analyzing the Donaldjohnson data. They’ll refine mass estimates, model its orbital history, and compare its spectra to other asteroids and meteorite samples found on Earth. It may even be used as a calibration point for future missions to binary systems or as a benchmark for asteroid classification models.
As we look forward to Lucy’s next targets and the unfolding saga of the Trojan asteroids, Donaldjohnson remains an early milestone—quietly orbiting in the shadow of a larger companion, but making a big mark in the story of our solar system’s past.
Clear skies!
