Scientists have released a series of previously unseen images of the asteroid Donaldjohanson captured by NASA’s Lucy spacecraft during an April 2025 flyby.
The team behind the photos’ release said the Lucy spacecraft, which was named for the infamous hominin fossil discovered by anthropologist Donald Johanson, captured critical details about the small main-belt asteroid’s surface features and motion that could help clarify the space rock’s origin and evolution.
The data could also inform studies of the Solar System’s formation, including how asteroids move and evolve over extended timescales.
Craters on Asteroid Donaldjohanson Confirm Its Age
According to a statement from team leader Simone Marchi and colleagues, images captured during the deep-space rendezvous revealed that the oddly shaped rock consists of two cratered ‘lobes’ connected by a comparatively smooth central “neck” section. The researchers noted that Donaldjohanson measured over 8.8 kilometers by 4.4 km by 3.1 km.
An analysis of the surface features helped the team pinpoint the asteroid’s likeliest age to a set of asteroids belonging to the Erigone family, a group that broke apart a larger “parent” body into smaller fragments. The team notes that this ancient age “implies that DJ is a fragment of a larger parent body that was destroyed in a collision about 155 million years ago.”
Phase: 34.4 deg. Image Width: 6.5 km. Image Credit: NASA/GSFC/SwRI/JHU-APL.
Although an examination of the craters helped place the asteroid’s likely age, they noted that craters less than 0.4 kilometers “have been preferentially erased.” The researchers suggest that this preferential erasure of smaller craters might have been caused by “seismic shaking” following a more recent impact event.
“DJ Rotates Slowly in a Tumbling State”
Along with surface features, the newly released images revealed the asteroid’s motion. Specifically, the team determined that Donaldjohanson has a slow, tumbling movement rather than a simple rotation.” Instead of an impact, the team suspects that the asteroid’s motion could have been produced gradually by “torques” resulting from thermal radiation.
“DJ rotates slowly in a tumbling state, likely owing to spin-down by radiative forces,” the team writes.
A spectral analysis of the rock’s cratered surface also revealed a similar composition to other Erigone family asteroids, particularly the presence of iron-bearing phyllosilicates. The team notes these phyllosilicates indicate an “aqueous evolution” on the parent body. However, they also note that the water-induced mineral alteration was likely halted “at an early stage” due to insufficient water or heat.
Next Mission Encounter Planned for 2027
Although the newly released Lucy images were captured in 2025, the team notes that the Donaldjohanson flyby mission was one leg of a larger set of 8 planned Lucy asteroid flybys, with the entire set expected to take 12 years to complete.
“Over its 12-year mission, Lucy will explore a record-breaking number of asteroids: it will fly by three in the belt of asteroids that circle the Sun between the orbits of Mars and Jupiter, and then eight Trojans, which includes five asteroid targets and the satellites of three of those,” a NASA statement explained. “Lucy also will fly by Earth three times to get a push from its gravity, making it the first spacecraft to return to the vicinity of Earth from the outer solar system.”
The study “The Lucy flyby of asteroid (52246) Donaldjohanson: A bilobed object with a tumbling rotation” was published in Science.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.