The Lucy spacecraft will make a close flyby of the asteroid Donald Johanson on April 20, a systems practice before arriving at Jupiter's Trojan asteroids.
NASA's Lucy spacecraft is set to soon pass near asteroid (52246) Donaldjohanson, a strange, elongated rock in the main asteroid belt, about 4.8 kilometers wide. The expected encounter on April 20, 2025, is a full dress rehearsal before the spacecraft continues on its core mission – studying Jupiter's Trojan asteroid groups, considered "fossils of the planet-forming process."
The Lucy mission, led by Southwest Research Institute (SwRI), is embarking on a 6.4 billion-mile journey through the solar system. On April 20, Lucy will pass near Donald Johnson to test its systems and warm up for a future flyby of the Jupiter Trojans. These are two parallel asteroid clusters that orbit the Sun in sync with Jupiter and were captured billions of years ago. Scientists believe they hold important clues to how the solar system formed.
“The prospect of seeing these fossils from the early solar system up close is very exciting, but the asteroids we bumped into as warm-up objects are also interesting in their own right,” said Dr. Hal Levinson, principal investigator of the Lucy mission at SwRI. “In 2022, we discovered a strange companion in a contact binary called Selam near Dinkinesh. Ground-based observations show that Donaldjohanson also has a unique, elongated shape.”
New research at SwRI suggests that Donaldjohansson was formed about 150 million years ago, due to the explosion of a larger asteroid. Since then, its orbit and rotation have changed significantly, making it a living laboratory for studying asteroid evolution. “The data we collect may provide further insights into evolutionary processes based on its shape, geology and impact rate,” added Dr. Simone Marzi, Lucy’s deputy principal investigator.
Donaldjohansson is a silicate asteroid that likely also incorporates organics and clays, and is a member of the Erigone family—a group of main-belt asteroids formed by the explosion of a parent asteroid. The family's origin is close to the source regions of near-Earth asteroids such as (101955) Bennu and (162173) Ryugu, which were recently visited by the OSIRIS-REx and Hayabusa2 missions.
The upcoming flyby will help answer many questions, as Donaldjohansson's properties appear to be different from those of Bennu and Ryugu. The encounter could reveal unexpected connections and enrich our understanding of the evolution of main-belt asteroids.
The asteroid is named after paleontologist Donald Johnson, discoverer of the 1974 hominin skeleton Lucy from Ethiopia that inspired the mission. Like the hasty Lucy, Donald Johnson’s evolution could provide new insights into the history of the solar system, including our own planet. It is the only asteroid named after a living person that is expected to be visited in the near future.
"In addition to allowing us to take a closer look at these asteroids, the probe will allow us to conduct comprehensive tests of the spacecraft's systems before we reach our real destination - the Jupiter Trojans," concluded Levinson. "Lucy's instruments will allow unprecedented precision mapping of these remains, which are essentially fossils of the planet-forming process. They hold vital clues to deciphering the history of our solar system, including our home planet."
Key phrase: Lucy's mission
Synonyms: NASA Lucy, Trojan asteroids, Donaldjohansson
