NASA's Lucy spacecraft is preparing for a pivotal encounter on April 20, 2025, as it targets asteroid (52246) Donaldjohanson, a three-mile-wide object located in the main asteroid belt. This flyby, led by the Southwest Research Institute (SwRI), will serve as a rehearsal ahead of Lucy's primary mission: investigating the Trojan asteroids that share Jupiter's orbit.
These ancient Trojan ast by Clarence Oxford
Los Angeles CA (SPX) Apr 10, 2025
NASA's Lucy spacecraft is preparing for a pivotal encounter on April 20, 2025, as it targets asteroid (52246) Donaldjohanson, a three-mile-wide object located in the main asteroid belt. This flyby, led by the Southwest Research Institute (SwRI), will serve as a rehearsal ahead of Lucy's primary mission: investigating the Trojan asteroids that share Jupiter's orbit.
These ancient Trojan asteroids have remained gravitationally anchored in Jupiter's Lagrange points for billions of years and may hold essential clues to how the solar system formed. Lucy will become the first spacecraft to conduct close-range studies of these primordial bodies.
"While we can hardly wait to observe these fossils from the early solar system, the warm-up asteroids are proving to be quite interesting in their own right," said SwRI's Dr. Hal Levison, principal investigator of the Lucy mission. "Our 2022 flyby of Dinkinesh discovered Selam, a novel contact binary satellite of the main body. And ground-based observations suggest that Donaldjohanson is a peculiar, elongated object."
SwRI scientists believe that Donaldjohanson originated roughly 150 million years ago as a fragment from a much larger asteroid. Since its formation, the object has undergone significant changes in orbit and rotation.
"The data collected could provide independent insights on evolutionary processes based on its shape, surface geology and cratering history," said SwRI's Dr. Simone Marchi, Lucy deputy principal investigator. "Understanding the formation of Donaldjohanson could help explain its peculiarities."
The asteroid belongs to a category commonly composed of silicate materials, potentially mixed with clays and organic compounds. It is likely part of the Erigone asteroid family, created from a parent body that disintegrated in the inner main belt. This region is also believed to be the origin point for near-Earth asteroids Bennu and Ryugu, explored in recent years by NASA's OSIRIS-REx and JAXA's Hayabusa2 missions.
"The flyby will answer some questions, because, as of now, Donaldjohanson's characteristics appear very distinct from Bennu and Ryugu. The flyby may uncover unexpected connections," Marchi said.
Named after the famed paleoanthropologist who discovered the hominin fossil Lucy in 1974, Donaldjohanson is uniquely special as the only named asteroid to be visited while its namesake is still alive. The fossil discovery helped illuminate human origins, while the Lucy mission aims to do the same for Earth's planetary beginnings.
"Encounters with main belt asteroids not only provide a close-up view of those bodies but also allow us to perform an end-to-end test of the spacecraft's systems before we get to the Trojans," Levison said. "The instruments aboard Lucy will allow unprecedented precision in mapping these relics, which are effectively fossils of the planet formation process. The vital clues to deciphering the history of our solar system, including our home planet."
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